John D. Tovar

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Name: Tovar, John D.

Organization: Johns Hopkins University , USA

Department: Department of Chemistry

Title: (PhD)

TOPICS

Material Chemistry

Polymer

Organic Chemistry

Chemicals
References

Variation of Formal Hydrogen-Bonding Networks within Electronically Delocalized π-Conjugated Oligopeptide Nanostructures

Co-reporter:Brian D. Wall, Yuecheng Zhou, Shao Mei, Herdeline Ann M. Ardoña, Andrew L. Ferguson, and John D. Tovar

Langmuir September 30, 2014 Volume 30(Issue 38) pp:11375-11385

Publication Date(Web):September 2, 2014

DOI:10.1021/la501999g

This photophysical study characterizes the generality of intermolecular electronic interactions present within nanomaterials derived from self-assembling oligopeptides with embedded π-conjugated oligophenylenevinylene (OPV) subunits stilbene and distyrylbenzene that in principle present two distinct β-sheet motifs. Two different synthetic approaches led to oligopeptides that upon self-assembly are expected to self-assemble into multimeric aggregates stabilized by β-sheet-like secondary structures. The target molecules express either two C-termini linked to the central OPV core (symmetric peptides) or the more common N-termini to C-termini polarity typical of natural oligopeptides (nonsymmetric peptides). Both peptide secondary structures were shown to form extended 1-D peptide aggregates with intimate intermolecular π-electron interactions. Differences in length of the π-conjugated OPV segments resulted in differing extents of intermolecular interactions and the resulting photophysics. The peptides containing the shorter stilbene (OPV2) units showed little ground state interactions and resulted in excimeric emission, while the longer distyrylbenzene (OPV3) peptides had different ground state interactions between adjacent π-conjugated subunits resulting in either perturbed electronic properties arising from exciton coupling or excimer-like excited states. Molecular dynamics simulations of nascent aggregate formation predict peptide dimerization to be a spontaneous process, possessing thermodynamic driving potentials in the range 2–6 kcal/mol for the four molecules considered. Antiparallel stacking of the peptides containing an OPV3 subunit is thermodynamically favored over the parallel orientation, whereas both arrangements are equally favored for the peptides containing an OPV2 subunit. This study validates the generality of peptide-π-peptide self-assembly to provide electronically delocalized supramolecular structures and suggests flexibility in peptide sequence design as a way to tune the material properties of π-conjugated supramolecular polymers.

Supramolecular Polymorphism: Tunable Electronic Interactions within π-Conjugated Peptide Nanostructures Dictated by Primary Amino Acid Sequence

Co-reporter:Brian D. Wall, Ashley E. Zacca, Allix M. Sanders, William L. Wilson, Andrew L. Ferguson, and John D. Tovar

Langmuir May 27, 2014 Volume 30(Issue 20) pp:5946-5956

Publication Date(Web):May 27, 2014

DOI:10.1021/la500222y

We present a systematic study of the photophysical properties of one-dimensional electronically delocalized nanostructures assembled from π-conjugated subunits embedded within oligopeptide backbones. The nature of the excited states within these nanostructures is studied as a function of primary amino acid sequence utilizing steady-state and time-resolved spectroscopies, and their atomistic structure is probed by molecular simulation. Variations introduced into the amino acid side chains at specific residue locations along the molecular peptide backbone lead to pronounced changes in the observed photophysical behavior of the fibrillar structures (spanning H-like excitonic coupling and disordered excimeric coupling) that arise from subtle changes in the π-stacking within them. These results indicate that residue modification—in terms of relative size, solvation properties, and with respect to the distance from the central π-electron core—enables the ability to tune chromophore packing and the resulting photophysics of supramolecular assemblies of π-conjugated bioelectronic materials in a rational and systematic manner.

Cross-Linking Approaches to Tuning the Mechanical Properties of Peptide π-Electron Hydrogels

Co-reporter:Wathsala Liyanage, Herdeline Ann M. Ardoña, Hai-Quan Mao, and John D. Tovar

Bioconjugate Chemistry March 15, 2017 Volume 28(Issue 3) pp:751-751

Publication Date(Web):November 11, 2016

DOI:10.1021/acs.bioconjchem.6b00593

Self-assembling peptides are extensively exploited as bioactive materials in applications such as regenerative medicine and drug delivery despite the fact that their relatively weak noncovalent interactions often render them susceptible to mechanical destruction and solvent erosion. Herein, we describe how covalent cross-linking enhances the mechanical stability of self-assembling π-conjugated peptide hydrogels. We designed short peptide–chromophore–peptide sequences displaying different reactive functional groups that can form cross-links with appropriately modified bifunctional polyethylene glycol (PEG)-based small guest molecules. These peptides self-assemble into one-dimensional fibrillar networks in response to pH in the aqueous environment. The cross-linking reactions were promoted to create a secondary network locked in place by covalent bonds within the physically cross-linked (preassembled) π-conjugated peptide strands. Rheology measurements were used to evaluate the mechanical modifications of the network, and the chemical changes that accompany the cross-linking were further confirmed by infrared spectroscopy. Furthermore, we modified these cross-linkable π-conjugates by incorporating extracellular matrix (ECM)-derived Ile–Lys–Val–Ala–Val (IKVAV) and Arg–Gly–Asp (RGD) bioactive epitopes to support human neural stem and progenitor cell (hNSCs) differentiation. The hNSCs undergo differentiation into neurons on IKVAV-derived π-conjugates while RGD-containing peptides failed to support cell attachment. These findings provide significant insight into the biochemical and electronic properties of π-conjugated peptide hydrogelators for creating artificial ECM to enable advanced tissue-engineering applications.

Kinetically Controlled Coassembly of Multichromophoric Peptide Hydrogelators and the Impacts on Energy Transport

Co-reporter:Herdeline Ann M. Ardoña, Emily R. Draper, Francesca Citossi, Matthew Wallace, Louise C. Serpell, Dave J. Adams, and John D. Tovar

Journal of the American Chemical Society June 28, 2017 Volume 139(Issue 25) pp:8685-8685

Publication Date(Web):June 5, 2017

DOI:10.1021/jacs.7b04006

We report a peptide-based multichromophoric hydrogelator system, wherein π-electron units with different inherent spectral energies are spatially controlled within peptidic 1-D nanostructures to create localized energy gradients in aqueous environments. This is accomplished by mixing different π-conjugated peptides prior to initiating self-assembly through solution acidification. We can vary the kinetics of the assembly and the degree of self-sorting through the choice of the assembly trigger, which changes the kinetics of acidification. The hydrolysis of glucono-δ-lactone (GdL) provides a slow pH drop that allows for stepwise triggering of peptide components into essentially self-sorted nanostructures based on subtle pKa differences, whereas HCl addition leads to a rapid formation of mixed components within a nanostructure. Using 1H NMR spectroscopy and fiber X-ray diffraction, we determine the conditions and peptide mixtures that favor self-sorting or intimate comixing. Photophysical investigations in the solution phase provide insight into the correlation of energy-transport processes occurring within the assemblies to the structural organization of the π-systems.

