Absolute piezo-optic constants of Rochelle salt crystals

The effect of uniaxial mechanical pressures applied along the main crystallophysical axes and the corresponding bisector directions on the birefringence of Rochelle salt crystals has been studied. The temperature (77–300 K) and spectral (300–700 nm) curves of the combined, π _im ⁰ and absolute, π_im, piezo-optic constants of crystals are calculated. It is found that the disperse π_im curves are intersected in the vicinity of the inversion of the birefringence sign, which indicates a higher symmetry of the piezo-optic constant tensor. The temperature dependences of the absolute piezo-optic constants show no clearly pronounced anomalies in the vicinity of the phase transitions in the Rochelle salt crystals.     

Crystal Structure,Conformation and Vibrational Analysis of a Mannich Base: 2-[(phenylamino) methyl]-isoindole-1,3-dione

Abstract  

The crystal structure of 2-[(phenylamino) methyl]-isoindole-1,3-dione, C₁₅H₁₂N₂O₂, crystallizes in the triclinic space group Pī with cell parameters of a = 7.1176 (2) ?, b = 8.5533 (3) ?, c = 10.9163 (4) ?, α = 95.937 (2)°, β = 102.975 (2)°, γ = 108.474 (2)°, V = 603.18 (4) ?³ and Z = 2. This indole derivative is a Mannich base in which a methyl group bridges the molecules of phthalimide and aniline molecules. The dihedral angle between the phthalimide and aniline is 75.47 (3)°. The molecules of the title compound forms a centrosymmetric hydrogen-bonded dimer through a pair of N–H···O hydrogen bonds. C–H···π and an extensive π···π interactions, in addition, stabilize the molecular structure. The compound presented here is V-shaped, the angle at the methyl bridge [N–C–N] being 115.04 (12)°. Present study reports the conformation and hydrogen bonding interactions which play an important role in biological functions. Vibration analysis complement the structure analysed.     

Synthesis and Crystal Structure of a Fe(III) Complex with an Isonicotinyl Hydrazone Ligand, [Fe(N-Isonicotinamidosalicylaldimine)Cl<Subscript>2</Subscript>]

Abstract  

A new complex [Fe(N-isonicotinamidosalicylaldimine)Cl₂] has been synthesized by template reaction at room temperature and structurally characterized by X-ray single-crystal analysis. The complex crystallizes in triclinic crystal system, Pī space group, a = 7.273(6) ?, b = 10.015(8) ?, c = 10.479(8) ?, α = 71.067(10)°, β = 89.964(11)°, γ = 75.528(10)°, V = 696.4(9) ?³ and Z = 2. The coordination geometry around the Fe(III) ion is a distorted trigonal bipyramid with a O₂N₁Cl₂ donor set. In the crystal structure, N–H···Cl, C–H···O and C–H···Cl hydrogen bonds and π···π stacking interactions involving aromatic and unclosed π-systems link the molecules to form supramolecular double layers.     

Supramolecular Network via Hydrogen Bonding and π–π Stacking in 4,4′-Bipyridin-1-ium Perchlorate Dihydrate

Abstract The crystal structure of 4,4′-bipyridin-1-ium perchlorate dihydrate, [C₁₀H₉N₂](ClO₄) · 2H₂O, is determined by room temperature X-ray diffraction. The compound crystallizes in the triclinic space group P-1 with a = 8.122(3) ?, b = 9.726(3) ?, c = 17.648(6) ?, α = 78.181(4)°, β = 82.797(5)°, γ = 67.439(4)°, Z = 2, V = 1258.4(7) ?³. In the compound, monoprotonated 4,4′-bipyridin-1-ium cations are self-assembled into supramolecular chains along the a-axis through N–H···N hydrogen bonds in a head-to-tail fashion. The chains are stacked via π–π stacking interactions to create two-dimensional sheets. The interlayer space is occupied by the hydrogen-bonded water chains that are linked to the organic sheets via C–H···O interactions and the perchlorate anions that are linked to the water chains and the organic sheets via O–H···O and C–H···O hydrogen bonds, respectively, thus generating a three-dimensional supramolecular architecture. Index Abstract Supramolecular Network via Hydrogen Bonding and π–π Stacking in 4,4′-Bipyridin-1-ium perchlorate dihydrate Jian-Yong Zhang, Ai-Ling Cheng and En-Qing Gao* Monoprotonated 4,4′-bipyridin-1-ium cations are self-assembled into supramolecular chains along the a-axis through N–H···N hydrogen bonds, and these chains are stacked via π–π stacking and hydrogen bond interactions involving water molecules and perchlorate anions.      

