Synthesis and studies of symmetric dibenzothienylcyclopentenes

Abstract

Various symmetric 5,5′-substituted dibenzo[b]thienylcyclopentenes were synthesized from the corresponding dibromide with a formation of new C–C, C–N, C–O, C–Si, and C–I bonds. The influence of the introduced substituent on the photochromic properties of the obtained compounds was systematically researched in both solution and solid state. The ratio of antiparallel and parallel conformers in solution was determined by NMR spectroscopy. Only one compound of the series—5,5′-diphenoxy-substituted—has displayed photochromism in the single crystal. High resolution X-ray diffraction showed that intermolecular S⋯π and S⋯H contacts kept two benzothiophene rings together in the molecule, hence decreasing the distance between the two reactive centers responsible for the photocyclization reaction. DFT calculations of the isolated molecules appeared to be in good agreement with the obtained XRD data, and therefore could also essentially assist a researcher in the design of photochromic molecules.