A new redox-active tetradentate ONNO-type ligand containing electron-withdrawing chlorine substituents in the phenylene ring, namely N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-4,5-dichloro-1,2-phenylenediamine (LH4), has been synthesized. Its coordination behavior was studied with tin(IV), zinc(II), and cadmium(II) ions. The reaction with Sn(IV) precursor yields the complex LSnMe2 (1), where the ligand is fully deprotonated and coordinated in its dianionic form. However, in solution, L undergoes intramolecular cyclization within the metal coordination sphere, resulting in the formation of a phenoxazine moiety and, consequently, a new ligand L' in the isolated complex L'SnMe2 (2). For Zn(II) and Cd(II), the structures of the resulting compounds - (LH)2Zn (3), (LH)2Cd (4), L'2Zn (5), and L'2Cd (6) - are determined by the choice of oxidant (p-benzoquinone or atmospheric oxygen) used during the synthesis. The structures of the synthesized complexes were established using a combination of NMR, IR, and UV spectroscopy, along with elemental analysis. SC-XRD was carried out for the tin(IV) and zinc(II) compounds. It was shown that the obtained derivatives possess redox-amphoteric properties and exhibit intense absorption in the near-IR region.

Noval unstable o-iminobenzoquinone, namely, 3,4-dibenzhydryl-6-[(2,6-diisopropylphenyl)imino]cyclohex-2-en-1-one, bearing non-shielded chelating site was synthesized in the zinc coordination sphere as a neutral ligand. The bis-o-iminosemiquinonate NII compound was prepared by the reaction of zinc o-iminoquinolate complex with Ni(CO)4 and characterized by NMR spectroscopy and X-ray diffraction analysis.

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.

A new redox-active tetradentate ONNO-type ligand containing electron-withdrawing chlorine substituents in the phenylene ring, namely N,N'-bis(3,5-di‑tert‑butyl‑2-hydroxyphenyl)-4,5-dichloro-1,2-phenylenediamine (LH4), has been synthesized. Its coordination behavior was studied with tin(IV), zinc(II), and cadmium(II) ions. The reaction with Sn(IV) precursor yields the complex LSnMe2 (1), where the ligand is fully deprotonated and coordinated in its dianionic form. However, in solution, L undergoes intramolecular cyclization within the metal coordination sphere, resulting in the formation of a phenoxazine moiety and, consequently, a new ligand L' in the isolated complex L'SnMe2 (2). For Zn(II) and Cd(II), the structures of the resulting compounds — (LH)2Zn (3), (LH)2Cd (4), L'2Zn (5), and L'2Cd (6) — are determined by the choice of oxidant (p-benzoquinone or atmospheric oxygen) used during the synthesis. The structures of the synthesized complexes were established using a combination of NMR, IR, and UV spectroscopy, along with elemental analysis. SC-XRD was carried out for the tin(IV) and zinc(II) compounds. It was shown that the obtained derivatives possess redox-amphoteric properties and exhibit intense absorption in the near-IR region.

The reactions of the amino-bis-(3,5-di-tert-butyl-2-hydroxyphenyl) ligand (ON(H)OH2) with one equivalent of Lappert's germylene or stannylene (E[N(SiMe3)2]2, where E = Ge, Sn) afforded the corresponding germylene ON (H)OGe (1) and stannylene ON(H)OSn (2) in satisfactory yields. According to NMR spectroscopic data (1H, 13C, 119Sn, DOSY), compound 2 adopts a dimeric structure in solution. In contrast, X-ray diffraction analysis of 1 reveals a monomeric structure in the solid state, with the tetrel atom having a coordination number of three. The tin compound 2 was further structurally characterized as its hydrazine adduct, [ON(H)OSn]2 & sdot;N2H4 (3). When the ON(H)OH2 ligand was fully deprotonated in the reaction with Lappert's stannylene, a trinuclear complex ONO2Sn3 (4) containing two ligands in trianionic state was obtained. The molecular structures of compounds 1, 3, 4 were determined by single-crystal X-ray diffraction. All synthesized compounds demonstrated high catalytic activity in the hydroboration of benzaldehyde and phenyl isocyanate under ambient conditions, achieving turnover numbers (TON) of up to 1 & times; 104 at a catalyst loading of 0.01 mol%. Probable reaction pathways for the hydroboration of benzaldehyde and phenyl isocyanate, both uncatalyzed and catalyzed, were investigated using density functional theory calculations.