Self-Assembly and Associated Photophysics of Dendron-Appended Peptide-π-Peptide Triblock Macromolecules

Co-reporter:Tejaswini S. Kale, Jeannette E. Marine, and John D. Tovar

Macromolecules July 25, 2017 Volume 50(Issue 14) pp:5315-5315

Publication Date(Web):July 13, 2017

DOI:10.1021/acs.macromol.7b00821

Peptide-π-peptide triblock molecules can self-assemble into 1-D nanostructures with extensive hydrogen-bonding networks under appropriate pH conditions. These materials are of interest due to the embedded π-electron units that can facilitate energy and charge transport within biocompatible peptide matrices. Interactions among amino acid residues presented along these hydrogen-bonded structures lead to hierarchical bundling into larger fibrillar assemblies. This complicates the analysis of individual fibrils, an understanding of which is important for tailoring the functionality of the resulting nanomaterials. Appending large bulky groups onto the peptides should frustrate these bundling interactions and significantly alter the self-assembly behavior by restricting the formation of higher order assemblies. Here we evaluate the self-assembly behavior of peptide-π-peptide molecules appended with poly(alkyl ether) dendrons containing tetraethylene glycol functionalities. These dendrons render the peptide–dendron hybrid (PDH) molecules incapable of assembly under conditions that typically promote assembly of the parent peptides. However, 1,1,1,3,3,3-hexafluoro-2-propanol, a fluorinated alcohol known to denature proteins, triggers the aqueous assembly of the PDH molecules, thus yielding platelike nanostructures with narrow size distributions. This presents a new methodology for generating self-assembled nanostructures from peptide-π-peptide materials and provides an opportunity for orthogonal functionalization using motifs with varying degrees of hydrophilicity and functions. The effects of peptide sequence and dendron position along the peptide backbone on the assembly behavior were investigated using UV–vis, photoluminescence, and circular dichroism spectroscopies, and the morphologies of the resulting self-assembled nanostructures were investigated using transmission electron microscopy.

Solid-Phase Synthesis of Self-Assembling Multivalent π-Conjugated Peptides

Co-reporter:Allix M. Sanders, Tejaswini S. Kale, Howard E. Katz, and John D. Tovar

ACS Omega February 2017? Volume 2(Issue 2) pp:409-409

Publication Date(Web):February 7, 2017

DOI:10.1021/acsomega.6b00414

We present a completely solid-phase synthetic strategy to create three- and four-fold peptide-appended π-electron molecules, where the multivalent oligopeptide presentation is dictated by the symmetries of reactive handles placed on discotic π-conjugated cores. Carboxylic acid and anhydride groups were viable amidation and imidation partners, respectively, and oligomeric π-electron discotic cores were prepared through Pd-catalyzed cross-couplings. Due to intermolecular hydrogen bonding between the three or four peptide axes, these π-peptide hybrids self-assemble into robust one-dimensional nanostructures with high aspect ratios in aqueous solution. The preparation of these systems via solid-phase methods will be detailed along with their self-assembly properties, as revealed by steady-state spectroscopy and transmission electron microscopy and electrical characterization using field-effect transistor measurements.Topics: Bioelectronics; Catalysts; Electron microscopy; Molecular structure; Nanostructured materials; Nanostructures; Peptides and Proteins; Self-assembly; Solid phase synthesis;

Benzo[b]thiophene Fusion Enhances Local Borepin Aromaticity in Polycyclic Heteroaromatic Compounds

Co-reporter:Reid E. Messersmith, Sangeeta Yadav, Maxime A. Siegler, Henrik Ottosson, and John D. Tovar

The Journal of Organic Chemistry December 15, 2017 Volume 82(Issue 24) pp:13440-13440

Publication Date(Web):November 14, 2017

DOI:10.1021/acs.joc.7b02512

This report documents the synthesis, characterization, and computational evaluation of two isomeric borepin-containing polycyclic aromatics. The syntheses of these two isomers involved symmetrical disubstituted alkynes that were reduced to Z-olefins followed by borepin formation either through an isolable stannocycle intermediate or directly from the alkene via the trapping of a transient dilithio intermediate. Comparisons of their magnetic, crystallographic, and computational characterization to literature compounds gave valuable insights about the aromaticity of these symmetrically fused [b,f]borepins. The fusion of benzo[b]thiophene units to the central borepin cores forced a high degree of local aromaticity within the borepin moieties relative to other known borepin-based polycyclic aromatics. Each isomer had unique electronic responses in the presence of fluoride anions. The experimental data demonstrate that the local borepin rings in these two compounds have a relatively high amount of aromatic character. Results from quantum chemical calculations provide a more comprehensive understanding of local and global aromatic characters of various rings in fused ring systems built upon boron heterocycles.

Photoinduced Electron Transfer within Supramolecular Donor–Acceptor Peptide Nanostructures under Aqueous Conditions

Co-reporter:Allix M. Sanders; Timothy J. Magnanelli; Arthur E. Bragg

Journal of the American Chemical Society 2016 Volume 138(Issue 10) pp:3362-3370

Publication Date(Web):February 22, 2016

DOI:10.1021/jacs.5b12001

We report the synthesis, self-assembly, and electron transfer capabilities of peptide-based electron donor–acceptor molecules and supramolecular nanostructures. These modified peptides contain π-conjugated oligothiophene electron donor cores that are peripherally substituted with naphthalene diimide electron acceptors installed via imidation of site-specific lysine residues. These molecules self-assemble into one-dimensional nanostructures in aqueous media, as shown through steady-state absorption, photoluminescence, and circular dichroism spectra, as well as transmission electron microscopy. Excitation of the oligothiophene donor moieties results in electron transfer to the acceptor units, ultimately creating polar, charge-separated states that persist for over a nanosecond as observed with transient absorption spectroscopy. This study demonstrates how transient electric fields can be engineered into aqueous nanomaterials of biomedical relevance through external, temporally controlled photonic inputs.

