Structural Studies of a Series of Organic Non-Linear Optical Materials

1997 ◽  
Vol 53 (5) ◽  
pp. 812-821 ◽  
Author(s):  
J. C. Cole ◽  
J. M. Cole ◽  
G. H. Cross ◽  
M. Farsari ◽  
J. A. K. Howard ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Ground State ◽  
Optical Materials ◽  
Dipole Moments ◽  
Solvent Polarity ◽  
Structural Studies ◽  
Acta Cryst ◽  
X Ray ◽  
Solution State ◽  
X Ray Crystallography

The crystal structures of {4-[bis(diethylamino)methylium]phenyl}dicyanomethanide (I), {4-[cyano(4-methylpiperidyl)methylium]phenyl } dicyanomethanide (II), {4-[cyano(1-pyrrolidinyl)methylium]phenyl}dicyanomethanide (IV) and (Z)-{4-[1,3-dicyano-3-(diethylamino)-2-propenylium]phenyl} dicyanomethanide have been determined by X-ray crystallography. Together with (Z)-{4-[1-cyano-3-(diethylamino)-2-propenylium]phenyl}dicyanomethanide [(III): Cole, J. C., Howard, J. A. K., Cross, G. H. & Szablewski, M. (1995). Acta Cryst. C51, 715–718], these compounds exhibit varying degrees of quinoidal characteristics and yet have predominantly zwitterionic ground state character. The presence of high dipole moments in the crystal can thus be inferred and are substantiated by measurements of high solution-state dipole moments. Negative solvatochromism (hypsochromism on increasing solvent polarity) confirms the zwitterionic character in at least two of the series.

An amino–imino resonance study of 2-amino-4-methylpyridinium nitrate and 2-amino-5-methylpyridinium nitrate

2012 ◽  
Vol 69 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Xing-Chen Yan ◽  
Yu-Hua Fan ◽  
Cai-Feng Bi ◽  
Xia Zhang ◽  
Zhong-Yu Zhang
Keyword(s):  
Density Functional Theory ◽  
Ir Spectroscopy ◽  
Ground State ◽  
Density Functional ◽  
Acta Cryst ◽  
Functional Theory ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ground State Structures

The contributions of the amino and imino resonance forms to the ground-state structures of 2-amino-4-methylpyridinium nitrate, C6H9N2+·NO3−, and the previously reported 2-amino-5-methylpyridinium nitrate [Yan, Fan, Bi, Zuo & Zhang (2012).Acta Cryst.E68, o2084], were studied using a combination of IR spectroscopy, X-ray crystallography and density functional theory (DFT). The results show that the structures of 2-amino-4-methylpyridine and 2-amino-5-methylpyridine obtained upon protonation are best described as existing largely in the imino resonance forms.

scholarly journals Crystal structures of a novel NNN pincer ligand and its dinuclear titanium(IV) alkoxide pincer complex

2017 ◽  
Vol 73 (2) ◽  
pp. 122-126 ◽  
Author(s):  
Jakub Pedziwiatr ◽  
Ion Ghiviriga ◽  
Khalil A. Abboud ◽  
Adam S. Veige
Keyword(s):  
Metal Complex ◽  
Crystal Structures ◽  
Rotation Axis ◽  
Organic Ligand ◽  
Ligand Complex ◽  
Tetrahedral Geometry ◽  
Acta Cryst ◽  
X Ray ◽  
Site Occupation ◽  
X Ray Crystallography