This work presents tin coordination compounds designed for a specific practical application: the development of LL'CT (ligand-to-ligand charge transfer) chromophores. The obtained complexes are built using two types of redox-active ligands and exhibit ligand-to-ligand charge transfer. The donor part of the LL'CT system is represented by the doubly reduced form of 3,6-di-tert-butyl-o-benzoquinone, while the acceptor part is the neutral form of polycyclic phenanthroline derivatives. The complexes were characterized by X-ray diffraction analysis, UV-vis spectroscopy, cyclic voltammetry (CV), and DFT calculations. Both thermal and photothermal properties of the target complexes were investigated. The electronic absorption spectra of the hexacoordinated tin complexes presented herein exhibit a ligand-to-ligand charge transfer band in the visible and near-infrared region, with an extinction coefficient of approximately 8 & times; 102 dm3 & sdot;mol-1 & sdot;cm-1. Charge transfer occurs from the donor (catecholate) ligand to the acceptor (diimine) ligand. The data obtained are in good agreement with the results of quantum-chemical calculations. It is shown that the HOMO and LUMO are predominantly localized on the catecholate and diimine ligands, respectively. The design of the complexes, realized by varying the diimine substituent, allows the photochemical properties to be tuned, thereby controlling the magnitude of the HOMO-LUMO gap.

Novel antimony( v ) complexes featuring ONNO redox-active ligands exhibit strong NIR absorption, photothermal activity, and high optical stability.

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.

Two new heteroleptic cobalt(II) complexes (3,6-Cat)Co(R-DAD) (where (3,6-Cat)2− is a dianion of 3,6-di-tert-butyl-o-benzoquinone, R-DAD is diisopropyl-1,4-diaza-1,3-butadiene (R = i-Pr (1)) or dicyclohexyl-1,4-diaza-1,3-butadiene (R = c-Hex (2)) have been synthesized and characterized in detail by IR, UV–Vis–NIR spectroscopy, and elemental analysis. The molecular structure of 1 was determined by X-ray diffraction analysis. Magnetic properties of 1 and 2 were measured both in a solid state and in a solution. According to the single-crystal X-ray diffraction analysis, the metal ion in 1 has a planar coordination environment, but magnetic susceptibility measurements of the microcrystalline samples of 1 and 2 indicate the formation of both forms with tetrahedral (d7, h.s., SCo = 3/2) and planar (d7, l.s., SCo = ½) coordination environments of the metal ion. Absorption spectra of crystalline samples of 1 and 2 possess intense absorption band in the NIR region. Electrochemical measurements of 1 and 2 were also performed.

Magnetically bistable compounds attract considerable attention due to their possible applications in molecular electronics and spintronics devices. Of special interest are spin-crossover (SCO) systems that can interconvert between the low-spin and high-spin states leading to switching of the magnetic properties. Synthesis and comprehensive characterization of a family of ionic ferric-dioxolene complexes [(TPA)Fe(HO-DBCat)]ClO4 (1), [(TPA)Fe(NO2-DBCat)]ClO4 (2) and [(TPA)Fe(MeOCH2-DBCat)]ClO4 (3) (TPA = tris(2-pyridylmethyl)amine; HO-DBCat = dianion of 4,6-di-tert-butyl-1,2,3-trihydroxybenzene, NO2-DBCat = dianion of 4,6-di-tert-butyl-3-nitro-1,2-dihydroxybenzene and MeOCH2-DBCat = dianion of 4,6-di-tert-butyl-3-methoxymethyl-1,2-dihydroxybenzene) are reported. Variable temperature structural, magnetic and spectral analyses revealed that compounds 1-3 undergo a thermally induced SCO in the solid state between the high-spin (S = 5/2) and low-spin (S = 1/2) states. Alternating current magnetic susceptibility measurements indicated that the nitro-substituted complex 2 shows a field supported slow magnetic relaxation in the low-spin state at 5000 Oe. Such duality of magnetic properties makes complex 2 the first ferric compound which demonstrates a complete S = 5/2 → S = 1/2 SCO with a single molecule magnet behavior (SMM, S = 1/2). Electronic structures and magnetic properties of 1, 2 and 3 were investigated with the aid of DFT and SA-CASSCF/NEVPT2 calculations.

