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The triplet state was found to involve in the photoconverion of bis(15-crown-5)-1,3-distyrylbenzene A mechanism of T-T-dismutation leading to the formation of radical photoreaction products is proposed. In the presence of Pb2+ or Ba2+, the formation of complexes 2 I ⋅2M2+ is probably accompanied by [2 + 2]-cycloaddition reaction. L.S. Atabekyan, V.G. Avakyan, A.K. Chibisov, V.N. Nuriev, A.V. Medvedko, A.V. Koshkin, S.P. Gromov "Photoprocesses in bis(15-crown-5)-1,3-distyrylbenzene and its complexes with metal perchlorates". [Display omitted] • The triplet state was found to involve in the photoconverion of bis(15-crown-5)-1,3-distyrylbenzene. • The T-T dismutation, resulting in the formation of radical products of the photoreaction (R– ⋅ + R+ ⋅). • In the presence of Pb2+ or Ba2+, the formation of complexes 2 I ∙2M2+ is probably accompanied by [2 + 2]-cycloaddition reaction. • Quantum chemical calculations indicate the formation of bis-complexes 2 I ∙2Ba2+ and their proneness to photocycloaddition. Photoprocesses in bis (15-crown-5)-1,3-distyrylbenzene (DSB) and its complexes with barium and lead perchloatewere studied in MeCN by absorption, luminescence, and laser kinetic spectroscopy. The triplet DSB molecules are involved in the degradation of electronic excitation energy, together with fluorescence processes. The most efficient intersystem crossing accompanied by a decrease in the DSB fluorescence quantum yield, occurs for the lead perchlorate complex. Using quantum chemistry methods (DFT and TDDFT), the geometry, structure, and transition energies to the S 1 state were calculated for trans - and cis -isomers of DSB in the gas phase and with allowance for the solvent and for 1:1 and 2:2 DSB complexes with barium cation in the ground and excited states. The orbital structures of the 2:2 complexes were calculated by ab initio method, and conclusions were drawn about the possibility of [2 + 2]- photocycloaddition reaction. [ABSTRACT FROM AUTHOR]

Photoprocesses of bis(18-crown-6)-1,3-distyrylbenzene (DSB) and its complexes with barium and lead perchlorates in a MeCN–CH 2 Cl 2 (9:1, v/v) mixture were studied by absorption, luminescence, and laser kinetic spectroscopies. Unlike its strongly conjugated 1,4-isomer, 1,3-derivative shows almost independent behavior of its chromophoric subunits and is capable of phototransformations not observed in 1,4-distyrylbenzenes. Triplet DSB complexes are involved in the radiationless deactivation of the excited state along with the fluorescence processes. The most effective intersystem crossing was observed for the complex with lead perchlorate. The process is accompanied by a drastic decrease in the quantum yield of DSB fluorescence. Quantum chemistry (DFT and TDDFT) is used to calculate the geometric structure and absorption spectra of DSB and its complexes with barium and lead cations and to explain the observed results. • The nano- and microsecond kinetics of bis(18-crown-6)-1,3-distyrylbenzene and its complexes with Ba2+ and Pb2+ is studied. • 1,3-Distyrylbenzenes show independent behavior of their chromophoric subunits and are capable of novel phototransformations. • Quantum chemistry explains the experimental data. The results are useful for the rational design of photoswitches and sensors. [ABSTRACT FROM AUTHOR]