Syntheses and Crystal Structures of Two Apigenin Alkylation Derivatives

Abstract Two apigenin alkylation derivatives, 4′,7-dimethoxyl-5-hydroxyflavone (I) and 4′,7-diethoxyl-5-hydroxyflavone (II), have been synthesized and their crystal structures were determined by ¹H NMR and single crystal X-ray diffraction study. (I) is triclinic, space group P−1 with a = 7.120(5) ?, b = 7.297(5) ?, c = 13.559(10) ?, α = 89.313(12)°, β = 86.298(12)°, γ = 83.999(13)° and Z = 2. (II) is monoclinic, space group P 2₁ /c with a = 16. 309(4) ?, b = 7.303(2) ?, c = 15.185(4) ?, α = 90.00°, β = 115.70(2)°, γ = 90.00° and Z = 4. They have the same flavone skeleton which is composed of a benzopyranone moiety and a phenyl moiety. Molecules of (I) are linked into a two-dimensional network by a combination of C–H···O hydrogen bond and π–π stacking interactions. (II) shows some discrepancies with (I) and the molecules are linked into a column by π–π stacking interaction. Graphical Abstract Two apigenin alkylation derivatives, 4′,7-dimethoxyl-5-hydroxyflavone (I) and 4′,7-diethoxyl-5-hydroxyflavone (II) were synthesized and their crystal structures were determined by single-crystal X-ray diffraction. Hydrogen bonding and π–π stacking interactions assemble (I) into a two-dimensional network, and in the crystal structure of (II), π–π stacking interaction leads to the formation of a column.      

Conformational diversity: Six conformers side-by-side in the crystal cell of 2,2′,7,7′-tetramethoxy-9,9′-spiro-9-silabifluorene

X-ray crystal structure analysis of a sublimation-grown spiro silabifluorene, that is highly fluorescent in the violet-blue, established that there are six cocrystallized ordered conformers in the asymmetric unit. Crystals were grown by a vapor transport method under argon gas flow at temperatures between 255–280°C. As expected, there are no cocrystallized solvent molecules. There is no π-stacking of the aryl groups. There is no possibility for normal hydrogen bond formation; however, several CH⋯π bonds occur. The packing is efficient with a density of 1.24 g/cc. Each conformer deviates from tetrahedral geometry around the Si atom. Cell data are: C₂₈H₂₄O₄Si×12, sp. gr. P, a=16.2750(5) ?, b=20.6613(5) ?, c=23.8289(5) ?, α=102.025(2)°, β=94.252(2)°, and γ=109.916(2)°, V=7275(1) ?³.     

The co-crystal of iron(II) complex hydrate with hydroxybenzoic acid: [Fe(Phen)<Subscript>3</Subscript>]Cl(p-hydroxybenzoate).2(p-hydroxybenzoic acid).7H<Subscript>2</Subscript>O

