Azo-oximate metal-carbonyl to metallocarboxylic acid via the intermediate Ir(III) radical congener: quest for co-ligand driven stability of open- and closed-shell complexes

The redox non-innocent behavior of the diaryl-azo-oxime ligand L^NOH1 has been accentuated via the synthesis of metastable anion radical complexes of type trans-[Ir(L^NO˙-)Cl(CO)(PPh₃)₂] 2 (CO is trans to azo group of the ligand) by the oxidative coordination reaction of 1 with Vaska's complex. The stereochemical role of co-ligands vis-à-vis the interplay of π-bonding has been found to be decisive in controlling the aptitude of the coordinated redox non-innocent ligand to accept or reject an electron. This has been clarified via the isolation of quite a few complexes as well as the failure to synthesize some others. The oxidized analogues of type trans-[Ir(L^NO-)Cl(CO)(PPh₃)₂]⁺2+ (CO and azo group of the ligand are trans) as well as its cis isomer cis-[Ir(L^NO-)Cl(CO)(PPh₃)₂]⁺3+ (CO and azo group of the ligand are cis) have been structurally characterized but the radical anion congener of the latter could not be synthesized. Furthermore, the closed shell complexes [Ir(L^NO-)Cl₂(PPh₃)₂] 4 and [Ir(L^NO-)₂Cl(PPh₃)] 5 have been well characterized by diffraction as well as spectral techniques but their corresponding azo anion radical complexes could not be isolated and this is attributed to the trans influence of ancillary ligands. The anion radical complexes trans-[Ir(L^NO˙-)Cl(CO)(PPh₃)₂] 2 may be rapidly transformed to the metallocarboxylic acids trans-[Ir(L^NO-)Cl(CO₂H)(PPh₃)₂] 6via a proton-coupled electron transfer (PCET) process, thereby demonstrating the role of odd electron over the coordinated ligand framework to trigger metal-mediated carbonyl to carboxylic acid functionalization. Complexes 6 are further stabilized via intramolecular -CO₂H⋯ON- (carboxylic acid⋯oximato) H-bonding. The optoelectronic properties as well as the origin of transitions in the complexes were analyzed by TD-DFT and theoretical analysis, which further disclose that the odd electron in trans-[Ir(L^NO˙-)Cl(CO)(PPh₃)₂] 2 is primarily azo-oxime centric with very low contribution from the iridium center.

Morphology-engineered carbon quantum dots embedded on octahedral CdIn2S4 for enhanced photocatalytic activity towards pollutant degradation and hydrogen evolution

In recent years, carbon quantum dots (CQDs) and CdIn₂S₄ have considered as the representatives of the most potential photocatalysts applied in the field of photocatalysis for efficiently solving energy shortage and environmental pollution. In this work, a novel CQDs hybridized CdIn₂S₄ (CQDs/CIS) heterostructure with 2D nanosheet/3D nanooctahedra morphology was successfully fabricated by a simple in-situ solvothermal method. Most interestingly, the morphology of hybrid gradually evolved from 3D octahedron to 2D nanosheet with the increase of CQDs. This unique 2D/3D structure and synergistic effect between CQDs and CdIn₂S₄ increased the multi-dimensional active reaction sites and enhanced the quantum yield and the separation efficiency of photogenerated electron pairs. Therefore, CQDs/CIS hybrids showed excellent photocatalytic activities of H₂ generation, RhB and TCH degradation. Especially, CQDs/CIS-3 heterostructure presented the highest photocatalytic efficiency and its hydrogen generation activity (956.79 μmol g^-1 h^-1) was 7.57-fold improvement by contrast with pure CdIn₂S₄ (126.35 μmol g^-1 h^-1). Moreover, RhB and TCH degradation rate constants of CQDs/CIS-3 were about 8.14 and 2.32 times higher than those of CdIn₂S_4, respectively. Furthermore, the effect of CQDs on the evolution of heterostructure morphology and photocatalytic mechanism were also proposed. This research work would offer useful enlightenment for elucidating the affect of CQDs on the morphology evolution and construction of CQDs-based hybrid with excellent performances for H₂ production and pollutant removal.

Ruthenocycles of benzothiazolyl and pyridyl hydrazones with ancillary PAHs: synthesis, structure, electrochemistry and antimicrobial activity

The antimicrobial activity of ruthenocycles of pyridyl and benzothiazolyl hydrazones has been investigated. The study established that such activity is comparatively higher for the complex containing benzothiazolyl hydrazone.