Magnetic and structural properties of dinuclear singly bridged-phenoxido metal(ii) complexes

Abstract

The reaction of a methanolic solution containing the bi-compartmental phenolic ligand 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenol (L(Cl)-OH) with MCl2·nH2O in the presence of NH4PF6 or NaClO4 afforded the dinuclear bridged-phenoxido dichlorido-metal(ii) complexes [Co2(μ-L(Cl)O)(H2O)2Cl2][Co2(μ-L(Cl)O)(MeOH)2Cl2](PF6)2 (), [Ni2(μ-L(Cl)O)(MeOH)2Cl2]PF6 (), [Ni2(μ-L(Cl)O)(MeOH)(H2O)Cl2]ClO4·1.25H2O (), [Cu2(μ-L(Cl)O)Cl2]PF6·1/2MeOH () and [Zn2(μ-L(Cl)O)Cl2]PF6·MeOH (). The complexes were characterized by elemental microanalyses, conductivity measurements, IR and UV-Vis spectroscopy, mass spectrometry and single crystal X-ray crystallography. Each M(ii) center within the dinuclear complex cations is octahedrally coordinated in complexes , and five-coordinated distorted square pyramidal in and . Magnetic susceptibility measurements at variable temperature of the complexes revealed weak to moderate antiferromagnetic coupling with |J| values = 8.38, 39.0, 30.2 and 0.79 cm(-1), respectively. The results of DFT calculations correlate well with the experimentally determined antiferromagnetic coupling and show that the magnetic exchange coupling occurs mainly through the phenoxido bridge M-O-M. Implications of geometry around the central metal ion, MM distance, M-O-M bond angle and overlapping of magnetic orbitals on the magnetic exchange coupling are discussed.

Efficient Artificial Nucleases for Mediating DNA Cleavage Based on Tuning the Steric Effect in the Pyridyl Derivatives of Tripod Tetraamine‐Cobalt(II) Complexes

“…The complexes C1‐ClO 4 and C3‐ClO 4 ·H 2 O·CH 3 OH displayed a strong single band around 1090 cm –1 attributable to the stretching ν as (O–Cl) of the ClO 4 – counterion, whereas the corresponding hexafluorophosphate complexes C1‐PF 6 , C2‐PF 6 and C4‐PF 6 ·2H 2 O revealed a very strong band around 840 cm –1 attributable to ν(P–F) stretching frequency of the PF 6 – counterion. The medium broad bands observed in C3‐ClO 4 ·H 2 O·CH 3 OH and C4‐PF 6 ·2H 2 O at 3435 and 3432 cm –1 , respectively are attributable to ν(H–O) of the stretching frequency of lattice H 2 O and/or MeOH , , …”

Synthesis, structure and magnetic characterization of dinuclear copper(ii) complexes bridged by bicompartmental phenolate

“…Thus, we calculated the isotropic exchange parameters J using the ORCA 3.0 soware for compounds 1-3 and extended the calculations also for compounds 4 and 5 for comparison purposes. Following our previous study 1 we used the B3LYP functional and def2-TZVP(-f) basis set to calculate the energy difference D, between high spin (HS) and broken-symmetry (BS) spin states:…”

“…In many of these compounds, the coordination environment around the central metal ions is "coordinatively unsaturated" and/or the metal ion(s) is coordinated to "weakly bound" ligand(s). 1,2,[4][5][6][10][11][12][13] This property made this class of compounds to serve as good candidates to mimic biological systems and as a consequence they have been extensively employed to elucidate the structural spectroscopic parameters and to mimic the mechanism of metalloenzymes in catecholase oxidases, Mn catalases, metallo-b-lactamases (MbL) 7,13,[26][27][28][29][30] and particularly in the hydrolytic systems. 8,21,31,32 These includes phosphodiester bonds of biomolecules such as DNA, purple acid phosphatases and Zn phosphesterases.…”

“…[1][2][3][4][5][6][7][8][9][10][11] These ligands are known to accommodate two homo-or hetero-metallic 3d metal ions and hence producing dinuclear metal complexes bridged by the deprotonated phenolic group and in some cases by one or two other groups such as acetate, benzoate or hydroxide ions. In many of these compounds, the coordination environment around the central metal ions is "coordinatively unsaturated" and/or the metal ion(s) is coordinated to "weakly bound" ligand(s).…”

Experimental and Computational Study of Unique Tetranuclear µ3‐Chloride and µ‐Phenoxo/Chloro‐Bridged Defective Dicubane Cobalt(II) Clusters

“…However, a moderate antiferromagnetic interaction is anticipated for the phenoxo exchange pathway with Co–O–Co angles ( β , in Figure 3) in the range 110.09–112.93°. For this pathway, antiferromagnetic couplings were found for Co–O–Co angles larger than about 100°,21 whereas smaller angles induced ferromagnetic coupling. Nevertheless, in the cases of 1 and 2 , the computational data does not follow this trend perfectly (see Figure S2 in the Supporting Information) and better correlation can be found between the J values and the Co–Cl–Co angle.…”