This report describes a synthetic protocols and the crystal structures involving a novel pincer-type H3[NNN] ligand, namely di-μ-bromido-μ-{2-(2,2-dimethylpropanimidoyl)-N-[2-(2,2-dimethylpropanimidoyl)-4-methylphenyl]-4-methylaniline}-bis[(diethyl ether)lithium], [Li2Br2(C24H33N3)(C4H10O)2] (1) and a dinuclear metal complex, namely di-μ-bromido-2:3κ4Br:Br-bis{2-(2,2-dimethylpropanimidoyl)-N-[2-(2,2-dimethylpropanimidoyl)-4-methylphenyl]-4-methylaniline}-1κ3N,N′,N′′;4κ3N,N′,N′′-tetra-μ-isopropanolato-1:2κ4O:O;3:4κ4O:O-diisopropanolato-1κO,4κO-2,3-dilithium-1,4-dititanium, [Li2Ti2Br2(C24H32N3)2(C3H7O)6] or {[NHNNH]Ti(OiPr)3(LiBr)2}2(2). Complex1, which sits on a twofold rotation axis, is a rare example of a pincer-type ligand which bears ketimine side arms. A unique feature of complex1is that the ketimine N atoms have an LiBr(Et2O) fragment bonded to them, with the Li atom adopting a distorted tetrahedral geometry. This particular fragment creates an LiBr bridge between the two ketimine sidearms, which leads to a cage-type appearance of the ligand. Complex2consists of the previously described ligand and a TiIVmetal atom in an octahedral environment, and is located on an inversion center. Complex2crystallizes as a dinuclear species with the metal atoms being bridged by an LiBr entity [the Br atoms are disordered and refined in two positions with their site occupation factors refining to 0.674 (12)/0.372 (12)], and the Li cation being bonded to the isopropoxide O atoms (Li having a tetrahedral coordination as in1). The organic ligand of compound2exhibits disorder in its periphery groups; isopropyl andtert-butyl groups (occupation factors fixed at 0.6/0.4). The novel [NNN]H3pincer-type ligand was characterized by multinuclear and multidimensional NMR, HRMS and X-ray crystallography. The dinuclear metal complex2was characterized by X-ray crystallography. Although each structure exhibits donor N—H groups, no hydrogen bonding is found in either one, perhaps due to the bulky groups around them. One of the ethyl groups of the ether ligand of1is disordered and refined in two parts with site-occupation factors of 0.812 (8) and 0.188 (8). One and a half toluene solvent molecules are also present in the asymmetric unit of2. The toluene molecules were significantly disordered and could not be modeled properly, thusSQUEEZE[Spek (2015).Acta Cryst.C71, 9–18] was used to remove their contributions to the overall intensity data.

Holographic methods in X-ray crystallography. III. First numerical results

1993 ◽  
Vol 49 (6) ◽  
pp. 866-871 ◽  
Author(s):  
G. J. Maalouf ◽  
J. C. Hoch ◽  
A. S. Stern ◽  
H. Szöke ◽  
A. Szöke
Keyword(s):  
Experimental Data ◽  
Crystal Structures ◽  
Numerical Experiments ◽  
Numerical Results ◽  
Crystallographic Data ◽  
Viable Alternative ◽  
Holographic Method ◽  
Acta Cryst ◽  
X Ray ◽  
X Ray Crystallography

The holographic method for the completion of crystal structures, described in paper II [Szöke (1993). Acta Cryst. A49, 853–866], is implemented numerically. The purpose of these modest calculations is to show that the holographic method can handle real crystallographic data in easy problems and to test various algorithms for its implementation. Both synthetic and experimental data are used and sources of error are systematically introduced. The numerical experiments support the theory presented in paper II and show that the holographic method may be a potentially viable alternative to conventional methods for the completion of crystal structures.

scholarly journals A mixed chirality α-helix in a stapled bicyclic and a linear antimicrobial peptide revealed by X-ray crystallography

2021 ◽  
Author(s):  
Stéphane Baeriswyl ◽  
Hippolyte Personne ◽  
Ivan Di Bonaventura ◽  
Thilo Köhler ◽  
Christian van Delden ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Crystal Structures ◽  
X Ray ◽  
X Ray Crystallography ◽  
Α Helix

We report the first X-ray crystal structures of mixed chirality α-helices comprising only natural residues as the example of bicyclic and linear membrane disruptive amphiphilic antimicrobial peptides containing seven l- and four d-residues.

