New complexes of Cu(II) with dipicolinate and pyridyl-based ligands: An experimental and DFT approach

Abstract The three novel mononuclear copper(II) complexes with dipicolinate and pyridyl-based ligands [Cu(dipic)(L)(OH 2 )] (L = 4-picoline, vinylpyridine, 4-styrylpyridine; dipic 2 −  = dipicolinate) were afforded and structurally characterized. X-ray diffraction studies accounted for slight distorted square-pyramidal structures in which the dianion dipic 2 − acts as a tridentate ligand in a mer -fashion, the N -donor species occupy an in-plane position, and a water molecule was detected apically coordinated. To assess the effect of the nature of the pyridyl-substituent ( para position) on electronic properties, other complexes were also synthesized: [Cu(dipic)(py)(OH 2 )], [{Cu(dipic)(OH 2 )} 2 ( μ -pyz)] and [{Cu(dipic)(OH 2 )}( μ -pypy){Cu(dipic)}] (py = pyridine, pyz = pyrazine, pypy = ( E )-1,2-bis(pyridine-4-yl)ethane). Absorptive behavior in the UV–VIS region was studied in solution and in the solid state (reflectance measurements). Additionally, geometry and population analyses were conducted by means of DFT calculations. Electronic UV–VIS spectra were simulated for both dinuclear complexes in the framework of the TD-DFT methodology to assign the origin of the absorption bands.