Substituent's size in pyrazole derivative ligands as determining factor on nuclearity in Cu(II) complexes

New copper(II) nitrate compounds [Cu(mu-NO3)(NO3)(PyTn)](n) (1), [{Cu(NO3)(DMPyTn)}(2)(mu-NO3)(2)] (2) and [Cu(NO3)(2)(DPhPyTn)] (3) containing pyrazole/thiazoline ligands [PyTn = 2-(pyrazol-1-yl)-2-thiazoline; DMPyTn = 2-(3,5-dimethylpyrazol-1-yl)-2-thiazoline; DPhPyTn = 2-(3,5-diphenylpyrazol-1-yl)-2-thiazoline] have been synthesized and characterized by elemental analysis, IR, electronic spectra, ESI-MS, thermal analysis, magnetic susceptibility measurements and single crystal X-ray diffraction. With respect to the environment around copper(II), complexes 1 and 2 are five-coordinate with a geometry of distorted square pyramid whereas 3 is six-coordinate with octahedral geometry. The role played by ligands substituents size on nuclearity of complexes has been analyzed. Thus, 1 is a polymer, 2 is a dimer and 3 presents a monomeric structure. This could be a consequence of the steric strain induced by the organic ligands. (C) 2014 Elsevier Ltd. All rights reserved.