Ming Li

Our calculations find that the base strength is the primary factor that controls the catalytic capability of cocatalysts CH3CN, Propargylic acetates (1a) and Et3N. In the proton-transfer process, the trend of catalytic activity increases in the order: Et3N > 1a > CH3CN, which matches well with the enhanced trend of base strength (Et3N > 1a > CH3CN). Et3N is the most appropriate for the present Cu-catalyzed cycloisomerization of propargylic acetates, which is in agreement with the experimental phenomena. Besides, our calculations give a reasonable explanation for the effects of terminal substituents (H- vs. Ph-) of alkyne on the catalytic reaction.Download high-res image (332KB)Download full-size image

Influence of Base Strength on the Proton-Transfer Reaction by Density Functional Theory

Co-reporter:Binfang Yuan;Rongxing He;Wei Shen

European Journal of Organic Chemistry 2017 Volume 2017(Issue 27) pp:3947-3956

Publication Date(Web):2017/07/25

DOI:10.1002/ejoc.201700562

DFT methods have been used to investigate base-assisted effects on proton-transfer reactions, including the cleavage of C–H bonds in metal-catalyzed organic synthesis. Anion ligands (OTf–, BF4–, or SbF6–) have been shown to effectively promote cleavage of the C–H bond and then assist proton migration as a proton-transfer shuttle. Importantly, the calculations revealed that the catalytic activity (OTf– > BF4– > SbF6–) in the C–H bond-breaking step is controlled by the Brønsted/Lewis basicity of the anion ligand (OTf– > BF4– > SbF6–) through a hydrogen-bonding (base···C–H) interaction. Additives play a similar role to the anion ligands, and the use of a strong base as an additive is much more effective in promoting cleavage of the C–H bond than a weak base. In short, the present study has provided a greater understanding of the effects of base strength on proton-transfer reactions involving C–H bond cleavage and offers guidance for the future design of new catalysts and new reactions.

Rational design of bis(4-methoxyphenyl)amine-based molecules with different π-bridges as hole-transporting materials for efficient perovskite solar cells

Co-reporter:Xiaorui Liu, Chengzhi Huang, Ming Li

Dyes and Pigments 2017 Volume 139(Volume 139) pp:

Publication Date(Web):1 April 2017

DOI:10.1016/j.dyepig.2016.12.024

•A series of new hole-transporting materials were designed.•Tuning the π-bridged units is a feasible way to improve the performance of HTMs.•The designed HTMs process high hole mobility.•The designed HTMs process good stability.Exploration on alternative organic hole-transporting materials (HTMs) especially for high-efficiency perovskite solar cells (PSCs) has attracted great attention recently. In this work, a strategy to tune π-bridged units of the small molecular HTM which consists of bis(4-methoxyphenyl)amine as arm and spiro[fluorene-9,9'-xanthene] as π-bridge were theoretically presented for improvement of the PSC efficiency. The π-bridged tunings could promote the contribution of the highest occupied molecular orbital (HOMO) to delocalize throughout whole molecules in order to be favorable for enhancing the hole transfer integral and hole mobility. Compared with the parent HTM, the new designed HTMs in PSC applications exhibit better performance with higher HOMO energy levels, larger Stokes shifts, little exciton binding energy, better stability and higher hole mobility. Therefore, the strategy on basis of modulating the π-bridge units of small molecules can effectively change the performance of HTMs and thereby provide a useful guideline of π-bridge screening for the design of excellent HTMs in PSC applications. In view of the excellent properties, the designed molecules as HTMs can act as a promising candidates for providing a large efficiency in PSC applications.Download high-res image (241KB)Download full-size image

Theoretical insights into the effect of a conjugated core on the hole transport properties of hole-transporting materials for perovskite solar cells

Co-reporter:Zemin Zhang;Weixia Hu;Jianyu Cui;Rongxing He;Wei Shen

Physical Chemistry Chemical Physics 2017 vol. 19(Issue 36) pp:24574-24582

Publication Date(Web):2017/09/20

DOI:10.1039/C7CP04754A

Conjugated bifluorenylidene and naphthalene central cores are introduced into hole-transporting materials DT1 and DT2 to replace the spiro-core of the reported, highly efficient FDT. The effects of the conjugated core on the geometrics, electronic properties and hole transport properties are investigated by using density functional theory coupled with Marcus theory and the Einstein relation. The calculated results show that DT1 (−5.21 eV) and DT2 (−5.23 eV) have lower HOMO levels than FDT (−5.15 eV), which indicates that the perovskite solar cells with conjugated hole-transporting materials can have higher open-circuit voltages. The introduction of the conjugated core is beneficial to the more efficient face-to-face packing pattern of the dimer, resulting in a larger intermolecular electronic coupling. Importantly, it is found that DT1 (1.6 × 10−3 cm2 V−1 s−1) and DT2 (2.7 × 10−2 cm2 V−1 s−1) exhibit relatively higher hole mobilities than FDT (1.3 × 10−4 cm2 V−1 s−1) owing to the larger electronic coupling. Therefore, enhanced hole transport ability can be achieved by switching from the spiro-core to the conjugated core. The present work provides a new strategy to improve the hole transport properties of hole-transporting materials, which will contribute to the development of conjugated small molecules as hole-transporting materials in efficient perovskite solar cells.

DFT study on the CuBr-catalyzed synthesis of highly substituted furans: effects of solvent DMF, substrate MeOH, trace H2O and the metallic valence state of Cu

Co-reporter:Binfang Yuan, Rongxing He, Wei Shen, Weixia Hu and Ming Li

RSC Advances 2016 vol. 6(Issue 24) pp:20294-20305

Publication Date(Web):12 Feb 2016

DOI:10.1039/C5RA24967H

The CuBr-catalyzed 2-(1-alkynyl)-2-alken-1-ones are selected as a research system to explore the effects of solvent DMF, substrate MeOH, trace H2O and the valence state of Cu on the synthesis of highly substituted furans using the BHandHLYP density functional. Our calculations suggest that DMF, MeOH and H2O can be used as hydrogen-bond acceptors to accelerate intermolecular nucleophilic addition. More importantly, they play the role of proton shuttles to assist H migration significantly by reducing the free energy barrier of the H-transfer process. Due to the participation of DMF, MeOH or H2O, the rate-determining step is changed from the H-transfer process (96.0 kJ mol−1) to the intramolecular cyclization step (57.6 kJ mol−1). In addition, calculated results also show that the yield can be further improved when CuBr is replaced by CuBr2. In short, the present study can provide insight into the metal-catalyzed reactions involving H-transfer processes and can act as a guideline for the design of new catalysts for metal-catalyzed reaction applications.