Regulation of peptide-π-peptide nanostructure bundling: the impact of ‘cruciform’ π-electron segments

Co-reporter:Tejaswini S. Kale, John D. Tovar

Tetrahedron 2016 Volume 72(Issue 40) pp:6084-6090

Publication Date(Web):6 October 2016

DOI:10.1016/j.tet.2016.07.064

The self-assembly and photophysical properties of peptide-π-peptide molecules with ‘cruciform’ presentation of the π-electron core were studied. Derivatives of 1,4-bis(phenylethynyl)benzene were incorporated into a peptide backbone via the alkynylation of a central phenyl biscarboxamide core to yield peptide-π-peptide trimers wherein the π-conjugated unit was oblique to the peptide backbone. These molecules exhibited pH triggered self-assembly and yielded 1-D nanostructures with controlled diameters closely corresponding to their molecular lengths. We postulate that this size control is due to the oblique oligophenyleneethynylene (OPE) chromophores effectively blocking the hierarchical associations among the peptide stacks initially formed after self-assembly. Although the molecular design appeared to frustrate the higher order assembly, regardless of the peptide or OPE composition, significant variations in the photophysical properties were observed. The molecular design principles described here can be used to develop fundamental understanding of properties of self-assembled peptide based nanostructures of interest in biotechnological applications.

Aromaticity Competition in Differentially Fused Borepin-Containing Polycyclic Aromatics

Co-reporter:Reid E. Messersmith, Maxime A. Siegler, and John D. Tovar

The Journal of Organic Chemistry 2016 Volume 81(Issue 13) pp:5595-5605

Publication Date(Web):May 25, 2016

DOI:10.1021/acs.joc.6b00927

This report describes the synthesis and characterization of a series of borepin-based polycyclic aromatics bearing two different arene fusions. The borepin synthesis features streamlined Ti-mediated alkyne reduction, leading to Z-olefins, followed by direct lithiation and borepin formation. These molecules allow for an assessment of aromatic competition between the fused rings and the central borepin core. Crystallographic, magnetic, and computational studies yielded insights about the aromaticity of novel, differentially fused [b,f]borepins and allowed for comparison to literature compounds. Multiple borepin motifs were also incorporated into polycyclic aromatics with five or six rings in the main backbone, and their properties were also evaluated.

Chain Dynamics, Relaxation Times, and Conductivities of Bithiophene–Acene Copolymers Measured Using High Frequency Saturation Transfer EPR

Co-reporter:Alicia M. Fraind, Lev R. Ryzhkov, and John D. Tovar

The Journal of Physical Chemistry B 2016 Volume 120(Issue 5) pp:1033-1039

Publication Date(Web):January 21, 2016

DOI:10.1021/acs.jpcb.5b11212

We present a study to probe the formation of localized aromatic sextets and their effects on the charge transport properties in polymers with acene cores. Bithiophene–acene copolymers containing benzene, naphthalene, or anthracene as acene cores were synthesized using Yamamoto polymerization. Drop-casted polymer films were chemically doped and analyzed using high frequency saturation transfer EPR (HF ST-EPR), a method which has proven useful in the study of conducting polymers. The spin–spin and spin–lattice relaxation times were determined for these polymers at low temperatures (4 to 20 K) and used to obtain inter- and intrachain spin diffusion rates and conductivities. Similar interchain spin diffusion rates were seen across all polymer systems; however, anthracene containing polymer poly(hexylTTATT) was found to have the largest intrachain spin diffusion rate. The poly(hexylTTATT) intrachain spin diffusion rate may be artificially high if the anthracene ring restricts the diffusion of spin to the hexylated quaterthiophene segment in poly(hexylTTATT) whereas the spins diffuse through the acene cores in the benzene and naphthalene derivatives. Alternatively, as both the spin diffusion rates and conductivities vary unpredictably with temperature, it is possible that the π-electron localization previously seen in the anthracene core could be relieved at lower temperatures.

Energy transfer within responsive pi-conjugated coassembled peptide-based nanostructures in aqueous environments

Co-reporter:Herdeline Ann M. Ardoña and John D. Tovar

Chemical Science 2015 vol. 6(Issue 2) pp:1474-1484

Publication Date(Web):05 Dec 2014

DOI:10.1039/C4SC03122A

Steady-state and time-resolved photophysical measurements demonstrate energy transfer within π-conjugated peptide nanostructures composed of oligo-(p-phenylenevinylene)-based donor units and quaterthiophene-based acceptor units in completely aqueous environments. These peptide-based assemblies encourage energy migration along the stacking axis, thus resulting in the quenching of donor emission peaks along with the development of new spectral features reminiscent of acceptor emission. These spectral changes were observed even at minute amounts of the acceptor (starting at 1 mol%), suggesting that exciton migration is involved in energy transport and supporting a funnel-like energy transduction mechanism. The reversibility of nanostructure formation and the associated photophysical responses under different conditions (pH, temperature) were also studied. This unique material design incorporates two different semiconducting units coassembled within peptide nanostructures and offers a new platform for the engineering of energy migration through bioelectronic materials in aqueous environments.

Sequence-dependent mechanical, photophysical and electrical properties of pi-conjugated peptide hydrogelators

Co-reporter:Herdeline Ann M. Ardoña, Kalpana Besar, Matteo Togninalli, Howard E. Katz and John D. Tovar

Journal of Materials Chemistry A 2015 vol. 3(Issue 25) pp:6505-6514

Publication Date(Web):11 Mar 2015

DOI:10.1039/C5TC00100E

The ability to modulate intermolecular interactions in such a way as to impact nano-, micro- and even macroscale properties is an attractive aspect of self-assembling systems. We present an investigation of sequence-dependent rheological, photophysical and electrical properties of semiconducting peptide hydrogelators. Five different π-conjugated peptides containing a quaterthiophene core were studied, wherein the relative size and hydrophobicity of the amino acid residues adjacent to the π-electron core were varied in order to assess the impact of molecular variation on nanoscale and bulk material properties. Steady-state spectroscopic measurements of the peptides once assembled into 1D-nanostructures show distinct spectral characters as the relative size of the amino acid side chain adjacent to the π-electron core increases. Those peptides that formed hydrogels differed in network topography and rheological properties, with storage modulus (G′) values ranging from ∼3 to 20 kPa. The electrical properties of the peptide nanostructures were characterized by measuring the sheet resistance of dried peptide films on glass substrates. This study provides insights on the effects of amino acid sequence on the nanoscale to the macroscale electrical transport and mechanical properties of nanostructure-forming π-conjugated peptides.

