Ni(II) complexes of a new tetradentate NN'N''O picolinoyl-1,2-phenylenediamide-phenolate redox-active ligand at different redox levels

Phenoxazinyl Zn(II) diradical complex formed via redox-driven cyclization of a 2-aminophenol-based N3O ligand. Isolation of the modified N3 ligand radical and its Ni(II) complex

Aerobic reaction between the pyridine-2-carboxamide-2-aminophenol N3O ligand (H3L1) and Zn(ClO4)2·6H2O in CH3CN affords an N3 phenoxazinylate coordinated Zn(II) complex; its diradical electronic structure [ZnII{(L1*)˙-}2] has been elucidated from redox, spectroscopic (UV-VIS and EPR), and magnetic measurements and DFT calculations. Isolation and characterization of the metal-assisted redox-driven modified N3 ligand as a radical cation (H2L1*)˙+ and its Ni(II)-diradical complex [NiII{(L1*)˙-}2] have also been achieved.

Electronic Transition and Magnetic Coupling Regulation in Trimetallic Complexes Featuring a New Bridging Ligand Obtained by Oxidative Addition

A series of trimetallic complexes [Fe^III(μ-L)(py)]₂M^II(py)_n (n = 2, M^II = Mn^II, 1; Fe^II, 2; Co^II, 3; Zn^II, 4; n = 3, M^II = Cd^II, 5) with a new bridging ligand L^4- (deprotonated 1,2-N¹,N²-bis(2-mercaptoanil) oxalimidic acid) were synthesized and fully characterized by elemental analysis, single-crystal X-ray crystallography, IR, and Mössbauer spectra. Interestingly, the bridging ligand was obtained by oxidative addition of the (gma^•)^3- ligand from the mononuclear precursor Fe(gma)py (gma = glyoxal-bis(2-mercaptoanil)). In the obtained complexes, the bridging ligand L^4- coordinates to the terminal Fe^III ions (intermediate-spin with S_Fe = 3/2) by the N, S atoms, and coordinate to the central metal M^II ion by the four O atoms. The resonance structure of the bridging ligand can be described as the two 4π-electron delocalized systems connected by one single-bond (C₁-C₂), which is different from the electronic structure of the precursor Fe(gma)py. Remarkably, the magnetic coupling interaction can be regulated through the central metal. The ferromagnetic coupling constant J gradually decreases as M^II changes from Fe^II to Co^II and Mn^II, while the paramagnetic behaviors are presented when M^II = Zn^II and Cd^II, confirmed by the magnetic susceptibility measurements and further supported by using the PHI program. Furthermore, the bridging ligand to the terminal Fe^III charge transfer (LMCT) transitions emerged in all complexes but the central Fe^II to terminal Fe^III charge transfer (MMCT) only presented in complex 2, strongly supported by the UV/vis-NIR electronic spectra and TDDFT calculations.

Where is the unpaired electron density? A combined experimental and theoretical finding on the geometric and electronic structures of the Co(iii) and Mn(iv) complexes of the unsymmetrical non-innocent pincer ONS ligand

The geometry and electronic structures of the Co and Mn complexes of the pincer H3LONS ligand composed of both hard and soft donor atoms at the coordinating sites are reported.