Andrei V. Churakov

H-bond network in amino acid cocrystals with H2O or H2O2. The DFT study of serine-H2O and serine-H2O2.

The structure, IR spectrum, and H-bond network in the serine-H(2)O and serine-H(2)O(2) crystals were studied using DFT computations with periodic boundary conditions. Two different basis sets were used: the all-electron Gaussian-type orbital basis set and the plane wave basis set. Computed frequencies of the IR-active vibrations of the titled crystals are quite different in the range of 10-100 cm(-1). Harmonic approximation fails to reproduce IR active bands in the 2500-2800 frequency region of serine-H(2)O and serine-H(2)O(2). The bands around 2500 and 2700 cm(-1) do exist in the anharmonic IR spectra and are caused by the first overtone of the OH bending vibrations of H(2)O and a combination vibration of the symmetric and asymmetric bendings of H(2)O(2). The quantum-topological analysis of the crystalline electron density enables us to describe quantitatively the H-bond network. It is much more complex in the title crystals than in a serine crystal. Appearance of water leads to an increase of the energy of the amino acid-amino acid interactions, up to ~50 kJ/mol. The energy of the amino acid-water H-bonds is ~30 kJ/mol. The H(2)O/H(2)O(2) substitution does not change the H-bond network; however, the energy of the amino acid-H(2)O(2) contacts increases up to 60 kJ/mol. This is caused by the fact that H(2)O(2) is a much better proton donor than H(2)O in the title crystals.

Synthesis, Structure, Spectroscopic Studies, and Complexation of Novel Crown Ether Butadienyl Dyes

Butadienyl dyes of the benzothiazole series with various fragments of benzocrown ethers 1a-c were synthesized for the first time. The structures and spectral properties of crown-containing butadien ...

Palladium nitrosyl carboxylate complexes X-ray structures of Pd4(μ-NO)2(μ-OCOCMe3)6 and Pd3(NO)2(μ-OCOCF3)4·2C6H5Me

Abstract Two types of palladium nitrosyl carboxylate complexes were synthesized and their structures were characterized by several methods including an X-ray diffraction analysis. The tetranuclear complexes Pd4(μ-NO)2(OCOR)6 (R=CMe3, Me, Ph, CHMe2, CH2Cl, IIa–e, respectively) were synthesized by the reaction of Pd(NO)Cl with silver carboxylates Ag(OCOR). The structure of IIa was determined by a single crystal X-ray diffractometry. Crystals of IIa are monoclinic, space group P21/n, a=12.104(7), b=23.970(8), c=15.495(4) A, β=90.30(4)°, V=4496(4) A3. The least-square structure refinement on F2 was converged to R=0.0714 for 6228 reflections [I>2σ(I)]. In IIa the palladium atoms form near regular rectangle Pd4, with the edges bridged by the ligands. Two bridging NO groups occupying the opposite sides of the rectangle are in the cis-positions with respect to the Pd4 plane. These groups are symmetric, with the PdNO angles ranging from 120.4(5) to 121.8(5)°. The coordination polyhedrons of the Pd atoms are close to square planar ones. The reaction of the Pd4(CO)4(OCOCF3)4 clusters with nitrogen monoxide leads to a substitution of the carbonyl groups and formation of the low stable complex Pd4(NO)4(OCOCF3)4 (III) that was characterized by the spectroscopic and analytical data. The transformation of III during slow recrystallization from toluene gives Pd3(NO)2(OCOCF3)4·2C6H5Me (IV) and palladium black. The structure of IV was determined by an X-ray diffraction analysis. Crystals of IV are monoclinic, space group P21/n, a=9.2340(2), b=9.2859(2), c=18.0460(4) A, β=92.339(1)°, V=1546.08(6) A3. The least-square refinement on F2 was converged to R=0.0205 for 3209 reflections [I>2σ(I)]. In the linear tri-nuclear molecule of IV, any adjacent metal atoms are linked with a couple of the CF3CO2 ligands and are separated by 3.0755(2) A. Additionally, the terminal Pd atoms bear the NO and the η2-toluene ligands. The configuration of the N atoms corresponds to the ideal sp2-hybridization. The PdNO angle is 117.2(2)°. The N atoms form short contacts with the aromatic rings. The distance between the center of the ring and the nitrogen atom is 2.70 A. Complex IV is the first example of the Pd complex with the terminal nitrosyl ligand. The scheme of transformation of complex III to complex IV was proposed.

