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Two-dimensional Sheets (two-dimensional + sheet)
Selected AbstractsEpitaxial graphene: a new materialPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2008Th. Seyller Abstract Graphene, a two-dimensional sheet of sp2 -bonded carbon arranged in a honeycomb lattice, is not only the building block of fullerenes, carbon nano tubes (CNTs) and graphite, it also has interesting properties, which have caused a flood of activities in the past few years. The possibility to grow graphitic films with thicknesses down to a single graphene layer epitaxially on SiC{0001} surfaces is promising for future applications. The two-dimensional nature of epitaxial graphene films make them ideal objects for surface science techniques such as photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy. The present article summarizes results from recent photoemission studies covering a variety of aspects such as the growth of epitaxial graphene and few layer graphene, the electronic and structural properties of the interface to the SiC substrate, and the electronic structure of the epitaxial graphene stacks. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A pair of diastereomeric 1:2 salts of (R)- and (S)-2-methylpiperazine with (2S,3S)-tartaric acidACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010Hiroshi Katagiri The crystal structures of a pair of diastereomeric 1:2 salts of (R)- and (S)-2-methylpiperazine with (2S,3S)-tartaric acid, namely (R)-2-methylpiperazinediium bis[hydrogen (2S,3S)-tartrate] monohydrate, (I), and (S)-2-methylpiperazinediium bis[hydrogen (2S,3S)-tartrate] monohydrate, (II), both C5H14N22+·2C4H5O6,·H2O, each reveal the formation of well-defined head-to-tail-connected hydrogen tartrate chains; these chains are linked into a two-dimensional sheet via intermolecular hydrogen bonds involving hydroxy groups and water molecules, resulting in a layer structure. The (R)-2-methylpiperazinediium ions lie between the hydrogen tartrate layers in the most stable equatorial conformation in (I), whereas in (II), these ions are in an unstable axial position inside the more interconnected layers and form a larger number of intermolecular hydrogen bonds than are observed in (I). [source] Two two-dimensional hydrogen-bonded coordination networks: bis(3-carboxybenzoato-,O)bis(4-methyl-1H -imidazole-,N3)copper(II) and bis(3-methylbenzoato-,N)bis(4-methyl-1H -imidazole-,N3)copper(II) monohydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Ziliang Wang The title two-dimensional hydrogen-bonded coordination compounds, [Cu(C8H5O4)2(C4H6N2)2], (I), and [Cu(C8H7O2)2(C4H6N2)2]·H2O, (II), have been synthesized and structurally characterized. The molecule of complex (I) lies across an inversion centre, and the Cu2+ ion is coordinated by two N atoms from two 4-methyl-1H -imidazole (4-MeIM) molecules and two O atoms from two 3-carboxybenzoate (HBDC,) anions in a square-planar geometry. Adjacent molecules are linked through intermolecular N,H...O and O,H...O hydrogen bonds into a two-dimensional sheet with (4,4) topology. In the asymmetric part of the unit cell of (II) there are two symmetry-independent molecules, in which each Cu2+ ion is also coordinated by two N atoms from two 4-MeIM molecules and two O atoms from two 3-methylbenzoate (3-MeBC,) anions in a square-planar coordination. Two neutral complex molecules are held together via N,H...O(carboxylate) hydrogen bonds to generate a dimeric pair, which is further linked via discrete water molecules into a two-dimensional network with the Schläfli symbol (43)2(46,66,83). In both compounds, as well as the strong intermolecular hydrogen bonds, ,,, interactions also stabilize the crystal stacking. [source] Two novel silver(I) coordination polymers: poly[(,2 -2-aminopyrimidine-,2N1:N3)bis(,3 -thiocyanato-,3S:S:S)disilver(I)] and poly[(2-amino-4,6-dimethylpyrimidine-,N)(,3 -thiocyanato-,3N:S:S)silver(I)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Geng-Geng Luo 2-Aminopyrimidine (L1) and 2-amino-4,6-dimethylpyrimidine (L2) have been used to create the two novel title complexes, [Ag2(NCS)2(C4H5N3)]n, (I), and [Ag(NCS)(C6H9N3)]n, (II). The structures of complexes (I) and (II) are mainly directed by the steric properties of the ligands. In (I), the L1 ligand is bisected by a twofold rotation axis running through the