Fine structural tuning of diketopyrrolopyrrole-cored donor materials for small molecule-fullerene organic solar cells: A theoretical study

Co-reporter:Lvyong Zhang, Wei Shen, Rongxing He, Xiaorui Liu, Xiaoqin Tang, Yuehong Yang, Ming Li

Organic Electronics 2016 Volume 32() pp:134-144

Publication Date(Web):May 2016

DOI:10.1016/j.orgel.2016.01.023

•We presented two novel strategies to tune diketopyrrolopyrrole and its derivatives.•Our strategies synergistically reduced the HOMO level and the energy gap of donors.•The new designed donors show more favorable solar cell performance.•We studied the absorption of CT states by investigated the donor-PCBM complexes.•Our strategies can be used to improve the properties of other DPP-based structures.Two novel strategies to tune diketopyrrolopyrrole and its derivatives by lactam-lactim and alkoxy-thioalkoxy exchange were theoretically presented for improving the efficiency of bulk heterojunction solar cells. The structural tunings could synergistically reduce the HOMO level and the energy gap of donors due to the disrupted aromaticity of the linked pyrrole derivatives. Compared with the parent molecule, the new designed donors not only create a more red-shift of absorption spectrum but also show better hole transport rates, larger fill factor, higher open circuit voltage and more favorable solar cell efficiency. Moreover, the arrangements at the interface and the optical properties of the donor-PCBM complexes were computationally investigated to get insight into the absorption of charge transfer states. Consequently, the strategies are judicious approaches to enhance their intrinsic properties of donors and can be used for further improving the performance of other DPP-based molecules in bulk heterojunction solar cells.

Rational design of carbazolyl and aryl phosphine oxide (APO) based ambipolar host materials for blue electrophosphorescence: a density functional theory study

Co-reporter:Dongmei Zhang, Wei Shen, Xiaguang Zhang, Huili Sun, Rongxing He and Ming Li

RSC Advances 2016 vol. 6(Issue 42) pp:35416-35424

Publication Date(Web):21 Mar 2016

DOI:10.1039/C6RA02808J

We have designed 10 host molecules for blue/green electrophosphorescence by combining the electron donor carbazolyl unit and the electron acceptor aryl phosphine oxide unit into a single molecular unit by density functional theory. In addition, we have systematically investigated the influence of the phenyl spacers, phenyl substitution and the type of bridge (diphenylether-bridge or diphenylamine-bridge) on an array of electronic properties of the designed ambipolar hosts. For all designed host molecules, host molecule 5 in which the phenyl ring with carbazolyl and phenyl substituted at the o-position was directly combined with phosphine oxide through a diphenylether-bridge linkage could retain a high triplet energy and showed great potential for blue phosphorescent organic light-emitting diodes. Furthermore, the Förster and Dexter energy transfer mechanisms between all designed host molecules and guests are thermodynamically feasible. In addition, we built a host–guest model to investigate the charge transfer mechanism, and the results indicate that a good intermolecular charge transfer can be attained between host and guest materials.

DFT insights into the cycloisomerization of ω-alkynylfuran catalyzed by planar gold clusters: mechanism and selectivity, as compared to Au(I)-catalysis

Co-reporter:Miao Yang, Zhongzhu Chen, Yafei Luo, Jin Zhang, Dianyong Tang, Rongxin He, Wei Shen and Ming Li

RSC Advances 2016 vol. 6(Issue 27) pp:22709-22721

Publication Date(Web):22 Feb 2016

DOI:10.1039/C5RA26156B

A detailed reaction mechanism of the triatomic gold cluster-catalyzed cycloisomerization of ω-alkynylfuran was systemically investigated via density functional theory at the TPSSh/def2-TZVP level. The computational results indicated that the 5-exo Friedel–Crafts-type mechanism is the most favorable mechanism to form the phenol derivatives. The strong interaction between the gold and vinyl fragments in the Friedel–Crafts adduct is essential for the priority of the 5-exo Friedel–Crafts-type mechanism. Then, the 5-exo Friedel–Crafts-type mechanism on the various planar gold clusters (Au4–10) was studied to clarify the size-effects of the planar gold clusters catalyzed ω-alkynylfuran cycloisomerization. The appropriate interactions between the alkyne group in the substrate and gold clusters play a key role for the 5-exo cyclization step. The energy barriers of the ring-closure of the dienone carbene–gold intermediate step show an interesting “odd–even” behavior respective to the number of gold atoms. The Au3 and Au4 clusters are the most active catalysts for the ω-alkynylfuran cycloisomerization to the phenol derivative. We also found that the active catalyst of the ω-alkynylfuran cycloisomerization catalyzed by the gold(I) complexes should be the gold(0) complexes of the in situ generation. The catalytic activity of the gold(0) complex is comparable with that of the planar gold clusters. These findings may guide the rational design of highly active gold catalysts for the ω-alkynylfuran cycloisomerization to phenol derivatives.

Density functional study on the effect of aromatic rings flanked by bithiophene of novel electron donors in small-molecule organic solar cells

Co-reporter:Lvyong Zhang, Wei Shen, Rongxing He, Xiaoqin Tang, Yuehong Yang, Ming Li

Materials Chemistry and Physics 2016 Volume 175() pp:13-21

Publication Date(Web):1 June 2016

DOI:10.1016/j.matchemphys.2016.01.062

•A series of novel donors were designed based on a previously reported molecule.•A study on the effects of aromatic rings flanked by bithiophene was performed.•HOMO energy level goes up while Eg goes down along with the cycle extension.•The charge transfer/transport characteristics of the molecules were investigated.•The final designed compounds show more favorable photoelectronic properties.In order to further improve the short-circuit current (JSC) and the overall performance of the already synthesized donor molecule (1s) used in organic heterojunction solar cells, six new A-A-D-A-A type small molecules composed of different donor (D, electron rich) and same acceptor (A, electron poor) moieties were designed and characterized by using density functional theory (DFT), time-dependent density functional theory (TD-DFT) and Marcus theory. Through calculating frontier molecular orbital energy levels and spectra properties, we found that HOMO level goes up while Eg goes down along with the cycle extension of the center part flanked by bithiophene. Next, character of excited state, ionization potentials (IPs) and charge transport properties were also investigated to provide an in-depth insight into the charge transfer/transport characteristics and the JSC of organic solar cells. The results reveal that compounds 3c, 3n and 3° exhibit favorable JSC and comparable performance to original molecule (1s) and show promising potential in organic solar cells.

Theoretical Investigation on Porphyrin-Based Small Molecules as Donor Materials for Photovoltaic Applications

Co-reporter:Xiaorui Liu, Chengzhi Huang, and Ming Li

The Journal of Physical Chemistry C 2016 Volume 120(Issue 48) pp:27148-27158

Publication Date(Web):November 11, 2016

DOI:10.1021/acs.jpcc.6b09437

An effective strategy to improve the efficiency of organic solar cells (OSCs) is to incorporate the porphyrin derivatives as electron-rich units into the acceptor–donor–acceptor molecules. To achieve this goal, starting from the parent molecules DTS(PTTh2)2 and DTS(FBTTh2)2 which are based on a dithieno(3,2-b;2′,3′-d)silole (DTS) electron-rich unit connected to each of two electron-withdrawing units ([1,2,5]thiadiazolo[3,4-c]pyridine (PT) and 5-fluorobenzo[c][1,2,5]thiadiazole (FBT)), we designed two types of porphyrin-based small molecules by replacing DTS unit with the porphyrin derivatives in DTS(PTTh2)2 and DTS(FBTTh2)2, respectively. From the calculated results, the porphyrin-based molecules in OSC applications not only yield an enhanced light absorptions with a redshift and stronger spectra and increased hole mobility, which is conducive to enhance the short circuit current and fill factor, but also exhibit smaller exciton binding energy and better electron transfer properties at donor/acceptor (D/A) interface in comparison with the parent molecules. According to the predicted crystal structure for porphyrin-based molecules, the hole mobilities of the porphyrin-based molecules (S1b, S1c, S2b, and S2c) are 0.240, 0.166, 0.124, 0.511 cm2 V–1 s–1, respectively. In view of the excellent properties, the porphyrin-based molecules as donor materials can act as a good candidates for providing a large short-circuit current and fill factor in OSC applications.

