Mononuclear copper(II) complexes of bis-triazole-based macrocyclic Schiff base hydrazones: direct synthesis, EPR studies, magnetic and thermal properties

Abstract

Mononuclear copper(II) complexes of 1,2,4-triazole-based Schiff base macrocyclic hydrazones, III and IV, have been reported. The prepared amorphous complexes have been characterized by spectroscopic methods, electron spray ionization mass spectrometry, and elemental analysis data. Electrochemical studies of the complexes in DMSO show only one quasi-reversible reduction wave at +0.43 V (ΔE = 70 mV) and +0.42 V (ΔE = 310 mV) for III and IV, respectively, which is assigned to the Cu(II) → Cu(I) reduction process. Temperature dependence of magnetic susceptibilities of III and IV has been measured within an interval of 2–290 K. The values of χM at 290 K are 1.72 × 10−3 cm3 mol−1 and 1.71 × 10−3 for III and IV, respectively, which increases continuously upon cooling to 2 K. EPR spectra of III and IV in frozen DMSO and DMF were also reported. The trend g|| > g⊥ > ge suggests the presence of an unpaired electron in the dx2−y2 orbital of the Cu(II) in both complexes. Furthermore, spectral and antimicrobial properties of the prepared complexes were also investigated.