Peptide π-Electron Conjugates: Organic Electronics for Biology?

Co-reporter:Herdeline Ann M. Ardoña and John D. Tovar

Bioconjugate Chemistry 2015 Volume 26(Issue 12) pp:2290

Publication Date(Web):October 6, 2015

DOI:10.1021/acs.bioconjchem.5b00497

Highly ordered arrays of π-conjugated molecules are often viewed as a prerequisite for effective charge-transporting materials. Studies involving these materials have traditionally focused on organic electronic devices, with more recent emphasis on biological systems. In order to facilitate the transition to biological environments, biomolecules that can promote hierarchical ordering and water solubility are often covalently appended to the π-electron unit. This review highlights recent work on π-conjugated systems bound to peptide moieties that exhibit self-assembly and aims to provide an overview on the development and emerging applications of peptide-based supramolecular π-electron systems.

Peptide Nanostructures with -Ways: Photophysical Consequences of Peptide/-Electron Molecular Self-Assembly

Co-reporter:John D. Tovar

Israel Journal of Chemistry 2015 Volume 55( Issue 6-7) pp:622-627

Publication Date(Web):

DOI:10.1002/ijch.201400161

Abstract

This article provides a summary of the electronic outcomes that result as oligopeptides with embedded π-conjugated units are drawn together into hierarchical 1D assemblies reminiscent of amyloid plaques or other protein deposits associated with neurodegenerative diseases. The baseline photophysics of prototype molecules are presented, followed by a description of how subtle molecular variations further perturb these responses in manners relevant to several cutting-edge optoelectronic applications. For example, the influence of amino acid residue steric bulk/hydrophobicity and peptide N-to-C sequence variation are explicated, showing excited-state variations in the excimeric or excitonic nature of the intermolecular π-electron delocalization that result as the π-conjugated peptides are driven to assemble into extended 1D fibrillar assemblies.

Assessment of the aromaticity of borepin rings by spectroscopic, crystallographic and computational methods: a historical overview

Co-reporter:Reid E. Messersmith

Journal of Physical Organic Chemistry 2015 Volume 28( Issue 6) pp:378-387

Publication Date(Web):

DOI:10.1002/poc.3422

This review presents a chronological discussion of the evolution of our conceptual and experimental understanding of aromaticity as pertaining to the borepin ring structure. Borepin is the boron-containing charge-neutral analogue of the carbocyclic tropylium ion, and many molecular variations involving the borepin motif have been synthesized over the past half century. The aromaticity of the borepin system has been probed with ultraviolet–visible (UV–vis), photoluminescence and infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography and computational analysis. Recently, the focus of borepin-containing compounds has shifted to π-electron materials, building on the foundation of a firm understanding of the physical organic properties of the borepin motif that will allow for electronic fine-tuning toward desired applications. Copyright © 2015 John Wiley & Sons, Ltd.

Thiophene-Fused Borepins As Directly Functionalizable Boron-Containing π-Electron Systems

Co-reporter:David R. Levine ; Maxime A. Siegler

Journal of the American Chemical Society 2014 Volume 136(Issue 19) pp:7132-7139

Publication Date(Web):April 16, 2014

DOI:10.1021/ja502644e

Synthetic protocols were developed for the gram-scale preparation of two isomeric dithienoborepins (DTBs), boron-containing polycyclic aromatics featuring the fusion of borepin and thiophene rings. DTBs exhibit reversible cathodic electrochemistry and boron-centered Lewis acidity in addition to enhanced electronic delocalization relative to benzo-fused analogues. Boron’s precise position within the conjugation pathway of DTBs significantly affected electronic structure, most clearly demonstrated by the variation in spectroscopic responses of each isomer to fluoride ion binding. In addition to excellent stability in the presence of air and moisture, DTBs could also be subjected to electrophilic aromatic substitution and metalation chemistry, the latter enabling the direct, regiospecific functionalization of the unsubstituted thiophene rings. Subsequent tuning of molecular properties was achieved through installation of donor and acceptor π-substituents, leading to compounds featuring multistep electrochemical reductions and polarizable electronic structures. As rare examples of directly functionalizable, π-conjugated, boron-containing polycyclic aromatics, DTBs are promising building blocks for the next generation of organoboron π-electron materials whose development will demand broad scope for molecular diversification in addition to chemical robustness.

Heteroaromatic variation in amorphous 1,6-methano[10]annulene-based charge-transporting organic semiconductors

Co-reporter:Benjamin C. Streifel, Josué F. Martínez Hardigree, Howard E. Katz and John D. Tovar

Journal of Materials Chemistry A 2014 vol. 2(Issue 37) pp:7851-7858

Publication Date(Web):06 Aug 2014

DOI:10.1039/C4TC01326C

π-Conjugated 1,6-methano[10]annulene-diketopyrrolopyrrole copolymers containing thiophene and/or furan rings were synthesized to determine the tolerance of heteroaromatic composition for amorphous semiconductors. Thiophene and furan were incorporated within the conjugated main chain adjacent to the annulene and diketopyrrolopyrrole comonomers to influence the optoelectronic properties of the highly disordered bulk materials. All polymers synthesized were shown to be amorphous by differential scanning calorimetry despite the relatively low alkyl chain substitution. The furan-containing copolymers showed higher energy bandgaps (HOMO–LUMO gaps) than the thiophene-based polymers, but increasing furan substitution resulted in higher hole mobilities: values ranged from 1.6 × 10−4 cm2 V−1 s−1 for all-thiophene polymers to 7.0 × 10−4 cm2 V−1 s−1 for all-furan polymers. AFM images reveal that the furan containing polymers form higher-quality films upon solution processing, a consequence of the higher solubility of the furan-based polymers. These results add to the growing literature precedent illustrating the value of furan as a component of both semicrystalline and now amorphous conjugated polymers.

Prospecting in Hckel-space: From Hinokitiol to Non-benzenoid Organic Electronics

Co-reporter:John D. Tovar

The Chemical Record 2014 Volume 14( Issue 1) pp:214-225

Publication Date(Web):

DOI:10.1002/tcr.201300034

Note from the Editor:

Science is about connections. Some of these are connections between dreams and reality. Surely, dreams are the source of energy necessary to produce great science. In chemistry, the most obvious connections are the bonds: bonds between atoms, bonds between people. It was this metaphor that inspired the title “Bonding Beyond Borders” for the Nozoe Autograph Book publication project.