Theoretical studies on the effect of a bithiophene bridge with different substituent groups (R = H, CH3, OCH3 and CN) in donor–π–acceptor copolymers for organic solar cell applications

Co-reporter:Zhiyong Fu, Wei Shen, Rongxing He, Xiaorui Liu, Huili Sun, Wanqiang Yin and Ming Li

Physical Chemistry Chemical Physics 2015 vol. 17(Issue 3) pp:2043-2053

Publication Date(Web):26 Nov 2014

DOI:10.1039/C4CP04103H

An effective way to enhance the efficiency of bulk heterojunction (BHJ) solar cells is to insert suitable bridges (π) between donor units (D) and acceptor units (A) in D–π–A copolymers. This work is devoted to uncovering how the characteristics of a HT (the substituent groups via head- to-tail (HT) connection) bithiophene bridge with different substituent groups (R = H, CH3, OCH3 and CN) affect the ground state structure, electronic, optical and charge transport properties of D–π–A copolymers for improving the photovoltaic performance. Based on the D–π–A copolymer PPBzT2-CEHβ (P1) with a HT bridge of 3,4′-diethylhexyl-2,2′-bithiophene (π1), we designed six new copolymers (P2–P6′) by introducing six kinds of HT bridges. From the calculated results, the introduction of different substituent groups into the bithiophene-bridge can markedly affect the HOMO and LUMO levels, band gaps, light-absorbing efficiency and hole transport ability of the copolymers. In particular, the copolymer P6 combining the cyano and methoxyl groups into the bridge has remarkable electronic and optical properties and hole transport ability among all the copolymers P1–P6′, and it can be a candidate for donor materials of organic solar cells. We hope that the present results could provide a theoretical guidance for designing efficient donors in organic solar cells.

Theoretical investigation of dihydroacridine and diphenylsulphone derivatives as thermally activated delayed fluorescence emitters for organic light-emitting diodes

Co-reporter:Xiaguang Zhang, Wei Shen, Dongmei Zhang, Yongzhen Zheng, Rongxing He and Ming Li

RSC Advances 2015 vol. 5(Issue 64) pp:51586-51591

Publication Date(Web):01 May 2015

DOI:10.1039/C5RA04929F

A series of donor–acceptor–donor type compounds containing 9,9-dimethyl-9,10-dihydroacridine and diphenylsulphone as thermally activated delayed fluorescence emitters are designed and investigated, and their broad application prospects in organic light emitting diodes are predicted by density functional theory (DFT). The results show that the orbital interaction of the atom between the acceptor and the donor is an important factor to influence the singlet–triplet energy difference. Effective intermolecular singlet–singlet, singlet–triplet and triplet–triplet energy transfers from hosts to emitters, in which donors and acceptors are linked by C–N bonds, would occur. The para- and meta-linked compounds exhibit blue emission and the ortho-linked compounds show green emission in these emitters.

The DFT study on non-conjugated polymer host materials based on styrene derivatives for phosphorescent polymer light-emitting diodes

Co-reporter:Xiaguang Zhang;Wei Shen;Huili Sun;Pei Yu;Rongxing He

Journal of Physical Organic Chemistry 2015 Volume 28( Issue 8) pp:554-563

Publication Date(Web):

DOI:10.1002/poc.3448

A series of poly(4,4-vinyltriphenylamine) based non-conjugated polymer as host molecules are designed and studied by density functional theory. The results show that the substituent has a great influence on the properties of polymer. The parent molecule directly linked para-carbazole, β-pyrrole and triphenylamine are favorable to hole injection, and para-carbazole could significantly increase E_T of the host molecules. The large changes of structural parameters between the lowest triplet state and ground state can cause the decrease of E_T. Moreover, parent molecule directly linked carbazole and triphenylamine units possess strong intramolecular charge transfer and low singlet and triplet energy difference (∆E_ST). The calculated results also show that all designed host molecules are suitable for green emitter by comparing with the E_T. S₁ S₁ and T₁ T₁ energy transfer mechanism between host and guest is thermodynamically feasible. In addition, host–guest model is built to study the charge transfer nature, and the results indicate that a good intermolecular charge transfer can be achieved between host and guest materials. In the designed host molecules, the N atom of parent molecule linked para-carbazole substituent shows a great potential for the green phosphorescent polymer light-emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.

Theoretical Strategy To Design Novel n-Type Copolymers Based on Anthracene Diimide and Pyrido[2,3-g]quinoline Diimide for Organic Solar Cells

Co-reporter:Zhiyong Fu, Wei Shen, Xiaoqin Tang, Min He, Rongxing He, and Ming Li

The Journal of Physical Chemistry A 2015 Volume 119(Issue 26) pp:6884-6896

Publication Date(Web):June 3, 2015

DOI:10.1021/acs.jpca.5b03731

The design and synthesis of efficient electron-transporting materials have been an active area of research in the area of organic solar cells (OSCs), organic field-effect transistors (OFETs), and organic light-emitting diodes (OLEDs). This paper is focused on designing novel n-type donor–acceptor (D–A) copolymers as electron-transporting materials for replacing the widely used fullerene acceptor materials in OSC applications. We first present a strategy which can remarkably improve the photovoltaic performances of D–A copolymer acceptors by means of adjusting the molecular planarity and intensifying the electron-withdrawing ability of electron-deficient units. Then we further analyze the role played by the D–A copolymer acceptor in the light-absorbing performance of the active layer. On the basis of two reported two D–A copolymer acceptors (PNDIT and P(NDI2OD-T2)) which are composed of an electron-deficient naphthalene diimide (NDI) unit and different electron-rich units of thiophene or bithiophene, replacement of the NDI unit with an anthracene diimide (ADI) unit and a pyrido[2,3-g]quinoline diimide (PQD) unit can produce two types of copolymer acceptors (P2, P3 and P2a, P3a). From the calculated results, the introduction of ADI and PQD units to replace the NDI unit can significantly improve the optoelectronic properties, light-absorbing efficiencies, and intermolecular electron transport abilities of the copolymers as well as exciton separation efficiencies at donor/acceptor interface. Finally, this study would give us a theoretical guidance to design efficient D–A copolymer acceptors for replacing fullerene acceptors in organic solar cells.

