Synthesis, structures and magnetic properties of three copper(II) complexes of 2-(1 H -pyrazol-3-yl) pyridine

Three Cu(II) complexes: [Cu 2 ( μ -L) 2 (HCOO) 2 (H 2 O) 2 ] ( 1 ), [Cu 2 ( μ -L) 2 (NO 3 ) 2 ] ( 2 ), and [Cu 4 ( μ -L) 6 (CH 3 COO) 2 ]·2H 2 O ( 3 ) constructed from 2-(1 H -pyrazol-3-yl) pyridine (HL) were synthesized and structurally characterized by X-ray single-crystal diffraction. The X-ray analyses revealed that all three complexes feature a di-ligand-bridged Cu 2 unit, which is nearly planar. Each deprotonated ligand chelates one copper atom by means of N , N (pyridine-pyrazole) pocket and simultaneously bridges the other one by the N , N (pyrazole) groups. The remaining coordination sites of the Cu(II) centers are either occupied by different anionic coligands to balance the charge, or bridged by another L to develop a tetranuclear structure. Magnetic investigations reveal that the distortion of the Cu(II) coordination geometry (as described by the τ values) and the coplanarity of the Cu–(N=N) 2 –Cu unit have cooperative effects on the antiferromagnetic strength of these systems.