Self-Assembled Hydrogen-Bonding Chains of Copper(II) 2-Nitrobenzoate with Nicotinamide

The synthesis, spectral characterization and crystal structure of two new nitrobenzoatocopper(II) complexes, namely, [Cu-2(2-O(2)Nbz)(4)(nia)(2)]center dot ACN (1) and [Cu-2(2-O(2)Nbz)(4)(ACN)(2)] (2) (where 2-O(2)Nbz = 2-nitrobenzoate, nia = nicotinamide and ACN = acetonitrile) are reported. The complexes 1 and 2 form dinuclear units of the paddle-wheel type around the crystallographic inversion centers. The copper ions are bridged by four 2-nitrobenzoate anions and the neutral N-donor ligands, viz. nicotinamide in 1 and acetonitrile in 2, are coordinated at apical positions. Selected geometric parameters of both complexes are compared with values for related tetra-2-nitrobenzoate complexes of copper(II) as well as the other dimeric copper(II) carboxylates with apical nicotinamide and acetonitrile ligands. The molecules of 1 are linked with N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds. The pi-pi stacking interactions in 1 are observed between benzene rings of 2-nitrobenzoate anions and pyridine rings of nicotinamide and also between acetonitrile molecules and benzene rings of 2-nitrobenzoate anions. The C-H center dot center dot center dot O hydrogen-bonds and CH/pi interactions are observed in crystal structure of 2.