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Sm, Er, and Yb complexes containing anionic (4,5,6,7-tetrafluorobenzothiazol-2-yl)-2-(3,4,5,6-tetrafluoro)phenolate (SONF) and 3-(2-benzothiazol-2-yl)-2-naphtholate (NpSON) and neutral 1,10-phenathroline or 2,2'-bipyridine ligands were synthesized. The structures of complexes Yb(SONF)2-(NpSON)(DME)1.5 (II) and previously synthesized Er(SONF)3(DME) (I) were determined by X-ray diffraction (CIF files CCDC nos. 1972769 and 1972770, respectively). Upon excitation by light at λ 405 nm, all complexes showed luminescence of the ligands and Ln3+ ions. The OLED devices based on samarium complexes showed moderate intensi metal-centered emission of moderate intensity at a 19 V voltage.

2,5-Dihydroxy-3,6-di-tert-butyl-p-benzoquinone (QtBuDiol) reacts with Ph3SbBr2 in toluene in the presence of triethylamine to yield the ionic complex [Et3NH]+[(DionetBuDiolate)SbPh3Br]– (I). The same reaction in methanol leads to complete displacement of bromide ions from the antimony coordination sphere and gives triphenylantimony(V) 1,2-diolate (DionetBuDiolate)SbPh3 · MeOH (II · MeOH). The molecular structure of the complexes was determined by X-ray diffraction (CIF files CCDC no. 1960681 (I · toluene) and 1960682 (II · 2MeOH)). Both complexes are characterized by quinoid bond distribution in the six-membered carbon rings and by C=O double bonds in the Ph3SbO2C6(t-Bu)2O2 moieties. Formally, the complexes can be considered as 3,6-di-tert-butyl-o-benzoquinone derivatives with the organometallic Ph3SbO2 group in positions 4 and 5 of the quinone ring. The electrochemical reduction of II · MeOH in dichloromethane occurs at E1/2 = –1.52 V, which is significantly shifted to the cathodic region relative to the data for 3,6-di-tert-butyl-o-benzoquinone (E1/2 = –0.51 V). This redox potential shift indicates a significant decrease in the electron-withdrawing properties of the o-quinoid moiety, which is caused by the effect of the electron-donating catecholate metallacycle.

Metal tris-o-dioxolene (o-quinone, o-semiquinone, and catecholate) complexes represent an interesting and vivid model system for the demonstration of a relationship between the structure and magnetic properties when considering a series of objects of the same type. After publishing the reviews [1, 2], the metal tris-o-dioxolene complexes containing the symmetric 3,6-di-tert-butyl-o-benzoquinone derivatives with substituents in positions 4 and 5 are described in a number of works. In addition, some earlier unpublished structures of the complexes of this type are reviewed. The substituents in the lateral chains enhance the steric protection of the metal center and, as a consequence, result in the formation of coordination polyhedra uncharacteristic of the tris(dioxolene) complexes, such as a trigonal prism. In turn, the distortion of the structure affects the magnetic properties of the complexes. Only the complexes with the derivatives of sterically hindered o-quinones, 3,5- and 3,6-di-tert-butyl-o-benzoquinones, are considered in the present review. On the one hand, bulky tert-butyl groups prevent the formation of direct intermolecular contacts and, on the other hand, prevent organic reactions to occur at the benzoquinone cycle.

3a,6a-Diaza-1,4-diphosphapentalene (DDP) with indium triiodide forms the [In(DDP)I3] complex (I) with the ratio In : DDP = 1 : 1. The DDP ligand reacts with antimony(III) chloride to form a coordination polymer, the treatment of which with pyridine in the presence of pyridine hydrochloride affords the [PyH]+[Sb(DDP)Cl4)]– complex (II) (CIF files CCDC nos. 1937822 (I) and 1937823 (II)). The metal is coordinated to the phosphorus atom at an angle to the plane of the heteropentalene cycle (101.9(1)° and 106.0(1)° for In and Sb, respectively). This indicates that the coordination occurs due to electrons of the heteroaromatic π system.