Synthesis and structural characterization of a family of germanium-dioxolene complexes with ditopic N-donor ligands (L 1 -L 5 ) (L 1 =1,2-bis(pyridin-2-ylmethylene)hydrazine L 2 =1,6-bis-(pyridin-2-yl)-2,5-diaza-1,5-hexadiene, L 3 =N,N-bis(pyridin-2-ylmethylene)-1,4-benzenediamine, L 4 =N,N-bis(pyridin-2-ylmethylene)-(biphenyl)-4,4-diamine, L 5 =2,2’-azopyridine) is reported. The reaction of germanium bis-catecholate with bridging ligands L 1 – L 4 , differing by the nature of the linker between pyridine sites gives rise to dinuclear digermanium complexes (36Cat 2 Ge) 2 L 1−4 (36Cat=dianion of 3,6-di- tert -butylcatechol) 1–4 of DMAMD type (donor-metal-acceptor-metal-donor) with a charge transfer in the UV-Vis region. In opposite, the interaction of the 36Cat 2 Ge with 2,2’-azopyridine (L 5 ) results in the two-electron transfer from the donor 36Cat 2− ligands to the azopyridine bridge forming stable open-shell complex 5 [(36SQ)(36CatGe)] 2 (L 5 ) 2− (36SQ=radical-anionic semiquinonate ligand). Molecular structures of compounds 3 and 5 were determined by single crystal X-ray diffraction analysis. Electronic structures of complexes 1–5 were studied by means of DFT calculations.

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.

New charge-transfer complexes with pyrazine are synthesized from germanium(IV) and silicon(IV) bis(catecholates): 36Сat2Ge, 35Cat2Ge, and 36Сat2Si (36Сat and 35Cat are 3,6- and 3,5-di-tert-butylpyrocatechol dianions, respectively). The synthesized compounds in the crystalline state are 1D coordination polymers with the octahedral environment of the complexing agent. The electronic absorption spectra of suspensions of the crystalline compounds in Nujol demonstrate an absorption in a range of 450–800 nm causing their intense color. A set of the spectral and theoretical studies indicates that the synthesized metal-organic frameworks of silicon and germanium can be considered as donor–acceptor chromophores with the photoinduced interligand charge transfer between the donor catecholate and acceptor pyrazine ligands.

A series of dimethylindium complexes of general formula (R-ONN)InMe2 (R = H (1), Me (2), Cl (3), NO2 (4)) have been synthesized by the reaction of Me3In with an appropriate...

Reactions of Schiff base ligands HL1-4 (wherein HL1 is 2-((pyridin-4-ylmethylene)amino)phenol, HL2 is 4-methyl-2-((pyridin-4-ylmethylene)amino)phenol, HL3 is 4-chloro-2-((pyridin-4-ylmethylene)amino)phenol, HL4 is 4-nitro-2-((pyridin-4-ylmethylene)amino)phenol) with Me3In in a molar ratio of 1:1 lead to the formation of dimethylindium complexes of the general formula (L1-4)InMe2 (1-4). The molecular structures of 1-4 have been determined by single crystal X-ray analysis. In the crystal, all complexes form centrosymmetric dimers via coordination of bridging mu 2-O atoms of the phenolate fragment to the metal atom of the neighboring molecule. The crystal packing of 1-4 represents infinite chains due to short contacts between each indium in the dimer and the pyridine nitrogen of the adjacent dimeric molecule. UV-vis absorption spectra of 1-4 have been recorded in various organic solvents. The position of the absorption band assigned to intraligand charge transfer (ILCT) in the UV-vis absorption spectra of 1-4 depends on the nature of the substituent in the phenolate moiety of L1-4 and shifts hypsochromically with increasing of the electron acceptor properties of the substituents in the Schiff bases. The HOMO-LUMO energy gap calculated from the CV measurements for 1-3 also narrows with the introduction of the electron donor substituents in the ligand L. All complexes show fluorescence with broad emission bands in the range of 500-700 nm both in Me-THF solution and in the solid state.

