Two new Cu(II) complexes with 3-(2-pyridyl)pyrazol-based ligands: Synthesis, crystal structures, and magnetic properties

In our efforts to investigate the relationships between the structures of ligands and their complexes, two structurally related 3-(2-pyridyl)pyrazole-based ligands, 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]benzene (L1) and 3-[3-(2-pyridyl)pyrazol-1-ylmethyl]pyridine (L2), and their two Cu(II) complexes, [Cu(L1)2(NO3)](NO3)(CH3CH2OH) (1) and [Cu2(L2)2(Cl)4] (2), were synthesized and structurally characterized by elemental analyses, IR spectra and single crystal X-ray diffraction analysis. Complex 1 has a mononuclear structure, while 2 takes the dinuclear structure, which were further linked into higher-dimensional supramolecular networks by intra- or inter-molecular weak interactions, such as C–H⋯O hydrogen-bonding, C–H⋯π, and π⋯π stacking interactions. The structural differences of 1 and 2 can be attributed to the difference of counter anions and the different pendant aromatic groups of L1 and L2, in which the benzene and pyridine rings act as the directing group for π⋯π stacking and C–H⋯π interactions. Moreover, magnetic properties of 2 have been further investigated in detail.