Synthesis and crystal structure of two new copper(II) coordination polymers involving in situ-generated formate ligand under different conditions

Two new copper(II) coordination polymers, {[Cu(bimb)₁.₅(HCOO)(NO₃)]·H₂O}ₙ ((bimb = 1,4-bis(1H-imidazol-1-yl)butane) ( 1 ) and {[Cu₂(imp)₂(sip)(HCOO)]·DMF·1.5H₂O}ₙ ( 2 ), (imp 1,3-bis(1H-imidazol-1-yl)propane and sip: 5-sulfoisophthalate) were obtained as crystalline materials in DMF-based solvents. In both cases, the formate ligand was generated in-situ from the decomposition of DMF, either at room temperature after a long crystallization period (case of 1 ) or under solvothermal conditions (case of 2 ). Single-crystal X-ray diffraction revealed pentacoordinated Cu(II) centers in distorted trigonal bipyramidal geometries in both materials. This polyhedron is built in 1 by three N atoms from three different 1,4-bis(1H-imidazol-1-yl)butane ligands, and two O atoms from the nitrate and formate molecules. In 2 , two copper ions, Cu1 and Cu2,are involved. The polyhedron around Cu1 involves two imidazole nitrogen atoms from two different imp ligands, one carboxylate oxygen atom from the formate ligand, and two carboxylate oxygen atoms from two different sip ligands. The one around Cu2 ion is built by N atoms from two different imp ligands, and two O atoms from two different carboxylate groups from formate ligand, and one carboxylate oxygen atom from the sip ligand. Both compounds form a two-dimensional framework in which tapes built by 1 are connected with hydrogen bonds, while in 2 , binuclear copper clusters connected by sip and formate ligands build a different tape connected with hydrogen bonds. FTIR spectroscopy confirmed the presence of formate and other functional groups, while thermogravimetric analyses demonstrated their thermal stability. This work highlights the in-situ generation of formate ligands from DMF during the synthesis of two new coordination polymers and reviews previously reported instances. Synopsis Two copper(II) coordination polymers are formed via in situ generation of formate from the decomposition of dimethylformamide.