In the following essay accompanying the publication of the ninth segment of the Nozoe Autograph Books, J. D. Tovar of Johns Hopkins University illustrates many connections. He connects some of the signatory's dreams, in the form of their real or projected novel compounds written decades ago, to today's state-of-the-art. He connects theory with experiment. He connects structure with novel optoelectronic or electrical properties. He broadly and firmly connects his own research program with that of the greater novel aromatics community, a remarkable demonstration of progress given that he is barely a decade from receipt of his Ph.D. degree.

We are pleased to have this splendid contribution to the Nozoe Autograph Books project.

— Jeffrey I. Seeman

Guest Editor

University of Richmond

Richmond, Virginia 23173, USA

E-mail: jseeman@richmond.edu

Supramolecular Polymorphism: Tunable Electronic Interactions within π-Conjugated Peptide Nanostructures Dictated by Primary Amino Acid Sequence

Co-reporter:Brian D. Wall, Ashley E. Zacca, Allix M. Sanders, William L. Wilson, Andrew L. Ferguson, and John D. Tovar

Langmuir 2014 Volume 30(Issue 20) pp:5946-5956

Publication Date(Web):2017-2-22

DOI:10.1021/la500222y

Variation of Formal Hydrogen-Bonding Networks within Electronically Delocalized π-Conjugated Oligopeptide Nanostructures

Co-reporter:Brian D. Wall, Yuecheng Zhou, Shao Mei, Herdeline Ann M. Ardoña, Andrew L. Ferguson, and John D. Tovar

Langmuir 2014 Volume 30(Issue 38) pp:11375-11385

Publication Date(Web):September 2, 2014

DOI:10.1021/la501999g

Supramolecular Construction of Optoelectronic Biomaterials

Co-reporter:John D. Tovar

Accounts of Chemical Research 2013 Volume 46(Issue 7) pp:1527

Publication Date(Web):March 11, 2013

DOI:10.1021/ar3002969

Peptide self-assembly is a powerful method to create functional nanoscale materials such as optoelectronically relevant organic nanostructures. The enormous potential that may come from bringing π-conjugated electronic function into biological environments is poised to impact cell and tissue engineering, biosensors, and related biomedical applications. However, very little synthetic guidance is available with respect to uniting these two different materials sets in a generally applicable manner.In this Account, I describe my group’s work to synthesize and assemble peptidic nanostructures built around organic electronic elements. The Account begins with a very brief background to the area of supramolecular electronics, followed by a description of areas where these nanomaterials could be useful in biology. I then discuss the synthetic approaches that we utilized to embed a variety of π-electron units directly within peptide backbones. A key supramolecular challenge with respect to subsequent self-assembly of these new molecules is balancing electrostatic contributions within the resulting nanomaterials, because the suitable geometries for stabilizing peptide assemblies may not necessarily correspond to those suitable for maximizing intermolecular π-electron interactions. Regardless of the respective magnitudes of these two major influences, the assembly paradigm is fairly robust. Variation of the π-electron units and the peptide sequences that make up the “peptide-π-peptide” triblock molecules consistently leads to fairly uniform tape-like nanostructures that maintain strong electronic coupling among the component π-electron units. We explored a diverse range of π-electron units spanning fluorescent oligo(phenylene vinylene)s, electron-accepting rylene diimides, and hole-transporting oligothiophenes.I then describe the characterization of the nanomaterials that form after molecular self-assembly in order to understand their internal structures, electronic interactions, and morphologies as existing within self-supporting hydrogel matrices. I also describe how a facile shearing process provided globally aligned macroscopic collections of one-dimensional electronic fibrils in hydrogel matrices. These general assembly processes influence intermolecular π-stacking among the embedded chromophores, and the assemblies themselves can facilitate the covalent cross-linking and polymerization (for example, of reactive diyne units). The latter offers an exciting possibility to create peptidic nanostructures comprised of single polymer chains.Finally, I discuss electronic properties as manifested in the interactions of transition dipoles within the nanomaterials and electrical properties resulting from field-effect gating. The ability to tune the observable electrical properties of the nanostructures externally will allow for their transition to in vitro or in vivo platforms as a powerful new approach to regulating biological interactions at the nanoscale.

Polydiacetylene-Peptide 1D Nanomaterials

Co-reporter:Stephen R. Diegelmann

Macromolecular Rapid Communications 2013 Volume 34( Issue 17) pp:1343-1350

Publication Date(Web):

DOI:10.1002/marc.201300423

Charge Delocalization through Benzene, Naphthalene, and Anthracene Bridges in π-Conjugated Oligomers: An Experimental and Quantum Chemical Study

Co-reporter:Alicia M. Fraind, Gjergji Sini, Chad Risko, Lev R. Ryzhkov, Jean-Luc Brédas, and John D. Tovar

The Journal of Physical Chemistry B 2013 Volume 117(Issue 20) pp:6304-6317

Publication Date(Web):April 30, 2013

DOI:10.1021/jp401448a

To understand the influence of orthogonal conjugation pathways fused directly to π-conjugated polymer backbones, we synthesized and studied three series of thiophene-based model compounds containing benzene, naphthalene, and anthracene peri-substituted central cores as representative acenes. These models were functionalized with methyl groups at the reactive thiophene positions in order to generate and observe oxidized species without complications from follow-up polymerization. The neutral monomers and their oxidized charged counterparts were subjected to cyclic voltammetry, spectroelectrochemistry, and EPR spectroscopy as appropriate, and these results were further corroborated with thorough density functional theory studies. This joint experimental and theoretical analysis allowed us to determine that benzene-based conjugated linkers led to more delocalized charge carriers on account of the quinoidal character maintained within the benzene core. In contrast, anthracene-based linkers displayed very localized carriers due to torsional strain between the adjacent aryl groups and to the local evolution of formal aromatic sextets on the benzo-fused rings orthogonal to the backbone in the quinoidal state. In some cases, the electronics of the thiophene-based substituent dominated the electronic properties of the oxidized species regardless of the nature of the central acene linker. These results highlight the dramatic influence that orthogonal conjugation pathways can exert on the electronic properties of π-conjugated materials.