Biradical mononuclear SQ2 $${\text{ZnL}}_{2}^{4}$$ and SQ2ZnL5 complexes, binuclear SQ2Zn(L3)ZnSQ2 complex, and coordination polymers (SQ2ZnL1(2))n are synthesized by the reactions of bis(3,6-di-tert-butyl-o-benzosemiquinonato)zinc (SQ2Zn) with the bidentate N-donor ligands (L1–5) (pyrazine (L1), 4,4'-dipyridyl (L2), phenazine (L3), 4-cyanopyridine (L4), and pyrimidine (L5)). The structures of the synthesized compounds are determined by X-ray diffraction analysis (СIF files CCDC nos. 1846558–1846563). The binuclear SQ2Zn(L3)ZnSQ2 and mononuclear SQ2ZnL5 complexes contain pentacoordinated metal atoms, whereas zinc in the compounds based on the L1,2,4 ligands exists in the octahedral environment with the trans-arranged o-semiquinonate ligands. The coordination polymers (SQ2ZnL1(2))n are capable of depolymerizing on dissolution in organic solvents. According to the data of measuring the temperature dependence of the magnetic susceptibility, the antiferromagnetic exchange between unpaired electrons of the organic radical anions is observed in crystals of the synthesized compounds.

New catecholate complexes of triphenylantimony(V), (Etgly-3,6-DBCat)SbPh3 (I), (Propgly-3,6-DBCat)SbPh3 (II), and (Cat-3,6-DBCat)SbPh3 (III), based on analogs of sterically hindered 3,6-di-tert-butyl-o-benzoquinone, 5,8-di-tert-butyl-2,3-dihydrobenzo[b][1,4]dioxine-6,7-dione (L1), 6,9-di-tert-butyl-2,3-dihydrobenzo[b][1,4]dioxepine-7,8-dione (L2), and 1,4-di-tert-butyl-dibenzo[b,e][1,4]dioxine-2,3-dione (L3), which are the 2,3-dihydrobenzo[b][1,4]dioxine, 2,3-dihydrobenzo[b][1,4]dioxepine, and dibenzo[1,4]dioxine derivatives, respectively, have been synthesized. At room temperature catecholates I and II react with molecular oxygen adding an O2 molecule to form the corresponding spiroendoperoxides IV and V. Catecholate III reacts with oxygen with the deep oxidation of the complex and formation of neutral o-benzoquinone. The molecular structures of complexes I and III are determined by X-ray diffraction analysis (CIF files CCDC nos. 1840299 (I · toluene) and 1840300 (III)).

The electron density distribution in Ph3Sb(O2CC(Me)=CH2)2 ⋅ C6H6 and structural and energy aspects of the phase transition in the crystals of this compound were investigated using a series of common (Ib−Ie) and high-precision (Ia) X-ray diffraction experiments. A considerable difference between the root-mean-square atomic displacements in two chemically equivalent methyl groups of the methacrylate ligands was revealed. This difference was shown to be caused by considerable energy difference of the intra- and intermolecular contacts of the corresponding methyl groups.

Heptacoordinated tin complexes with pentadentate redox-active ligands containing the diiminopyridine fragment combined with two sterically hindered phenolate coordination centers, LSn-Cl2 and L'SnCl2 (L and L' are dianions of deprotonated 2,6-bis[2,4-di-tert-butyl-6-(methylidenylamino) phenol]pyridine and 2,6-bis[2,4-di-tert-butyl-6-(ethylidenylamino)phenol]pyridine, respectively), are synthesized. The molecular and electronic structures of the synthesized compounds were studied by X-ray diffraction analysis (for complex I, CIF file CCDC no. 1557838), a set of spectral methods, and quantum-chemical calculations. The redox properties of the obtained complexes are characterized by cyclic voltammetry.

The oxidative addition of bis-o-benzoquinone Q–(CH=N–N=CH)–Q (L), in which two 3,5-ditert-butyl-o-benzoquinones are linked to each other in positions 6 via the CH=N–N=CH group, to triphenylstibine gave a new binuclear triphenylantimony(V) bis-catecholate complex, Ph3Sb(Cat–(CH=N–N=CH)–Cat)SbPh3 (I). Recrystallization of I from a methanol–trichloromethane mixture resulted in an additional coordination of a methanol molecule to each antimony atom to give the binuclear complex, (CH3OH)Ph3Sb(Cat–(CH=N–N=CH)–Cat)SbPh3(CH3OH) (I · 2CH3OH), the crystals of which (I · 2CH3OH) · 2CH3OH · CHCl3 (II) contain additionally two methanol solvate molecules, which fix the geometry of the nitrogen-containing bridging group, and a trichloromethane molecule. The molecular structure of compound II in the crystalline state was determined by X-ray diffraction (CIF file CCDC no. 1560840).

