New diorganotin(IV) complexes based on a redox-active tetradentate ONNO ligand, namely N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (LH₄), were synthesized. A methodology for the stepwise oxidation of tin(IV)-ONNO derivatives with a stoichiometric amount of p-benzoquinone was developed. This allowed the preparation of tin(IV) complexes containing the ligand in the tetraanionic doubly deprotonated form, in the dianionic state, and a controlled intraligand cyclization to be carried out. It has been found that the diorganotin(IV) compounds with the dianionic form of the ONNO ligand have a ground singlet spin state, but an increase in temperature leads to partial populating of the triplet state and a transition from the diamagnetic form of these complexes to the paramagnetic biradical ones. The UV-vis-NIR spectrum of L²⁻SnPh₂ shows an intense absorption band in the range of 600–1400 nm, corresponding to the intraligand charge transfer (ILCT). The coordination ability of the solvent strongly influences the position of this solvatochromic band. Cyclic voltammetry revealed that this compound undergoes two sequential reversible single-electron oxidations and two sequential reversible single-electron reductions. This cyclic voltammetry remains unchanged even after 100 cycles have been performed.

A new cage-like dimeric nickel(II) complex Ni₂L₂(DMSO)₄ based on a ditopic redox-active hydroxy-para-iminobenzoquinone type ligand LH₂ (L is 4,4′-(1,3-phenylene-bis(azaneylylidene))-bis(3,6-di-tert-butyl-2-oxycyclohexa-2,5-dien-1-one dianion) was synthesized in DMSO at 120 °C. The molecular structure of the synthesized compound was determined by X-ray diffraction analysis. The complex Ni₂L₂(DMSO)₄ is almost insoluble in all organic solvents, probably due to the presence of a large number of intermolecular contacts in its structure. The electronic spectrum and thermal stability of the crystalline compound have been studied.

Based on a series of substituted o-iminobenzoquinones (6-((2,6-di-iso-propylphenyl)imino)-2,4-bis(2,4,4-trimethylpentan-2-yl)cyclohexa-2,4-dien-1-one (L¹), 4-(tert-butyl)-6-((2,6-di-iso-propylphenyl)imino)-3-methoxycyclohexa-2,4-dien-1-one (L²), and 6-((2,6-di-iso-propylphenyl)imino)-3-methoxy-4-(2,4,4-trimethylpentan-2-yl)cyclohexa-2,4-dien-1-one (L³)), indium(III) iodide complexes were synthesized containing a redox-active ligand in the neutral form. The o-iminobenzoquinone L¹ was synthesized for the first time. It was found that the structure of the obtained complexes depends on the degree of shielding of the carbonyl oxygen atom in the starting o-iminobenzoquinone. The sterically hindered L¹ forms a 1 : 1 adduct with InI₃ (complex (L¹)InI₃ (I)). The absence of a substituent at position 2 of the o-iminobenzoquinone ring promotes the formation of bisligand ionic derivatives {[(L²)₂InI₂]InI₄} (II) and {[(L³)₂InI₂]InI₄} (III). The molecular structure of L¹ and complexes I·0.5 toluene, II·toluene·0.5 hexane was established by X-ray diffraction analysis (CCDC nos. 2440874 (L¹), 2440875 (I·0.5 toluene), 2440876 (II·toluene·0.5 hexane)). The optical and electrochemical properties of the starting o-iminobenzoquinones and their indium(III) complexes were studied. It was shown that complexation significantly enhances the oxidative properties of L¹, L², and L³.

New catecholates of iodine gallium(III) with iminopyridine ligands 1-4 were synthesized and investigated. The crystal structures all obtained complexes were confirmed using single-crystal X-ray diffraction. All five-coordinate gallium catecholates obtained exhibit ligand-to-ligand charge transfer in the near-infrared region, in the range of 500–900 nm. Compounds 1 and 2 demonstrated photothermal conversion efficiencies of 36.7% and 42.2%, respectively, in the therapeutically relevant 808 nm region.

Upon the reaction of glyoxal-bis(2-hydroxy-5-chlorophenyl)imine LH₂ with diethyltin dichloride in the presence of a base (Et₃N) in DMSO, the 1D-coordination polymer 1 was obtained, in which formally the L’(SnEt₂)₂ fragment acts as a monomeric unit. It was found that during the reaction, the initial ligand L undergoes transformation in the tin atom’s coordination sphere. This transformation results in the formation of a new ditopic 1,4-bis((5-chloro-2-oxidophenyl)imino)but-2-ene-2,3-bis(olate) ligand L’. The structure of the resulting complex 1 was examined by single-crystal X-ray diffraction analysis, elemental analysis, IR, and UV spectroscopy.