Reversible [2+2] Photocycloaddition in Supramolecular Covalently Bound Dyad with 3-(4-Oxystyryl)benzo[f]quinoline as Photochrome and o-Xylene Bridge Group

Resumo

Reaction of [2+2] photocycloaddition has been observed in the covalently bound bichromophoric dyad, in which the styrylbenzoquinoline (CBQ) photochromes are linked by the o-xylylene bridge group. Cyclobutane CB4M with two identical vicinal benzoquinoline (BQ) substituents undergoes reversible cycle opening (retro-photocycloaddition). A comparison with structurally similar cyclobutane CB4N, which bears the same BQ substituents linked by another bridge group and does not enter into the retro-photocycloaddition, shows that the photochemical properties can be controlled by varying the bridge group. Quantum-chemical calculations in the DFT approximation predict the existence of conformers with π-stacking interactions of SBQ photochromes in the dyad and BQ substituents in cyclobutane.