Crystal of [Fe(Phen)₃]Cl(PHB).2(PHBH).7H₂O (1) is triclinic, space group P-1 with a = 12.0388(11) ?, b = 15.5286(14) ?, c = 15.7794(14) ?, α = 89.759(2)°, β = 75.818(2)°, γ = 71.900(2)° and Z = 2, (phen = phenanthroline, PHBH = p-hydroxybenzoic acid, PHB = p-hydroxybenzoate anion). The phen in adjacent Fe(phen)₃ ²⁺ cations are π–π interacted forming offset face to face (OFF) motifs. Juxtaposition of four phen ligands from two cations encapsulate an R₂ ²(8) dimeric unit of H-bonded PHBH molecules within a centrosymmetric box froming a filled aryl box motif (FAB). Alternation of OFF and FAB motifs form {OFF⋯FAB}∞ strands. The Fe(phen)₃ ²⁺ cation engages its phen ligands in π–π and/or CH–π interactions with two crystalographically different PHBH molecules and one PHB anion. Seven water molecules and a chloride anion per iron(II) trisphenanthroline cation fill empty spaces in the structure forming a hydrophilic cluster. Extensive intermolecular H-bond interactions occur between water molecules, chloride anions, PHBH molecules, and PHB anions. Thermal analysis of (1) was done under N_2(g). The TG, and dTG curves revealed the expected mass losses. All associated processes are endothermic as shown in the DSC curve.     

Structures of Two (<Emphasis Type="Italic">E</Emphasis>)-3-Substituted Cinnamoylbenzotriazole 1-Oxides

Abstract  

The molecule of (E)-3-(3-MeOC₆H₄CH=CHCO)-benzotriazole 1-oxide, 2, has a very near planar structure, while the 2-nitrophenyl ring is rotated out of the plane of the remaining atoms in (E)-3-(2-O₂NC₆H₄CH=CHCO)-benzotriazole 1-oxide, 1. The nitrogen oxide bond lengths in 1 and 2 are 1.258 (6) and 1.2683 (15) ?, respectively, and are in the region found for related compounds. There are no strong intermolecular hydrogen-bonds in either compound, instead there are weak C–H···O intermolecular hydrogen-bonds and π···π stacking interactions in 1, and C–H···O, C–H···π, and π···π stacking interactions in 2. Different three-dimensional arrays are generated in each case. Compound 1 crystallises in the orthorhombic space group Pna2₁, with a = 25.061 (2) ?, b = 3.6997 (2) ?, c = 14.2623 (12) ? and Z = 4. Compound 2 crystallises in the triclinic space group P-1, with a = 5.7297 (3) ?, b = 10.8440 (6) ?, c = 11.4965 (6) ?, α = 89.689 (3)°, β = 76.019 (3)°, γ = 75.047 (3)°, Z = 2.     

Synthesis and Crystal Structure of a Novel Double-Chain Coordination Polymer [Zn<Subscript>2</Subscript>(bipy)<Subscript>2</Subscript>(btec)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]<Subscript>n</Subscript> (bipy = 2,2′-bipyridine; btec = 1,2,4,5-benzenetetracarboxylate)

Abstract  A novel aromatic polycarboxylate polymer, [Zn₂(bipy)₂(btec)(H₂O)₂]_n (1), has been synthesized and structurally characterized by the single crystal X-ray diffraction. Compound 1 belongs to the triclinic crystal system, space group P-1; a = 7.7449(6) ?, b = 8.9286(8) ?, c = 10.7422(8) ?, α = 80.95(1)°, β = 70.21(1)°, γ = 78.14(1)°, V = 680.93(10) ?³, Z = 2. The coordination geometry of Zn(II) atom is distorted trigonal bipyramidal with two nitrogen atoms of one 2,2′-bipy group, two oxygen atoms from two different btec ligands, and one water. The 16-membered rings are alternately arranged forming an infinite 1-D double-chain structure. A 3-D network was constructed by interlayer C···H–O, O···H–O hydrogen bonds and π–π stacking interactions. Compound 1 exhibits fluorescence at room temperature in the solid state. Graphical Abstract  A 1-D double-chain aromatic polycarboxylate polymer, [Zn₂(bipy)₂(btec)(H₂O)₂]_n (1), has been synthesized and structurally characterized by the single crystal X-ray diffraction. A 3-D network was constructed by intermolecular C···H–O, O···H–O hydrogen bonds and π–π stacking interactions. Compound 1 exhibits fluorescence at room temperature in the solid state.      

