Effects of the substituents of pyrazole/thiazine ligands on nuclearity of Cu(II) nitrate complexes

[Cu(H2O)(PzTz)(2)](NO3)(2) (1), [Cu(mu-NO3)(NO3)(DMPzTz)](n) (2), and [{Cu(NO3)(DPhPzTz)}(2) (mu-NO3)(2)] (3) [PzTz=2-(1-pyrazolyl)-1,3-thiazine, DMPzTz=2-(3,5-dimethyl-1-pyrazolyl)-1,3-thiazine, DPhPzTz=2-(3,5-diphenyl-1-pyrazolyl)-1,3-thiazine] have been prepared and characterized by elemental analysis, electronic spectroscopy, IR spectroscopy, electron paramagnetic resonance spectroscopy, magnetic susceptibility measurements, and single-crystal X-ray diffraction. Influence of ligand size on coordination to Cu(II) has been analyzed. The three complexes are five-coordinate and the coordination geometry can be described as a distorted trigonal bipyramid for 1 or a distorted square pyramid for 2 and 3. As a consequence of the strain induced by the ligands, 1 is a monomeric complex cation whereas 2 is a polymer and 3 is a dimer.