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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. [ABSTRACT FROM AUTHOR]

A controlled reaction in DMF/CH3CN between a facially disposed tricyanide-containing building block (nBu4N)[FeIII(Tp)(CN)3] (Tp(--) = tris(pyrazol-1-yl)borate anion) and tailor-made Mn(II) and Cu(II) complexes of two tripodal tetradentate ligands providing two 1-methylbenzimidazole, a pyridyl, and a tertiary amine as donor sites, differing only in the (2-pyridyl)alkylamine chain length, has been employed to assemble cyanide-bridged complexes. The heterobimetallic complexes [FeIII(Tp)(CN)2(μ-CN)MnIICl(L¹)]·3DMF·3H2O (1), [FeIII(Tp)(CN)2(μ-CN)MnIICl(L²)]·DMF (2), [FeIII(Tp)(CN)2(μ-CN)CuII(L¹)](ClO4)·2CH3OH (3), and [FeIII(Tp)(CN)2(μ-CN)CuII(L²)](ClO4)·2CH3CN (4) [L¹ = bis{(N-methyl-benzimidazol-2-yl)methyl}(2-pyridylmethyl)amine; L² = bis{(N-methyl-benzimidazol-2-yl)methyl}(2-pyridylethyl)amine (L²)] have been structurally authenticated, revealing single cyanide-bridged discrete dimers with Fe(III)(μ-CN)Mn(II) and Fe(III)(μ-CN)Cu(II) structural motifs. In 1 and 2, both the metal ions have a distorted octahedral geometry. In 3 and 4, the Fe(III) centres are six-coordinate, but the two five-coordinate Cu(II) centres assume two different geometries: distorted trigonal bipyramidal in 3 and almost ideal square pyramidal in 4. Investigation of the magnetic properties reveals an antiferromagnetic interaction through the cyanide bridge between the six-coordinate low-spin Fe(III) (S = 1/2) ions and high-spin six-coordinate Mn(II) (S = 5/2) ions in 1 and 2 with the total spin St = 2 ground state; while 3 exhibits a ferromagnetic interaction between the cyanide-bridged Fe(III) (S = 1/2) and Cu(II) (S = 1/2) ions with the St = 1 state, 4 displays an antiferromagnetic interaction leading to the St = 0 state. [ABSTRACT FROM AUTHOR]

Developing a self-sensitized catalyst from earth-abundant elements, capable of efficient light harvesting and electron transfer, is crucial for enhancing the efficacy of CO 2 transformation, a critical step in environmental cleanup and advancing clean energy prospects. Traditional approaches relying on external photosensitizers, comprising 4d/5d metal complexes, involve intermolecular electron transfer, and attachment of photosensitizing arms to the catalyst necessitates intramolecular electron transfer, underscoring the need for a more integrated solution. We report a new Cu(ii) complex, K[CuNDPA] (1[K(18-crown-6)]), bearing a dipyrrin amide-based trianionic tetradentate ligand, NDPA (H 3 L), which is capable of harnessing light energy, despite having a paramagnetic Cu(ii) centre, without any external photosensitizer and photocatalytically reducing CO 2 to CO in acetonitrile : water (19 : 1 v/v) with a TON as high as 1132, a TOF of 566 h -1 and a selectivity of 99%. This complex also shows hemilability in the presence of water, which not only plays a role in the proton relay mechanism but also helps stabilize a crucial Cu(i)-NDPA intermediate. The hemilability was justified by the formation of N 3 O (2) and N 2 O 2 (3) coordinated congeners of the N 4 bound complex 1. The overall mechanism was further investigated via spectroscopic techniques such as EPR, UV-vis, and spectroelectrochemistry, culminating in the justification of a single electron-reduced Cu(i)NDPA species as a proposed intermediate. In the next step, the binding of CO 2 to the Cu(i) complex and subsequent electron transfer to form Cu(ii)-COO ·- was indirectly probed by a radical trapping experiment via the addition of p -methoxy-2,6-di- tert -butylphenol that led to the formation of a phenoxyl radical. This work provides new strategies for designing earth-abundant robust molecular catalysts that can function as photocatalysts without the aid of any external photosensitizers., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

CuF 2 /DMAP has been established as an excellent catalytic system for vinylsilane-promoted N-vinylation of amides and azoles at room temperature without an external fluoride source. A mechanism has been proposed on the basis of the isolation of reactive intermediate [Cu(DMAP) 4 Cl 2 ], fluoride ion-assisted transmetalation, and ultraviolet-visible spectroscopic studies. The catalytic efficiency of the synthesized and structurally characterized [Cu(DMAP) 4 Cl 2 ] complex has been demonstrated. The valuable monomers for water-soluble polymers, viz., NVP, NVC, and NVIBA, were synthesized on a gram scale.