Synthesis, spectral properties, and conformations of nonlinear crossconjugated polyenes containing pyrane or dihydropyridine fragment

Article abstract of DOI:10.1007/s11172-013-0292-x

New cross conjugated ω, ωdimethylaminopolyenes containing the central pyrane or N-methyldihydropyridine fragment were synthesized. In new compounds, the interaction of the aminopolyene chromophores occurs through the dicyanomethylidene, 1-cyano-1-(4-nitrophenyl)methylidene, or 1,3-dioxoindan-2-ylidene groups in position 4 of the heterocycle. The conformation of the synthesized compounds was determined by 2D ¹? NMR spectroscopy (NOESY and ROESY): The chromophores are arranged at an acute or obtuse angle in the structures with the pyrane or dihydropyridine fragment, respectively. The conformational dif ferences in polyenes result in a drastic change in their spectral properties: for the dyes with an acute angles between the chromophores, the longwavelength absorption band is less intense, as a rule, than the shorterwavelength band, while the situation is opposite for the compounds with an obtuse angle. The absorption spectra of the synthesized compounds with dinitrile and other acceptor groups lie in a longerwavelength region than the absorption spectra of the corresponding compounds with carbonyl acceptor groups. The central bridging substituent NMe decreases the energy of interaction of the chromophores.