First enantiopure phosphapalladacycle with planar chirality. X-Ray study of the racemic dimer and (Spl,SCSN)-diastereomer of its prolinate derivative

Abstract The first P , C -cyclopalladated complex with planar chirality was prepared by direct cyclopalladation of prochiral di- tert -butyl(ferrocenylmethyl)phosphine. Resolution of the racemic dimer was achieved through separation of its diastereomeric ( S )-prolinate derivatives. The palladacycle structure was confirmed by the 1 H NMR spectra of the dimer and its triphenylphosphine adduct and an X-ray diffraction study of the racemic dimeric complex. The absolute configuration of the planar chirality was determined by an X-ray diffraction investigation of one of two diastereomers of the ( S )-prolinate derivative.

Supramolecular assemblies of photochromic benzodithia-18-crown-6 ethers in crystals, solutions, and monolayersElectronic supplementary information (ESI) available: crystal data, data collection, and structure solution and refinement parameters. See http://www.rsc.org/suppdata/nj/b1/b110630a/

We studied the assembly of dithiacrown ether styryl dye (CSD) molecules in crystals, solutions, and films in the presence of metal cations. X-Ray diffraction data allowed us to conclude that the anion affects the supramolecular architecture of CSDs in the crystal, specifically, the type of stacking of the dye molecules. In solution, in the presence of Pb2+, CSD molecules with the betaine structure spontaneously form dimeric complexes consisting of two dye molecules and two metal cations, with a fixed mutual arrangement of the double bonds. The dimer complex is stable due to coordination between the anion substituent of one molecule and the metal cation located in the crown ether cavity of the other molecule. Irradiation of the dimer complexes leads to regio- and stereoselective [2 + 2]-cycloaddition, giving only one cyclobutane derivative of the eleven theoretically possible products. The other photoreaction studied for CSDs is reversible Z–E isomerization. Due to its specific structure, the betaine-type CSD is able to form the ‘anion-capped’ Z-isomer. Intramolecular coordination in the ‘anion-capped’ isomer enhances its stability and causes a sharp deceleration of its dark Z–E isomerization. The amphiphilic CSD forms relatively stable monolayers on distilled water and various aqueous salt subphases. The results obtained indicate that it is possible to distinguish between two types of the dye monolayer structures based on the presence of alkali or heavy metal cations in the aqueous subphase.

4-Styrylquinolines: synthesis and study of [2 + 2]-photocycloaddition reactions in thin films and single crystals

Four new (E)-4-styrylquinoline compounds containing two methoxy substituents or an 18-crown-6-ether fragment were synthesized in order to investigate the [2 + 2]-photocycloaddition (PCA) reaction in the solid state. These compounds reveal different abilities to undergo the photoreaction depending on the packing of the quinoline molecules in thin polycrystalline films and single crystals. The only products from the irradiation of (E)-4-styrylquinolines were an rctt isomer of 1,2,3,4-tetrasubstituted cyclobutane and, rarely, a Z isomer of the styrylquinoline. The rctt cyclobutane derivative was formed as a result of the PCA of centrosymmetric syn-‘head-to-tail’ dimeric pairs of the reactant species that are preorganized in such a way as to promote this reaction. Peculiarities in the crystal packing motifs that are typical for single crystals of 4-styrylquinoline compounds are discussed. The solvate molecules can affect significantly the packing of styrylquinolines. Benzene solvate molecules create a soft, flexible, shell about the dimeric pairs that facilitates the PCA in the single crystal without causing degradation of the crystal. In crystal packing that contains CH2Cl2 and H2O solvate molecules, they are prone to form complicated systems of hydrogen bonds with crown-ether oxygen atoms and each other. This results in distorting the organic molecule geometry toward non-planarity and accomplishing a new type of crystal packing uncommon for styrylheterocycles, in which the PCA is impossible. The topochemical single-crystal-to-single-crystal PCA reaction was monitored for one of the species. Two cyclobutane derivatives obtained in single crystals were subjected to recrystallization from a solution. The new single crystals formed belong to different crystal systems, with different unit cell parameters as compared with initial single crystals; significant differences in the geometry of the cyclobutane molecules were also found. This implies that the cyclobutane derivatives obtained in the solid phase have a molecular geometry that is somewhat stressed.

