Title Compound (title + compound)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


ChemInform Abstract: Titanium(III) Chloride Mediated Synthesis of Furan Derivatives: Synthesis of (.+-.)-Evodone.

CHEMINFORM, Issue 42 2010
S. K. Mandal
Abstract Title compounds (IV) and (VI) including the naturally occurring furanoterpene evodone (IVb) are synthesized by a radical cyclization reaction using titanocene(III) chloride, generated in situ from TiCl2(Cp)2 and zinc dust, as radical source. [source]


ChemInform Abstract: Simple and Efficient Synthesis of 2-Aryl-2,3-dihydroquinolin-4(1H)-ones Using Silica Chloride as a New Catalyst under Solvent-Free Conditions.

CHEMINFORM, Issue 40 2010
M. Muthukrishnan
Abstract Title compounds (II) are also obtained from a similar one-pot reaction between 2-aminoacetophenone and aromatic aldehydes, but yields are only poor. [source]


Vibrational, optical and microhardness studies of trimethoprim DL -malate

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2009
S. Franklin
Abstract Trimethoprim malate, an organic crystal, has been synthesized using slow evaporation method from its aqueous solution. Structural, optical and the mechanical properties of the grown crystal have been investigated by various characterization techniques which include FTIR spectra, single crystal XRD, UV-Vis spectra and Vickers microhardness testing. The structure of the compound predicted by analysing the recorded FTIR spectrum compliments the structure determined using single crystal X-ray diffraction. Single crystal X-ray diffraction study reveals that the crystals are monoclinic [P21/c, a=12.9850 , b=9.3038 , c=15.6815 and ,=111.065]. The UV-Vis spectrum exhibits maximum transparency (98%) for a wide range suggesting the suitability of the title compound for optical applications. The optical constants have been calculated and illustrated graphically. Microhardness tests have been performed on the cystal under study and the Vicker hardness number has been calculated. The work hardening coefficient is found to be 2.85 which suggest that the crystal belongs to the family of soft materials. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Synthesis and crystal structure of a new inorganic , organic complex: (4-ClC7H6NH3)9[Nd(P6O18)2]9H2O

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2007
O. Amri
Abstract Single crystals of (4-ClC7H6NH3)9[Nd(P6O18)2]9H2O were synthesized in aqueous solution. This compound crystallizes in a triclinic P1 unit-cell, with a = 14.898(6), b = 18.049(7), c = 20.695(6), , = 102.04(3), , = 100.49(3), , = 98.82(3), V = 5245(4) 3 and Z = 2. The crystal structure has been solved and refined to R = 0.043 (Rw = 0.061) for 20420 observed reflections. The atomic arrangement of the title compound can be described as infinite layers built by complex of Neodyme [Nd(P6O18)2] and nine water molecules. The organic cations are located in the space delimited by the successive inorganic layers. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Growth and characterisation of potassium cobalt nickel sulfate hexahydrate for UV light filters

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2006
Xinxin Zhuang
Abstract A new single crystal for ultraviolet light filter, KCNSH (Potassium Cobalt Nickel Sulfate Hexahydrate) was designed and its crystal structure was studied using X-ray diffraction in this paper. The empirical of the title compound is K2Co0.1Ni0.9(SO4)2.6H2O with formula weight 437.15. KCNSH crystal belongs to the monoclinic space group P2(1)/c, a=6.1390(3), b=12.1839(6), c=9.0095(4), ,=,=90, ,=105.060(2), V=650.74(5)3, Z=2, Dc=2.231g/cm3. Using the cooling solution method, we have grown a deep green KCNSH crystal with dimension of 121240mm3. The transmission spectrum of KCNSH in the range from UV to near IR wavelengths, its thermal properties, and the relationship between the structure and optical transmission properties are also studied and further discussed in this paper. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Magnetic and Electrochemical Properties of a Heterobridged ,-Phenoxido,,1,1 -Azide Dinickel(II) Compound: A Unique Example Demonstrating the Bridge Distance Dependency of Exchange Integral

