Yan V. Zubavichus

New complexes of fullerenes C60 and C70 with organic donor DBTTF: synthesis, some properties and crystal structure of DBTTF . C60 . C6H6 (DBTTF = dibenzotetrathiafulvalene)

Abstract New complexes of fullerenes C 60 and C 70 with dibenzotetrathiafulvalene (DBTTF), DBTTF·C 60 ·C 6 H 6 , DBTTF·C 60 ·Py and DBTTF·C 70 ·C 6 H 6 , were obtained. The crystal structure of DBTTF·C 60 ·C 6 H 6 was determined. The arrangement of fullerene molecules is approximately simple cubic packing where each C 60 molecule is located in slightly distorted octahedral surrounding. DBTTF molecules have a concave conformation. X-ray photoelectron spectroscopy (XPS) and IR spectroscopy show only weak charge transfer in these compounds. A weak charge transfer band near 900 nm was found in the UV-Vis-NIR absorption spectrum of DBTTF·C 60 ·C 6 H 6 single crystals. DBTTF molecules are coordinated on C 60 ones by π-π and n-π interactions. It was shown that the steric discrepancy between DBTTF and C 60 molecules does not provide favourable conditions for charge transfer in the DBTTF·C 60 ·C 6 H 6 complex.

X-ray absorption fine structure study of the atomic and electronic structure of molybdenum disulfide intercalation compounds with transition metals

Abstract The local structures of ‘host’ and ‘guest’ layers of MoS2 intercalated with M(OH)2 (MMn, Co and Ni) prepared via interaction of single-layer MoS2 dispersions and solutions of M2+ salts were studied by X-ray absorption spectroscopy. According to M K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) results, the electronic structure and atomic environment of the M atoms in the intercalates are similar to that of the crystalline hydroxides M(OH)2. In the Ni intercalate, Mo K-edge EXAFS revealed a structural change of the ‘host’ MoS2 layers similar to that reported for water dispersions of MoS2 single layers. S K-edge XANES data indicate that the change is associated with increased electron density on the S atoms in the matrix. SO42− and Mo″− (4

Alkane oxidation with peroxides catalyzed by cage-like copper( ii ) silsesquioxanes

Isomeric cage-like tetracopper(II) silsesquioxane complexes [(PhSiO1.5)12(CuO)4(NaO0.5)4] (1a), [(PhSiO1.5)6(CuO)4(NaO0.5)4(PhSiO1.5)6] (1b) and binuclear complex [(PhSiO1.5)10(CuO)2(NaO0.5)2] (2) have been studied by various methods. These compounds can be considered as models of some multinuclear copper-containing enzymes. Compounds 1a and 2 are good pre-catalysts for the alkane oxygenation with hydrogen peroxide in air in an acetonitrile solution. Thus, the 1a-catalyzed reaction with cyclohexane at 60 °C gave mainly cyclohexyl hydroperoxide in 17% yield (turnover number, TON, was 190 after 230 min and initial turnover frequency, TOF, was 100 h−1). The alkyl hydroperoxide partly decomposes in the course of the reaction to afford the corresponding ketone and alcohol. The effective activation energy for the cyclohexane oxygenation catalyzed by compounds 1a and 2 is 16 ± 2 and 17 ± 2 kcal mol−1, respectively. Selectivity parameters measured in the oxidation of linear and branched alkanes and the kinetic analysis revealed that the oxidizing species in the reaction is the hydroxyl radical. The analysis of the dependence of the initial reaction rate on the initial concentration of cyclohexane led to a conclusion that hydroxyl radicals attack the cyclohexane molecules in proximity to the copper reaction centers. The oxidations of saturated hydrocarbons with tert-butylhydroperoxide (TBHP) catalyzed by complexes 1a and 2 exhibit unusual selectivity parameters which are due to the steric hindrance created by bulky silsesquioxane ligands surrounding copper reactive centers. Thus, the methylene groups in n-octane have different reactivities: the regioselectivity parameter for the oxidation with TBHP catalyzed by 1a is 1 : 10.5 : 8 : 7. Furthermore, in the oxidation of methylcyclohexane the position 2 relative to the methyl group of this substrate is noticeably less reactive than the corresponding positions 3 and 4. Finally, the oxidation of trans-1,2-dimethylcyclohexane with TBHP catalyzed by complexes 1a and 2 proceeds stereoselectively with the inversion of configuration. The 1a-catalyzed reaction of cyclohexane with H216O2 in an atmosphere of 18O2 gives cyclohexyl hydroperoxide containing up to 50% of 18O. The small amount of cyclohexanone, produced along with cyclohexyl hydroperoxide, is 18O-free and is generated apparently via a mechanism which does not include hydroxyl radicals and incorporation of molecular oxygen from the atmosphere.