amine N atom and opposite C atoms of the pyrimidine ring. The thiocyanate anion adopts the rare ,3 -,3S coordination mode to link three tetrahedrally coordinated AgI ions into a two-dimensional honeycomb-like 63 net. The L1 ligands further extend the two-dimensional sheet to form a three-dimensional framework by bridging AgI ions in adjacent layers. In (II), with three formula units in the asymmetric unit, the L2 ligand bonds to a single AgI ion in a monodentate fashion, while the thiocyanate anions adopt a ,3 -,1N,,2S coordination mode to link the AgL2 subunits to form two-dimensional sheets. These layers are linked by N,H...N hydrogen bonds between the noncoordinated amino H atoms and both thiocyanate and pyrimidine N atoms. [source] Poly[[diaqua-,-4,4,-bipyridine-dinitratodi-,- l -tyrosinato-dicopper(II)]: a chiral two-dimensional coordination polymerACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Shuo Zhang The title compound, [Cu2(C9H10NO3)2(NO3)2(C10H8N2)(H2O)2]n, contains CuII atoms and l -tyrosinate (l -tyr) and 4,4,-bipyridine (4,4,-bipy) ligands in a 2:2:1 ratio. Each Cu atom is coordinated by one amino N atom and two carboxylate O atoms from two l -tyr ligands, one N atom from a 4,4,-bipy ligand, a monodentate nitrate ion and a water molecule in an elongated octahedral geometry. Adjacent Cu atoms are bridged by the bidentate carboxylate groups into a chain. These chains are further linked by the bridging 4,4,-bipy ligands, forming an undulated chiral two-dimensional sheet. O,H...O and N,H...O hydrogen bonds connect the sheets in the [100] direction. This study offers useful information for the engineering of chiral coordination polymers with amino acids and 4,4,-bipy ligands by considering the ratios of the metal ion and organic components. [source] A two-dimensional lanthanide coordination framework with a new amide-type tripodal ligand,2,2,,2,-nitrilotris{[(2,-benzylaminoformyl)phenoxy]ethyl}amineCHINESE JOURNAL OF CHEMISTRY, Issue 6 2004Jun Fan Abstract The La(III) complex with a new amide-type tripodal ligand,2,2,.2,-nitrilotris{[(2,-benzylaminofomyl)-phenoxylethyl)amine (L), was synthesized and characterized by X-ray crystallographic analysis. Crystal data: C48H55.50LaN7O18.75, Mr=1169.40, monoclinic. space group, P21/n, a= 1.0644(3) nm. b=2.3889(5) nm, c= 2.1917(5) nm, ,=90.65°, V=5.573(2) nm3, Z=1, Dc=1.394 g°cm,3, R1=0.0487, wR [1>2s,(I)]=0.1266. The results reveal that each La(III) ion binds to 9 oxygen atoms, three of which belong to carbonyl groups from three tripodal ligands and six to three bidentate nitrate groups and a two-dimensional sheet of 4.82 networks is assembled by metal-ligand coordination interaction. L, a heptadentate compound, merely acts as a tridentate bridging spacer due to its steric hindrance and links the La(III) ions as three-connected nodes. [source] Structural characterization of anhydrous naloxone- and naltrexone hydrochloride by high resolution laboratory X-ray powder diffraction and thermal analysisJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2007Kunihisa Sugimoto Abstract The crystal structures of the analgesic compounds anhydrous naloxone and naltrexone hydrochloride were determined ab initio from high resolution laboratory X-ray powder diffraction data. Both compounds crystallize in the orthorhombic space group P212121 with lattice parameters of a,=,14.6588(10) Å, b,=,17.4363(9) Å, c,=,7.96200(22) Å, and V,=,2035.06(23) Å3 for naloxone hydrochloride and a,=,15.4560(5) Å, b,=,14.9809(4) Å, c,=,7.84121(18) Å, and V,=,1815.58(11) Å3 for naltrexone hydrochloride. The crystal structure of anhydrous naloxone hydrochloride forms one-dimensional chains through hydrogen bonds. In the crystal structure of anhydrous naltrexone hydrochloride, two-dimensional sheets are formed by hydrogen bonds. The dehydration processes of naloxone hydrochloride dehydrate and naltrexone hydrochloride tetrahydrate was analyzed by DTA, DSC, TG, and MG. