Coordination polymers based on copper carboxylates and angular 2,5-bis(imidazol-1-yl)thiophene (thim2) ligand: sequential structural transformations

Abstract

Four CPs [Cu(thim₂)(OOCCH₃)₂]_n (1), [Cu₂(thim₂)(μ₂-OOCC₆H₅)₄]_n (2), [Cu₂(thim₂)₂(μ₂-OOCC₆H₅)₂(OOCC₆H₅)₂]_n (3) and {[Cu₂(thim₂)₂(μ₂-OH₂)(OOCC₆H₅)₄]·4H₂O} (4) have been synthesized and characterized. 1D helical CP (1) was formed by using copper acetate and 2,5-bis(imidazol-1-yl)thiophene (thim₂), whereas addition of two equivalents of benzoic acid resulted in the formation of a 1D zig-zag chain (2) consisting of paddle wheel copper benzoate units. Interestingly, CP 2 undergoes one pot sequential SC–SC transformations in an A–B–C manner to another kinetically more stable 1D ladder type chain (3) in the presence of air and excess ligand in solution before forming a thermodynamically stable 2D network (4) in mother solution. The cause for these transformations (2–4) and the magnetic behavior (1–3) of the CPs have been discussed.