Self-assembly of a metal-organic cage-like structure bearing cofacial redox-active bis-(-semiquinone) copper(II) units.

Ditopic di--quinone with a resorcinol bridge exhibits the ability to self-assemble in a reaction with copper, giving a cage-like binuclear complex that, due to the cofacially placed metal ions, is capable of encapsulation of different solvent molecules as guest ligands. Notably, the geometry of the internal cavity of this complex adjusts depending on the coordinating properties of the encapsulated molecule (mono- or bidentate). A feature of this species is that the cage-forming units are copper(II) bis-semiquinonate moieties, capable of undergoing ligand-centered redox transformations.

Annulation of a 1,3-dithiole ring to a sterically hindered -quinone core. Novel ditopic redox-active ligands.

The fused 1,3-dithiole spacer seems to be very suitable for the functionalization of sterically hindered -quinones with additional groups capable of coordination of metal ions and/or possessing a redox activity. An effective method for the synthesis of sterically hindered -quinones containing 1,3-diketonate, dinitrile and -quinone-methide functional groups at the periphery of the ligand has been developed. The novel compounds have rigid and conjugated structures and exhibit properties typical of -quinones.

Single Crystal X-ray Diffraction Studies of Two Polymorphic Modifications of the Dicarbonyl--Semiquinonato Rhodium Complex at Different Temperatures. Destruction Stimulated by Cooling Versus Stability.

It was found that the dicarbonyl-rhodium--semiquinonate complex (which thread-like crystals can bend reversibly under light/warm activation) can form two polymorphic modifications: isometric prisms () and sticks (). Some thin sticks can bend as mentioned above. X-ray diffraction studies of polymorphic modifications at different temperatures were carried out.

Imine-Based Catechols and -Benzoquinones: Synthesis, Structure, and Features of Redox Behavior.

Novel sterically hindered catechols of the type 3-(RN=CH)-4,6-DBCatH with iminoalkyl or iminoaryl groups in the third position of the aromatic ring have been synthesized and characterized in detail. The -benzoquinones 3-(RN=CH)-4,6-DBBQ have been synthesized by the oxidation of the corresponding catechols. The oxidation of methylimino-substituted catechol with K[Fe(CN)] in alkaline medium leads to the formation of two products: -quinone and diene-dione, the product of the water addition to the corresponding -quinone.

Photo- and Thermosensitive Molecular Crystals. Valence Tautomeric Interconversion as the Cause of the Photomechanical Effect in Crystals of Bis(dioxolene)cobalt Complex.

Especially grown crystals (elongated plates) of the complex (1,10-phen)Co(3,6-DBSQ) () reversibly elastically bend under laser excitation (532 or 808 nm) and/or heating in the temperature interval ∼242-265 K (1,10-phen = 1,10-phenanthroline, 3,6-DBSQ = anion-radical and 3,6-DBCat = dianion of 3,6-di--butyl--benzoquinone). The abrupt interconversion of valence tautomers is observed in this temperature range: (phen)Co(3,6-DBCat)(3,6-DBSQ) ⇌ (phen)Co(3,6-DBSQ). Solving the problem of design of photo- (thermo-) actuators with preset parameters, the series of solid solutions of general formula (phen)(bpy)Co(3,6-DBSQ) was obtained and crystallized as thin elongated plates.

Ferrocene-Containing Tin(IV) Complexes Based on -Benzoquinone and -Iminobenzoquinone Ligands. Synthesis, Molecular Structure, and Electrochemical Properties.

