High-spin enforcement in first-row metal complexes of a constrained polyaromatic ligand: synthesis, structure, and properties

Abstract

The coordination chemistry of a rigid tetradentate polypyridyl ligand has been developed with first-row transition metals Mn(ii), Fe(ii), Co(ii), Ni(ii), and Zn(ii).

Field-Induced Single Molecule Magnetic Behavior of Mononuclear Cobalt(II) Schiff Base Complex Derived from 5-Bromo Vanillin

“…This can also be supported by the linear N-N distance of 4.169 Å in Co1, whereas 4.163 Å is in the Co2 center. All of the Co-O and the Co-N bond lengths of the molecule are in good agreement with the reported bond distances with high spin Co II ions [36,55,56].…”

“…All these factors are important to obtaining 3d-based SMMs and SIMs because in 3d metals, the orbital angular momentum is readily quenched by the ligand field [14,34]. For mononuclear 3d metal compounds showing slow magnetic relaxation, a low coordination number which leads to a relatively weak Schiff base ligand field is needed because they reduce the 3d orbital splitting energy, thereby enhancing magnetic anisotropy [35][36][37][38][39]. In addition, this type of ligand can be well used as a coordinative moiety of transition metal complexes or as a building block for supramolecular assemblies by taking advantage of π-conjugation.…”

Synthesis of Cytotoxic Iron‐Containing Macrocycles Through Unexpected C(sp2)−C(sp2) Bonds Formation

“…The electronic absorption spectra of complex 1PF 6 (Figure 1) showed intense bands in the 250–340 nm region, which can be assigned to π–π* transitions centered on the bi‐CNN ligand. This complex also displayed a weak band at 463 nm (ϵ=744 M −1 cm −1 ), which could be attributed to a metal‐to‐ligand charge transfer (MLCT) transition [23a,b] . However, it cannot be ruled out that a d‐d transition is also occurring [23c] …”

“…A quasi‐reversible one electron wave can be observed at 0.28 V (vs Ag/AgCl) that can be attributed to the Fe(II) to Fe(III) oxidation. Between −2.0 and −0.9 V, series of waves can be assigned to the bi‐CNN ligand coordinated to the iron center [23a] . At −0.24 and −0.38 V, oxidation waves are associated with adsorption processes on the electrode surface [24–26] …”

Synthesis of a Redox-Active NNP-Type Pincer Ligand and Its Application to Electrocatalytic CO2 Reduction With First-Row Transition Metal Complexes

“…The experimental values are close to previously reported values of similar octahedral complexes and characteristic of 1, 2, and 1 unpaired electron(s) for the Co(II), Ni(II), and Cu(II) complexes, respectively. The relatively high μ eff value for cobalt (2.6) is typical of cobalt polypyridyl complexes, and indicates significant orbital contribution (Chen et al, 2018).…”