X-ray structure analysis of 1-(4-bromophenyl)-3-(4-chlorophenyl)-prop-2-en-1-one

The title compound crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 15.6239(15) ?, b = 14.0537(14) ?, c = 5.8396(5) ?, β = 92.666(3)°, V = 1280.8 (2) ?³, and Z = 4. The final reliability index is 0.0538 for 2921 observed reflections. Two phenyl rings of the title molecule are not coplanar, with a dihedral angle of 46.3(0)°. The molecular planarity of this substituted chalcone is strongly affected by the 4′-bromo group. The crystal cohesion is accentuated by π···π, C–H···Br interactions and R₃ ¹ (11) hydrogen bond.     

Synthesis and Crystal Structure of a New Ion-Pair Complex Based on [Ni(tdas)<Subscript>2</Subscript>]<Superscript>2−</Superscript> Anion and Triphenylphosphinium Cation

Abstract  A new ion-pair complex, bis(1-benzyltriphenylphosphinium) bis(1,2,5-thiadiazole-3,4-dithiolato)nickelate(II), [BzTPP]₂[Ni(tdas)₂](1), has been prepared and characterized by elemental analyses, UV, IR, MS spectrum, molar conductivity and single crystal X-ray diffraction. The title complex crystallizes in the triclinic space group P-1, a = 9.098(1) Å, b = 9.666(1) Å, c = 29.573(3) Å, α = 83.81(1)°, β = 81.97(1)°, γ = 78.83(1)°, V = 2,517.5(4) ų, Z = 2. The unit cell contains two [BzTPP]⁺ and two halves of [Ni(tdas)₂]²⁻ anions in which the anion exhibits a quasi-planar structure. The [BzTPP]⁺ cation adopts a conformation where four phenyl rings are twisted to the C–C–P reference plane. The weak cation–cation C–H···π, π···π interactions and anion–cation C–H···N hydrogen bonds between the anion and cation play an important role in the stacking and stabilizing of the title complex. Graphical Abstract  The title new ion-pair complex, bis(1-benzyltriphenylphosphinium) bis(1,2,5-thiadiazole-3,4-dithiolato)nickelate(II), [BzTPP]₂[Ni(tdas)₂](1), contains two [BzTPP]⁺ and two halves of [Ni(tdas)₂]²⁻ anions in which the weak cation–cation C–H···π, π···π interactions and anion−cation C–H···N hydrogen bonds between the anion and cation play an important role in the stacking and stabilizing of the title complex.      

Br···HN, N···HC, Br···HC, and Br···Br intermolecular interactions as supramolecular synthons: Synthesis and crystal structure of bis(2-amino-5-methylpyridinium) tetrabromomercurate(II)

The bis(2-amino-5-methylpyridinium) tetrabromomercurate(II) (C₆H₉N₂)₂[HgBr₄] salt is triclinic, P1, with the following cell parameters: a=8.060(8) ?, b=9.035(9) ?, c=14.964(10) ?, α=96.032(19)°, β=90.317(15)°, γ=113.32(2)°, V=993.8(15) ?³, with Z=2 formula units. The crystal structure consists of alternating stacks of inorganic HgBr₄ ²⁻ anions and organic layers of 2-amino-5-methylpyridinium cations parallel to c-axis. The cohesion forces that connect molecules in the organic layers are N···HC hydrogen bonding and π–π stacking. The HgBr₄ ²⁻ units in the inorganic stacks are attracted via Br···Br intermolecular interactions.Supplementary material CCDC 270395 contains the supplementary crystallographic data. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by e-mailing at data_request@ccdc.cam.ac.uk, or by contacting the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: + 44(0)1223-336033.     

A supramolecular structure of bis(1,3-diphenyl-1,3-propanedionato-O,O′) (1,10-phenanthroline-N,N′)cobalt(II) based on C–H…O, C–H…π and π…π interactions

The compound bis(1,3-diphenyl-1,3-propanedionato-O,O′) (1,10-phenanthroline-N, N′)cobalt(II) (Co(DBM)₂(1,10-phe)) was investigated as a potential host component for functional inclusion materials. The molecules of the complex in the crystal (a=21.015(5) ?, b=17.456(5) ?, c=9.503(3) ?, β=107.04(2)°, s.g. C 2/c) are centrosymmetric and assemble by way of C–H···O and C–H···π hydrogen bonds as well as π···π stacking interactions to provide a supramolecular ladder-like motif that is accompanied by a variant of the six phenyl-embrace synthon.     

Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid

Abstract  The Ni(II) complex, [Ni(H₂biim)₂(PABA)₂]Cl₂·2H₂O, H₂biim being 2,2′-biimidazole, PABA being 4-aminobenzoic acid has been synthesized and the crystal structure determined using X-ray crystallography. The complex crystallizes in triclinic system, space group P − 1 with unit cell parameters a = 8.3920(9) ?, b = 9.8436(11) ?, c = 9.8874(11) ?, α = 94.862(2)°, β = 109.142(2)°, γ = 90.992(2)°, V = 767.95(15) ?³ and Z = 1. The molecules of the complex in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure. Index Abstract  Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid Yanping Li and Pin Yang* The molecules of the title complex [Ni(H₂biim)₂(PABA)₂]Cl₂·2H₂O in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure.      

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

Abstract  The title compound, C₁₈H₁₈BrN₃O₃S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal] reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these angles which therefore play a role in stabilizing crystal packing. Graphical Abstract  Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C₁₈H₁₈BrN₃O₃S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis,Crystal Structure and ab Initio Studies of 5-Phenylamino-3-phenylimino-3H[1, 2]dithiole-4-carboxylic acid ethyl ester

Abstract  

5-Phenylamino-3-phenylimino-3H[1, 2]dithiole-4-carboxylic acid ethyl ester, C₁₈H₁₆N₂O₂S₂, (I), has been synthesized and the structure has been solved by X–ray diffraction. The crystals are triclinic, space group P[`1] P\bar{1} , with a = 5.7127(2) ?, b = 12.1757(5) ?, c = 14.0734(5) ?, α = 112.1217(16)°, β = 97.786(2)°, γ = 100.694(2)°, Mr = 356.45, V = 868.11(6) ?³, Z = 2 and R = 0.0373. In the title compound there is an intramolecular N–H···O hydrogen bond. The crystal structure is stabilized only by weak C–H···π and π···π interactions as well as by van der Waals forces. The geometry of the isolated molecule was optimized by ab initio quantum mechanical calculations, employing both molecular orbital Hartree-Fock (HF) and density functional theory (DFT) methods. In the DFT calculation the minimum energy was achieved for a conformation very similar to that of the solid-state molecule.     

Synthesis,Crystal Structure and Luminescent Properties of One Silver Complex with 3,5-Diphenylpyrazole

Abstract  

A new Ag(I) complex Ag(HL)₂(NO₃) 1 has been synthesized with 3,5-diphenylpyrazole (HL) and characterized by IR spectrum, elemental analysis and X-ray crystallography. The crystallographic data for the complex 1: triclinic P[`\text1] P{\bar{\text{1}}} , a = 10.4369(17) ?, b = 10.4837(18) ?, c = 12.963(2) ?, α = 69.318(2)°, β = 86.733(3)°, γ = 88.263(2)°, V = 1324.7(4) ?³, Z = 2, Dc = 1.530 Mg m⁻³, F(000) = 620, μ = 0.803 mm⁻¹, R ₁ = 0.0251, wR ₂ = 0.0638. Ag(I) atom is bound to two nitrogen atoms from two ligands. In solid state there are π···π interactions and C–H···π interactions between adjacent units to generate 2D supramolecular structure. The title complex shows strong luminescent emission at 389 and 467 nm in solid state at room temperature.     