Synthesis and Alignment of Discrete Polydiacetylene-Peptide Nanostructures

Co-reporter:Stephen R. Diegelmann ; Nikolaus Hartman ; Nina Markovic

Journal of the American Chemical Society 2012 Volume 134(Issue 4) pp:2028-2031

Publication Date(Web):January 10, 2012

DOI:10.1021/ja211539j

Oligopeptides bearing internal diacetylene units are shown to self-assemble in water into one-dimensional nanostructures and aligned macroscopic hydrogels. The diacetylene units can be photopolymerized into polydiacetylenes that run coincident to the nanostructure and noodle long axes, and the resulting nanostructures show evidence for ambipolar charge transport. This self-assembly, alignment and polymerization technique provides a rapid way to produce globally aligned collections of conjugated polymer chains.

Meta-B-entacenes: new polycyclic aromatics incorporating two fused borepin rings

Co-reporter:David R. Levine, Anthony Caruso, Maxime A. Siegler and John D. Tovar

Chemical Communications 2012 vol. 48(Issue 50) pp:6256-6258

Publication Date(Web):24 Apr 2012

DOI:10.1039/C2CC32500D

The synthesis of new boron-containing acenes (meta-B-entacenes) is reported. These compounds exhibit slightly non-planar core geometries with blue-shifted spectral properties and more negative electrochemical reduction potentials relative to known para isomers. Polarizable π-extended architectures were realized via cross-coupling procedures with chloro-functionalized precursors.

Peptide-Based Supramolecular Semiconductor Nanomaterials via Pd-Catalyzed Solid-Phase “Dimerizations”

Co-reporter:Allix M. Sanders, Thomas J. Dawidczyk, Howard E. Katz, and John D. Tovar

ACS Macro Letters 2012 Volume 1(Issue 11) pp:1326

Publication Date(Web):October 30, 2012

DOI:10.1021/mz3004665

We report a streamlined method for the synthesis of peptides embedded with complex and easily variable π-conjugated oligomeric subunits from commercially available precursors. These modified peptides self-assemble under aqueous conditions to form one-dimensional nanomaterials containing networks of π-stacked conduits, despite the inclusion of π-conjugated oligomers with quadrupoles extended over larger areas. The procedure has circumvented solubility and other synthetic issues to allow for the facile formation of a diverse library of bioelectronic nanomaterials, including a complex sexithiophene-containing peptide whose nanostructures display gate-induced conductivity within field effect transistors.

Torsional Influences within Disordered Organic Electronic Materials Based upon Non-Benzenoid 1,6-Methano[10]annulene Rings

Co-reporter:Benjamin C. Streifel, Patricia A. Peart, Josué F. Martínez Hardigree, Howard E. Katz, and John D. Tovar

Macromolecules 2012 Volume 45(Issue 18) pp:7339-7349

Publication Date(Web):September 14, 2012

DOI:10.1021/ma301408w

Conjugated polymers and small molecules containing the nonplanar aromatic 1,6-methano[10]annulene were synthesized in an effort to understand how torsional differences between planar and nonplanar π-electron components influence the electronic properties of π-conjugated materials. The polymers and small molecule model systems contain commonly employed aromatic subunits such as thiophene, diketopyrrolopyrrole, and 2,1,3-benzothiadiazole, leading to electron donor and donor–acceptor polymers. The curved geometry of 1,6-methano[10]annulene can lead to reduced local torsional strain in semiconducting polymers relative to large planar aromatics, potentially increasing intrapolymer conjugation. The relative amount of effective conjugation length increase granted by the annulene in each system of regioisomers was interrogated through the use of UV–vis and photoluminescence spectroscopy and electrochemistry, and it was found that 1,6-methano[10]annulene relieves some torsional strain associated with solubilizing alkyl chains clashing with aromatic rings along the polymer backbone. The polymers were also found to be highly disordered in thin films yet still provided reasonable hole mobilities (ca. 10–4 cm2/(V s)) in OFET devices. These results suggest that methano[10]annulene or other curved aromatics may prove useful in the future development of organic electronics.

Supramolecular Materials: Aligned Macroscopic Domains of Optoelectronic Nanostructures Prepared via Shear-Flow Assembly of Peptide Hydrogels (Adv. Mater. 43/2011)

Co-reporter:Brian D. Wall;Stephen R. Diegelmann;Shuming Zhang;Thomas J. Dawidczyk;William L. Wilson;Howard E. Katz;Hai-Quan Mao

Advanced Materials 2011 Volume 23( Issue 43) pp:

Publication Date(Web):

DOI:10.1002/adma.201190172

Aligned Macroscopic Domains of Optoelectronic Nanostructures Prepared via Shear-Flow Assembly of Peptide Hydrogels

Co-reporter:Brian D. Wall;Stephen R. Diegelmann;Shuming Zhang;Thomas J. Dawidczyk;William L. Wilson;Howard E. Katz;Hai-Quan Mao

Advanced Materials 2011 Volume 23( Issue 43) pp:5009-5014

Publication Date(Web):

DOI:10.1002/adma.201102963

Influence of Annulene Ratio on the Electrochemical and Spectroscopic Properties of Methano[10]Annulene–Thiophene Random Copolymers

Co-reporter:Giselle A. Elbaz, Lindsay M. Repka, and John D. Tovar

ACS Applied Materials & Interfaces 2011 Volume 3(Issue 7) pp:2551

Publication Date(Web):May 30, 2011

DOI:10.1021/am200409b

We describe a series of copolymerization studies whereby the nonbenzenoid aromatic methano[10]annulene is incorporated into three different types of random copolymers, two based on polythiophenes (from bithiophene and terthiophene monomers) and one based on poly(ethylene dioxythiophene). Copolymers where the annulene component was in the majority had optical and electrochemical behaviors reminiscent of the annulene homopolymer. In contrast, we found that the annulene influenced polymer electronics at very low feed ratios where the commercial comonomer was in the majority. Copolymerizations are useful approaches to dilute the complex annulene monomers into functional polymers without losing the optoelectronic properties of the annulene homopolymers. These electrochemical results provide important design rules that can be employed for the chemical synthesis of related random copolymers.Keywords: annulenes; conducting polymers; electropolymerization; polythiophenes; spectroelectrochemistry;

Main-chain photochromic conducting polymers

Co-reporter:Christopher P. Harvey and John D. Tovar

Polymer Chemistry 2011 vol. 2(Issue 12) pp:2699-2706

Publication Date(Web):26 Aug 2011

DOI:10.1039/C1PY00304F

The optoelectronic properties of photochromic materials change in response to exposure to certain wavelengths of light. These alterations arise from specific electronic reorganization of conjugation pathways due to photochemically-triggered cyclizations and conformational changes. Polymers with photochromic switches pendent to the backbone retain monomer-like optoelectronic photoswitching responses while incorporation of photochromic switches directly into a conjugated backbone allows for greater, and often more dramatic, influence on the polymer optoelectronic properties. This ability for light-controlled variation of optoelectronic properties has driven research in the field of main-chain photochromic conducting polymers, and recent developments in this area will be discussed.