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009
Rajesh Koner
Abstract The synthesis, structure, magnetic and electrochemical properties of the heterobridged ,-phenoxido,,1,1 -azide dinickel(II) compound [NiII2(HL1)3(,1,1 -N3)]3H2O (1) derived from the tetradentate Schiff base ligand N -(2-hydroxyethyl)-3-methoxysalicylaldimine (H2L1) are described. The title compound crystallizes in the triclinic system (space group P). Electrochemical analyses reveal that compound 1 exhibits two-step quasireversible couples in the reduction window with E1/2 values of ,1412 and ,1762 mV. The variable-temperature (2,300 K) magnetic susceptibilities at 1 T of the title compound were measured. The interaction between the metal centres is weak ferromagnetic (J = 5.0 cm,1, g = 2.23, D1 = 29.2 cm,1 and D2 = 10.7 cm,1). Comparison of the exchange integral of 1 with that of the only reported ,-phenoxido,,1,1 -azide dinickel(II) compound results in the emergence of a unique example of the dependence of strength of magnetic exchange interaction on the metal,ligand bridge distance. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


A Novel Copper(I) Halide Framework Templated by Organic,Inorganic Hybrid Polyoxometalate Chains Formed In Situ: A New Route for the Design and Synthesis of Porous Frameworks

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2006
Hua Jin
Abstract A 1D organic,inorganic hybrid polyoxometalate chain has been used as a non-coordinating anionic template for the construction of a novel 3D copper halide 4,4,-bipy framework, namely [Cu3ICl(4,4,-bipy)4][CuII(1,10-phen)2Mo8O26]. X-ray diffraction experiments revealed that the title compound consists of chloride-bridged trinuclear CuI units linked by neutral organic 4,4,-bipy groups into a 3D framework with hexagon-like channels in which 1D organic,inorganic hybrid polyoxometalate chains reside. This is the first example of a 1D organic,inorganic hybrid polyoxometalate chain functioning as a novel anionic template for the construction of a 3D framework. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


A New Spherical Metallacryptate Compound [Na{Cu6(Thr)8(H2O)2(ClO4)4}]ClO45,H2O: Magnetic Properties and DFT Calculations

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2005
Sheng-Chang Xiang
Abstract The hexanuclear copper(II) complex with threoninato acid has been synthesized. Its structure can be described as an octahedron cage with D2h symmetry in which six copper ions are bound by eight threoninato acids with a [3.11223130] coordination mode and one Na+ cation being captured within the center of the cage. In contrast with other hexanuclear copper compounds containing amino acids, the title compound has a prolate Cu6 octahedron with the longest axial distance and a rectangle equatorial plane, as well as special coordinated perchlorate ions. Compared with classic cryptate, hexanuclear copper(II) compounds with amino acids can be regarded as a new topologic type of spherical macrotricyclic metallacryptates [2,2,2,2] whose cages have a high selectivity for sodium ions. The analysis of magnetic susceptibility data shows that the threoninato compound has a ground state with spin S = 3. The computing coupling constant between the equatorial Cu centers and the axial ones is 4.4 cm,1,calculated by using DFT methods for a model compound. This is close to three known experimental values of 1.39, 0.56 or 0.43 cm,1 for complexes with 4-hydroxy- L -prolinato, L -prolinato or L -threoninato acid as ligands, respectively. The dominant ferromagnetic interactions for these complexes can be essentially attributed to the orthogonality between the magnetic orbitals, dxz or dyz orbitals for the equatorial CuII centers and d orbitals for the axial ones. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]


In Quest of the Double Rotaxane Formation of the Bis(coronand) (1,5),(2,4)-Durenetetrayl-bis(18-crown-5) with Organomagnesium Compounds

