Coordination polymers based on µ2η1:η1 and µ2η2:η2 bridging mode of pyridyl carboxylate: ionic liquid-induced hydrothermal synthesis, structural and thermogravimetric analysis

Abstract

Two coordination polymers of formula [Cu(2-picolinate)(nicotinate)]n (1), [Mn(2-picolinate)2]n (2), using pyridine-2/3-carboxylic acid and metal salt acetate, have been synthesized hydrothermally at 120 °C for 48 h in presence of ionic liquid tetraethylammonium hydroxide (25% aqueous solution). Although all reported complexes were synthesized in same experimental conditions, they show diversity in their structural features, 2 crystallize in monoclinic crystal system where as 1 shows higher symmetry space group, orthorhombic. The 3D structure in 1 is based on anti-syn Cu–O–C–O–Cu chain with µ2η1:η1 coordinative mode of carboxylate ion and ligand bridging through carboxylate oxygen and pyridyl nitrogen of nicotinate ion while 2D sheet structure in 2 is due to Mn–O–Mn chain involving µ2η2:η2 coordinative mode together with syn-anti Mn–O–C–O–Mn chain via µ2η1:η1 coordinative mode of carboxylate ion of picolinate ion only. It is observed that these chains are the structure factors for dimensionality of reported CPs. Both coordination polymers are insoluble in almost all organic solvents as well as in water and show good thermal stability between 280 and 450 °C.