Mechanistic Insights into the Cu(I)- and Cu(II)-Catalyzed Cyclization of o-Alkynylbenzaldehydes: The Solvent DMF and Oxidation State of Copper Affect the Reaction Mechanism

Co-reporter:Binfang Yuan, Rongxing He, Wei Shen, Cheng Huang, and Ming Li

The Journal of Organic Chemistry 2015 Volume 80(Issue 13) pp:6553-6563

Publication Date(Web):June 2, 2015

DOI:10.1021/acs.joc.5b00523

A computational study with the BhandHLYP density functional is conducted to elucidate the mechanisms of Cu(I)- and Cu(II)-catalyzed reactions of o-alkynylbenzaldehydes with a nucleophile (MeOH). Our calculations suggest the following. (a) The use of CuCl as a catalyst deceases significantly the energy barrier and promotes intramolecular cyclization. (b) Solvent DMF is critical in the stepwise hydrogen-transport process involved in an intermolecular nucleophilic addition because it can greatly reduce the free energy barrier of the hydrogen-transfer process as a proton shuttle. In addition, we find that substrate MeOH also plays a role similar to that of DMF in the hydrogen-transport reaction. (c) The 6-endo product P1 is formed exclusively using a catalytic system consisting of CuCl and DMF, whereas a mixture of 6-endo product P1 and 5-exo product P2 in a ratio of ∼1:1 is produced using CuCl2 and DMF as a catalytic system. Our theoretical calculations reproduce the experimental results very well. This study is expected to improve our understanding of Cu(I)- and Cu(II)-catalyzed reactions involving Lewis base solvents and to provide guidance for the future design of new catalysts and new reactions.

Identifying efficient blue-phosphorescent polymer light-emitting diode host materials based on carbazole derivatives with C/Si-centered substituents using density functional theory

Co-reporter:Xiaguang Zhang;Wei Shen;Huili Sun;Rongxing He

Journal of Molecular Modeling 2015 Volume 21( Issue 7) pp:

Publication Date(Web):2015 July

DOI:10.1007/s00894-015-2725-y

Two series of carbazole derivatives were designed and studied that could potentially be used in polymer light-emitting diodes (PLEDs) as host molecules. These carbazole-based host molecules incorporated substituents with C or Si at their centers at the 3- and 6-positions on the carbazole moiety. Density functional theory calculations were performed to investigate the influence of the substituent on energy and charge transfer, and to predict whether each molecule could act as an effective host material in PLEDs. The results show that, for the series in which the carbazole moiety is linked to the substituent via the central C/Si atom (“cbz-sub series”), triplet-state electron transitions and triplet excitons arise from the carbazole moiety. Members of the cbz-sub series also exhibited higher triplet energies (ET) than the series in which the carbazole moiety is linked to the C/Si-centered substituent via an extra phenyl group (“cbz-ph-sub series”). Moreover, members of the cbz-sub series presented strong molecular orbital interactions and suitable singlet and triplet energy differences (ΔEST). Further investigations showed that, in each series, the presence of an Si atom was more likely to inhibit charge and exciton delocalization, and inserting a methyl or tert-butyl group at the 2- and 7-position, respectively, of the carbazole moiety in the cbz-ph-sub molecules improved their ET values and led to clear intramolecular charge-transfer character. A comparison of the energies of host and guest molecules showed that all of the molecules designed in this work are suitable for use with blue-light guest materials.

Mechanisms for the synthesis of conjugated enynes from diphenylacetylene and trimethylsilylacetylene catalyzed by a nickel(0) complex: DFT study of ligand-controlled selectivity

Co-reporter:Cheng Huang;Rongxing He;Wei Shen

Journal of Molecular Modeling 2015 Volume 21( Issue 5) pp:

Publication Date(Web):2015 May

DOI:10.1007/s00894-015-2672-7

Density functional theory (DFT) was utilized to elucidate the reaction mechanisms of and the key factors that influence the Ni(0)-catalyzed cross-dimerization and -trimerization of trimethylsilylacetylene (R1) and diphenylacetylene (R2). Calculated results revealed that the electron-donating ability of the ligand plays a crucial role in determining the regionselectivity of this tandem reaction. The use of strongly electron-donating ligands favors the formation of cross-dimer intermediates, whereas cross-trimer products can easily be synthesized using weakly electron-donating ligands. A simple method of estimating the electron-donating abilities of different ligands based on the Mulliken charge distribution of the ligand–ligand pair was employed. The present theoretical results allow us to elucidate the reaction mechanisms for and to identify the factors that exert the greatest influence on the ligand-controlled cross-dimerization and -trimerization of trimethylsilylacetylene and diphenylacetylene. Guidelines for the design of novel ligand systems with Ni(0) catalysts are also proposed.

Density functional study on the effect of a new ladder-type structure with different substituent groups (R = H, CH3, OCH3 and CN) for donor–acceptor copolymers

Co-reporter:Zhiyong Fu, Wei Shen, Rongxing He, Xiaorui Liu, Pei Yu, Xian Peng and Ming Li

RSC Advances 2014 vol. 4(Issue 69) pp:36656-36664

Publication Date(Web):07 Aug 2014

DOI:10.1039/C4RA05954A

A series of ladder-type fused-ring D–A (donor–acceptor) copolymers have been designed and synthesized as electron donors for BHJ photovoltaic cells, in previous work, and almost all of them focus on electron-rich units. The aim of this paper is to explore the effect of a new ladder-type multifused electron-deficient unit (DCDTBT) with different substituent groups (R = H, CH3, OCH3 and CN) on the ground state structure, electronic, optical and charge transfer properties of D–A copolymers for the improvements of photovoltaic performance. Based on the reported D–A copolymer (P1) which was composed of an electron-rich benzo[1,2-b:4,5-b′]dithiophene unit (BDT) and an electron-deficient 4,7-di(4-hexyl-2-thienyl)-2,1,3-benzothiadiazole unit (4DTBT), the 4DTBT unit was replaced with the ladder-type di[4,4-dicyclopenta]dithienylbenzothiadiazole (DCDTBT) unit to form a new copolymer (P2). The calculated results reveal that P2 has better planarity, wider and stronger optical absorption, and smaller reorganization energy than P1. Then the substituent groups (CH3, OCH3 and CN) were introduced at the bridging carbons of the DCDTBT unit to design seven new donor copolymers (P2a–P2c, P2a′–P2c′ and P3). From the calculated results, the introduction of the substituent groups into the DCDTBT unit can markedly improve the electronic, optical and charge transfer properties of those copolymers, but have a little influence on molecular backbone planarity. In particular, the introduction of the cyano-group into the DCDTBT unit can obviously reduce the HOMO/LUMO levels of the copolymers. Interestingly, the copolymers (P2c/P2c′) combining the cyano-group and methyl or methoxyl into the same bridging carbon of DCDTBT unit have excellent electronic, optical properties and charge transfer ability, as promising donor polymers for high-efficiency (∼7% for P2c, ∼9% for P2c′) organic solar cells. In this work, a design strategy is used to select a suitable ladder-type electron-deficient unit for further improving the photovoltaic performance of donors in solar cells.

