Structures and chromotropic properties of imidazole derivatives produced from 3,6-bis(4,5-diphenyl-2H-imidazol-2-ylidene)cyclohexa-1,4-diene

Sakaino, Yoshiko

doi:10.1039/p19830001063

Cited by 9 publications

(3 citation statements)

References 5 publications

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“…63 Interestingly, the quinoidal 56 isomerized on heating to the benzenoid diradical 57, which reversed to the original quinoidal form on cooling. 64 At room temperature, compound 56 showed that about 0.1% of the molecules in a solution are paramagnetic, and the population of 57 increased with increasing temperature as revealed by the combined studies of UV and ESR measurements. 65 Such obvious evidence points to the contribution of diradical character in a pro-aromatic molecule.…”

Section: Para-quinodimethane Analogues Containing Hetero Atomsmentioning

confidence: 98%

“…In all these isomers, monocyclic conjugated annulenelike structures containing either 16 (in 61, 65) or 12 (in 62-64) p-electrons fused by one or two aromatic benzenoid rings can be drawn and thus they can be regarded as an anti-aromatic system. On the other hand, some of them can be regarded as a p-QDM (62,64) or o-QDM (63) bridged pro-aromatic system. The resonance between the closed-shell form and the open-shell diradical form implies that they are potential diradicaloids.…”

Section: Anti-aromatic Indenofluorenes and Analoguesmentioning

confidence: 99%

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Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals

et al. 2015

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Aromaticity is an important concept to understand the stability and physical properties of π-conjugated molecules. Recent studies on pro-aromatic and anti-aromatic molecules revealed their irresistible tendency to become diradicals in the ground state. Diradical character thus becomes another very important concept and it is fundamentally correlated to the physical (optical, electronic and magnetic) properties and chemical reactivity of most of the organic optoelectronic materials. Molecules with distinctive diradical character show unique properties which are very different from those of traditional closed-shell π-conjugated systems, and thus they have many potential applications in organic electronics, spintronics, non-linear optics and energy storage. This critical review first introduces the fundamental electronic structure of Kekulé diradicals within the concepts of anti-aromaticity and pro-aromaticity in the context of Hückel aromaticity and diradical character. Then recent research studies on various stable/persistent diradicaloids based on pro-aromatic and anti-aromatic compounds are summarized and discussed with regard to their synthetic chemistry, physical properties, structure-property relationships and potential material applications. A summary and personal perspective is given at the end.

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Section: Para-quinodimethane Analogues Containing Hetero Atomsmentioning

confidence: 98%

Section: Anti-aromatic Indenofluorenes and Analoguesmentioning

confidence: 99%

Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals

et al. 2015

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“…[4][5][6] Thus, the lifetime of the lophyl radical ranges between several minutes to hours in ordinary solvents down to milliseconds or microseconds in ionic liquids. [4][5][6] Nevertheless, the study of this photoreaction has received the attention of researchers with a focus on both optical properties, such as photochromism, [7][8][9][10][11][12][13][14][15][16][17][18] and magnetic properties, using ESR to explore the properties of the radicals generated and the cleavage mechanism. This can occur through a radical triplet-pair.…”

Section: Introductionmentioning

confidence: 99%

Extended mechanistic aspects on photoinitiated polymerization of 1,6-hexanediol diacrylate by hexaarylbisimidazoles and heterocyclic mercapto compounds

Berdzinski

Strehmel

Lindauer

et al. 2014

Photochem Photobiol Sci

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Chlorine substituted hexaarylbisimidazole (o-Cl-HABI) efficiently initiates radical polymerization of multifunctional acrylic esters in the presence of a heterocyclic mercapto compound if the latter can form its tautomeric thione. Exposure of o-Cl-HABI results in lophyl radicals, which efficiently add to the thione in the first step while the second step releases a highly reactive thiyl radical from this intermediate. LC-MS and CID-MS measurements support this reaction scheme. Furthermore, photo-DSC experiments applying UV light between 320 and 380 nm showed that mercaptotriazole and phenylmercaptotriazole exhibited the best reactivity in the monomer 1,6-hexanediol diacrylate (HDDA) while alkyl substituted mercaptotriazoles showed less reactivity. Change of the triazole heterocycle by mercaptoimidazole resulted in a significant decrease of photoinitiation efficiency. This heterocycle does not form the corresponding thione in HDDA as shown by NMR measurements. Replacement of mercaptotriazole by an alkylthiol leads to a system showing the lowest photoinitiation efficiency in this series. Formation of thione structure in the case of heterocyclic mercapto compounds may cause higher reactivity of the heterocyclic mercapto compounds with the lophyl radical in the monomer chosen.

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Imidazole as a Donor/Acceptor Unit in Charge‐Transfer Chromophores with Extended π‐Linkers

Kulhánek

Bureš

Pytela

et al. 2011

Chemistry An Asian Journal

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Eleven new, stable, push-pull systems that feature 4,5-bis[4-(N,N-dimethylamino)phenyl]imidazole and 4,5-dicyanoimidazole as the donor and acceptor moieties and the systematically extended and varied π-linker were prepared and investigated. Evaluation of the measured UV/Vis spectra, electrochemical data (cyclic voltammetry (CV), rotating-disc voltammetry (RDV), and polarography) and calculated β and γ polarizabilities showed efficient charge transfer (CT) in biimidazole-type chromophores. Push-pull system 27, which features a planar thiophene-derived π-linker, was revealed to be the most efficient chromophore within the studied series. This chromophore possessed the most bathochromically shifted CT band, the lowest electrochemical gap, and highest β and γ polarizabilities. The CT transition was most significantly affected by structural features such as π-linker length, planarity, conjugating arrangement, and the presence of olefinic/acetylenic or 1,4-phenylene/thiophene subunits in the π-linker.

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Structures and chromotropic properties of imidazole derivatives produced from 3,6-bis(4,5-diphenyl-2H-imidazol-2-ylidene)cyclohexa-1,4-diene

Cited by 9 publications

References 5 publications

Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals

Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals

Extended mechanistic aspects on photoinitiated polymerization of 1,6-hexanediol diacrylate by hexaarylbisimidazoles and heterocyclic mercapto compounds

Imidazole as a Donor/Acceptor Unit in Charge‐Transfer Chromophores with Extended π‐Linkers

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