Synthesis and Magneto‐Structural Study of Distorted Octahedral Co^II Complexes with Picolinamide and Azide (μ_1,1)‐Bridge

Abstract

Two compounds [Co2(pa)2(μ1,1‐N3)2]n (1) and [Co4(pa)6(μ1,1‐N3)6] (2), (pa=picolinamide) were obtained and studied by electronic and magnetic spectroscopies. 1 is a polymer and 2 is a tetramer of mixed‐valence CoII/III. The N3− anions act as bridges between cobalt ions in the μ1,1 coordination mode. UV‐Vis spectrum analysis showed the octahedral distortion of the compounds. ESR solution spectra revealed a low‐spin ground state, s=1/2 (dz2 ) for CoII. The energy gap was J>kT between levels, S=0 to S=±1 , of 2; consequently, its transition would not be observed. 1 showed zero‐field splitting of the excited level S=±1 with D∼0.31 cm−1. Hyperfine (59Co, I=7/2) and superhyperfine (14N, I=1) couplings were observed. Magnetic susceptibility studies (3–300 K) revealed antiferromagnetic exchange interactions in 1 and 2 with exchange coupling constants, J1=−108 cm−1 and J2=−20 cm−1, g=2 and s=1/2 , for the Co(2)‐Co(2) magnetic exchange pathways.

Synthesis of Co-Doped Tungsten Phosphide Nanoparticles Supported on Carbon Supports as High-Efficiency HER Catalysts

“…On the one hand, competitive chelation exists during the complexing of different atoms . The preference temperature of the chelation for cobalt is about 50 and 90 °C for tungsten. − Therefore, an aging treatment at 50 °C avails the atomic coordination of Co. On the other hand, due to its organic essence, citric acid is apt to aggregate at a high temperature, and this self-aggregation is bound to hinder the close combination of WP and the supports. The bonding energy result illustrates that instead of the dissociative Co atoms in the former two electrocatalysts, element Co is testified to have intruded in the lattice of WP to form Co δ+ by the means of two-step aging, which corresponds to the result in XRD patterns.…”

Magneto‐structural correlations of oximato‐bridged dinuclear copper(II) complex: A theoretical perspective

“…The density functional theory combined with the broken symmetry approach (DFT‐BS) by Noodleman et al [40, 41] was used to evaluate J values. This method is well‐established for estimating the magnetic coupling constants for various dinuclear and multicore complexes [42–64]. In this study, all calculations were performed in ORCA 5.0.3 software [65, 66], using a tight SCF convergence (1 × 10 −8 Eh in energy).…”