Nitric oxide generation study of unsymmetrical β-diketiminato copper() nitrite complexes

β-Diketiminato copper( ii ) L 1 CuCl- L 4 CuCl and their nitrite complexes L 1 Cu(O 2 N) and L 2 Cu(O 2 N) have been synthesized and characterized. X-ray analysis of the L 1 CuCl- L 4 CuCl complexes clearly reveals their mononuclear structure with a four-coordinated Cu( ii ) center bound by one chloride and three nitrogen atoms of unsymmetrical β-diketiminato ligands. Cyclic voltametric analysis of the Cu( ii ) complexes shows that the length of the pyridyl arm controls the Cu( ii )/Cu( i ) redox process. DFT and EPR results confirm that the geometry of the Cu( ii ) complexes is also controlled by the length of the chelating pyridyl arm. The oxygen atom transfer nitrite reduction of the Cu( ii ) nitrite complexes leads to the formation of copper( i )-PPh 3 and O&z.dbd;PPh 3 which were confirmed by 1 H and 31 P NMR. The length of the pyridyl arm of the copper( ii ) nitrite complexes governs the NO-releasing ability. These findings illustrate the important bioinspired behaviour and NO generation from nitrite via oxygen atom transfer of the unsymmetrical β-diketiminato copper( ii ) complexes as compared to symmetrical β-diketiminato copper( ii ) complexes. An investigation into the role of the pyridyl arm in the reduction of nitrite via OAT in unsymmetrical β-diketiminato copper( ii ) nitrite complexes.