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2004
Gerard P. M. van Klink
Abstract The interaction between the title compound, bis(coronand) 8,and the diarylmagnesium compounds Ph2Mg and (p - tBuC6H4)2Mg in diethyl ether leads to the formation of 1:2 complexes (9 and 10, respectively), irrespective of the initial ratio of the components. In [D8]toluene, the three complex types can be discerned by 1H NMR spectroscopy: double side-on (9a, 10a), side-on/rotaxane (9b, 10b), and, to a very minor extent, double rotaxane (9c, 10c). In the case of 10a and 10b, the temperature dependence showed that rotaxane formation is enthalpically favored at the expense of a more negative entropy. As crystals suitable for structure determination could not be obtained from 9 and 10, the interaction of 8 with the sterically less demanding Hg(SCN)2 was studied. In this case, analogous pseudorotaxanes are formed exclusively, and both the 1:2 complex [8{Hg(SCN)2}2] (11) and its 1:1 analogue 12 were observed. The double rotaxane structure of 11 was confirmed by X-ray crystal structure determination. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Structural Characterization and a New One-Pot Synthesis of trans -Chloro(phenyl)bis(triphenylphosphane)nickel(II)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2003
Alexander Zeller
Abstract trans -[NiCl(Ph)(PPh3)2], the organometallic precursor for a new class of neutral polymerization catalysts, has been synthesized via a new synthetic route. The previously used alkylaluminum compounds are replaced by zinc dust for the reduction of the nickel(II) salt in the presence of triphenylphosphane forming the intermediate Ni(PPh3)4. In a one-pot reaction, chlorobenzene then adds oxidatively to the intermediate to form the title compound, which was structurally characterized, in high yields. Its geometry is compared to known structures of the higher homologues of group 10. All complexes adopt a distorted square-planar geometry, but the parent structure shows significantly shorter metal-ligand bond lengths than its Pd and Pt congeners, as expected. Density functional theory calculations (B3LYP/6,31G*) on the full structure are in very good agreement with the solid-state structure. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]


Dynamic Enzymatic Kinetic Resolution of Methyl 2,3-Dihydro-1H -indene-1-carboxylate

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2009
Jrg Pietruszka
Abstract A new reaction setup for kinetic enzymatic resolution was established and is demonstrated for the case of the hydrolase-catalysed conversion of methyl 2,3-dihydro-1H -indene-1-carboxylate (1) in conjunction with a base-catalysed racemisation. The system allows controlled racemisation, resulting in efficient dynamic kinetic resolution (DKR) of the title compound. Short reaction times and high enantioselectivities were obtained with CAL-B and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene). Compound (R)- 1 (ee 95,%) served as a starting material in a domino reaction that led to the biaryl indanyl ketone (R)- 8, a lead compound for novel inhibitors of peptidyl-prolyl- cis/trans -isomerases, in 94,% ee. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Synthesis of Enantiopure Tricarbonyl(indan-1,2-dione)chromium

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2005
Dirk Leinweber
Abstract A multistep synthesis of the planar chiral tricarbonyl(,6 -indan-1,2-dione)chromium, based on acetal protection of the keto groups, is presented. Since common deacetalization procedures failed, an oxidative deprotection with triphenylcarbenium tetrafluoroborate was used. Tricarbonyl(,6 -indan-1,2-dione)chromium is regarded as a potential precursor for dianionic oxy-Cope rearrangements upon alkenyllithium diaddition. As an unexpected side product in the synthesis, an indan-1,2-dione complex with a triphenylmethyl substituent at C-3 was obtained. Attempts directed towards the formation of enantiomerically pure material include the first reported investigation into an enantioselective ketone reduction with two methoxy substituents present in the , position. Although enantiomeric excesses of up to 84.5,% were achieved, the chemical yields decreased with increasing ee. A classical resolution was therefore undertaken, giving access to the enantiomerically pure title compound (99.4,% ee). The absolute configuration was verified by an X-ray structure analysis of an intermediate. First experiments concerning the alkenyllithium addition showed that a single addition is possible while a second one does not occur, presumably due to enolate formation. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]


Photocyclodimerization of 5-Methyl-2H -pyran-3(6H)-one

HELVETICA CHIMICA ACTA, Issue 12 2008
Ljubov Groesch
Abstract The structures of the main products resulting from photocyclodimerization of the title compound 2 and of other 3-methyl-substituted ,oxacyclohex-2-en-1-ones' (=dihydropyranones) were determined by X-ray crystallography. In connection, the 13C-NMR chemical shifts of the cyclobutane C-atoms of these dimers allow a clear differentiation between head-to-head and head-to-tail regioisomers, all structurally related to those of isophorone (1). [source]