Pharmaceutical Cocrystals of Diflunisal and Diclofenac with Theophylline

Pharmaceutical cocrystals of nonsteroidal anti-inflammatory drugs diflunisal (DIF) and diclofenac (DIC) with theophylline (THP) were obtained, and their crystal structures were determined. In both of the crystal structures, molecules form a hydrogen bonded supramolecular unit consisting of a centrosymmetric dimer of THP and two molecules of active pharmaceutical ingredient (API). Crystal lattice energy calculations showed that the packing energy gain of the [DIC + THP] cocrystal is derived mainly from the dispersion energy, which dominates the structures of the cocrystals. The enthalpies of cocrystal formation were estimated by solution calorimetry, and their thermal stability was studied by differential scanning calorimetry. The cocrystals showed an enhancement of apparent solubility compared to the corresponding pure APIs, while the intrinsic dissolution rates are comparable. Both cocrystals demonstrated physical stability upon storing at different relative humidity.

Titanium complexes based on chiral enantiopure dialkanolamines: synthesis, structures and catalytic activity

New chiral enantiopure tridentate ligands (dialkanolamines) RN(CHR3CR1R2OH)(CHR4CR5R6OH) 10–17 were synthesized by the opening of the epoxide ring by the action of the amines or alkanolamines. Titanium complexes, viz. [RN(CHR3CR1R2O)(CHR4CR5R6O)]Ti(O-i-Pr)218–23 and [RN(CHR3CR1R2O)(CHR4CR5R6O)]2Ti 25–31 were synthesized by treatment of Ti(O-i-Pr)4 with one or two equivalents of corresponding dialkanolamines. Complex (R)-PhCH(Me)N(CH2C(Me)2O)2TiCl2*HNMe224 was obtained from the reaction of one equivalent of dialkanolamine 10 with (Me2N)2TiCl2. The composition and structure of all novel compounds were established by 1H and 13C NMR spectroscopy as well as elemental analysis. The possible solution structures of 18–31 are discussed. The single-crystal X-ray diffraction study of 23, 25–28, 30, 31 indicates monomeric structures in the solid state. Chiral complexes 20, 22, 23, 25, 26, 30 were tested as chiral catalysts in the Abramov reaction and demonstrated moderate enantiomeric activity.

Synthesis and structure of a series of new haloaryl imido complexes of molybdenum

Abstract The synthesis of a series of mono- and bis-haloarylimido molybdenum(VI) complexes is described. Two methods of introducing the electron poor imido functionality are employed, first the condensation of substituted anilines with Na2MoO4 in the presence of Me3SiCl/NEt3, secondly the sulfinyl amine metathesis with [Mo(O)2Cl2(dme)] (1). The latter method works even in cases, when the first one does not work. Crystal structures of three complexes [Mo(NC6F5)(O)Cl2(dme)] (2a), [Mo(N-2,6-Cl2C6H3)2Cl2(dme)] (3b) and [Mo(N-2,4,6-Br3C6H2)2Cl2(dme)] (4) are reported. The unusually small MoNC(Ar) angle of 149.1(5)° has been found in the structure of 4.

New approach to 1-(phenylethynyl)germatranes and 1-(phenylethynyl)-3,7,10-trimethylgermatrane. Reactions of 1-(phenylethynyl)germatrane with N-bromosuccinimide and bromine

Abstract Reaction of N(CH 2 CHRO) 3 GeBr ( 2a, b ) with LiCCPh affords N(CH 2 CHRO) 3 GeCCPh ( 1a , b ) ( a , R=H; b , R=Me). Compound ( 1b ) was also obtained by treatment of Cl 3 GeCCPh ( 3 ) with N(CH 2 CHMeOSnEt 3 ) 3 ( 4 ). ( 1a ) reacts with N -bromosuccinimide to yield N(CH 2 CH 2 O) 3 GeC(Br) 2 C(O)Ph ( 5 ). Cis -N(CH 2 CH 2 O) 3 GeC(Br)C(Br)Ph ( 6 ) is formed by the reaction of 1a with Br 2 in equivalent amounts. All compounds were characterized by 1 H- and 13 C-NMR spectroscopy and mass spectrometry. Single crystal structures of 1a and 6 were determined by X-ray diffraction studies.