Theory study on the properties of thiadiazole polymer donors for organic solar cells

Co-reporter:Xian Peng;Wei Shen;Xiaorui Liu;Yan Zhang

Journal of Physical Organic Chemistry 2014 Volume 27( Issue 2) pp:99-105

Publication Date(Web):

DOI:10.1002/poc.3244

In this work, the properties of [1,2,5] thiadiazolo [3,4-c] pyridine -alt-cyclopenta [2,1-b:3,4-b′] dithiophene (PT-CDT) and [1,2,5] thiadiazolo [3,4-c] pyridine-6-carbonitrile-alt-cyclopenta [2,1-b:3,4-b′] dithiophene (PCNT-CDT) as donors were investigated by means of Density Functional Theory. The electronic properties and optical absorption properties were discussed, and hole-transfer properties of donors were studied by Marcus electron transfer theory. The results indicate that the linear structure of PCNT-CDT and PT-CDT is more stable than the spiral structure of PCNT-CDT and PT-CDT; the absorption peak in visible region of PCNT-CDT is stronger and wider, and the absorption spectrum is more matchable to solar spectrum than PT-CDT, while the maximum absorption wavelength of PCNT-CDT has an obvious red shift; the two designed materials show strong intramolecular and intermolecular charge transfer properties; PCNT-CDT owns a large open-circuit voltage and low reorganization energy, as well as high hole mobility. Therefore, the newly designed PCNT-CDT can be a potential donor material of organic solar cell. Copyright © 2013 John Wiley & Sons, Ltd.

Acylation and deacylation mechanism of Helicobacter pylori AmiF formamidase: A computational DFT study

Co-reporter:Rongxing He, Qinlei Yang, Ming Li

Chemical Physics Letters 2014 Volume 599() pp:92-99

Publication Date(Web):18 April 2014

DOI:10.1016/j.cplett.2014.02.005

•Constructed a large active site, in which Glu60, Glu141 and His167 were included.•Explained the crucial role played by residues Glu60, Glu141 and His167.•Proposed a new mechanism in which thiol group attacks carbon atom of formamide.The acylation and deacylation mechanisms of Helicobacter pylori AmiF formamidase were investigated using DFT method. In the constructed active site, residues Glu60, Glu141 and His167 were taken into account besides Lys133 and Cys166. Calculations provided insight on the details of mechanism and explained crucial roles played by Glu60, Glu141 and His167. For acetylation, we proposed a new stepwise mechanism in which the thiol group first attacks the carbon atom of formamide and produces tetrahedral intermediate. In deacylation, Glu60 activates a water molecule to perform nucleophilic attack and then forms an intermediate, which is different from the usually suggested mechanism.Graphical abstractThe active site of AmiF.

An easy route to exotic 9-epimers of 9-amino-(9-deoxy) cinchona alkaloids with (8S, 9R) and (8R, 9S)-configurations through two inversions of configuration

Co-reporter:Jing-Wei Wan, Xue-Bing Ma, Rong-Xing He, Ming Li

Chinese Chemical Letters 2014 Volume 25(Issue 4) pp:557-560

Publication Date(Web):April 2014

DOI:10.1016/j.cclet.2013.12.008

Four exotic chiral organocatalysts, 9-amino-(9-deoxy) cinchona alkaloids with (8S, 9R) and (8R, 9S)-configurations, were conveniently synthesized for the first time in 27–72% total yields through two conversions of configuration at the 9-stereogenic centers of commercially available cinchona alkaloids.Four exotic chiral organocatalysts, 9-amino-(9-deoxy) cinchona alkaloids with (8S, 9R) and (8R, 9S)-configurations, were conveniently synthesized for the first time in 27%–72% total yields through two conversions of configuration at the 9-stereogenic centers of commercially available cinchona alkaloids.

Strategy to Modulate the Electron-Rich Units in Donor–Acceptor Copolymers for Improvements of Organic Photovoltaics

Co-reporter:Xiaorui Liu ; Wei Shen ; Rongxing He ; Yafei Luo

The Journal of Physical Chemistry C 2014 Volume 118(Issue 31) pp:17266-17278

Publication Date(Web):July 9, 2014

DOI:10.1021/jp503248a

We present an effective strategy to modulate the electron-rich capability in donor–acceptor (D-A) polymers for improving the performances of organic solar cell (OSC) devices. In order to confirm this strategy, based on a series of the reported D–A polymers ((PCPDTBT(Pa1), PCPDTFBT (Pa2), and PCPDTDFBT (Pa3)) which contain the electron-donating cyclopentadithiophene (CPDT) and differently electron-withdrawing units of benzo[c][1,2,5,]thiadiazole (BT), 5-fluorobenzo[c][1,2,5]thiadiazole (FBT), and 5,6-difluorobenzo[c] [1,2,5]thiadiazole (DFBT), we replace CPDT with electron-donating dithienogermolodithiophene (DTTG) in polymers Pa1–Pa3, respectively, and design a series of new D–A polymers Pb1–Pb3. Compared with the polymers Pa1–Pa3, the new designed polymers Pb1–Pb3 not only yield a greater red-shift of the absorption spectrum of the donor polymer and result in a larger absorption region within the solar emission spectrum and an improved light-absorbing efficiency but also exhibit much better electron transfer efficiency in active layer, larger hole transport rates and higher open circuit voltage. Moreover, the estimated power conversion efficiency of the designed polymers in OSC applications reaches up to ∼8.4%. Conclusively, the approach based on modulating the electron-donating capability in D–A polymer chain is a feasible way to enhance their intrinsic properties of donor polymers and thereby achieving the purpose that improves the performances of the OSC devices.

Theoretical design study on photophysical property on oligomers based on spirobifluorene and carbazole-triphenylamine for PLED applications

Co-reporter:Xiao-Hua Xie;Wei Shen;Rong-Xing He

Journal of Molecular Modeling 2013 Volume 19( Issue 1) pp:139-149

Publication Date(Web):2013 January

DOI:10.1007/s00894-012-1529-6

The photophysical properties of five blue light-emitting polymers based on spirobifluorene applied in polymer light-emitting diodes (PLED) materials have been studied by quantum chemistry. In order to understand the intrinsic reasons for the different performances displayed by the polymers, we carried out density functional theory (DFT) and Marcus theory investigations on their oligomers in terms of structure and properties stability, absorption and emission properties, and carrier injection and transport properties. Especially, some important parameters which had not been reported to our knowledge were given in this contribution, such as the ionization potentials (IPs), electron affinities (EAs), reorganization energies (λ), ke/kh (the ratio between the electron transfer rate (ke) and hole transfer rate (kh)), and the radiative lifetimes (τ). The main results indicate that the co-oligomers of PCC-1, PCC-2, and PCC-3 with push-pull interactions produced by the existing D-A segments have better carrier injection and transport properties than the oligomers of PSF and PCF. Especially PCC-2 co-oligomer, its large radiation lifetime (7.46 ns) and well balanced and adequate carrier transport guarantee its champion performance for PLED. The calculated results coincide with the experimental ones. Besides, PNF structurally similar to PCC-2 has similar photoelectric properties to PCC-2 in theory, and the fluorescence emission of PNF co-oligomer is superior to PCC-2 co-oligomer. Therefore, we predict that PNF is a promising candidate for PLED.