5-Pyridine 4-yl-3H-(1,3,4) Oxadiazole-2 Thione Hydrochloride Monohydrate, (I), and 4 [5-Ethylsulfanyl)-(1,3,4) Thiadiazole-2-yl]-Pyridinium Perchlorate, (II)

Abstract  

The title compounds C₇H₈ClN₃O₂S, (I), and C₉H₁₀ClN₃O₄S_2, (II), both crystallize in monoclinic space group P2₁ /c with unit cell parameters (I) a = 7.9402(7), b = 10.6312(9), c = 11.7626(10), ?, β = 99.271(5)°, Z = 4 and (II) a = 5.1439(2), b = 9.0636(4), c = 27.1814 (7), ?, β = 95.116(2)°, Z = 4. In (I) the molecule consists of a 5-pyridine-4-yl group bonded to the carbon atom at the 5 position of (1, 3, 4) oxadiazole-2 thione hydrochloride monohydrate. The angle between the mean planes of the oxadiazole and pyridine rings is 9.6(6)°. Crystal packing in (I) is stabilized by strong N–H···O hydrogen bonds in concert with a solvent water molecule and weak O–H···Cl, O–H···S, N–H···Cl intermolecular interactions. The crystal structure of compound (II) consists of 4 [5-ethylsulfanyl)-(1, 3, 4) thiadiazole-2-yl]-pyridinium perchlorate, (C₉H₁₀N₃S₂)⁺(ClO₄)⁻, cation–anion pairs, containing strong intermolecular N–H···O hydrogen bonds and weak C–H···O and N–H···O intermolecular interactions operating between the ionic species that form a cooperative hydrogen-bonded, infinite chain O–H···O–H···O–H network which generates a sheet motif structure in the unit cell. It is also supported by weak intermolecular Cg···Cg π–π and Cl–O···Cg π-ring interactions which gives additional support to molecular packing stability in the unit cell. Geometry optimized MOPAC AM1 computational calculations on each compound provides support to the structural features in their respective crystal structures.     

Solvent-controlled structures. Synthesis and characterization of complexes Cu(L)2(CH3COO)2 and [Cu2(μ-CH3COO)4(L)2](L)2 [L = N-(4′-methylaniline)-4-pyridinecarboxamide]

Two complexes Cu(L)₂(CH₃COO)₂ (1) and [Cu₂(μ-CH₃COO)₄(L)₂](L)₂ (2) (L = N-(4′-methylaniline)-4-pyridinecarboxamide) have been prepared and their crystal structures have been determined by single-crystal X-ray diffraction. The complexes are obtained by using the same raw materials and reaction conditions except solvents. The presence or absence of water controls the coordination mode to give rise to different structures. The structure of 1 has a triclinic space group P-1 with a = 8.381(3) ?, b = 8.545(4) ?, c = 11.357(5) ?, α = 110.654(6)°, β = 102.388(7)°, γ = 97.889(7)°, V = 722.9(5) ?³, and Z = 1. The structure of 2 has a triclinic space group P-1 with a = 9.121(3) ?, b = 9.454(3) ?, c = 17.233(5) ?, α = 77.374(5)°, β = 89.827(6)°, γ = 74.342(6)°, V = 1393.8(7) ?³, and Z = 1. Supramolecular assemblies have also been found via noncovalent bonds such as hydrogen bonds, π–π stacking interactions.     

PM3 semiempirical study and its comparison with X-ray crystal structure of 4-[2-Methyl-4-(4-methoxyphenylazo)] phenoxyphtalonitrile

  The molecular and crystal structures of the title compound, C₂₂H₁₆N₄O₂, were determined by single crystal X-ray diffraction technique. The title compound crystallizes in monoclinic space group P1 2 ₁ /n1, with a=12.7811(9) ?, b=8.2002(4) ?, c=17.8772(14) ?, Z=4, D _calc=1.3112(1) g/cm³, μ (Mo-K_α)=0.087 mm⁻¹. The structure was solved by direct methods and refined to a final R=0.056 for 1891 reflections with I > 2σ (I). The asymmetric unit in the crystal structure contains only one neutral molecule. The positions of nitrogen atoms in the azo groups were disordered. There is no classic hydrogen bond in the crystal structure. The molecules in the crystal structure are stacked by π–π stacking and one edge-to-face interactions. In order to determine conformational flexibility and crystal packing effects on the molecules, molecular energy profile of the title compound was obtained with respect to the selected torsion angle, which is varied from −180° to +180° in every 10° via PM3 semi-empirical method.