l‑Tyrosinatonickel(II) Complex: Synthesis and Structural, Spectroscopic, Magnetic, and Biological Properties of 2{[Ni(l‑Tyr)2(bpy)]}·3H2O·CH3OH

The complex 2­{[Ni­(l-Tyr)2(bpy)]}·3H2O·CH3OH [1, where l-Tyr = l-tyrosine; bpy = 2,2′-bipyridine (2,2′-bpy)] was obtained in crystalline form and characterized by X-ray and spectroscopic (FT-IR, NIR–vis–UV, and HFEPR) and magnetic methods. The complex crystallized in the hexagonal system with a = b = 12.8116(18) Å, c = 30.035(6) Å, and space group P3221. The six-coordination sphere around the Ni2+ ion is formed by two N and two O l-tyrosinato atoms and completed by two N atoms of the 2,2′-bpy molecule. Neighboring [Ni­(l-Tyr)2(bpy)] units are joined via weak hydrogen bonds, which create a helical polymeric chain. The coordinated atoms form a strongly distorted cis-NiN2N2′O2 octahedral chromophore. The solid-state electronic spectrum of complex 1 was analyzed assuming D2h symmetry, and the observed bands were assigned to 3B1g → 3Ag, 3B1g → 3B3g, 3B1g → 3B2g, 3B1g → 3B3g, 3B1g → 3B1g, and 3B1g → 3B2g transitions for the I and II d–d bands, respectively. The crystal-field parameters found for D2h symmetry are Dq = 1066 cm–1, Ds = 617 cm–1, Dt = −93 cm–1, B22 = 7000 cm–1, and Racah B = 812 cm–1. Magnetic studies revealed the occurrence of hydrogen-bonded metal pairs. The spin Hamiltonian parameters D = −3.262 cm–1 and E = −0.1094 cm–1, determined from high-field, high-frequency electron paramagnetic resonance spectra, together with a weak antiferromagnetic exchange parameter J = −0.477 cm–1, allowed us to reproduce the powder magnetic susceptibility and field-dependent magnetization of the complex. The biological activity of 1 has been tested by using the Fusarium solani, Penicillium verrucosum, and Aspergillus flavus fungi strains and Escherichia coli, Pseudomonas fluorescens, Serratia marcescens, and Bacillus subtilis bacterial strains.