Facile synthesis of 3-spiroindolines

HETEROATOM CHEMISTRY, Issue 3 2002
Yehia A. Allam
Cyanoacetyldiazoindol-2-one (3), the condensation product of cyanoacetohydrazide with isatin (1), could be cyclized in acidic medium via its CN group and its enolic OH to give cyanomethyloxadiazole-spiroindoline (4). The presence of the methylcyano side chain could be invested,through oximation, diazotization, or condensation with aldehydes,to form polyfunctional spiroindolines 5, 8,10. Also, a second route for preparing the title compound could be achieved through a nucleophilic attack on position 3 in the isatin derivatives, followed by subsequent ring closure to give 6 and 7. 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:207,210, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10020 [source]


Efficient Synthesis of Either Enantiomer of Ethyl 5-Hydroxyhept-6-enoate

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8-9 2007
Thomas Fischer
Abstract The application of alcohol dehydrogenases as a key-step for the synthesis of the title compound is reported. 5-Hydroxyhept-6-enoates are versatile intermediates, e.g., for the synthesis of a variety of arachidonic acid metabolites. [source]


A practical and stereoselective synthesis of (+/,)- trans -4-benzyloctahydropyrrolo[3,4- b][1,4]oxazine

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2010
Daniel P. Walker
trans -Octahydropyrrolo[3,4- b][1,4]oxazine is an important heterocycle within the pharmaceutical industry for the preparation of biologically active analogs, including the phase III drug, finafloxacin. A practical synthesis of the title compound (2) is described in eight steps and ca. 10% overall yield. The key synthetic step is the formation of the pyrrolo[3,4- b][1,4]oxazine core 20via a one pot double N -alkylation of the corresponding bis-tosylate 18 with 4-nitrobenzenesulfonamide. Subsequent removal of the nosyl group occurred under mild conditions. J. Heterocyclic Chem., (2010). [source]


Aromatization and ring cyclization: A better understanding on the ring cyclization mechanism of 3-amino-6-hydrazino-1,2,4-triazin-5(2H)-one reacted with acetic acid in N,N -dimethylformamide

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2005
Long-Chih Hwang
In this paper we report that the title compound (3) reacts with excess N,N -dimethylformamide (DMF) containing two equivalents of acetic acid to afford 6-amino-1,2,4-triazolo[3,4- f][1,2,4]triazin-8(7H)-one (1). When 3-amino-2-benzyl-6-hydrazino-1,2,4-triazin-5(2H)-one (6), the N-2 benzylated derivative of 3, is treated under the same conditions, ring cyclization does not occur; instead, 3-amino-2-benzyl-6-(2-formyl-hydrazino)-1,2,4-triazin-5(2H)-one (7) is formed. Single-crystal X-ray analysis of a 3-ethyl derivative of compound 1 reveals the predominant tautomeric structure to be the 7H -tautomer (7H - 1). From these results, we propose a reasonable cyclization mechanism that incorporates two important points: (1) the tautomerism of the N-2 hydrogen with the C-5 oxo group aromatizes the 1,2,4-triazine ring, and (2) the DMF is proto-nated by acetic acid on the nitrogen atom, then deamination occurs where DMF is attacked by the 6-hydrazino group of 3 or 6. [source]


Synthesis of 1-(3,4-dimethoxyphenylmethyl)-3-phenyl-6,7,8-trimethoxy-3,4-dihydroisoquinoline

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2005
Adriana F. Ibaez
In an attempt to ascertain the scope of using ethyl polyphosphate in the Bischler-Napieralsky annelation reaction, a title compound was synthesized and reduced to the respective 1-(3,4-dimethoxyphenylmethyl)-3-phenyl-6,7,8-trimethoxy-1,2,3,4-tetrahydroisoquinoline. [source]


A short synthesis of 5,7-bis(dialkylamino)-2-methyl- 8 -hydroxyquinolines

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2001
George B. Okide
The bromine atoms of the title compound were replaced by the requisite amino compound to afford the desired derivatives in high yields. Thus, six target compounds viz- bis(diethylamino)-, bis(dibutylamino)-, bis(dicyclohexylamino)-, dipyrrolidino-, dipiperidino-, and dipiperazino-derivatives were obtained and characterized by spectral and elemental analyses. [source]


Synthesis of 13C3 -hydroxyacetone

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 9 2003
Christopher W. Dicus
Abstract 13C3 -Hydroxyacetone is prepared in three steps from 13C2 -2-bromoacetic acid. Bromide displacement by sodium p -methoxybenzyl alkoxide followed by treatment of the carboxylic acid with 13C-methyl lithium furnishes PMB-protected hydroxyacetone. Deprotection using DDQ delivers the title compound. Copyright 2003 John Wiley & Sons, Ltd. [source]


