Synthesis and photophysical properties of conformationally restricted difluoroboron β-diketonate complexes of 1-indanone derivatives

A series of conformationally restricted difluoroboron beta-diketonate complexes (BF(2)bdks) was easily synthesized from (Z)-2-(1-arylhydroxyliden)-1-indanone derivatives in good to excellent yields. These dyes displayed the lowest energy absorption maxima in the range of 370-408 nm and possess molar absorption coefficients (epsilon) ranging from 8000 to 47 000 M-1 cm(-1) in CH2Cl2. All the absorption spectra of the BF(2)bdks systems were red shifted (5-43 nm) as compared to the parent difluoroboron 1,3-diphenyl-beta-diketonate complex (BF(2)dbm). Their emission maxima were centered on 406-432 nm and the fluorescence quantum yields (Phi) were in the range of 0.33-0.87, which are in all cases much higher than the found for BF(2)dbm. These observations demonstrate the effectiveness of improving the dye quantum yield by restricting the intramolecular C-C bond rotation. (C) 2020 Elsevier Ltd. All rights reserved.