C60complexes with dianthracene and triptycene: synthesis and crystal structures

Abstract New molecular complexes of fullerene C 60 with aromatic hydrocarbons TPC·C 60 and DAN·C 60 (C 6 H 6 ) 3 , were obtained. For the first time a three-dimensional packing of fullerene molecules is observed in TPC·C 60 . The DAN·C 60 (C 6 H 6 ) 3 complex has a layered structure with alternating sheets of C 60 and donor molecules. Complexes with strong van der Waals interaction were formed due to the shape concordance between the TPC, DAN and spherical C 60 molecules. XPS spectroscopy of the complexes showed the suppression of π-π * transitions in TPC and DAN phenyl rings in the complexes due to the donor- C 60 interaction.

A Heterometallic (Fe6Na8) Cage-like Silsesquioxane: Synthesis, Structure, Spin Glass Behavior and High Catalytic Activity

The exotic “Asian Lantern” heterometallic cage silsesquioxane [(PhSiO1.5)20(FeO1.5)6(NaO0.5)8(n-BuOH)9.6(C7H8)] (I) was obtained and characterized by X-ray diffraction, EXAFS, topological analyses and DFT calculation. The magnetic property investigations revealed that it shows an unusual spin glass-like behavior induced by a particular triangular arrangement of Fe(III) ions. Cyclohexane and other alkanes as well as benzene can be oxidized to the corresponding alkyl hydroperoxides and phenol, respectively, by hydrogen peroxide in air in the presence of catalytic amounts of complex I and nitric acid. The I-catalyzed reaction of cyclohexane, c-C6H12, with H216O2 in an atmosphere of 18O2 gave a mixture of labeled and non-labeled cyclohexyl hydroperoxides, c-C6H11–16O–16OH and c-C6H11–18O–18OH, respectively, with an 18O incorporation level of ca. 12%. Compound I also revealed high efficiency in the oxidative amidation of alcohols into amides: in the presence of complex I, only 500 ppm of iron was allowed to reach TON and TOF values of 1660 and 92 h−1.

Heterometallic Na6Co3 Phenylsilsesquioxane Exhibiting Slow Dynamic Behavior in its Magnetization

A heterometallic phenylsilsesquioxane [(PhSiO1,5)22(CoO)3(NaO0.5)6]⋅(EtOH)6⋅(H2O) 1 cage architecture of Co(II) ions in a triangular topology exhibits a slow dynamic behavior in its magnetization, induced by the freezing of the spins of individual molecules.

One-pot polymorphism of nonlinear optical materials. First example of organic polytypes

Two nonlinear optical materials 1,1-dicyano-4-(4-dimethylaminophenyl)-1,3-butadiene (I) and 3-methoxydicyanovinylbenzene (II) have been investigated with regard to crystal growth, polymorphism, structure characterization and physical properties. It was found that both compounds form one-pot (concomitant) polymorphs, that might also be described as organic polytypes. Both polymorphs of compounds I and II form identical molecular layers with molecules located in the layer plane. In the two phases of compound I the layers superposition and their sequence differs significantly. This circumstance most probably determines the different color of the two crystal modifications. In the two crystal phases of compound II molecular layers and their superposition types are almost identical. The only difference between the phases is the sequence of the layer superposition. Single crystal and powder X-ray diffraction techniques, powder test for second harmonic generation, UV spectroscopy, and computational methods were used for characterization of these compounds.