Functionalized Dibenzoborepins as Components of Small Molecule and Polymeric π-Conjugated Electronic Materials

Co-reporter:Anthony Caruso Jr. and John D. Tovar

The Journal of Organic Chemistry 2011 Volume 76(Issue 7) pp:2227-2239

Publication Date(Web):February 25, 2011

DOI:10.1021/jo2001726

We present the synthesis and characterization of dibenzo[b,f]borepins (DBBs) functionalized at the para and meta position with respect to the boron center in order to understand how regiochemical issues influence photophysical and electrochemical properties. An expanded synthetic repertoire is presented, using palladium catalysis (to perform Stille, Suzuki, Buchwald−Hartwig, and Sonogashira cross-coupling reactions) and lithium−halogen exchange to synthesize a series of extended π-conjugated DBBs. These chemistries are enabled by the use of a sterically bulky Mes* (2,4,6-tri-tert-butylphenyl) group on boron and the inclusion of reactive bromide handles on the DBB core. Photophysical, electrochemical, and computational analyses of these compounds indicate that relative to the protio-DBB the installation of groups at the meta positions decreases the optical band gap while para substitution raises the electron affinity of the system. Thus, both the HOMO−LUMO gap and specific frontier molecular orbital levels can be tuned by the installation of different conjugated substituents.

Pi-conjugated chain extenders for the synthesis of optoelectronic segmented polyurethanes

Co-reporter:Christopher P. Harvey

Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 22) pp:4861-4874

Publication Date(Web):

DOI:10.1002/pola.24937

Abstract

The optical properties of mechanochromic materials change under mechanical stress. Segmented polyurethanes are elastomers composed of amorphous, saturated chain soft segments, and rigid pi-conjugated hard domains. Within aggregates of hard domains pi–pi interactions may form and result in perturbation of the optoelectronic properties of the system. Disruption and restoration of these electronic interactions within the material may lead to observable mechanochromic response. A series of oligothiophene diols and diamines, as well as a naphthalene diimide diol, have been synthesized for incorporation into the hard domains of segmented polyurethanes and polyureas using long poly(tetramethylene oxide) chains as soft segments. The resulting polymers were evaluated to determine their extent of polymerization and their thermal stability. The optical properties of the materials were studied in solution and as thin films. Where possible the electrochemical properties of the polymers were also explored. The length of the soft segment chains in the segmented polyurethanes hindered electronic coupling of hard domains. Future work involving smaller, more solubilizing soft segments may allow for easier material characterization and mechanochromic response. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

On-resin dimerization incorporates a diverse array of π-conjugated functionality within aqueous self-assembling peptide backbones

Co-reporter:Geeta S. Vadehra, Brian D. Wall, Stephen R. Diegelmann and John D. Tovar

Chemical Communications 2010 vol. 46(Issue 22) pp:3947-3949

Publication Date(Web):29 Apr 2010

DOI:10.1039/C0CC00301H

We report a convenient method to incorporate π-electron units into peptides that assemble into amyloid-like supramolecular polymers, discussing the scope of the process and preliminary characterization of the resulting nanomaterials. Self-assembly manipulates these “electronic peptides” into delocalized sub-10 nm 1-D nanostructures under completely aqueous conditions.

Synthesis of Functionalizable Boron-Containing -Electron Materials that Incorporate Formally Aromatic Fused Borepin Rings

Co-reporter:Anthony Caruso Jr.;MaximeA. Siegler ;JohnD. Tovar

Angewandte Chemie 2010 Volume 122( Issue 25) pp:4309-4313

Publication Date(Web):

DOI:10.1002/ange.201000411

Synthesis of Functionalizable Boron-Containing -Electron Materials that Incorporate Formally Aromatic Fused Borepin Rings

Co-reporter:Anthony Caruso Jr.;MaximeA. Siegler ;JohnD. Tovar

Angewandte Chemie International Edition 2010 Volume 49( Issue 25) pp:4213-4217

Publication Date(Web):

DOI:10.1002/anie.201000411

Comparative Survey of Conducting Polymers Containing Benzene, Naphthalene, and Anthracene Cores: Interplay of Localized Aromaticity and Polymer Electronic Structures

Co-reporter:Alicia M. Fraind and John D. Tovar

The Journal of Physical Chemistry B 2010 Volume 114(Issue 9) pp:3104-3116

Publication Date(Web):February 16, 2010

DOI:10.1021/jp9101459

We present a systematic study to understand to what extent the localization of aromaticity in an orthogonal sense to the main polymer conjugation pathway will influence the observed optical and electrical properties as the polymers undergo oxidation and doping into conductive materials. Three classes of electropolymerizable monomers were prepared where the critical electronic unit was chosen to foster different degrees of aromatic localization pendant to the conjugation pathway: specifically, those based upon benzene, naphthalene, and anthracene cores. The expectation was that the benzene unit would foster extensive intramolecular delocalization upon adoption of the quinoidal electronic structure on account of the strong polyene character. On the other hand, resonance contributors can be rationalized for naphthalene and anthracene whereby one or two aromatic sextets evolve within the quinoidal structure thereby leading to a more localized electronic structure. Monomer and polymer electronics were probed with UV−vis spectroscopy and cyclic voltammetry as well as through in situ profiling of the conductive states of the respective polymers. A semiempirical analysis of the frontier orbital wave functions was employed to further understand the influences of competing aromaticity pendant to the polymer backbones. Our findings indicate the potential for complex and tunable π-conjugated polymers whose properties can be externally controlled through local alterations of aromatic character within units fused or cross-conjugated to polymer main chains.