Six new coordination polymers (CPs) of cadmium based on an extended anilate-type ligand, 4,4 '-(1,4-phenylenebis(azanylylidene))bis(3,6-di-tert-butyl-2-hydroxycyclohexa-2,5-dienone) (H2L), have been synthesized. The series of coordination polymers includes [Cd(L)(DMF)] (1), 1D-CP [Cd(L)(dipy-1)]2DMF (2A) and 2D-CP [Cd(L)(dipy-1)]DMF (2B), [Cd2(L)2(dipy-2)(DMF)2] (3), [Cd(HL)(CH3COO)(dabco)] (4) and [Cd(L)(ur)2](H2L) (5) (where L - deprotonated form of H2L, DMF - N,N '-dimethylformamide, dipy-1 - 4,4 '-trimethylenedipyridine, dipy-2 - 4,4 '-dipyridyl, dabco - 1,4-diazabicyclo[2.2.2]octane, ur - urotropine). The crystal structure and thermal decomposition of 1D- and 2D-coordination polymers are reported. The structural diversity of the synthesized compounds was found to depend on the additional neutral donor ligands in the cadmium coordination sphere. Thus, the introduction of the flexible N-donor ligand dipy-1 into the cadmium coordination sphere leads to the formation of two types of coordination polymers (1D and 2D). The use of the rigid ligand dipy-2 promotes the formation of "honeycomb" 2D-CPs. The use of shorter N-donor ligands dabco and ur leads to linear derivatives in which the ligands being coordinated by cadmium don't act as "crosslinkers" of the chains in the network. The extended anilate ligand is an excellent platform for designing MOFs with diverse structures and topologies.

The oxidative addition of sterically hindered 3,6-dicyclohexyl-o-benzoquinone (L1), 3,5-di-tert-octyl-o-benzoquinone (L2), 4-tert-octyl-o-benzoquinone (L3), and 3,5-bis(2-phenylpropyl)-o-benzoqui-none (L4) to tin(II) chloride in THF affords the corresponding tin(IV) catecholate complexes with the generalformula RCatSnCl2 · 2THF, where Cat is the catecholate fragment; and R is 3,6-с-Hex (I), 3,5-tert-Oct (II), 4-tert-Oct (III), and 3,5-C(Me)2 Ph (IV), regardless of the molar ratio of the starting reactants. The molecu-lar structures of substituted o-benzoquinone L4 and complexes I and III in the crystalline form are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2259370 (L4), 2259371 (I), and 2259372 (III)). The oxidation-reduction properties of synthesized compounds I–IV are studied by cyclic voltammetry.

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.

Study of the thermal behavior were performed for the first time for a series of ligand-to-ligand charge transfer complexes of "alpha-diimine-Ni-II-catecholate" type: Ni-II(3,6-Cat)(bipy) (1), Ni-II(3,6-Cat)(bipy(tBu)) (2) and Ni-II(3,6-Cat)(DAD(dipp)) (3), where 3,6-Cat is 3,6-di-tert-butyl-catecholate, bipy and bipy(tBu) are 2,2 '-bipyridine and its 4,4 '-di-tert-butyl-substituted analog, DAD(dipp) is 1,4-bis(2,6-di-iso-propylphenyl)-1,4-diaza-1,3-butadiene. The phase transition behavior, vapor phase composition, volatility, and thermodynamics of the sublimation process (enthalpy and entropy calculations) of chromophores 1-3 were examined using DSC, TGA, EI-MS, and the Knudsen effusion method with weight registration of the sublimated substance. The Hirshfeld surface analysis was implemented to establish a relationship between the characteristics of the crystal packing, and the thermal properties. The compounds 1-3 are distinguished by the high thermal stability and good volatility, as well as the completeness of the transition to the gas phase under low pressure conditions. An increase in ligand's bulkiness leads to a "rarefaction" of the crystal packing of the chromophore, and a corresponding rise of volatility in the order 1 <= 2 < 3.