The addition of different substituted -benzoquinones and -iminobenzoquinones to tin(II) bis(-iminophenolates) of the types (Fc-IP)Sn and (Fc-4,6-IP)Sn (where Fc-IP is anion 2-(ferrocenylmethyleneamino)phenolate [Fc-C(H)═N(CH)O] and Fc-4,6-IP is anion 2-(ferrocenylmethyleneamino)-4,6-di--butylphenolate [Fc-C(H)═N(4,6-tBu-CH)O]) in tetrahydrofuran leads to the oxidation of Sn(II) to Sn(IV) with formation of the corresponding tin(IV) catecholates (Fc-4,6-IP)Sn(3,6-Cat) (), (Fc-IP)Sn(3,6-Cat) (), (Fc-4,6-IP)Sn(4-Cl-3,6-Cat) (), (Fc-IP)Sn(4-Cl-3,6-Cat) (), (Fc-4,6-IP)Sn(4,5-Cl-3,6-Cat) (), and (Fc-IP)Sn(4,5-Cl-3,6-Cat) () or the -amidophenolates (Fc-4,6-IP)Sn(AP-Me) (), (Fc-IP)Sn(AP-iPr) (), and (Fc-4,6-IP)Sn(AP-iPr) (). Here ligands 3,6-Cat, 4-Cl-3,6-Cat, and 4,5-Cl-3,6-Cat are dianions 3,6-di--butyl-, 4-chloro-3,6-di--butyl-, and 4,5-dichloro-3,6-di--butylcatecholates, respectively, and AP-Me and AP-iPr are dianions 4,6-di--butyl--(2,6-dimethylphenyl)--amidophenolate and 4,6-di--butyl--(2,6-diisopropylphenyl)--amidophenolate, respectively. Complexes - have been characterized in detail by IR spectroscopy, cyclic voltammetry, and H, C, and Sn NMR spectroscopy.

Novel dioxolene nickel complexes with sterically hindered diazabutadienes. Coupling of aza-ligands coordinated to nickel.

A square-planar bis-o-semiquinonato nickel complex interacts with N,N'-disubstituted 1,4-diazabutadienes-1,3 forming six-coordinate compounds. The X-ray structural study indicates complex geometry to be close to the octahedral. Magnetic properties are determined by metal-ligand ferromagnetic exchange interactions which are promoted by complex geometry.

Valence-Tautomeric Interconversion in a Bis(dioxolene)cobalt Complex with Iminopyridine Functionalized by a TEMPO Moiety. Phase Transition Coupled with Monocrystal Destruction.

Iminopyridine modified by TEMPO nitroxide was utilized for the synthesis of an octahedral bis(o-semiquinonato)cobalt complex. Variable-temperature magnetic susceptibility measurements detect a valence tautomeric transformation in the temperature range 200-300 K. A reproducible hysteresis loop of about 40 K width is observed on the magnetic moment temperature dependence in the transition region.

Ferromagnetic Coupling in the Heterospin Bis-Catecholato-Manganese(IV) Complex with Pyridine Substituted by Nitronyl-nitroxide.

A new bis(3,6-di-tert-butyl-catecholato)manganese complex with two 4-NIT-Py ligands was synthesized and characterized [4-NIT-Py = pyridine substituted at position 4 with nitronyl-nitroxide radical, 2-(pyridin-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl]. X-ray diffraction indicated an octahedral environment of the manganese atom with a trans arrangement of ligands. Bonds lengths in the inner coordination core of the metal and in the chelate cycles that are representative of the charge distribution between the metal and ligands displayed a Mn(IV)(Cat) charge distribution.

Protonated paramagnetic redox forms of di--quinone bridged with -phenylene-extended TTF: A EPR spectroscopy study.

The chemical oxidation and reduction processes of deprotonated, direduced -quinone-exTTF--quinone in protic solvents were studied by EPR spectroscopy. The formation of relatively stable paramagnetic protonated redox forms of the parent triad was very surprising. The character of spin-density distribution in the semiquinone-quinone and semiquinone-catechol redox forms indicates that the -phenylene-extended tetrathiafulvalene connector provides a quite effective electronic communication channel between dioxolene coordination sites.

Cooperative reduction by Ln(2+) and Cp*(-) ions: synthesis and properties of Sm, Eu, and Yb complexes with 3,6-di-tert-butyl-o-benzoquinone.

The first examples of samarium, europium, and ytterbium complexes with 3,6-di-tert-butyl-o-benzoquinone(3,6-dbbq) in the form of catecholate have been obtained by reactions of the quinone with the corresponding lanthanocenes, [LnCp2*(thf)n] (n = 1 or 2) in solution. In the course of the reactions lanthanide ions lose one or two Cp* ligands, which take part in reduction of a quinone molecule into a catecholate anion (dbcat, 2(-)). As a result of the reactions, Sm and Yb clearly yield dimeric complexes[(LnCp*)2(dbcat)2], where each Ln ion loses one Cp* ligand.