Synthesis, Characterisation and Structural Studies of [Zn(phen)3][Fe(CN)5(NO)]·2H2O·0.25MeOH and [(bipy)2(H2O)Zn(μ-NC)Fe(CN)4(NO)]·0.5H2O

2003 ◽  
Vol 58 (9) ◽  
pp. 916-921 ◽  
Author(s):  
Amitabha Datta ◽  
Samiran Mitra ◽  
Georgina Rosair
Keyword(s):  
Infrared Spectroscopy ◽  
Thermogravimetric Analysis ◽  
Octahedral Geometry ◽  
Distorted Octahedral Geometry ◽  
Structural Studies ◽  
Crystal Lattices ◽  
X Ray ◽  
X Ray Crystallography ◽  
Distorted Octahedral ◽  
Solvent Molecules

Two new bimetallic complexes [Zn(phen)3][Fe(CN)5(NO)] · 2 H2O · 0.25 MeOH, (1) and [(bipy)2(H2O)Zn(μ-NC)Fe(CN)4(NO)] · 0.5 H2O, (2), have been isolated (where phen = 1,10-phenanthroline and bipy = bipyridyl) and characterised by X-ray crystallography [as the 2 H2O · 0.25 CH3OH solvate for (1) and hemihydrate for (2)] infrared spectroscopy and thermogravimetric analysis. Substitution of phenanthroline for bipyridyl resulted in a cyano-bridged bimetallic species rather than two discrete mononuclear metal complexes. The bond angles of Fe-N-O were shown to be practically linear for both 1 [179.2(7)°] and 2 [178.3(3)°], and the Zn atoms have distorted octahedral geometry. The solvent molecules in both crystal lattices take part in forming hydrogen-bonded networks.

Bis(1-phenyl-1-propyne) complexes of tungsten(II): crystal structures of [WI2(CO)(NCR)(η2-MeC2Ph)2] (R = Me, Et, or Ph)

2001 ◽  
Vol 79 (3) ◽  
pp. 263-271
Author(s):  
Paul K Baker ◽  
Michael GB Drew ◽  
Deborah S Evans
Keyword(s):  
Carbon Monoxide ◽  
Solid State ◽  
Crystal Structures ◽  
Octahedral Geometry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Alkyne Complexes ◽  
First Time

Reaction of [WI2(CO)3(NCMe)2] with two equivalents of 1-phenyl-1-propyne (MeC2Ph) in CH2Cl2, and in the absence of light, gave the bis(1-phenyl-1-propyne) complex [WI2(CO)(NCMe)(η2-MeC2Ph)2] (1) in 77% yield. Treatment of equimolar quantities of 1 and NCR (R = Et, i-Pr, t-Bu, Ph) in CH2Cl2 afforded the nitrile-exchanged products, [WI2(CO)(NCR)(η2-MeC2Ph)2] (2-5) (R = Et (2), i-Pr (3), t-Bu (4), Ph (5)). Complexes 1, 2, and 5 were structurally characterized by X-ray crystallography. All three structures have the same pseudo-octahedral geometry, with the equatorial sites being occupied by cis and parallel alkyne groups, which are trans to the cis-iodo groups. The trans carbon monoxide and acetonitrile ligands occupy the axial sites. In structures 1 and 2, the methyl and phenyl substituents of the 1-phenyl-1-propyne ligands are cis to each other, whereas for the bulkier NCPh complex (5), the methyl and phenyl groups are trans to one another. This is the first time that this arrangement has been observed in the solid state in bis(alkyne) complexes of this type.Key words: bis(1-phenyl-1-propyne), carbonyl, nitrile, diiodo, tungsten(II), crystal structures.

Comparative Structural Studies on Three-Coordinate Copper(I) Halide Complexes With Tertiary Phosphines. Crystal Structures of [(PPh2Mes)CuX]2 and [(PPhMes2)CuX]2 (Mes = Mesityl X = Cl, Br, I)

1992 ◽  
Vol 45 (7) ◽  
pp. 1155 ◽  
Author(s):  
GA Bowmaker ◽  
D Camp ◽  
RD Hart ◽  
PC Healy ◽  
BW Skelton ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Copper Atom ◽  
Structural Studies ◽  
Coordination Environment ◽  
X Ray ◽  
Tertiary Phosphines ◽  
Structure Determinations ◽  
Halide Complexes ◽  
The Subject

