FSRC "Crystallography and Photonics", Photochemistry Center of RAS, Russian Academy of Sciences, Novatorov Str. 7A-1, Moscow 119421, Russia.
Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, Moscow 119991, Russia.
Int J Mol Sci. 2023 Aug 29;24(17):13362. doi: 10.3390/ijms241713362.
Photophysical properties of a series of bis(arylydene)cycloalkanone dyes with various donor substituents are studied using quantum chemistry. Their capacity for luminescence and nonradiative relaxation through isomerization is related to their structure, in particular, to the donor capacity of the substituents and the degree of conjugation due to the central cycloalkanone moiety. It is shown that cyclohexanone central moiety introduces distortions and disrupts the conjugation, thus leading to a nonmonotonic change in their properties. The increasing donor capacity of the substituents causes increase in the HOMO energy (rise in the oxidation potential) and decrease in the HOMO-LUMO gap, which results in the red shift of the absorption spectra. The ability of the excited dye to relax through fluorescence or through isomerization is governed by the height of the barrier between the Franck-Condon and S1-S0 conical intersection regions on the potential energy surface of the lowest π-π* excited state. This barrier also correlates with the donor capacity of the substituents and the degree of conjugation between the central and donor moieties. The calculated fluorescence and isomerization rates are in good agreement with the observed fluorescence quantum yields.
用量子化学研究了一系列具有不同给体取代基的双（芳基）环烷酮染料的光物理性质。它们通过异构化发光和非辐射弛豫的能力与其结构有关，特别是与取代基的给体能力和由于中环烷酮部分的共轭程度有关。结果表明，环己酮中环部分引入了扭曲，破坏了共轭，从而导致其性质呈非单调变化。取代基给体能力的增加导致 HOMO 能量增加（氧化电位升高），HOMO-LUMO 能隙减小，从而导致吸收光谱红移。受激染料通过荧光或通过异构化弛豫的能力取决于最低π-π*激发态势能面上 Franck-Condon 和 S1-S0 锥形交叉区域之间的势垒高度。该势垒还与取代基的给体能力以及中环和给体部分之间的共轭程度相关。计算出的荧光和异构化速率与观察到的荧光量子产率吻合良好。
