Zhanna V. Dobrokhotova

A hybrid halobismuthate light-harvesting material with an optical band gap of 1.70 eV

A new organic–inorganic hybrid material (C15H14N4)BiBr5·H2O with an optical band gap of 2.24 eV, having 1-D chains of bromobismuthate anions in its composition, has been obtained from an aqueous solution and characterized. The partial replacement of Br by I resulted in the formation of a thermally stable (<155 °C) black compound (C15H14N4)BiBrI4·H2O with an optical band gap of 1.70 eV, which can be proposed as a promising light-harvesting material for dye-sensitized solid-state solar cells. Further replacement of Br by I results in the formation of red-orange colored (C15H14N4)BiI5 with a band gap of 2.10 eV.

A Copper–Nitroxide Adduct Exhibiting Separate Single Crystal-to-Single Crystal Polymerization–Depolymerization and Spin Crossover Transitions

A complex cascade of solid-state processes initiated by variation of temperature was found for the heterospin complex [Cu(hfac)2L(Me/Et)] formed in the reaction of copper(II) hexafluoroacetylacetonate [Cu(hfac)2] with stable nitronyl nitroxide 2-(1-methyl-3-ethyl-1H-pyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L(Me/Et)). The cooling of the compound below 260 K initiated a solid-state chemical reaction, which led to a depolymerization of chains and formation of a pair heterospin complex [Cu(hfac)2L(Me/Et)2][[Cu(hfac)2]3L(Me/Et)2]. Further decrease in temperature below 144 K led to a spin transition accompanied by a drastic decrease in the effective magnetic moment from 2.52 to 2.24 μB. When the compound was heated, the order of effects was reversed: at first, the magnetic moment abruptly increased, and then the molecular fragments of the pair cluster united into polymer chains. Two hysteresis loops correspond to this cascade of temperature-induced structural transformations on the experimental dependence μeff(T): one at high (T↑ = 283 K and T↓ = 260 K) and the other at low (T↑ = 161 K, T↓ = 144 K) temperature. The spin transitions were also recorded for the [[Cu(hfac)2]3L(Bu/Et)2] and [[Cu(hfac)2]5L(Bu/Et)4] molecular complexes, which are models of the trinuclear fragment of the {[Cu(hfac)2]3L(Me/Et)2} pair cluster.

Supramolecular aggregation of yttrium thiocyanate with 4,4′-bipyridine

The reaction of yttrium thiocyanate [Y(H2O)5(NCS)3]·H2O with 4,4′-bipyridine (bpy) was studied in various solvents. The complexes [Y(H2O)3EtOH(bpy)(NCS)3]·bpy (1), {(μ-bpy)[Y(H2O)3(NCS)3]2}·3bpy·2(i-PrOH) (2), and [Hbpy]2{(μ-bpy)[Y(H2O)3(NCS)4]2}·bpy (3) were isolated as the main phases (the former from ethanol, and the latter two from i-PrOH). Complex 3 formed also in MeCN and THF. Assemblies 1–3 were identified based on single-crystal and powder X-ray diffraction and IR spectroscopic data. Supramolecular aggregation in 1–3 occurs through OH⋯N(S) hydrogen bonds. Despite different compositions and arrangement of structural units, the crystal structures 1–3 are similar and consist of interpenetrating rectangular 3D networks. Thermal analysis showed that the decomposition of 1–3 occurs in a similar way. Coordinated water and alcohol molecules are eliminated at temperatures below 170 °C; at temperatures above 230 °C, the multistep elimination of bpy and decomposition of NCS take place. Photoluminescent characteristics of 1–3 provide evidence that bpy is involved in the energy transfer resulting in a long-wavelength shift of emission maxima.