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 3316,3323, 2007 [source] Hydrated salts of 3,5-dihydroxybenzoic acid with organic diamines: hydrogen-bonded supramolecular structures in two and three dimensionsACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2001Colin J. Burchell The trigonally trisubstituted acid 3,5-dihydroxybenzoic acid forms hydrated salt-type adducts with organic diamines. In 1,4-diazabicyclo[2.2.2]octane,3,5-dihydroxybenzoic acid,water (1/1/1) (1), where Z, = 2 in P21/c, the constitution is [HN(CH2CH2)3N]+·[(HO)2C6H3COO],·H2O: the anions and the water molecules are linked by six O,H,O hydrogen bonds to form two-dimensional sheets and each cation is linked to a single sheet by one O,H,N and one N,H,O hydrogen bond. Piperazine,3,5-dihydroxybenzoic acid,water (1/2/4) (2) and 1,2-diaminoethane,3,5-dihydroxybenzoic acid,water (1/2/2) (3) are also both salts with constitutions [H2N(CH2CH2)2NH2]2+·2[(HO)2C6H3COO],·4H2O and [H3NCH2CH2NH3]2+·2[(HO)2C6H3COO],·2H2O, respectively. Both (2) and (3) have supramolecular structures which are three-dimensional: in (2) the anions and the water molecules are linked by six O,H,O hydrogen bonds to form a three-dimensional framework enclosing large centrosymmetric voids, which contain the cations that are linked to the framework by two N,H,O hydrogen bonds; in (3) the construction of the three-dimensional framework requires the participation of cations, anions and water molecules, which are linked together by four O,H,O and three N,H,O hydrogen bonds. [source] Z and E isomers of butenedioic acid with 2-amino-1,3-thiazole: 2-amino-1,3-thiazolium hydrogen maleate and 2-amino-1,3-thiazolium hydrogen fumarateACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2010Jain John Maleic acid and fumaric acid, the Z and E isomers of butenedioic acid, form 1:1 adducts with 2-amino-1,3-thiazole, namely 2-amino-1,3-thiazolium hydrogen maleate (2ATHM), C3H5N2S+·C4H3O4,, and 2-amino-1,3-thiazolium hydrogen fumarate (2ATHF), C3H5N2S+·C4H3O4,, respectively. In both compounds, protonation of the ring N atom of the 2-amino-1,3-thiazole and deprotonation of one of the carboxyl groups are observed. The asymmetric unit of 2ATHF contains three independent ion pairs. The hydrogen maleate ion of 2ATHM shows a short intramolecular O,H...O hydrogen bond with an O...O distance of 2.4663,(19),Å. An extensive hydrogen-bonded network is observed in both compounds, involving N,H...O and O,H...O hydrogen bonds. 2ATHM forms two-dimensional sheets parallel to the ab plane, extending as independent parallel sheets along the c axis, whereas 2ATHF forms two-dimensional zigzag layers parallel to the bc plane, extending as independent parallel layers along the a axis. [source] Poly[,8 -4,4,-bipyridine-2,2,,6,6,-tetracarboxylato-dilead(II)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Su-Ping Zhou The PbII cation in the title compound, [Pb2(C14H4N2O8)]n, is seven-coordinated by one N atom and six O atoms from four 4,4,-bipyridine-2,2,,6,6,-tetracarboxylate (BPTCA4,) ligands. The geometric centre of the BPTCA4, anion lies on an inversion centre. Each pyridine-2,6-dicarboxylate moiety of the BPTCA4, ligand links four PbII cations via its pyridyl N atom and two carboxylate groups to form two-dimensional sheets. The centrosymmetric BPTCA4, ligand then acts as a linker between the sheets, which results in a three-dimensional metal,organic framework. [source] Three-dimensional hydrogen-bonded structures in the 1:1 proton-transfer compounds of l -tartaric acid with the associative-group monosubstituted pyridines 3-aminopyridine, 3-carboxypyridine (nicotinic acid) and 2-carboxypyridine (picolinic acid)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010Graham Smith The 1:1 proton-transfer compounds of l -tartaric acid with 3-aminopyridine [3-aminopyridinium hydrogen (2R,3R) -tartrate dihydrate, C5H7N2+·C4H5O6,·2H2O, (I)], pyridine-3-carboxylic acid (nicotinic acid) [anhydrous 3-carboxypyridinium hydrogen (2R,3R)-tartrate, C6H6NO2+·C4H5O6,, (II)] and pyridine-2-carboxylic acid [2-carboxypyridinium hydrogen (2R,3R)-tartrate monohydrate, C6H6NO2+·C4H5O6,·H2O, (III)] have been determined. In (I) and (II), there is a direct pyridinium,carboxyl N+,H...O hydrogen-bonding interaction, four-centred in (II), giving conjoint cyclic R12(5) associations. In contrast, the N,H...O association in (III) is with a water O-atom acceptor, which provides links to separate tartrate anions through Ohydroxy acceptors. All three compounds have the head-to-tail C(7) hydrogen-bonded chain substructures commonly associated with 1:1 proton-transfer hydrogen tartrate salts. These chains are extended into two-dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three-dimensional hydrogen-bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet struture of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O-atom acceptors of the primary tartrate chains, closing conjoint cyclic R44(8), R34(11) and R33(12) associations. Also, in (II) and (III) there are strong cation carboxyl,carboxyl O,H...O hydrogen bonds [O...O = 2.5387,(17),Å in (II) and 2.441,(3),Å in (III)], which in (II) form part of a cyclic R22(6) inter-sheet association. This series of heteroaromatic Lewis base,hydrogen l -tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two-dimensional hydrogen-bonded hydrogen tartrate or hydrogen tartrate,water sheet substructures which are expanded into three-dimensional frameworks via peripheral cation bifunctional substituent-group crosslinking interactions. [source] Asymmetric ruthenium-catalysed [2+2] cycloadditions between bicyclic alkenes and chiral aryl-substituted acetylenic acyl camphorsultam alkynesACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Jordan D. Goodreid The regio- and absolute stereochemistry of (7S)- N -[4-(3-thienyl)tricyclo[4.2.1.02,5]non-3-en-3-ylcarbonyl]-2,10-camphorsultam tetrahydrofuran hemisolvate, C24H29NO3S2·0.5C4H8O, and (7S)- N -[4-(4-tolyl)tricyclo[4.2.1.02,5]non-3-en-3-ylcarbonyl]-2,10-camphorsultam, C27H33NO3S, have been established. One contains a half-occupancy tetrahydrofuran solvent molecule located on a twofold axis and the other contains two crystallographically unique molecules which are nearly identical. The extended structures of both complexes can be explained via weak C,H...O interactions, which link the molecules together into two-dimensional sheets in the ab plane for the thienyl complex and ultimately into a three-dimensional structure for the tolyl derivative. The stereochemistry of both structures confirms that [2+2] cycloadditions of bicyclic alkenes and alkynes catalysed by ruthenium are exclusively exo. [source] 5-Amino-1-naphthol: two-dimensional sheets built up from R44(18) rings formed by O,H...N, N,H...O and ,,, interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Ewa Rozycka-Sokolowska The crystal structure of the title compound, C10H9NO, (I), contains intermolecular O,H...N and N,H...O hydrogen bonds which together form sheets parallel to the (001) plane containing rings with an unusual R44(18) motif. These rings are additionally stabilized by an intermolecular ,,, stacking interaction. The significance of this study lies in the comparison drawn between the molecular structure of (I) and those of related compounds (1,5-diaminonaphthalene, 8-amino-2-naphthol, 3-amino-2-naphthol and aniline), which shows a close similarity in the noncoplanar orientation of the amine group and the aromatic moiety. Comparison of the crystal structures of (I) and several of its simple analogues (1-naphthol, naphthalene-1,4-diol, naphthalene-1,5-diol and 4-chloro-1-naphthol) shows a close similarity in the packing of the molecules, which form ,-stacks along the shortest crystallographic axes with a substantial spatial overlap between adjacent molecules. [source] Two novel silver(I) coordination polymers: poly[(,2 -2-aminopyrimidine-,2N1:N3)bis(,3 -thiocyanato-,3S:S:S)disilver(I)] and poly[(2-amino-4,6-dimethylpyrimidine-,N)(,3 -thiocyanato-,3N:S:S)silver(I)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Geng-Geng Luo 2-Aminopyrimidine (L1) and 2-amino-4,6-dimethylpyrimidine (L2) have been used to create the two novel title complexes, [Ag2(NCS)2(C4H5N3)]n, (I), and [Ag(NCS)(C6H9N3)]n, (II). The structures of complexes (I) and (II) are mainly directed by the steric properties of the ligands. In (I), the L1 ligand is bisected by a twofold rotation axis running through the amine N atom and opposite C atoms of the pyrimidine ring. The thiocyanate anion adopts the rare ,3 -,3S coordination mode to link three tetrahedrally coordinated AgI ions into a two-dimensional honeycomb-like 63 net. The L1 ligands further extend the two-dimensional sheet to form a three-dimensional framework by bridging AgI ions in adjacent layers. In (II), with three formula units in the asymmetric unit, the L2 ligand bonds to a single AgI ion in a monodentate fashion, while the thiocyanate anions adopt a ,3 -,1N,,2S coordination mode to link the AgL2 subunits to form two-dimensional sheets. These layers are linked by N,H...N hydrogen bonds between the noncoordinated amino H atoms and both thiocyanate and pyrimidine