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Molecular Plane (molecular + plane)

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Chemistry	100%

Selected Abstracts

Molecular axes and planes as an Eigenvalue problem

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2008
Detlef-M.
A statistical approach is used to define the long molecular axis and the main molecular plane. While the concept of molecular axis and plane is immediately useful for simple rod-like or planar molecules, it can be easily generalized to arbitrary molecules as well as molecular subgroups. From the molecular axes and planes, the orientation of the molecule with respect to the lattice as well as intermolecular orientations can be characterized. The method is applied for a comparison of pentacene and para -quinquephenyl crystal structures. [source]

Redetermination of the crystal structure of ,-copper phthalocyanine grown on KCl

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003
Akitaka Hoshino
The crystal structure of a polymorph of copper phthalocyanine (CuPc) grown on a KCl substrate is redetermined by transmission electron diffraction. It has a triclinic unit cell containing one molecule; the crystal does not have a herringbone-type molecular arrangement, which is a common packing mode of planar phthalocyanines. The molecular packing is determined by the diffraction intensity with the aid of the calculation of molecular packing energy. One of the striking features of this polymorph is its stacking mode within a molecular column: the molecular stacking direction projected on a molecular plane is different by an angle of about 45° from that of the ,-modifications of platinum phthalocyanine (PtPc) and metal-free phthalocyanine (H2Pc). A powder X-ray diffraction profile calculated for the polymorph agrees well with that of so-called ,-CuPc and Rietveld analysis for ,-CuPc indicates that the CuPc crystals grown on KCl are actually ,-CuPc; hence, ,-CuPc is not isostructural with either ,-PtPc or ,-H2Pc. On the basis of the present results and the reported crystal structures of the planar phthalocyanines that form molecular columns, the polymorphs of the phthalocyanines can be classified into four types distinguished by the molecular stacking mode within the column: ,(×)-, ,(+)-, ,(×)- and ,(+)-types. [source]

X-ray and neutron structure of 1,8-(3,6,9-trioxaundecane-1,11-diyldioxy)-9,10-dihydro-10,10-dimethylanthracene-9-ol (P326); some pitfalls of automatic data collection

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2001
Rex A. Palmer
The structure of the crown ether 1,8-(3,6,9-trioxaundecane-1,11-diyldioxy)-9,10-dihydro-10,10-dimethylanthracene-9-ol, C24H30O6·H2O (1), code name P326, the parent compound for a series of derivatives, has been determined by both X-ray diffraction at room temperature and neutron diffraction at very low temperature. The unit cells are very similar at both temperatures and in both cases the crystals exhibit P21 symmetry with Z = 4 (two molecules, A and B, respectively, per asymmetric unit) and pseudosymmetry P21/c. The higher symmetry is broken mainly by the two independent water molecules in the unit cell, some reflections which would be absent in P21/c having strong intensities in both the X-ray and neutron data. In both molecules A and B hydrogen bonds involving the water molecule stabilize the macrocyclic ring structure, one involving the macrocyclic O(9) as a donor. Close contacts between the water and macrocyclic O atoms in each molecule also suggest the presence of two bifurcated hydrogen bonds, involving water HW2 to both O(16) and O(18), and water HW1 to both O(18) and O(20), respectively, with considerable variation in the geometry being present. Both molecules A and B exhibit very close pseudosymmetry across a plane perpendicular to the molecular plane and through atoms C(9) and O(18), and in addition are predominantly planar structures. The X-ray analysis failed to reveal one H atom per water molecule, each being subsequently included after location and refinement in the neutron analysis. [source]

Orientational disorder in ,-cobalt(III) sepulchrate trinitrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010
Andreas Schönleber
The crystal structure of ,-(1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane)cobalt(III) trinitrate, [Co(C12H30N8)](NO3)3, consists of a sepulchrate moiety that serves as a macrobicyclic nitrogen cage for the Co3+ cation, which is six-coordinated by N atoms, and three nitrate anions. The Co,sepulchrate group lies on a threefold axis (site symmetry 32), as do two symmetry-related and ordered nitrate groups (site symmetry 3), with which it is connected via N,H...O hydrogen bonds [Co,N = 5.1452,(12),Å]. The third nitrate group is disordered as a result of symmetry requirements around the origin (site symmetry 32), and is further away from the Co,sepulchrate cage [Co,N = 6.3160,(8),Å]. The structure is described by applying orientational disorder over six equivalent orientations for the disordered nitrate group, which is considered as an ideal planar molecule of regular trigonal geometry with its molecular plane rotated out of the ab plane and the molecular centre of gravity slightly shifted away from the origin. This new model for disorder clearly improves a previous crystal structure determination. [source]

(E)-4,4,-Bis(1,3-benzoxazol-2-yl)stilbene at 150 and 375,K

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010
M. Amine Fourati
The title compound, a chromophore of formula C28H18N2O2, crystallizes with the molecule lying on an inversion centre to give one-half of a crystallographically independent molecule in the asymmetric unit. The molecule is almost planar, with slight deviation of the benzene rings from the mean molecular plane. The structure is characterized by a herringbone packing arrangement arising from C,H..., and ,,, intermolecular interactions. The benzoxazole group is disordered between two orientations, with occupancy factors of 0.669,(10) and 0.331,(10) at 150,K [0.712,(7) and 0.288,(7) at 375,K]. [source]