Lattice-Modulated Phase Transition Coupled with Redox-Isomeric Interconversion of o-Semiquinone-Catecholato into Bis(o-semiquinonato) Cobalt Complexes.

Two redox-isomeric (valence tautomeric) complexes (2,2'-bpy)Co(3,6-DBSQ)2 (1) and (1,10-phen)Co(3,6-DBSQ)2 (2) (where 2,2'-bpy = 2,2'-dipyridine; 1,10-phen = 1,10-phenanthroline; 3,6-DBSQ = 3,6-di-tert-butyl-benzosemiquinone-1,2) reveal phase transitions that accompany redox-isomeric interconversions of semiquinone-catecholato isomer into a bis-(semiquinonato) one. Phase transitions differ one from another by thermodynamic parameters (transition temperature and interval, enthalpy, and entropy). Complexes 1 and 2 have the same crystal system and space group, and they form solid solutions with any molar ratio.

Heteroligand o-Semiquinonato-Formazanato Cobalt Complexes.

Two novel heteroligand o-semiquinonato-formazanato cobalt complexes [Co(3,6-SQ)(Form)] (1) and [Co(3,6-SQ)2(Form)] (2) (3,6-SQ is 3,6-di-tert-butyl-o-benzosemiquinonate radical anion; Form is 1,3,5-triphenylformazanate anion) were synthesized and characterized in detail. The molecular structures of [Co(3,6-SQ)(Form)] and [Co(3,6-SQ)2(Form)] were determined by X-ray analysis. Magnetic susceptibility measurements and spectroscopic studies have shown that square-planar complex 1 is diamagnetic with a residual paramagnetism due to antiferromagnetic exchange metal-ligand.

Indirect Magnetic Exchange between o-Iminosemiquinonate Ligands Controlled by Apical Substituent in Pentacoordinated Gallium(III) Complexes.

A number of pentacoordinated gallium complexes iSQ2GaR (1-7) (R = Et (1), Me (2), N3 (3), Cl (4), Br (5), I (6), NCS (7)) where iSQ is a radical anion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone were synthesized, and crystalline samples of 1-7 were characterized using magnetic susceptibility measurements. The character of magnetic exchange interaction between spins of o-iminosemiquinonate radicals was found to be strongly influenced by the nature of the apical substituent. The antiferromagnetic coupling is predominant when the apical position is occupied by halogens or other tested inorganic anions, and the value of exchange interaction parameter varies from -99 to -176 K for R = I and NCS, respectively.

Changes in the NMR characteristics of 3,6-di-tert-butylquinone on formation of paramagnetic complexes.

High-resolution NMR spectra of 3,6-di-tert-butylquinone were recorded and analyzed for the first time in a wide range of temperatures. The spectra were transformed by paramagnetic additives of cobalt, nickel, and copper complexes synthesized on the basis of metal semiquinolates. Chloroform, dimethylsulfoxide, toluene, and acetone were used as solvents.

The new C-C bond formation in the reaction of o-amidophenolate indium(III) complex with alkyl iodides.

The reaction of bis(4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolato)indium(III) anion with alkyl iodides is reported. This process includes oxidative addition of two RI (R = Me, Et) molecules to the non-transition metal complex and results in an alkyl transfer to ring carbon atoms with the formation of two new C-C bonds. The interaction proceeds at mild conditions and gives new indium(III) derivatives containing iminocyclohexa-1,4-dienolate type ligands.

Ferrocene-o-benzosemiquinonato tin(IV) electron-transfer complexes.

The interaction of ferrocene with tin(IV) o-benzosemiquinonato complexes in acetonitrile results in a reversible electron transfer (ET) from ferrocene to the redox-active ligand with the formation of electron-transfer complexes [(3,6-Cat)SnBr3](-)[Cp2Fe](+) (1) and [(3,6-Cat)(3,6-SQ)SnCl2](-)[Cp2Fe](+) (2), where 3,6-Cat is the 3,6-di-tert-butyl-catecholate dianion and 3,6-SQ is the 3,6-di-tert-butyl-o-benzosemiquinonato radical anion. The ET process and the solvent effect in the system "ferrocene-o-benzosemiquinonato tin(IV) complexes" were investigated on the basis of a combination of spectroscopic and X-ray diffraction methods. The molecular structures of 1 and 2 were confirmed by X-ray analysis.

