Structures and theoretical studies of three copper(II) complexes containing 2,2′-dipyridylamine and acrylato or methylacrylato ligands

A series of new complexes of copper(II): [Cu(CH2C(Me)CO2)(2)(dpa)] center dot H2O (1), [Cu(CH2=CHCO2)(2)(dpa)] center dot H2O (2), Cu(CH3CH=CHCO2)(2)(dpa)(H2O) (3) (dpa = 2,2'-dipyridylamine) have been prepared and characterized by elemental analysis, IR spectra, thermal analysis, density functional theory (DFT) calculations and X-ray structure analysis. The crystal structures of 1 and 2 consist of neutral [Cu(L)(2)(dpa)] (L=CH2=C(Me)CO2- and CH2=CHCO2-) units and one lattice water molecule in the unit cell, while in 3 the water molecule is found to coordinate to copper( II). The mononuclear units of 1 and 2 are linked via a similar triple-hydrogen-bonding uncoordinated water molecule into different supramolecular structures, 1D double chains for 1 and a 2D supramolecular network for 2. A detailed crystal structure analysis of 2 revealed that the presence of the C-H center dot center dot center dot O and C-H center dot center dot center dot C hydrogen bonds appear to be responsible for the difference in supramolecular structures differences between 1 and 2. In 3, 1D double chains are formed through hydrogen bonds and weak pi-pi stacking along the a-axis. In this context, we addressed the questions concerning the molecular energies, stabilities and atomic charges. The DFT calculation results proved that the water molecules coordinate to copper( II) atoms in complex 3, while the water molecules in complexes 1 and 2 are free.