The syntheses of the 2,6-di-tert-butyl-4-(2-hydroxybenzylideneamino)phenolate (L) complexes of Gd (I), Nd (II), Er (III), Yb (IV), Tm (V), Sm (VI), and Tb (VII) are described. The structures of the Gd and Er complexes are determined by X-ray diffraction analysis (CIF files CCDC nos. 1558820 (I) and 1558819 (III)). All synthesized compounds exhibit ligand-centered photoluminescence in a range of 405–485 nm. In addition, the luminescence spectra of solid samples of the neodymium and ytterbium complexes contain narrow bands of f–f transitions characteristic of Nd3+ and Yb3+ ions.

The following new triphenylantimony(V) catecholate complexes bearing the protonated imine group are synthesized from the new sterically hindered 3,5-di-tert-butylpyrocatechols (6-(CH=N-o-(C6H4–NH2))-3,5-Cat)H2 (H2L1) and (6-(CH=N-o-(C6H4–OH))-3,5-Cat)H2 (H2L2) containing in position 6 the iminomethyl group bonded to the aniline or phenol substituent: (6-(CH=NH+-o-(C6H4–NH2))-3,5-Cat)SbPh3X (X = Br (I), OMe (III)) and (6-(CH=NH+-o-(C6H4–OH))-3,5-Cat)SbPh3X (X = Br (II), OMe (IV)). The molecular structure of complex III · CH 3 OH in the crystalline state is determined by X-ray diffraction analysis (CIF file CCDC no. 1554694). The electrochemical properties of complexes III and IV are studied by cyclic voltammetry.

The experimental and theoretical electron densities in complexes [6-(2,6-di-iso-propylphenyl)imino-2,4-di-tert-butylcyclohexa-2,4-diene-1-peroxo-1-olato-N,O,O′]tris(p-chlorophenyl)antimony(V), (p-Cl–C6H4)3Sb(2,6-iso-Pr–Ph–AP) · O2 (I), and [6-(2,6-dimethylphenyl)imino-2,4-di-tert-butylcyclohexa-2,4-diene-1-peroxo-1-olato-N,O,O′]tris(p-chlorophenyl)antimony(V), (p-Cl–C6H4)3Sb(2,6-Me–Ph–AP) · O2 (II), where AP is 4,6-di-tert-butyl-N-o-iminobenzoquinone dianion, are studied on the basis of high-resolution X-ray diffraction data and theoretical calculations using the density functional theory (B3LYP/DGDZVP). The nature of chemical bonds and the charge distribution on atoms are studied, and the energy of molecular oxygen addition to the Sb(V) o-aminophenolate complexes is estimated. The structures are deposited with the Cambridge Crystallographic Data Centre (CIF files CCDC nos. 1560600 (spherical refinement) and 1560601 (multipole refinement) for complex I; 1560602 (spherical) and 1560603 (multipole) for complex II).

A series of the new tin(IV) complexes based on the 2-hydroxy-4-N-(phenyl)-3,6-di-tert-butyl-p-iminobenzoquinone ligand (LH) containing various hydrocarbon substituents R at the metal atom (R = Me, Et, n Bu, t Bu, and Ph) is synthesized. The structures of the synthesized compounds were determined by elemental analysis, IR spectroscopy, and 1H and 119Sn NMR spectroscopy. The X-ray diffraction analyses are carried out for the LSnPh3 (I) and L2SnEt2 (IV) complexes (CIF files CCDC no. 1557840 (I) and 1557839 (IV)). The main electrochemical characteristics in a solution are obtained for the whole series by cyclic voltammetry.

A series of new paramagnetic tin(IV) complexes based on sterically hindered o-iminobenzoquinones (R)ImQ differed in fragments (R) in the N-aryl fragment is synthesized. The thermal transformation of the tin(IV) complex, (iso-Pr)ImSQSn(tert-Bu)2Cl ((iso-Pr)ImSQ is the radical anion of 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone), is studied. The thermal transformation of the paramagnetic complex in nonane results in the formation of a new tin(II) bis(aminophenolate) derivative. The synthesized complexes and the thermolysis product are characterized by EPR, IR, and 1H, 13C, and 119Sn NMR spectroscopy and elemental analysis. The structures of the (tert-Bu)ImSQSn(tert-Bu)2Cl complex and the thermal decomposition product, {(iso-Pr)AmPh}2Sn ((iso-Pr)AmPh is 2-(2,6-di-iso-propylphenyl)amino-4,6-di-tert-butylphenolate), are determined by X-ray diffraction analysis.