N atoms. [source] Bis(1,3,5-triazine-2,4,6-triamine-,N1)silver(I) nitrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Al-shima'a A. Massoud The title compound, [Ag(C3H6N6)2]NO3, has an alternating two-dimensional bilayer structure supported by extensive hydrogen bonds. The [Ag(melamine)2]+ cationic monomers (melamine is 1,3,5-triazine-2,4,6-triamine) are connected via N,H...N hydrogen bonds to form two-dimensional sheets. Nitrate groups are sandwiched between two sheets through N,H...O hydrogen bonds. An almost perfectly linear coordination geometry is found for the AgI ions. The triazine ligands are slightly distorted due to ,,, interactions. [source] Unusual hydrate stabilization in the two-dimensional layered structure of quinacrinium bis(2-carboxy-4,5-dichlorobenzoate) tetrahydrate, a proton-transfer compound of the drug quinacrineACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009Graham Smith The crystal structure of the hydrated proton-transfer compound of the drug quinacrine [rac- N,-(6-chloro-2-methoxyacridin-9-yl)- N,N -diethylpentane-1,4-diamine] with 4,5-dichlorophthalic acid, C23H32ClN3O2+·2C8H3Cl2O4,·4H2O, has been determined at 200,K. The four labile water molecules of solvation in the structure form discrete ...O,H...O,H... hydrogen-bonded chains parallel to the quinacrine side chain, the two N,H groups of which act as hydrogen-bond donors for two of the water acceptor molecules. The other water molecules, as well as the acridinium H atom, also form hydrogen bonds with the two anion species and extend the structure into two-dimensional sheets. Between these sheets there are also weak cation,anion and anion,anion ,,, aromatic ring interactions. This structure represents the third example of a simple quinacrine derivative for which structural data are available but differs from the other two in that it is unstable in the X-ray beam due to efflorescence, probably associated with the destruction of the unusual four-membered water chain structures. [source] A two-dimensional network formed by self-associating silver(I) perchlorate with 3-[4-(2-thienyl)-2H -cyclopenta[d]pyridazin-1-yl]benzonitrileACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009Xiao-Yan Li In the organometallic silver(I) supramolecular complex poly[[silver(I)-,3 -3-[4-(2-thienyl)-2H -cyclopenta[d]pyridazin-1-yl]benzonitrile] perchlorate methanol solvate], {[Ag(C18H11N3S)](ClO4)·CH3OH}n, there is only one type of AgI center, which lies in an {AgN2S,} coordination environment. Two unsymmetric multidentate 3-[4-(2-thienyl)-2H -cyclopenta[d]pyridazin-1-yl]benzonitrile (L) ligands link two AgI atoms through ,,AgI interactions into an organometallic box-like unit, from which two 3-cyanobenzoyl arms stretch out in opposite directions and bind two AgI atoms from neighboring box-like building blocks. This results in a novel two-dimensional network extending in the crystallographic bc plane. These two-dimensional sheets stack together along the crystallographic a axis to generate parallelogram-like channels. The methanol solvent molecules and the perchlorate counter-ions are located in the channels, where they are fixed by intermolecular hydrogen-bonding interactions. This architecture may provide opportunities for host,guest chemistry, such as guest molecule loss and absorption or ion exchange. The new fulvene-type multidentate ligand L is a good candidate for the preparation of Cp,AgI -containing (Cp is cyclopentadienyl) organometallic coordination polymers or supramolecular complexes. [source] catena -Poly[[diaquamanganese(II)]-di-,-1,1,3,3-tetracyano-2-ethoxypropenido-,4N1:N3]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2003John A. Schlueter The crystal structure of the title compound, [Mn(C9H5N4O)2(H2O)2], conventionally denoted Mn(EtO-TCA)2(H2O)2, where EtO-TCA is 2-ethoxy-1,1,3,3-tetracyanopropenide, is described. The EtO-TCA anions bridge MnII centers through one of the nitrile N atoms of each of their two dicyanomethanide groups, thus forming dibridged chains along ab. These chains are linked into two-dimensional sheets through hydrogen bonding. The seven-atom bridge, which results in a long Mn,Mn intrachain interaction [9.0044,(4),Å], as well as the large interchain separations [8.3288,(4) and 8.5220,(4),Å] prohibit long-range magnetic ordering down to temperatures as low as 1.55,K. [source] | ||||||||||