Reversible binding of molecular oxygen to catecholate and amidophenolate complexes of SbV: electronic and steric factors.

Edge of reactivity: The reactions of reversible binding of molecular oxygen to catecholate and amidophenolate complexes of Sb(V) are investigated by analyzing the position of electronic (E(HOMO)) and steric (G-parameter) factors. The optimal electronic and steric parameters for such type reactions are found.

Sterically hindered o-quinone annulated with dithiete: a molecule comprising diolate and dithiolate coordination sites.

A new stable sterically hindered o-quinone annelated with a 1,2-dithiete ring was prepared by using mild conditions. The skeleton of the compound comprises diolate and dithiolate functions that have the potential to bind metals leading to the corresponding complexes. The reactivity of this compound as a ligand with respect to both coordination sites was studied.

Tin(IV) and lead(IV) complexes with a tetradentate redox-active ligand.

The coordination chemistry of a tetradentate redox-active ligand, glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil) (H(2)L), was investigated with the diorganotin(IV) and diphenyllead(IV) moieties. Complexes R(2)SnL (R = Me (1), Et (2), (t)Bu (3), Ph (4)) and Ph(2)PbL (5) have been prepared and characterized. The molecular structures of compounds 1, 3, and 5 have been determined by single crystal X-ray diffraction.

Experimental and theoretical investigation of topological and energetic characteristics of Sb complexes reversibly binding molecular oxygen.

The experimental distribution of electron density in Ph(3)(4,5-OMe-3,6-Bu(t)-Cat)Sb·MeCN (1*) and Ph(3)(4,5-N(2)C(4)H(6)-3,6-Bu(t)-Cat)Sb·MeOH (2*) complexes was studied. According to atoms in molecules theory, the Sb-C(Ph), Sb-O(catecholate), and Sb···N(O) bonds are intermediate, whereas the O-C and C-C bonds are covalent, respectively. The energy of the Sb···N(MeCN) and Sb···O(MeOH) bonds are 7.

Synthesis and molecular structure of indium complexes based on 3,6-di-tert-butyl-o-benzoquinone. Looking for indium(I) o-semiquinolate.

The interaction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with indium in toluene leads to the tris-o-semiquinolate derivative (3,6-SQ)(3)In (3,6-SQ - radical-anion of 3,6-Q). According to single-crystal X-ray diffraction analysis, this complex has a trigonal prismatic structure. Magnetic measurements revealed that the exchange interactions between odd electrons of the paramagnetic ligands in (3,6-SQ)(3)In are antiferromagnetic in character.

First structurally characterized mixed-halogen nickel(III) NCN-pincer complex.

A square-pyramidal mixed-halogen nickel(III) NCN-pincer complex (PipeNCN)NiClBr (where PipeNCN=2,6-bis(piperidinomethyl)phenyl) was structurally characterized. Bromine occupies apical position; pincer ligand and chlorine atom are in the basal plane. EPR detects that complex in solution exists as a mixture of two structural isomers with bromine or chlorine atoms in the top of pyramid.

Oxidation by oxygen and sulfur of Tin(IV) derivatives containing a redox-active o-amidophenolate ligand.

Oxidation of tin(IV) o-amidophenolate complexes [Sn(ap)Ph(2)] (1) and [Sn(ap)Et(2)(thf)] (2) (ap=dianion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (ImQ)) with molecular oxygen and sulfur in toluene solutions was investigated. The reaction of oxygen with 1 at room temperature forms a paramagnetic derivative [Sn(isq)(2)Ph(2)] (3) (isq=radical anion of ImQ) and diphenyltin(IV) oxide [{Ph(2)SnO}(n)]. Interaction of 1 with sulfur gives another monophenyl-substituted paramagnetic tin(IV) complex, [Sn(ap)(isq)Ph] (4), and the sulfide, [Ph(3)Sn](2)S.

o-Semiquinonic PCP-pincer nickel complexes with alkyl substituents: versatile coordination sphere dynamics.

o-Semiquinonic nickel pincer complexes (R2PCP)Ni(SQ) show a versatile coordination sphere dynamics via "swing" or "fan" oscillations depending on the steric properties of the phosphorus substituents.