2,4-Dimethoxybenzoic acid and 2,5-dimethoxybenzoic acid

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004
Dewey H. Barich
The title compounds (both C9H10O4) have nearly planar structures, and the methyl and/or carboxylic acid groups lie out of the molecular plane, as dictated by steric interactions. 2,5-Dimethoxybenzoic acid (2,5-DMBA) forms an unusual intramolecular hydrogen bond between the carboxylic acid group and the O atom of the methoxy group in the 2-position [O,O,=,2.547,(2),Å and O,H,O,=,154,(3)°]. 2,4-DMBA forms a typical hydrogen-bond dimer with a neighboring molecule. [source]

3-Butyl-1-(5-nitrobenzo[c][1,2]thiazol-3-yl)-3-phenyltriazene

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2004
Viktor Kettmann
The molecule of the title compound, C17H17N5O2S, consists of three , systems, viz. two aromatic rings and the triazene moiety, which are mutually deconjugated although coplanar. The n -butyl chain is roughly perpendicular to the molecular plane, with the terminal methylene and methyl groups disordered between two equally populated positions. The molecules in the crystal associate in an antiparallel fashion, forming dimers across the centre of symmetry, the principal intradimer interaction being stacking of the ,-electron portions of the molecules. [source]

Asymmetry Induction by Cooperative Intermolecular Hydrogen Bonds in Surface-Anchored Layers of Achiral Molecules,

CHEMPHYSCHEM, Issue 10 2006
Alexandre Dmitriev Dr.
Abstract The mesoscale induction of two-dimensional supramolecular chirality (formation of 2D organic domains with a single handedness) was achieved by self-assembly of 1,2,4-benzenetricarboxylic (trimellitic) acid on a Cu(100) surface at elevated temperatures. The combination of spectroscopic [X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS)], real-space-probe [scanning tunneling microscopy (STM)], and computational [density functional theory (DFT)] methods allows a comprehensive characterization of the obtained organic adlayers, where details of molecular adsorption geometry, intermolecular coupling, and surface chemical bonding are elucidated. The trimellitic acid species, comprising three functional carboxylic groups, form distinct stable mirror-symmetric hydrogen-bonded domains. The chiral ordering is associated with conformational restriction in the domains: molecules anchor to the substrate with an ortho carboxylate group, providing two para carboxylic acid moieties for collective lateral interweaving through H bonding, which induces a specific tilt of the molecular plane. The ease of molecular symmetry switching in domain formation makes homochiral-signature propagation solely limited by the terrace width. The molecular layer modifies the morphology of the underlying copper substrate and induces ,m-sized strictly homochiral terraces. [source]

Redox Activity and Structural Transition of Heptyl Viologen Adlayers on Cu(100),

CHEMPHYSCHEM, Issue 7 2010
Min Jiang Dr.
Abstract The redox behaviour and potential-dependent adsorption structure of heptyl viologen (1,1,-diheptyl-4,4,-bipyridinium dichloride, DHV2+) on a Cu(100) electrode was investigated in a chloride-containing electrolyte solution by cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC,STM). The dicationic DHV molecules generate a few pairs of current waves in CV measurements which are ascribed to two typical one-electron transfer steps. STM images obtained in a KCl-containing electrolyte solution disclose a well-ordered c(2×2) chloride adlayer on a Cu(100) electrode surface. After injecting DHV2+ molecules into the KCl electrolyte solution, a highly ordered 2D "dot-array" structure in STM images emerges on the c(2×2)-Cl modified Cu(100) electrode surface. DHV2+ molecules spontaneously arrange themselves with their molecular planes facing the electrode surface and their long molecular axis parallel to the step edge. Such adsorption structure can be described by mirror domains and rotational domains which stably exist between 200 mV and ,100 mV. One-electron reduction of the dications DHV2+ around ,150 mV causes a phase transition from a ,dot-array' assembly to a stripe pattern formed by DHV.+ radical monocations in STM images which has a bilayer structure. With a further decrease of the applied electrode potential, the structure of the DHV.+ adlayer undergoes a change from a loose stripe phase to a more compact stripe phase, a subsequent decay of the compact structure, and finally the formation of a new dimer phase. A further electron transfer reaction at ,400 mV causes the formation of an amorphous phase on the chloride free electrode surface. In a reverse anodic sweep, the reproduction of the ordered DHV.+ stacking phase occurs again on top of the chloride lattice. [source]

Preparation, Structural Characterization and Luminescent Property of Binuclear Silver (I) Complex Formed by Benzotriazole and 1-Hydroxymethyl Benzotriazole

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2002
Qing-Xiang Liu
Abstract Dinuclear silver (I) six-membered ring complex [Ag2 (bta)2 -(hmbta)2] (ClO4)2 (3) has been synthesized by the reaction of benzotriazole (bta) (1) and 1-hydroxymethyl benzotriazole (hmbta) (2) with Ag (CH3CN)4ClO4. The structures of compound 2 and Complex 3 have been studied by single crystal X-ray diffraction analysis. The change of luminescent intensity of 1, 2 and 3 was reported. Compound 2 crystallizes in the monoclinic system with space group P2 (1)/c, a = 0.7655 (10) nm, b = 1.0126 (14) nm, c =0.9502 (13) nm, , = 95.07 (2)°, V = 0.7337 (17) nm3 and Z = 4. Complex 3 crystallizes in the triclinic system with space group P1, a = 0.73611 (18) nm, b = 0.9152 (2) nm, c = 1.2277 (3) nm, , = 87.170 (5)°, V = 0.8221 (3) nm3 and Z = 1. The main structural feature of complex 3 is a symmetric dinuclear six-membered ring formed by two silver (I) atoms and four N-atoms from two benzotriazoles. The second structural feature of complex 3 is the ,-, stacking interaction between two adjacent molecular planes, which forms the two-dimentional layer structure. Besides, compared with 2, the luminescent intensity of complex 3 shows a remarkable enhancement. [source]