Highly Luminescent, Water‐Soluble Lanthanide Fluorobenzoates: Syntheses, Structures and Photophysics, Part I: Lanthanide Pentafluorobenzoates

Highly luminescent, photostable, and soluble lanthanide pentafluorobenzoates have been synthesized and thoroughly characterized, with a focus on Eu(III) and Tb(III) complexes as visible emitters and Nd(III) , Er(III) , and Yb(III) complexes as infrared emitters. Investigation of the crystal structures of the complexes in powder form and as single crystals by using X-ray diffraction revealed five different structural types, including monomeric, dimeric, and polymeric. The local structure in different solutions was studied by using X-ray absorption spectroscopy. The photoluminescence quantum yields (PLQYs) of terbium and europium complexes were 39 and 15 %, respectively; the latter value was increased almost twice by using the heterometallic complex [Tb0.5 Eu0.5 (pfb)3 (H2 O)] (Hpfb=pentafluorobenzoic acid). Due to the effectively utilized sensitization strategy (pfb)(-) →Tb→Eu, a pure europium luminescence with a PLQY of 29 % was achieved.

Layered compounds based on molybdenum disulfide and ruthenium arene complexes

Intercalation compounds of MoS 2 with monomeric or OH-bridged dimeric ruthenium arene cationic complexes have been obtained by interaction of MoS 2 single-layer dispersions with aqueous solutions of [(arene)Ru(H 2 O) 3 ]SO 4 [arene=C 6 H 6 , C 6 H 2 Me 4 -1,2,4,5, C 6 H 4 Me-1-Pr i -4]. The structural arrangement of these intercalation compounds is discussed on the basis of XRD and EXAFS data. The arene ligands are orientated roughly perpendicular to the MoS 2 slabs. Their nature determines the interlayer spacing as well as the intercalated cation content. Heating removes the organic ligands, while ruthenium-containing species remain in the van der Waals space of MoS 2 .

Highly flexible molecule "Chameleon": reversible thermochromism and phase transitions in solid copper(II) diiminate Cu[CF3-C(NH)-CF═C(NH)-CF3]2.

Three thermochromic phases (α, green; β, red; γ, yellow) and six polymorphic modifications (α(1), monoclinic, P2(1)/n, Z = 2; β(1), monoclinic, P2(1)/c, Z = 4; β(2), triclinic, P1[overline], Z = 4; β(3), monoclinic, P2(1)/n, Z = 4; γ(1) and γ(2), tetragonal, P4(2)/n, Z = 4) have been found and structurally characterized for copper(II) diiminate Cu[CF(3)-C(NH)-CF═C(NH)-CF(3)](2) (1). The α phase is stable under normal conditions, whereas the high-temperature β and γ phases are metastable at room temperature and transform slowly into the more stable α phase over several days or even weeks. X-ray diffraction study revealed that the title molecules adopt different conformations in the α, β, and γ phases, namely, staircase-like, twisted, and planar, respectively. The investigation of the α, β, and γ phases by differential scanning calorimetry showed that the three endothermic peaks in the range 283, 360, and 438 K are present on their thermograms upon heating/cooling. The two peaks at 283 and 360 K correspond to the solid-solid phase transitions, and the high-temperature peak at 438 K belongs to the melting process of 1. The temperature and thermal effect of all the observed transitions depend on the prehistory of the crystalline sample obtained. A reversible thermochromic single-crystal-to-single-crystal α(1)<--> β(1) phase transition occurring within a temperature interval of 353-358 K can be directly observed using a CCD video camera of the X-ray diffractometer. A series of other solid-solid α(1)→γ(1), β(2)→γ(1), β(3)→γ(1), and γ(1)<-->γ(2) phase transitions can be triggered in 1 by temperature. It has been suggested that, under equilibrium conditions, the α(1)→γ(1) and β(2)→γ(1) phase transitions should proceed stepwise through the α(1)→β(1)→β(2)→β(3)→γ(1) and β(2)→β(3)→γ(1) stages, respectively. The mechanism of the phase transitions is discussed on the basis of experimental and theoretical data.