A mechanism study of quinine-squaramide catalyzed enantioselective aza-Friedel–Crafts (aza-F–C) reaction is described using density functional theory (DFT). The most favorable pathway is obtained through the discussions of four possible modes of hydrogen bond interactions, in which the nucleophile is activated by the squaramide N–H groups (N–Ha and N–Hb) and the electrophile binds to the protonated amine by hydrogen bonding. Meanwhile, we have also studied the energy barrier of the stereocontrolling transition states that might play a role of stereoselectivity. In addition, noncovalent interaction (NCI) analyses show a series of favorable cooperative noncovalent interactions, including N–H···O and C–H···F hydrogen-bonding, and π···π interactions. The strong interactions and lower barrier were found for TS3R, indicating the preference for the R-configuration adduct, which is in good agreement with the experimental observations.

•We synthesize two novel boron complexes based on imidazo[1,2-a]pyridine and four imidazo[1,2-a]pyridine-BODIPY dyads.•DFT and TDDFT calculations have provided insight into interpreting the electronic properties.•Luminescent emissions were investigated, and one imidazo[1,2-a]pyridine-BODIPY dyad 4a can be used as effective cell imaging regent.Based on imidazo[1,2-a]pyridine derivatives, a series of mononuclear and binuclear fluorine-boron complexes 1a,b, 4a,b, and 5a,b have been designed and synthesized. X-ray crystal structures for single boron-core complexes 1b, 4a, 4b, and dual boron-core imidazo[1,2-a]pyridine-BODIPY dyad 5b were obtained, and intermolecular CH⋯F interactions were observed in their solid state. High absorption coefficients, strong emissions, and high photostabilities have been demonstrated for these boron complexes. DFT and TD-DFT studies reveal efficient electronic interactions between the imidazo[1,2-a]pyridine moiety and BODIPY plane for dyads 4a,b, and 5a,b. Cell imaging of 4a was tested to show good cellular uptake ability.Download high-res image (219KB)Download full-size image

The possible transition states of C–H activation on the dehydrogenate coupling of arenes with alcohols employing Ag(I) additives were investigated using B3LYP density functional theory. The AgOTf salt with Cu(OAc)2 was identified as the most active catalyst. The facile occurrence of the studied reactions is supported by the low activation energies of their respective transition states.

•Detailed ammonia borane dehydrogenation mechanism is investigated.•The ligand-assisted concerted FeCipso cooperation mechanism is most favorable.•FePOCOP pincer with a MeO group exhibits the highest catalytic activity.A quantum-chemical mechanistic investigation using density functional theory (DFT) on ammonia-borane dehydrogenation catalyzed by a series of iron bis(phosphinite) pincer complexes is reported. A metal-ligand cooperation mechanism has been proposed, in which the hydrogen atom of BH moves to metal Fe and proton of NH transfers to pincer ipso carbon simultaneously with the lowest activation barriers. DFT calculations and natural bond orbital (NBO) charge analysis suggest that FePOCOP complex with an electron-donating MeO group at the para position to the ipso carbon exhibits the highest catalytic activity. A plausible explanation of the observed catalytic activities is also given.

A new dodecanuclear cluster [CoII9CoIII3(MeOsalox)6(OAc)15(H2O)6]·2MeCN·2H2O (1) (H2MeOsalox = 3-methyloxysalicylaldoxime) was synthesized under solvothermal conditions and characterized by IR, elemental analyses (EA), single-crystal X-ray diffraction and powder XRD. Magnetic investigations reveal that complex 1 exhibits antiferromagnetic interactions between the cobalt centers.One mixed-valence cobalt(II/III) dodecanuclear cluster bridged by doubly deprotonated o-vanillin oxime and acetate anions has been assembled. Antiferromagnetic interactions between the cobalt ions are observed.

A new imidazo[1,5-a]pyridine-containing pyrrolyl ligand HL (HL = 3-(1H-pyrrol-2-yl)imidazo[1,5-a]pyridine) was synthesized and employed in the organometallic chemistry of titanium. The syntheses, structures, catalytic properties and antitumor activity of three titanium complexes supported by HL are reported. Reactions of Ti(NMe2)4 and Ti(NEt2)4 with 2 equivalents of HL, led to the production of titanium bisamido complexes TiL2(NMe2)2 (1) and TiL2(NEt2)2 (2), respectively. Treatment of Ti(OiPr)4 with 2 equivalents of HL resulted in the formation of TiL2(OiPr)2 (3). All complexes were characterized by elemental analyses and NMR studies. The solid-state structures of 2 and 3 were further established by single X-ray crystallography. The titanium bisamido complexes 1 and 2 are shown to be good pre-catalysts for the hydroamination of alkynes. Complex 1 was found to be an active catalyst for the ring-opening polymerization of ε-caprolactone. The cytotoxicity activities of 3 towards the tumor cells HCT-116, PC3 and MCF-7 were measured. Complex 3 exhibited good antitumor properties.

