Photophysics of hydrogen bonded diarylethene dimers in the liquid phase

Hydrogen bonded diarylethene dimers are formed through a carboxylic acid ligand, as is evident from concentration dependent OH stretching infrared spectra. Dimer formation leads to a red shift, enhancement and broadening of OH stretching absorption characteristic for cyclic carboxylic acid dimers. We compare the electronic spectra and photoinduced ring-opening and -closing kinetics of dimers and monomers. The S0–S1 absorption band of the closed form undergoes a slight red-shift when going from the monomer to the singly closed dimer and the doubly closed dimer. The photoreaction kinetics of dimer and monomer are identical. Consequently, the photochrome retains its original photophysical properties in the dimer state.