Mechanistic study on Mo(CO)6-catalyzed intramolecular [2+2] or [2+2+1] cycloaddition reaction of 5-allenyl-1-ynes

Co-reporter:Qingxi Meng

Journal of Physical Organic Chemistry 2012 Volume 25( Issue 1) pp:21-31

Publication Date(Web):

DOI:10.1002/poc.1860

Abstract

By means of density functional theory, the Mo(CO)₆-catalyzed intramolecular [2 + 2] or [2 + 2 + 1] cycloaddition reaction of 5-allenyl-1-ynes was investigated. All the intermediates and transition states were optimized completely at B3LYP/6-311++G(d,p) level (LANL2DZ(f) for Mo). Calculations indicate that the complexation of 5-allenyl-1-ynes with Mo(CO)₆ occurred preferentially at the triple bond to give the complex M1 and then the complexation with the distal double bond of the allenes generates the complex M5. In this reaction, Mo(CO)₆-catalyzed intramolecular [2 + 2] cycloaddition is more favorable than [2 + 2 + 1] cycloaddition. The reaction pathway Mo(CO)₆ + R M5 T7 M12 M13 T11 M18 P4 is the most favorable one, and the most dominant product predicted theoretically is P4. The solvation effect is remarkable, and it decreases the reaction energy barriers. Copyright © 2011 John Wiley & Sons, Ltd.

Theoretical analysis on geometries and electronic structures of antiaromatic pentalene and its N-substituted derivatives: monomer, oligomers and polymer

Co-reporter:Binyao Liu;Wei Shen;Xiaohua Xie;Lidan Deng

Journal of Physical Organic Chemistry 2012 Volume 25( Issue 4) pp:278-286

Publication Date(Web):

DOI:10.1002/poc.1907

The antiaromatic compounds have received a great deal of attention for several decades because of their unusual electronic structures. The electronic structures and properties of antiaromatic pentalene and its six nitrogen heterocyclic derivatives were systematically studied by the density functional theory at the Becke, three-parameter, Lee–Yang–Parr level with 6-31G* basis set. The results indicated that all the monomers have stable singlet states and remarkable bond-length alternations. From the dimer to polymer in those molecules, pentalene(P), cyclopenta[b]pyrrole(CPP), cyclopenta[d]imidazole(CPI), pyrrolo[2,3-b]pyrrole(PP1) and pyrrolo[3,2-d]imidazole(PI) are stable diradical structures; pyrrolo[3,2-b]pyrrole (PP2) and imidazo[4,5-d]imidazole(II) are stable singlet ground states. The electronic properties including bond length, bond-length alternation, electron density at bond critical points, Wiberg bond index and nucleus-independent chemical shift were analyzed. It was found that in diradical molecules the bond-length alternations are diminished, the charge tends to equilibrate, the π-electron delocalization and conjugation are strengthened. The electronic properties of singlet ground state molecules have nearly no variations from monomers to polymers. The band structure analysis shows that diradical structure molecules have small band gaps (<1.0 eV), wide bandwidth and small effective masses of holes and electrons which suggest that diradical structure molecules are very good candidates for conductive materials. Copyright © 2011 John Wiley & Sons, Ltd.

Theoretical studies on the Mo-catalyzed asymmetric intramolecular Pauson-Khand-type [2 + 2 + 1] cycloadditions of 3-allyloxy-1-propynylphosphonates

Co-reporter:Qingxi Meng

Journal of Molecular Modeling 2012 Volume 18( Issue 8) pp:3489-3499

Publication Date(Web):2012 August

DOI:10.1007/s00894-012-1361-z

Density functional theory (DFT) was used to investigate the Mo-catalyzed intramolecular Pauson-Khand reaction of 3-allyloxy-1-propynylphosphonates. All intermediates and transition states were optimized completely at the B3LYP/6-31 G(d,p) level [LANL2DZ(f) for Mo]. In the Mo-catalyzed intramolecular Pauson-Khand reaction, the C–C oxidative cyclization reaction was the chirality-determining step, and the reductive elimination reaction was the rate-determining step. The carbonyl insertion reaction into the Mo–C(sp3) bond was easier than into the Mo–C = C bond. And the dominant product predicted theoretically was of (S)-chirality, which agreed with experimental data. This reaction was solvent dependent, and toluene was the best among the three solvents toluene, CH3CN, and THF.

Molecular design and density functional theory investigation of novel low-band-gap copolymers between quinoid acceptors and aromatic donors

Co-reporter:Pansheng Ou;Wei Shen;Rongxing He;Xiaohua Xie;Chenglu Zeng

Polymer International 2011 Volume 60( Issue 9) pp:1408-1418

Publication Date(Web):

DOI:10.1002/pi.3094

Abstract

The structures and electronic properties of furo[3,4-b]pyridine-based alternating donor and acceptor conjugated oligomers, in which furan and pyrrole are used as donors, and their periodic polymers were investigated using density functional theory at the B3LYP/6-31G(d) level. The bond lengths, bond length alternation, bond critical point (BCP) properties, nucleus-independent chemical shift (NICS) and Wiberg bond index (WBI) were analyzed and correlated with conduction properties. The changes of bond length, BCP properties, NICS and WBI all show that the degree of conjugation increases with main chain extension. The changes of NICS also show that the conjugation is stronger in the central section than in the outer section. Hydrogen bonding interactions and nitrogen atom substitution in the acceptors play very important roles in the geometries, electronic structures and energy gaps. The theoretical results suggest that pyrrole-based polymers are good candidates for conducting materials, compared with furan-based polymers. With an increase of nitrogen atom substitution in the acceptors in these polymers, the intermolecular charge transfers along the polymeric axes are enhanced, and the bond length alternations and HOMO–LUMO energy gap for these polymers are decreased. The results suggest that the six polymers studied all have lower energy gaps (in the range 0.81–1.26 eV), which indicate that these proposed polymers are good candidates for n-doping conductive materials, especially poly(7-(furan-2-yl)furo[3,4-e][1,2,4]triazine) and poly(7-(1H-pyrrol-2-yl)furo[3,4-e][1,2,4]triazine). Copyright © 2011 Society of Chemical Industry

Molecular design and density functional theory investigation of novel low-band-gap benzobisthiadiazole-based systems: from monomer to polymer

Co-reporter:Yangwu Fu;Wei Shen

Polymer International 2011 Volume 60( Issue 2) pp:211-221

Publication Date(Web):

DOI:10.1002/pi.2928

Abstract

The electronic structure and properties of benzobisthiadiazole-based alternating donor–acceptor conjugated oligomers and their periodic copolymers of donor and acceptor units with ratios of 1:1 and 2:1 were investigated systematically using the density functional theory method. The donors include thiophene, thieno[3,2-b]thiophene and pyrrole. The ratio of donor to acceptor units (D:A ratio) plays a very important role in the geometric and electronic properties. The intramolecular charge transfer increases and the bond length alternation decreases with an increase in the D:A ratio for these oligomers and polymers. Moreover, an increase in D:A ratio can greatly reduce the band gap and effective mass of holes and electrons for these alternating donor-acceptor conjugated copolymers. The unusually large intramolecular charge transfer caused by intramolecular hydrogen bonds reveals that pyrrole is not only a strong electron donor but also a potential hydrogen bond donor. The theoretical results suggest those copolymers possessing a D:A ratio of 2:1 are better candidates for conducting materials compared to those with a D:A ratio of 1:1. The almost zero band gap, large bandwidth and small effective mass of holes and electrons of poly(4,8-bis(thieno[3,2-b]thiophene-2-yl)benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazole) indicate that it is a very good candidate for an electrically conductive material. Copyright © 2010 Society of Chemical Industry

