MONODENTATE VERSUS BIDENTATE COORDINATION OF THE NONOATE [ET2N(N2O2)](-) TO COPPER(II) COMPLEXES OF TETRADENTATE LIGANDS

Copper(II) complexes of [Et2N(N2O2)](-) with tetradentate, tripodal li gands composed of 1,4,7-triazacyclononanes with pyridine (L-Py), amide (L-HAmH) Or phenolate (L-R2, R = Me, or Bu-t phenolate substituents) groups as the fourth donor were prepared and characterized by spectros copic and X-ray crystallographic methods. Bidentate O,O-coordination o f [Et2N(N2O2)](-) was observed in the complexes supported by L-Py and L-HAmH, but the stronger phenolate donor in L-R2 induced novel monoden tate coordination via the terminal oxygen atom, defined by X-ray cryst allography for R = Bu-t. Comparison of the bonding parameters of [Et2N (N2O2)](-) when bound bidentate vel sus when bound monodentate reveale d subtle but significant differences in the N-O distances. The amount and rate of nitric oxide (NO) release from the compounds was measured using a chemiluminescence detection method. Despite the differences in [Et2N(N2O2)](-) structural parameters resulting from the divergent co ordination modes, insignificant variation of the rates of NO release t herefrom were found.