Poly(cyclopropenone)s: Formal Inclusion of the Smallest Hückel Aromatic into π-Conjugated Polymers#

Co-reporter:Patricia A. Peart and John D. Tovar

The Journal of Organic Chemistry 2010 Volume 75(Issue 16) pp:5689-5696

Publication Date(Web):July 26, 2010

DOI:10.1021/jo101108f

The synthesis of precursors to π-conjugated cyclopropenium polymers is described. Monomers for chemical and electrochemical manipulation are easily prepared through electrophilic substitution of in situ generated cyclopropenium cations that are then hydrolyzed to the respective cyclopropenones. The unusually strong dipole moment associated with the cyclopropenone renders this core formally aromatic, an electronic structure that becomes more important within individual monomers upon protonation of the carbonyl function with trifluoroacetic acid or alkylation with triethyloxonium salts. The electronic properties of cyclopropenone polymers in their pristine states and after acidification are discussed along with conjugated carbonyl-containing polymers that are also acid sensitive but without the added element of aromaticity. We find that the increased contributions of cyclopropenium cation aromaticity restrict the quinoidal charge carriers due to the energetically less favorable proposition of disrupting the local aromatic stabilization.

Expanding the Realm of Furan-Based Conducting Polymers through Conjugation with 1,6-Methano[10]annulene

Co-reporter:Patricia A. Peart and John D. Tovar

Macromolecules 2009 Volume 42(Issue 13) pp:4449-4455

Publication Date(Web):June 5, 2009

DOI:10.1021/ma9006494

The synthesis of a new bisfuranyl monomer, 2,7-bis(2-furanyl)-1,6-methano[10]annulene, is presented. Its properties and those of its polymer, synthesized via electropolymerization, are compared to those of the known furan−arene−furan monomers and their respective polymers. Investigation using UV−vis spectroscopy, cyclic voltammetry, and spectroelectrochemistry indicated that the 1,6-methano[10]annulene copolymer has properties rivaling those of the copolymers containing traditional aromatic cores. These results are rationalized in conjunction with DFT calculations, and they further the premise that 1,6-methano[10]annulene can be viewed as a viable building block for advanced π-conjugated electronic materials.

Conformationally Complex -Conjugated Molecular and Polymeric Materials: New Challenges for Organic Synthesis

Co-reporter:DarylA. Guthrie;JohnD. Tovar

Chemistry - A European Journal 2009 Volume 15( Issue 21) pp:5176-5185

Publication Date(Web):

DOI:10.1002/chem.200900398

Emerging Prospects for Unusual Aromaticity in Organic Electronic Materials: The Case for Methano[10]annulene

Co-reporter:Patricia A. Peart;Lindsay M. Repka

European Journal of Organic Chemistry 2008 Volume 2008( Issue 22) pp:

Publication Date(Web):

DOI:10.1002/ejoc.200800533

No abstract is available for this article.

Emerging Prospects for Unusual Aromaticity in Organic Electronic Materials: The Case for Methano[10]annulene

Co-reporter:Patricia A. Peart;Lindsay M. Repka

European Journal of Organic Chemistry 2008 Volume 2008( Issue 13) pp:2193-2206

Publication Date(Web):

DOI:10.1002/ejoc.200701102

Abstract

Unusual aromatics outside of the 6π-electron motif offer promise for functional electronic materials, and we frame this claim in the context of 10π-electron aromatics. The evolution of our understanding of 10π-electron aromatics is discussed briefly, from azulene to the [10]annulenes to finally 1,6-methano[10]annulene. A survey of annulene research of both fundamental and applied nature is then presented. Finally, our recent contributions to this area are highlighted with a comparison of annulene-based electronic materials to more classical benzenoid counterparts. The annulene core greatly facilitates the delocalization of mobile charges as determined through voltammetry and spectroelectrochemistry. We show that this important hydrocarbon can indeed be viewed as a viable building block for advanced polymeric semiconducting materials.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Corrigendum to “Regulation of peptide-π-peptide nanostructure bundling: The impact of ‘cruciform’ π-electron segments” [Tetrahedron 72 (2016) 6084–6090]

Co-reporter:Tejaswini S. Kale, John D. Tovar

Tetrahedron (2 March 2017) Volume 73(Issue 9) pp:1293-1294

Publication Date(Web):2 March 2017

DOI:10.1016/j.tet.2017.01.033

Heteroaromatic variation in amorphous 1,6-methano[10]annulene-based charge-transporting organic semiconductors

Co-reporter:Benjamin C. Streifel, Josué F. Martínez Hardigree, Howard E. Katz and John D. Tovar

Journal of Materials Chemistry A 2014 - vol. 2(Issue 37) pp:NaN7858-7858

Publication Date(Web):2014/08/06

DOI:10.1039/C4TC01326C

Meta-B-entacenes: new polycyclic aromatics incorporating two fused borepin rings

Co-reporter:David R. Levine, Anthony Caruso, Maxime A. Siegler and John D. Tovar

Chemical Communications 2012 - vol. 48(Issue 50) pp:NaN6258-6258

Publication Date(Web):2012/04/24

DOI:10.1039/C2CC32500D

On-resin dimerization incorporates a diverse array of π-conjugated functionality within aqueous self-assembling peptide backbones

Co-reporter:Geeta S. Vadehra, Brian D. Wall, Stephen R. Diegelmann and John D. Tovar

Chemical Communications 2010 - vol. 46(Issue 22) pp:NaN3949-3949

Publication Date(Web):2010/04/29

DOI:10.1039/C0CC00301H

Energy transfer within responsive pi-conjugated coassembled peptide-based nanostructures in aqueous environments

Co-reporter:Herdeline Ann M. Ardoña and John D. Tovar

Chemical Science (2010-Present) 2015 - vol. 6(Issue 2) pp:NaN1484-1484

Publication Date(Web):2014/12/05

DOI:10.1039/C4SC03122A

Sequence-dependent mechanical, photophysical and electrical properties of pi-conjugated peptide hydrogelators

Co-reporter:Herdeline Ann M. Ardoña, Kalpana Besar, Matteo Togninalli, Howard E. Katz and John D. Tovar

Journal of Materials Chemistry A 2015 - vol. 3(Issue 25) pp:NaN6514-6514

Publication Date(Web):2015/03/11

DOI:10.1039/C5TC00100E

Benzo[1''',?2''':1,?2;3''',?4''':1',?2';5''',?6''':1'',?2'']?triacenaphtho[5,?6-?cd:5',?6'-?c'd':5'',?6''-?c''d'']?tripyran-?1,?3,?8,?10,?15,?17-?hexone

CAS:1425651-65-5

Benzo[1''',?2''':1,?2;3''',?4''':1',?2';5''',?6''':1'',?2'']?triacenaphtho[5,?6-?cd:5',?6'-?c'd':5'',?6''-?c''d'']?tripyran-?1,?3,?8,?10,?15,?17-?hexone