Theoretical investigation of Ni(PMe3)4-catalyzed intermolecular hydroacylation of alkynes with benzaldehydes

Co-reporter:Qingxi Meng;Wei Shen;Rongxing He

Transition Metal Chemistry 2011 Volume 36( Issue 8) pp:793-799

Publication Date(Web):2011 November

DOI:10.1007/s11243-011-9533-8

Density functional theory (DFT) was used to investigate the Ni(PMe3)4-catalyzed intermolecular hydroacylation of alkynes with benzaldehyde. All intermediates and transition states were optimized completely at the B3LYP/6-31G(d,p) level. The results indicate that oxidative addition of benzaldehyde to the nickel center occurs prior to the coordination of the alkyne. In the five-coordinate Ni(PMe3)2(H)(benzoyl)(alkyne) complexes, hydrogen migration occurs prior to C–C bond formation. In the resulting four-coordinate Ni(PMe3)2(benzoyl)(alkenyl) complexes, reductive elimination to give the four-coordinate Ni(PMe3)2(enone) is more dominant than the carbonyl elimination reaction to the five-coordinate Ni(PMe3)2(phenyl)(CO)(alkenyl) complexes. Hence, hydroacylation is more favorable than decarbonylation. The theoretically predicted dominant product is the (E)-α,β-enone, which is consistent with experimental data.

Molecular designing of organic conductor based upon the model of polypyrrole

Co-reporter:Chenglu Zeng;Wei Shen;Xiaohua Xie

Polymer Science, Series A 2010 Volume 52( Issue 12) pp:1355-1360

Publication Date(Web):2010 December

DOI:10.1134/S0965545X1012014X

The electronic structure and properties of polypyrrole (p-Pyr) based substituting by the group of pyrazine (Pyz) and their model compounds were studied by the density functional theory (DFT) at the B3LYP level with 6-31G* basis set. The bond length, the topological analyses and nucleus-independent chemical shifts (NICS) were analyzed and correlated with the electronic properties. The bond length of all compounds is reduced with the increase in the degree of polymerization, and the band gap of these compounds is decreased. The change of NICS shows that the conjugation degree in central section of the polymeric axis is stronger than that in outer section, and the structure of central part was close to quinoid structure in polymers. The theoretical results suggest that the band gap of p-Pyz (polymer of Pyz) (0.37 eV) is much smaller than the band gap of polypyrrole (1.84 eV). The narrow band gap, large HOMO and LUMO bandwidths and small effective masses make p-Pyz have a remarkable elevation of the conductivity, so it may be considered as a very good candidate for conducting material.

Density functional theory investigation on the electronic structure of furo[3,4-b]pyridine-type heterocyclics: from monomer to polymer

Co-reporter:Pansheng Ou;Wei Shen;Xiaohua Xie;Chenglu Zeng

Structural Chemistry 2010 Volume 21( Issue 6) pp:1253-1261

Publication Date(Web):2010 December

DOI:10.1007/s11224-010-9667-x

The geometries and electronic properties of six polymers based on furo[3,4-b]pyridine-type heterocyclics were studied using density functional theory (DFT) at the B3LYP/6-31G(d) level. Bond lengths, bond critical point (BCP) properties, nucleus-independent chemical shift (NICS), and Wiberg bond indexes (WBIs) are analyzed and correlated with conduction properties. The changes of bond length, BCP properties, NICS, and WBIs all show that the conjugational degree is increased with main chain extension. The changes of NICS also show that the conjugation is stronger in the central section than in the outer section. And the HOMO–LUMO energy gap (Eg) is decreased steadily upon chain elongation. The results suggest that the six polymers all have lower energy gaps (in the range of 0.39–0.58 eV), which indicate that these proposed polymers are good candidates for the conductive materials.

Theoretical Studies on the Reaction Mechanisms of C3H2 (cyclopropenylidene) and O(3P) Radicals

Co-reporter:Xiaohua XIE;Wei SHEN;Rongxing HE;Jinsheng ZHANG

Chinese Journal of Chemistry 2009 Volume 27( Issue 1) pp:49-55

Publication Date(Web):

DOI:10.1002/cjoc.200990025

Abstract

The complex potential energy surface for the reaction of C₃H₂ (cyclopropenylidene) with O(³P) was explored computationally using a density functional and ab initio QCISD(T) methods. The geometries of all the stationary points (transition states, intermediates and products) were fully optimized at the B3LYP/6-311++G∗∗ computational level, and the single point calculation including full population analysis was performed by employing QCISD(T). Our results show that the product P1 (C₂H+HCO) is the major product, while the products P2 (C₂H₂+CO) and P3 (HC₃O+H) are minor products, as confirmed by experiment. Product P1 could be gained through the path: RIM1IM2P1, and the C₃H₂+O(³P) reaction was expected to be rapid. So, the C₃H₂+O(³P) reaction may be an efficient strategy for producing C₂H using cyclopropenylidene in atmosphere. The present results can lead us to understand deeply the mechanism of the title reaction.

Gold(I)-Catalyzed Cycloaddition of 1-(1-Alkynyl)cyclopropyl Ketones with Nucleophiles To Yield Substituted Furans: A DFT Study

Co-reporter:Jinsheng Zhang, Wei Shen, Longqin Li and Ming Li

Organometallics 2009 Volume 28(Issue 11) pp:3129-3139

Publication Date(Web):May 7, 2009

DOI:10.1021/om801115a

By means of density functional theory (DFT), the mechanism for the synthesis of highly substituted furan (2) from 1-(1-alkynyl)-cyclopropyl ketone (1) with nucleophile (MeOH) catalyzed by Au(I) was investigated. As demonstrated, both the intimate ion-pair [AuL]+·[OTf]− (L = PPh3, PMe3, and PH3, OTf = trifluoromethane sulfonate) and the cation [AuL]+ exhibit catalysis, and the former is dominant. Moreover, the bigger the ligand coordinated to gold is, the poorer the catalysis is. The theoretical study reveals that the nucleophiles such as MeOH are important for this reaction, that the reaction between the bicyclo[4.1.0]heptan and the carbinol is a stereospecific addition reaction, and how the proton migration goes through. In the proton migration process, both the anion OTf− and another nucleophile molecule such as MeOH act as a proton shuttle to transport a proton from the nucleophile to the 2-position carbon of alkynyl. The most favorable mechanism includes the activation of the substrate, nucleophile attraction, an addition reaction of the carbonyl triple bond, a stereospecific attack of the nucleophile on the activated cyclopropane, proton migration, and regeneration of the catalyst. The substrate 1 is activated by its combination with Au(I) and a molecule of nucleophile (MeOH), which leads to a decrease in the orbital energy of π*(C1≡C2) and σ*(C3−C5) and an increase in the dipole moment of the bent bond σ(C3−C5). On the whole, the solvent effects increase the reaction barriers.