Structural, spectroscopic, and theoretical studies of a very short OHO hydrogen bond in bis(4-(N -methylpiperidinium)-butyrate) hydrobromide

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2009
bieta Bartoszak-Adamska
Abstract The molecular structure of bis(4-(N -methylpiperidinium)-butyrate) hydrobromide, (MPBu)2HBr, has been characterized by single crystal X-ray diffraction, infrared and NMR spectroscopies, and by DFT calculations. The crystals of the title compound at 140,K are monoclinic, space group C2/c, with a,=,11.7118(4), b,=,7.8737(2), c,=,23.9240(8),3,, ,,=,90.431(3), V,=,2206.1(1),3, and Z,=,4. Two 4-(N -methylpiperidinium)-butyrate moieties are joined by a very short and centrosymmetric O.H.O hydrogen bond of 2.436(2),3,. The piperidine ring adopts a chair conformation with the methyl group in the equatorial and the bulky (CH2)3COO substituent in the axial position. The broad absorption band below 1500,cm,1 in the FTIR spectrum confirms the existence of a very short O,H,O hydrogen bond. The 1H and 13C NMR spectra are interpreted on the basis of 2D experiments and the calculated GIAO/B3LYP/6-31G(d,p) magnetic isotropic shielding tensors. In the optimized structure of the complex, a 4-(N -methylpiperidinium)-butyrate zwitterion interacts with a 4-(N -methylpiperidinium)-butyric acid cation forming an O,. HO hydrogen bond of 2.580,3,. Copyright 2008 John Wiley & Sons, Ltd. [source]


Matrix dependence of blue light emission from a novel NH2 -functionalized dicyanoquinodimethane derivative

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2006
Marek Szablewski
Abstract The reactions of primary and secondary amines with (cyclohexa-2,5-diene-1,4-diylidene)-dimalononitrile (TCNQ) lead to mono- and disubstituted dicyanoquinodimethane derivatives and fluorescence emission has been observed for several of these compounds. We report the luminescence properties, synthesis and crystal structure of the novel dicyanoquinodimethane derivative 2-{4-[amino-(2,6-dimethyl-morpholin-4-yl)-methylene]-cyclohexa-2,5- dienylidene}-malononitrile (Ammor), a unique example of an asymmetric dicyanoquinodimethane derivative in which one of the nitrile groups has been replaced with an NH2 moiety, which provides a reactive centre for potential further substitution or tethering to larger molecules or polymers. The luminescence properties of the title compound were investigated in a variety of environments, including alcohol solutions at room temperature and a glass-forming solvent at low temperature. The fluorescence quantum yields and Stokes' shifts of the blue emission were found to be very sensitive to the matrix. The crystal structure of the subject compound was determined, revealing that the molecules are non-planar in the ground state. The environmentally sensitive emission is discussed in terms of the conformational change during photoexcitation and the constraint imposed on this by the matrix. This behaviour is also compared with that of other related amino-functionalized dicyanoquinodimethane derivatives. Copyright 2006 John Wiley & Sons, Ltd. [source]


Density functional theory calculations and vibrational spectra of p -bromonitrobenzene

JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009
V. Krishnakumar
Abstract FT-IR and FT-Raman spectra of p -bromonitrobenzene (p-BNB) have been recorded in the region 4000,400 cm,1 and 4000,50 cm,1, respectively. The molecular structure, geometry optimization, vibrational wavenumbers have been investigated. The spectra were interpreted with the aid of normal coordinate analysis based on the density functional theory (DFT) using the standard B3LYP/6-31G method and basis set combination and was scaled using multiple scale factors yielding good agreement between observed and calculated wavenumbers. The results of the calculations are applied to simulate infrared and Raman spectra of the title compound which showed reasonable agreement with the observed spectra. Copyright 2009 John Wiley & Sons, Ltd. [source]


Conformational polymorphism in a Schiff-base macrocyclic organic ligand: an experimental and theoretical study