A theoretical understanding of the Pd-catalyzed C(sp3)–H activation of aliphatic amines has been examined using the B3LYP density functional theory. The concerted metalation–deprotonation (CMD) mechanism is identified in the rate-determining steps of all possible reaction pathways. The rate- and regio-determining step of the catalytic cycle is deprotonation of the Cmethyl–H bond through a six-membered cyclopalladation transition state. According to the relative activation barriers, the Cmethyl–H activation is kinetically and thermodynamically more favorable than the Cethyl–H activation. More important, the only acetoxylation product is located, ignoring the diethyl-substituted or the dimethyl-substituted in the morpholine and not producing the lactone amines molecules, which is in good agreement with the experimental observations.

The syntheses, structures and antitumor activity of four titanium isopropoxide complexes supported by pyrrolyl Schiff base ligands are reported. Treatment of Ti(OiPr)4 with 2 equivalents of HL1 (HL1 = N-(1H-pyrrol-2-ylmethylene)(2-pyridinyl)methanimine), HL2 (HL2 = 2-pyrrolecarbaldmethylimine), HL3 (HL3 = N-((1H-pyrrol-2-yl)methylene)(phenyl)methanimine) and HL4 (HL4 = N-((1H-pyrrol-2-yl)methylene)-2-phenylethanimine), respectively, results in the formation of Ti(OiPr)2(L1)2 (1), Ti(OiPr)2(L2)2 (2), Ti(OiPr)2(L3)2 (3) and Ti(OiPr)2(L4)2 (4). All complexes have been characterized by elemental analyses and NMR studies. The solid-state structures of complexes 1 and 3 have been further established by single X-ray crystallography. The cytotoxicity activities of 1–4 towards the tumor cells HCT-116, PC3 and MCF-7 were measured. Complexes 1, 2 and 3 showed good antitumor properties.

The syntheses, crystal structures and magnetic properties are described for a {Co16} cluster [CoII16O(OH)2(bha)12(PhCO2)4(Phen)2(MeOH)4]·2MeOH (1) and a 1-D MnII chain complex [Mn(Hbha)2]n·(2MeOH)n (2) (H2bha = benzohydroxamic acid; Phen = 1,10-phenanthroline). The 1:1:0.5 reaction of Co(O2CMe)2·4H2O, H2bha and 1,10-phenanthroline in MeOH at 100 °C under autogenous pressure gave cluster 1. Complex 2 was obtained from the 1:1 reaction mixture of Mn(O2CMe)2·2H2O and H2bha in MeOH under solvothermal conditions. The {Co16} cluster can be thought as a face-centered cube with two wings. The H2bha ligands show hydroximic form in 1 and exhibit hydroxamic mode in 2. The hydroximate ligands in 1 display three distinct binding modes, one of which is novel. Variable-temperature solid-state dc magnetic susceptibility studies have been performed in the 2.0–300 K range for complexes 1 and 2. Antiferromagnetic MII⋯MII exchange interactions were found for both 1 and 2. This work also demonstrates that solvothermal method is a potential synthetic approach for the design and growth of high nuclearity clusters or chain complexes of the H2bha ligand.

The syntheses, crystal structures and magnetic properties are described for a {Co16} cluster [CoII16O(OH)2(bha)12(PhCO2)4(Phen)2(MeOH)4]·2MeOH (1) and a 1-D MnII chain complex [Mn(Hbha)2]n·(2MeOH)n (2) (H2bha = benzohydroxamic acid; Phen = 1,10-phenanthroline). The 1:1:0.5 reaction of Co(O2CMe)2·4H2O, H2bha and 1,10-phenanthroline in MeOH at 100 °C under autogenous pressure gave cluster 1. Complex 2 was obtained from the 1:1 reaction mixture of Mn(O2CMe)2·2H2O and H2bha in MeOH under solvothermal conditions. The {Co16} cluster can be thought as a face-centered cube with two wings. The H2bha ligands show hydroximic form in 1 and exhibit hydroxamic mode in 2. The hydroximate ligands in 1 display three distinct binding modes, one of which is novel. Variable-temperature solid-state dc magnetic susceptibility studies have been performed in the 2.0–300 K range for complexes 1 and 2. Antiferromagnetic MII⋯MII exchange interactions were found for both 1 and 2. This work also demonstrates that solvothermal method is a potential synthetic approach for the design and growth of high nuclearity clusters or chain complexes of the H2bha ligand.