Geometries and Electronic Structures of Co-Oligomers and Co-Polymers Based on Tricyclic Nonclassical Thiophene: A Theoretical Study

Co-reporter:Yangwu Fu;Wei Shen

Macromolecular Theory and Simulations 2008 Volume 17( Issue 7-8) pp:385-392

Publication Date(Web):

DOI:10.1002/mats.200800041

DFT studies on the mechanism of Pd(II)-catalyzed intermolecular 1,2-diamination of conjugated dienes

Co-reporter:Youqing Yu;Wei Shen;Jinsheng Zhang;Rongxing He

Journal of Physical Organic Chemistry 2008 Volume 21( Issue 11) pp:979-987

Publication Date(Web):

DOI:10.1002/poc.1409

Abstract

The reaction mechanism of the palladium(II)-catalyzed addition of urea to dienes to form 1,2-diamine was studied using the B3LYP density functional theory (DFT) method. The results indicate that the first CN σ-bond formation is the rate-determining step, and that the covalent bonds are formed favorably by the terminal carbon atoms of dienes and nitrogen atom. The Pd(NCMe)-catalyst may significantly lower the energy barrier of the rate-determining step from the nonligand Pd(II)-catalyst counterpart. The results are in strong support of a recent experiment. Copyright © 2008 John Wiley & Sons, Ltd.

Theoretical investigation of direct amination of β-ketoesters catalyzed by copper(II)-bisoxazoline(BOX)

Co-reporter:Youqing Yu;Wei Shen;Jinsheng Zhang;Rongxing He

Journal of Molecular Modeling 2008 Volume 14( Issue 3) pp:237-247

Publication Date(Web):2008 March

DOI:10.1007/s00894-007-0266-8

The mechanism of the direct amination of β-keto esters catalyzed by copper(II)-bisoxazoline has been studied by means of density functional theory of B3LYP method. The computational results support the present mechanism, which involves (i) the generation of the enol from β-keto esters, which coordinates to copper(II)-bisoxazoline. The coordination step appears to be fast, exothermic, and irreversible. (ii) The formation of the σ(N-C) bond via a six-membered ring transition state after azo dicarboxylate coordination with the chiral catalyst. This step is chirality-control step. (iii) Intramolecular hydrogen migration generates a catalyst-product complex, which can finally yield product. The hydrogen shift is the rate-determining step, which affords the experimentally observed (R)-product. The stereochemical predictions have been rationalized in terms of steric repulsions, showing good agreement with experimental data.

DFT Study on the SnII-Catalyzed Diastereoselective Synthesis of Tetrahydrofuran from D–A Cyclopropane and Benzaldehyde

Co-reporter:Jinsheng Zhang;Wei Shen

European Journal of Organic Chemistry 2007 Volume 2007(Issue 29) pp:4855-4866

Publication Date(Web):30 JUL 2007

DOI:10.1002/ejoc.200700216

By means of density functional theory (DFT), the regio- and diastereoselective mechanism for the synthesis of 2,5-disubstituted tetrahydrofuran from a donor–acceptor (D–A) cyclopropane cycloaddition reaction with benzaldehyde catalyzed by Sn(OTf)₂ was investigated. As demonstrated, the overall reaction includes the activation of the D–A cyclopropane (S)-1, an unusual S_N2 attack on the activated cyclopropane, the formation of the tetrahydrofuran coordination complex and the regeneration of the catalyst. The D–A cyclopropane is activated by its combination with Sn(OTf)₂, which leads to a decrease in the natural bond orbital (NBO) energy ofσ*_(C1–C2) and an increase in the dipole moment and angular deviation of the bent bond σ_(C1–C2). Two nucleophilic reactions generates two chiral carbon centres, and the first one is rate controlling. In the S_N2 reaction, one molecule of trifluoromethane sulfonate forms a hydrogen-bond H_(CHO)···O_(OTf), which can control the stretching direction of the benzaldehyde. On the whole, the solvation energies of the species increase with increases in the molecular dipole moments, and the solvent effects increase the reaction barriers. The theoretically predicted dominant product is cis-(2R,5R)-tetrahydrofuran. So these can satisfactorily account for the experimental observations.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Theoretical study of borazine and its derivatives

Co-reporter:Wei Shen, Ming Li, Ying Li, Silei Wang

Inorganica Chimica Acta 2007 Volume 360(Issue 2) pp:619-624

Publication Date(Web):1 February 2007

DOI:10.1016/j.ica.2006.08.028

The density functional theory is used to study the geometries, electronic structures, and aromaticity of borazine and its fused ring derivatives. Some new evidences for the ionic nature of B–N bond are found. Geometry studies show that the B–N bond lengths are equal. The lone pair VSCCs of the N atoms are found. As shown, the B–N bonds are of ionic nature based on their positive Laplacian. Magnatic shielding constants also are computed. The shielding and deshielding contributions are divided into Lewis and non-Lewis parts by the NCS-NBO method. It is demonstrated in the NICS studies that there are the ring current effects on borazine and its derivatives are very weak. The aromaticity of borazine is weakened with the fused ring number increasing.The density functional theory is used to study the geometries, electronic structures, and aromaticity of borazine and its fused ring derivatives. The B–N bonds are of ionic nature based on their positive Laplacian. The aromaticity of borazine is weakened with the fused ring number increasing.

The influence of inserted thiophene into the (π-A'-π)-bridge on photovoltaic performances of dye-sensitized solar cells

Co-reporter:Zemin Zhang, Weixia Hu, Rongxing He, Wei Shen, Ming Li

Materials Chemistry and Physics (15 April 2017) Volume 191() pp:

Publication Date(Web):15 April 2017

DOI:10.1016/j.matchemphys.2017.01.042

•New D-π-A'-π-A type dyes were designed by inserting thiophene into (π-A'-π)-bridge.•The insertion of thiophene induces perfect electronic and photovoltaic performance.•Adsorbed dyes show good coupling interaction and photovoltaic properties on TiO2.•These novel dyes provide guiding strategy for improve efficiency of DSSCs.A series of metal-free D-π-A'-π-A type organic dyes have been designed by inserting one or two thiophene between the (π-A'-π)-bridge and the donor and/or acceptor moieties based on BZTP-1. The influence of inserted thiophene into the (π-A'-π)-bridge on photovoltaic performances of sensitizer was investigated in detail using the density functional theory (DFT) and its time-dependent density functional theory (TD-DFT) methods. Calculated results show that increasing the length of the conjugated-linker leads to a high planarity and very narrow HOMO-LUMO energy gap. Especially, dye T-T-BZTP-T-T that forms by inserting two thiophenes into two sides of BZTP exhibits the most obvious red-shifted and the strongest absorption, which leads to a high Voc. Moreover, we find that these dyes show a good character of electron injection and dye regeneration owing to the ideal ΔGinject, μnormal and ΔGreg. Therefore, the insertion of thiophene into the (π-A'-π)-bridge has a better influence on photovoltaic performance of designed dyes compared with BZTP-1. We hope the present work will be helpful for future experimental synthesis of organic dyes to improve the performance of DSSCs.Download high-res image (314KB)Download full-size image

Theoretical studies on the effect of a bithiophene bridge with different substituent groups (R = H, CH3, OCH3 and CN) in donor–π–acceptor copolymers for organic solar cell applications

Co-reporter:Zhiyong Fu, Wei Shen, Rongxing He, Xiaorui Liu, Huili Sun, Wanqiang Yin and Ming Li

Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 3) pp:NaN2053-2053

Publication Date(Web):2014/11/26

DOI:10.1039/C4CP04103H