Hydrothermal synthesis,crystal structure and fluorescence of a cyclic dimer copper compound constructed by 2-nitrobenzenedicarboxylate

The reaction of 2-nitro-1,4-benzenedicarboxylic acid (H₂nbdc) and 2,2′-bipyridine (2,2′-bipy) with CuCl₂ under hydrothermal conditions gives rise to a cyclic dimer [Cu(nbdc)(2,2′-bipy)(H₂O)]₂ · 2H₂O (1). X-ray structural analysis revealed that 1 crystallizes in a monoclinic space group P2₁/c with a = 7.3801(13) Å, b = 15.305(3) Å, c = 16.333(3) Å, β = 92.951(4)°, V = 1842.5(6) ų, and Z = 2. Compound 1 represents the first cyclic dimeric example with 1,4-benzenedicarboxylate or its derivatives, in which two carboxylates of the nbdc are nearly perpendicular due to the steric effect by the nitro group. Compound 1 also displays strong fluorescent emission in the solid state.