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2010
Leonardo Lo Presti
Polymorphism in the highly flexible organic Schiff-base macrocycle ligand 3,6,9,17,20,23-hexa-azapentacyclo(23.3.1.111,15.02,6.016,20)triaconta-1(29),9,11,13,15(30),23,25,27-octaene (DIEN, C24H30N6) has been studied by single-crystal X-ray diffraction and both solid-state and gas-phase density functional theory (DFT) calculations. In the literature, only solvated structures of the title compound are known. Two new polymorphs and a new solvated form of DIEN, all obtained from the same solvent with different crystallization conditions, are presented for the first time. They all have symmetry, with the macrocycle positioned on inversion centres. The two unsolvated polymorphic forms differ in the number of molecules in the asymmetric unit Z,, density and cohesive energy. Theoretical results confirm that the most stable form is (II), with Z, = 1.5. Two distinct molecular conformations have been found, named `endo' or `exo' according to the orientation of the imine N atoms, which can be directed towards the interior or the exterior of the macrocycle. The endo arrangement is ubiquitous in the solid state and is shared by two independent molecules which constitute an invariant supramolecular synthon in all the known crystal forms of DIEN. It is also the most stable arrangement in the gas phase. The exo form, on the other hand, appears only in phase (II), which contains both the conformers. Similarities and differences among the occurring packing motifs, as well as solvent effects, are discussed with the aid of Hirshfeld surface fingerprint plots and correlated to the results of the energy analysis. A possible interconversion path in the gas phase between the endo and the exo conformers has been found by DFT calculations; it consists of a two-step mechanism with activation energies of the order of 30,40,kJ,mol,1. These findings have been related to the empirical evidence that the most stable phase (II) is also the last appearing one, in accordance with Ostwald's rule. [source]


Charge-density analysis of the ground state of a photochromic 1,10-phenanthroline zinc(II) bis(thiolate) complex

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2010
Stephan Scheins
The charge density of the title compound was determined at 90,K, using a spherical crystal of 150,m diameter. The proper treatment of the Zn atom in the pseudo-tetrahedral environment is considered in detail. A satisfactory refinement is only obtained when anharmonic Gram,Charlier parameters are included as variables in the refinement. A successful combined anharmonic/multipole refinement indicates a small polarization of the 4s shell in the anisotropic environment. One of the two toluenethiols is approximately ,-stacked with the phenanthroline ligand. A bond path is found connecting the two ligands. In addition the Zn,S bond to this ligand is slightly extended compared with the same bond to the second toluenethiol. A separate photocrystallographic and theoretical study indicates the long wavelength emission of the title compound to be due to a ligand-to-ligand charge transfer (LLCT) from a toluenethiol to the phenanthroline ligand. The charge-density results do not provide a basis for deciding which of the thiole ligands is the source of the transferred electron density. This result is in agreement with the theoretical calculations, which show comparable oscillator strengths for charge transfer from either of the ligands. [source]


Polymorphism of 4-bromobenzophenone

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2007
Mikhail A. Strzhemechny
A combination of single-crystal and powder X-ray diffractometry was used to study the structure of two polymorphs of 4-bromobenzophenone over the temperature range from 100 to 300,K. One of the polymorphs of the title compound was known previously and its structure has been determined at room temperature [Ebbinghaus et al. (1997). Z. Kristallogr.212, 339,340]. Two crystal growth methods were employed, one of which (a modification of the Bridgman,Stockbarger technique) resulted in single crystals of a previously unknown structure. The basic physical properties of the stable polymorph are: growth method, from 2-propanol solutions or gradient sublimation; space group, monoclinic P21/c; melting point, Tm = 355.2,K; X-ray density (at 100,K), Dx = 1.646,g,cm,3. The same properties of the metastable polymorph (triclinic ) are: growth method, modified Bridgman,Stockbarger method; X-ray density (at 100,K), Dx = 1.645,g,cm,3; Tm = 354,K. Thermograms suggest that the melting of the metastable form is accompanied by at least a partial crystallization presumably into the monoclinic form; the transformation is therefore monotropic. Analysis of short distances in both polymorphs shows that numerous weak hydrogen bonds of the C,H,, type ensure additional stabilization within the respective planes normal to the longest dimension of the molecules. The strong temperature dependence of the lattice constants and of the weak bond distances in the monoclinic form suggest that the weak bond interactions might be responsible for both the large thermal expansion within plane bc and the considerable thermal expansion anisotropy. [source]


