An Experimental and Density Functional Study of the Interaction of Cu II Complexes of Diethylenetriamine (Dien) with Pyridine, Nicotinic Acid, and Nicotinamide: The Crystal Structure of [Cu(dien)(nicotinamide)(NO 3 ) 2 ]

The reaction of pyridine (py), nicotinamide (nica), nicotinic acid (nic), and its nicotinate anion (nic – ) with [Cu(dien)X 2 ] (dien = diethylenetriamine; X = Br – , NO 3 – ) in a 1:1 molar ratio affords the new compounds [Cu(dien)(py)(NO 3 ) 2 ], [Cu(dien)(nica)(NO 3 ) 2 ], [Cu(dien)(nic – )(NO 3 )(H 2 O)] · H 2 O, [Cu(dien)(nic – )(Br)(H 2 O)] · 2H 2 O, and [Cu(dien)(NO 3 )(nic – )(Guo)] · 5H 2 O. These compounds were characterized by elemental analysis, and their molecular structures were determined by spectroscopic methods (infrared and electronic spectra), magnetic susceptibility, and molar conductivity measurements, and further corroborated by geometry optimization using electronic structure calculation methods at the B3LYP/6‐31G(d,p) level of theory. The structural, bonding and electronic properties of the complexes are adequately described by B3LYP computational techniques. According to the experimental data, the complexes can be characterized in the solid state as mononuclear, with a distorted octahedral stereochemistry. The distorted octahedral stereochemistry adopted by the complexes was further confirmed by the X‐ray structure analysis of [Cu(dien)(nica)(NO 3 ) 2 ], which consists of a six‐coordinate Cu atom in a distorted octahedral environment constructed from four N atoms (three from dien and one from nica) and two O atoms from the loosely associated NO 3 – counteranions, with the former occupying the equatorial square plane of the octahedron and the latter the axial positions, Cu–O bond lengths being rather long (2.373 and 2.858 Å, respectively). Some substitution reactions have also been studied and are discussed in light of the electronic structure of the complexes computed at the B3LYP/6‐31G(d,p) level. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)