The 1 : 1 complexes of the substituted triphenylphosphine ligands mesityldiphenylphosphine and dimesitylphenylphosphine with copper(1) chloride, bromide and iodide have been the subject of single-crystal X-ray structure determinations at 295 K. All six complexes crystallize as air-stable dimeric molecules, [(PPh2Mes)CuX]2 and [ (PPhMes2)CUX]2 with each copper atom in a distorted trigonal PCuX2. coordination environment. Crystals of [(PPh2Mes)CuCl]2 (1) are monoclinic, P21/n, a 9.961(3), b 18.687(6), c 11.009(7) Ǻ, β 114.63(4)°; R was 0.049 for 2450 'observed' reflections. [(PPh2Mes)CuBrI2 (2) is monoclinic, P21/n, a 9.939(2), b 18.832(6), c 11.238(6) Ǻ, β 115.36(3)°; R was 0.046 for 1803 'observed' reflections. [(PPh2Mes)CuI]2.4/3 C6H6 (3) is rhornbohedral, R3, a 36.877(8), c 9.047(5) A; R was 0.039 for 2537 'observed' reflections. Crystals of [(PPhMes2)CuCl]2.2MeCN (4) are triclinic, Pi, a 15.783(7), b 9.570(4), c 8.914(4) Ǻ, α 72.43(3), β 76.37(3), γ 74.03(3)°; R was 0.045 for 3341 'observed' reflections. [(PPhMes2)CuBr]2.3C6H6 (5) is monoclinic, C2/c, a 9.694(6), b 30.15(2), c 20.66(2) Ǻ, β 98.00(7)°; R was 0.047 for 2117 'observed' reflections. [(PPhMes2)CuI]2.2MeCN (6) is orthorhombic, PP1nb, a 11.694(8), b 14.77(1), c 29.76(3) Ǻ; R was 0.049 for 3447 'observed' reflections. Cu-P bond lengths are: 2.196(2) A (1); 2.198(3) Ǻ (2); 2.222(5) and 2.226(5) Ǻ (3); 2.202(1) Ǻ (4); 2.197(3) A (5); 2.201(4) and 2.264(5) Ǻ (6). The geometries of the LCuX2 and CuX2Cu units are compared with data reported for other monomeric and dimeric compounds for both phosphorus- and nitrogen-based ligands L.

Structural Studies of Some o- and p-Nitrophenylcarbamates by IR Spectroscopy and X-Ray Diffraction

2008 ◽  
Vol 63 (12) ◽  
pp. 1402-1406
Author(s):  
Monika Simon ◽  
Carol Csunderlik ◽  
G. Jones
Keyword(s):  
Ir Spectroscopy ◽  
Crystal Structures ◽  
Ir Spectrum ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray

N-Alkyl-o-nitrophenylcarbamates as solids present two carbonyl stretching bands in the region 1700 - 1800 cm−1 but similar N-alkyl-p-nitrophenylcarbamates have only one such band in the IR spectrum. In solution both kinds of carbamate present one carbonyl stretching band, but for the former, the splittings occur when the carbamates crystallize. Four crystal structures were analyzed by X-ray diffraction. The two ortho derivatives have more than one molecule in the asymmetric unit, which is consistent with the IR observations.

scholarly journals The fluoride permeation pathway and anion recognition in Fluc family fluoride channels

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Benjamin C McIlwain ◽  
Roja Gundepudi ◽  
B Ben Koff ◽  
Randy B Stockbridge
Keyword(s):  
Binding Sites ◽  
Anion Recognition ◽  
Anion Binding ◽  
Structural Studies ◽  
Planar Bilayer ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molecular Determinants ◽  
Cytoplasmic Accumulation ◽  
Oriented System

Fluc family fluoride channels protect microbes against ambient environmental fluoride by undermining the cytoplasmic accumulation of this toxic halide. These proteins are structurally idiosyncratic, and thus the permeation pathway and mechanism have no analogy in other known ion channels. Although fluoride binding sites were identified in previous structural studies, it was not evident how these ions access aqueous solution, and the molecular determinants of anion recognition and selectivity have not been elucidated. Using x-ray crystallography, planar bilayer electrophysiology and liposome-based assays, we identify additional binding sites along the permeation pathway. We use this information to develop an oriented system for planar lipid bilayer electrophysiology and observe anion block at one of these sites, revealing insights into the mechanism of anion recognition. We propose a permeation mechanism involving alternating occupancy of anion binding sites that are fully assembled only as the substrate approaches.

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