Self-assembly and decay of Mn(II) pivalate–phosphonate complexes

A series of new manganese(II) pivalate–phosphonate complexes with various nuclearities (Mn4, Mn10, and Mn20) under aerobic conditions was synthesized by self-assembly of simple reagents. The constitution of polynuclear architectures is affected by the reaction temperature. The structures of the complexes were determined by single crystal X-ray analysis. Magnetic behavior of the compounds points to dominant antiferromagnetic exchange interactions. Antiferromagnetic coupling with JMn–Mn = −0.097(1) cm−1, gMn = 1.993(1) for an equilateral tetrahedron model simulates the magnetic behavior of the tetranuclear complex Mn4 with a cube-like core.

Platinum acetate blue: synthesis and characterization.

Platinum acetate blue (PAB) of the empirical formula Pt(OOCMe)2.5±0.25, a byproduct in the synthesis of crystalline platinum(II) acetate Pt4(OOCMe)8, is an X-ray amorphous substance containing platinum in the oxidation state between (II) and (III). Typical PAB samples were studied with X-ray diffraction, differential thermal analysis-thermogravimetric, extended X-ray absorption fine structure, scanning electron microscopy, transmission electron microscopy, magnetochemistry, and combined quantum chemical density functional theory-molecular mechanics modeling to reveal the main structural features of the PAB molecular building blocks. The applicability of PAB to the synthesis of platinum complexes was demonstrated by the preparation of the new homo- and heteronuclear complexes Pt(II)(dipy)(OOCMe)2 (1), Pt(II)(μ-OOCMe)4Co(II)(OH2) (2), and Pt(III)2(OOCMe)4(O3SPhMe)2 (3) with the use of PAB as starting material.

Multi-walled carbon nanotubes with the pyridine-containing fragment and copper(II) ions

Modified multi-walled carbon nanotubes (MWNT)-CO-L (L = NHCH2C5H4N) were synthesized. The possibility of their interaction with magnetically active binuclear complex Cu2(Piv)4(HPiv)2 was shown. The presence of copper(ii) ions on the surface of the reaction product, {Cu}@MWNT-CO-L, was suggested and confirmed by the data of thermogravimetry combined with mass spectral analysis, ESR spectroscopy, atomic absorption spectrophotometry, and electron microscopy (TEM and SEM).

CCDC 1519452: Experimental Crystal Structure Determination

Related Article: Andrey V. Gavrikov, Pavel S. Koroteev, Nikolay N. Efimov, Zhanna V. Dobrokhotova, Andrey B. Ilyukhin, Andreas K. Kostopoulos, Ana-Maria Ariciu, Vladimir M. Novotortsev|2017|Dalton Trans.|46|3369|doi:10.1039/C6DT04895A

Step-by-step thermal transformations of a new porous coordination polymer [(H{sub 2}O){sub 5}CuBa(Me{sub 2}mal){sub 2}]{sub n} (Me{sub 2}mal{sup 2-}=dimethylmalonate): Thermal degradation to barium cuprate

Abstract The reactions of CuSO4·5H2O, dimethylmalonic acid and Ba(OH)2·H2O (Cu: H2Me2mal: Ba=1: 2: 2) in aqueous and aqueous-ethanol solutions (H2O: EtOH=1: 1) resulted in formation of 3D-porous coordination polymers [(H2O)3(μ-H2O)2CuBa(μ3-Me2mal)(Me2mal)]n (1) and [(μ-H2O)CuBa(μ3-Me2mal)(μ4-Me2mal)]n (2), respectively. It has been shown that compound 2 was an intermediate in the thermal degradation of compound 1. Thorough studies of solid-state thermolysis of 1 and 2 allowed to detect formation of coordination polymer [CuBa(μ4-Me2mal)(μ5-Me2mal)]n (3), structure of which was determined by X-ray powder diffraction. It has been found that the channels in polymer 3 were accessible for guest molecules (MeOH). Theoretical estimation of methanol diffusion barrier was carried out. Complete solid-phase thermolysis of 1 and 2 leads to a mixture of BaCuO2, BaCO3, and CuO. Special conditions for obtaining of a crystalline phase of pure cubic BaCuO2 were determined.