Synthesis and molecular and crystal structure of 1-allyl-4-[2-cyano-2-(indan-1,3-dione-2-ylidene)ethylidene] -1, 4-dihydroquinoline

The reaction of 1-allyl-4-methylquinolinium bromide with 2-dicyanomethyleneindan-1,3-dione in the presence of a two-fold excess of triethylamine affords 1-allyl-4-[2-cyano-2-(indan-1,3-dione-2-ylidene) ethylidene]-1,4-dihydrogtiinoline, a representative of a new class of merocyanines. The structure of this compound has been established by X-ray structural analysis. A substantial intramolecular charge transfer and a hydrogen bond between the vinyl hydrogen atom and the indandione oxygen atom have been found.Dedeased in 1995Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 173–176, January, 1996.     

Molecular and crystal structure of di-and hexamethine merocyanine dyes — derivatives of 3<Emphasis Type="Italic">H</Emphasis>-indole and malononitrile — manifesting positive solvatochromism

Single crystal X-ray diffraction and IR spectroscopy are applied to examine the molecular and crystal structures of 2-[(2E)-2-(1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidine)ethylidene]-malononitrile (1) and 2-[(2E, 4E,6E)-6-2-(1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidine)-2,4-hexadienylidene]-malononitrile (2). It is shown that both in solution and crystalline state the studied merocyanines completely retain the trans-conformation and approach a neutral polyene. It is found that the polyene character is increased in transition from di-to hexamethinemerocyanine, which is caused by a partial violation of conjugation with the nitrogen lone pair due to its slight deviation from the plane of the chromophore. It is demonstrated that the stretching vibration frequency of the nitrile group in the IR spectra of malononitrile merocyanines can be used to examine polyene-polymethine electron relaxations. Electronic and spatial structures of merocyanine molecules are calculated by AM1, PM3, and ab initio methods. Theoretical results are compared to experimental ones.     

Efficient solution-processed bulk heterojunction solar cells by antiparallel supramolecular arrangement of dipolar donor-acceptor dyes

A series of dipolar donor–acceptor (D –A) chromophores with aminothiophene donor and different heterocyclic acceptor units is reported. By modulation of the acceptor strength, absorption bands over the whole visible spectrum are accessible as well as adjustment of the frontier molecular orbital levels. The performance of the chromophores in blends with fullerene acceptors in solution‐processed bulk heterojunction solar cells was studied and related to the molecular properties of the dyes. In particular, the effect of the large ground‐state dipole moments of these dyes was investigated by single crystal X‐ray analysis, which revealed antiparallel dimers, resulting in an annihilation of the dipole moments. This specific feature of supramolecular organization explains the excellent performance of merocyanine dyes in organic solar cells. With blends of HB366 :PC₇₁BM, the most efficient solar cell with a V_OC of 1.0 V, a J_SC of 10.2 mA cm^?2, and a power‐conversion efficiency of 4.5 % was achieved under standard AM1.5, 100 mW cm^?2 conditions. Under reduced lighting conditions, even higher efficiencies up to 5.1 % was obtained.     

The Fluorosolvatochromism of Brooker's Merocyanine in Pure and in Mixed Solvents

The fluorescence-based solvatochromism (fluorosolvatochromism) of 4-[(1-methyl-4(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (Brooker's merocyanine) was studied. The results revealed that the fluorescence emission band of the dye was dependent on the medium ( nm in water and nm in DMF). The fluorescence quantum yields (φ _f) were calculated for the dye in the solvents investigated. Low φ _f values ( < 10%) were obtained for the dye and in order to better comprehend the radiative and nonradiative decay processes of this dye, its fluorescence lifetime in methanol was measured and was found to be very short (230 ps). The results suggest that the dye in the excited state decays rapidly through nonradiative processes. The behavior of the probe in binary mixtures including a hydrogen-bond accepting solvent (acetonitrile, N,N-dimethylformamide, and dimethylsulfoxide) and a hydroxylic solvent (water, methanol, ethanol, propan-2-ol, and butan-1-ol) was also investigated. All data were successfully fitted to a model based on solvent exchange equilibria, which allowed the separation of the different contributions of the solvent species in the solvation shell of the dye. The data obtained for the mixed solvents were explained based on solute–solvent and solvent–solvent interactions.