Structure and hydrogen bonding in 2,4-dihydroxybenzoic acid at 90, 100, 110 and 150,K; a theoretical and single-crystal X-ray diffraction study

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2007
Andrew Parkin
A new polymorph of 2,4-dihydroxybenzoic acid is reported. The structure was characterized by multiple-temperature X-ray diffraction and solid-state DFT computations. The material shows a geometric pattern of hydrogen bonding consistent with cooperativity between the intermolecular carboxylic acid dimer and intramolecular hydrogen bonds. The presence of proton disorder within this hydrogen-bond system, which would support such a cooperative model, was not fully ruled out by the initial X-ray studies. However, solid-state calculations on the three possible end-point tautomers indicate that the dominant crystallographically observed configuration is substantially lower in energy than the other tautomers (by at least 9,kJ,mol,1), indicating that no disorder should be expected. It is therefore concluded that no disorder is observed either in the intra- or intermolecular hydrogen bonds of the title compound and that the cooperativity between the hydrogen bonds is not present within the temperature range studied. [source]


Poly[bis(,-benzene-1,4-dicarboxylato)bis[,-6-(4-pyridyl)-5H -imidazolo[4,5- f][1,10]phenanthroline]dilead(II)]: an interpenetrating ,-Po net

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
Zhan-Lin Xu
The asymmetric unit of the title compound, [Pb2(C8H4O4)2(C18H11N5)2]n, contains two PbII atoms, two benzene-1,4-dicarboxylate (1,4-bdc) dianions and two 6-(4-pyridyl)-5H -imidazolo[4,5- f][1,10]phenanthroline (L) ligands. Each PbII atom is eight-coordinated by three N atoms from two different L ligands and five carboxylate O atoms from three different 1,4-bdc dianions. The two 1,4-bdc dianions (1,4-bdc1 and 1,4-bdc2) show different coordination modes. Each 1,4-bdc1 coordinates to two PbII atoms in a chelating bis-bidentate mode. Each carboxylate group of the 1,4-bdc2 anion connects two PbII atoms in a chelating,bridging tridentate mode to form a dinuclear unit. Neighbouring dinuclear units are connected together by the aromatic backbone of the 1,4-bdc dianions and the L ligands into a three-dimensional six-connected ,-polonium framework. The most striking feature is that two identical three-dimensional single ,-polonium nets are interlocked with each other, thus leading directly to the formation of a twofold interpenetrated three-dimensional ,-polonium architecture. The framework is held together in part by strong N,H...O hydrogen bonds between the imidazole NH groups of the L ligands and the carboxylate O atoms of 1,4-bdc dianions within different ,-polonium nets. [source]


Supramolecular interactions in the 2,6-bis(benzimidazol-2-yl)pyridine,terephthalic acid,water (2/1/4) cocrystal

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
Hailian Xiao
In the title compound, 2C19H13N5C8H6O44H2O, the terephthalic acid molecule lies on a crystallographic inversion centre and the H atoms of one water molecule exhibit disorder. The maximum deviation of any atom from the mean plane through the C and N atoms of the 2,6-bis(benzimidazol-2-yl)pyridine molecule is only 0.161,(4),. In the crystal structure, the water molecules play an important role in linking the other molecules via hydrogen bonding. The structure forms a three-dimensional framework via strong intermolecular hydrogen bonding. In addition, there are ,,, stacking interactions between the imidazole, pyridine and benzene rings. [source]


10-Benzyl-4-oxo-2,3,4,10-tetrahydropyrimido[4,5- b]quinolin-2-iminium chloride sesquihydrate: a polarized electronic structure within a complex hydrogen-bonded sheet structure

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
Jorge Trilleras
In the title compound, C18H15N4O+Cl,1.5H2O, one water site is fully ordered with unit occupancy while the other, which lies close to an inversion centre in the space group C2/c, has only 0.5 occupancy. The cation exhibits bond fixation in the fused carbocyclic ring and electronic polarization in the terminal heterocyclic ring. The components are linked into complex sheets by a combination of N,H...O, N,H...Cl, O,H...O, O,H...Cl and C,H...O hydrogen bonds. [source]