Synthesis, crystal structure and photochromic property of a phenethyl viologen bismuth(III) chloride

Viologen bismuthate halides generally show photochromic properties. In the present work, phenylethyl alcohol was introduced into chloro bismuthates in the hope to prepare photochromic crystalline materials and finally a photochromic inorganic-organic hybrid, (PeV)₃(Bi₂Cl₉)₂ (1), based on an in situ generated PeV²⁺ cation (PeV²⁺ = phenethylviologen = N,N′-diphenethyl-4,4′-bipyridinium), has been obtained, whose microstructure contains a discrete dimer [Bi₂Cl₉]^3– counterion identified by single crystal X-ray diffraction. More importantly, 1 exhibits a typical photochromic behavior, which can be mainly attributed to the reversible inter-conversion between the monocation viologen radical [PeV]^+• and the viologen dication [PeV]²⁺.