Nitric oxide sensors based on copper(II) complexes of N-donor ligands

Two Cu(II) complexes, 1 and 2, were synthesized with N-donor ligands L1 and L2 [L1 = N1,N1-dimethylethane-1,2-diamine, L2 = N1,N1-dimethyl-N2-{(pyridin-2-yl)methyl}ethane-1,2-diamine], respectively, and were characterized. Complexes 1 and 2 upon reaction with NO, found to show reduction of Cu(II) to Cu(I) in various solvents. Ligands L3, L4 and L5 are the dansyl derivatives of L1, 2-(pyridin-2-yl)ethanamine and L2, respectively. Three Cu(II) complexes, 3, 4 and 5 were synthesized with ligands L3, L4 and L5 respectively. The fluorescence intensity of these ligands were found to be quenched significantly on complexation due to the paramagnetism of the Cu(II) center. However, when exposed to NO in methanol or aqueous medium, the fluorescence intensity of the fluorophores has been found to be restored because of reduction of paramagnetic Cu(II) to diamagnetic Cu(I).