Solvent control in the hydrothermal synthesis of two copper(i) iodide–benzimidazole coordination polymers

Copper(I) iodide and potassium iodide react with benzimidazole under hydrothermal conditions to form a photoluminescent μ3/μ4 iodo-bridged, four-legged, triple-ladder polymer [(CuI)2(C7H6N2)]n (1) as well as linear [Cu(2-IC7H4N2)]n (2), which has iodine in the heterocyclic entity that results from nucleophilic substitution. The compounds can be synthesized independently with a rational choice of different solvents: compound 1 is the sole product in acetonitrile whereas aqueous ammonia only results in the formation of compound 2. Compound 1 shows two emission peaks at 409 and 608 nm assigned to a combination of iodide to copper charge transfer (XMCT) and a metal centre d–sp transition.