500285-23-4Relevant articles and documents
Crystal structures, degree of charge transfer, and non-linear optical characteristics of intramolecular charge-transfer compounds: Indoline-substituted tricyanoquinodimethanes1
Murata, Tsuyoshi,Saito, Gunzi,Nishimura, Kazukuni,Chong, Chin-Hong,Makihara, Masaru,Honda, Genki,Enomoto, Yuichiro,Khasanov, Salavat,Yamochi, Hideki,Otsuka, Akihiro,Kamada, Kenji,Ohta, Koji,Kawamata, Jun
supporting information; experimental part, p. 1131 - 1146 (2009/05/06)
The substituent effect on the degree of intramolecular charge transfer (δ) and optical properties of donor-π-acceptor compounds comprised of l,3,3-trimethyl-2-rnethyleneindoline (I1) and substituted 7,8,8-tricyanoquinodimethane (=2-(4-cyanomethylene-2,5-cyclohexadienylidene) malononitrile, 3CNQ-R, R = substituent groups) moieties were investigated (I1-3CNQ-R). In the crystal structures, I1-3CNQ-R molecules stacked on indoline and/or 3CNQ-R moieties in a head-to-tail manner to cancel their dipole moments and established segregated or mixed stack columnar motifs. The δ values of I1-3CNQ-R molecules in solid and solution states were estimated using the bond length ratio in the crystal structures, molecular orbital calculation, and the solvatochromic shift of intramolecular charge-transfer absorption, respectively, and showed significant and reasonable dependences on substituents of the 3CNQ moiety. Structural analysis revealed that molecular conformation and planarity affect the δ values of I1-3CNQ-R molecules. Molecular orbital calculations revealed that molecular (hyper)polarizabilities can be modulated by tuning δ. I1 3CXQ-R exhibited a solvatochromic shift, and the ground state changed from neutral (δ ≤ 0.5) in less-polar solvents to ionic (δ ≥ 0.5) in polar solvents. Two-photon absorption properties of I 1-3CNQ-R showed a significant substituent effect and indicated that δ is a fundamental parameter for modulating non-linear optical properties.
