Synthesis and crystal structure of 4,4′-bis(4-pyridylethyl)biphenyl, noncovalently hydrogen bonded two-dimensional networks

A new pyridine containing compound, 4,4-bis(4-pyridylethyl)biphenyl 1, was synthesized and its structure was determined by X-ray crystallography. Two kinds of two-dimensional networks linked by hydrogen bonds were obtained with different crystal solvents: 1·2H₂O, monoclinic, space group P2₁/n with a = 8.3280(10), b = 5.5990(10), c = 24.054(4) Å, = 98.79(2)°, V = 1108.4(3) ų, Z = 2, Dc = 1.200 g cm^–3, R1 = 0.0558; 1·CH₃OH·2H₂O, triclinic, space group P-1 with a = 8.3310(10), b = 12.861(2), c = 13.111(2) Å, = 64.110(10), = 75.000(10), = 83.750(10)°, V = 1220.7(3) ų, Z = 2, Dc = 1.177 g cm^–3, R1 = 0.0529. It is interesting that in the hydrate the host molecule of 1 contains an essentially flat biphenyl section, while in the methanol complex the host molecule of 1 contains a substantial twist in the center of the biphenyl section. The compounds were also characterized by NMR and FTIR spectroscopies. The ¹H and ¹³C NMR assignments for 1 were carried out by 2D NMR spectral measurements in acetonitrile-d ₃.     

Synthesis of spinacine and spinacine derivatives: crystal and molecular structures of Nπ-hydroxymethyl spinacine and Nα-methyl spinaceamine

The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product with an excellent yield. The crystal structures of a synthetic intermediate, N^π-hydroxymethyl-spinacine, and a spinacine derivative, N^α-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H₂O, monoclinicP2 _i,a=8.571(1),b=6.682(1),c=8.588(1) Å, and β=94.67(1)^o. Spm(αMe)·2HCl·H₂O, triclinicP l,a=7.492(4),b=10.799(3),c=7.040(2) Å, α=91.88(2), β=98.36(3) and γ=73.34(3)^o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial position and forms a short electrostatic interaction of 2.618(2) Å between one of its oxygens and the protonated nitrogen of the tetrahydropyridine ring. The crystal packing is assured by strong O?H???O, O?H???N, N?H???N intermolecular hydrogen bonds and C?H???O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl^? anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C?N. The crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl^? anions and two water molecules linked together by hydrogen bonds.     

Synthesis and crystal structure of Mn(II) and Zn(II) complexes with 1,3,5-tris(carboxymethoxyl)benzene ligand

Two complexes (H₂bipy)[M₂(TB)₂(H₂O)₈]·5H₂O (M = Mn 1, Zn 2) (bipy = 4,4′-bipyridine, H₃TB = 1,3,5-tris(carboxymethoxyl)benzene) were synthesized by the reaction of the corresponding metal salt with ligand H₃TB and 4,4′-bipy in an aqueous methanol solution at room temperature, respectively. Their structures were determined by single crystal X-ray diffraction analysis. Both complexes 1 and 2 crystallize in the triclinic space group with the crystal parameters of 1: a = 9.725(12) ?, b = 10.651(13) ?, c = 10.882(13) ?, α = 91.72(2)°, β = 96.41(2)°, γ = 97.72(2)°, V = 1109(2) ?³, Z = 1 and 2: a = 9.610(10) ?, b = 10.55(2) ?, c = 10.83(2) ?, α = 91.60(4)°, β = 95.32(2)°, γ = 97.73(4)°, V = 1082(3) ?³, Z = 1. Complexes 1 and 2 have the same dinuclear structure, in which each metal atom is six coordinated with distorted octahedral geometry by two oxygen atoms from two different TB³⁻ ligands and four ones from four coordinated water molecules. The dinuclear units are further linked by hydrogen bonding and π–π interactions to form the three-dimensional framework structure.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P2₁/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure.     

Hydrogen bonds and π–π stacking interaction in 4′, 7-dimethoxylisoflavone and 4′,7-diacetyl-O-isoflavone

4′,7-dimethoxylisoflavone, C₁₇H₁₄O₄, (I), is linked into a supramolecular structure by a variety of weak but direction-specific intermolecular forces, the molecules are linked into chains through C–H⋅sO hydrogen bonds, these chains are further linked by face-to-face (F-tape) π–π stacking into a one-dimensional bi-chain, another type π–π stacking, edge-to-face (T-tape), assemble the bi-chain into framework together with C–H⋅sO hydrogen bonds. 4′,7-diacetyl-O-isoflavone, C₁₉H₁₅O₆, (II), shows some discrepancies with I and the molecules are assembled into framework all by C–H⋅sO hydrogen bonds. The molecules are linked into centrosymmetric dimers built from classic R₂² (8) rings by pairs of C–H⋅sO hydrogen bonds, the dimers are linked into (011) sheets by combination of the R₂² (8) ring and C–H⋅sO hydrogen bonds, another C–H⋅sO hydrogen bond assemble the sheets into three-dimensional network.     

Synthesis,spectral, X-ray diffraction and DFT studies on 1-(2-methyl-2-propenyl)-3-(2,3,4,5,6-pentamethylbenzyl)benzimidazolium chloride hydrate

A new benzimidazole based N-heterocyclic carbene (NHC) salt (1) was synthesized by the reaction of benzimidazole precursor with alkyl halide. The structure of 1 was determined by elemental analysis, FT-IR, ¹H NMR and ¹³C NMR spectroscopy tecniques and X-ray crystallography. The compound crystallized in the triclinic space group P-1 with two molecules in the unit cell. The optimization of 1 was firstly performed at B3LYP/6-311G++(d,p) level, then the theoretical spectral studies performed and compared with the experimental values. Besides the frontier molecular orbital energies and chemical reactivity analysis of 1, together with the electrostatic potential and molecular electrostatic potential analyses were performed at the same level of theory.     

Molecular structure of 4-(3,5-dimethylpyrazol-1-yl)benzoic acid trifluoroacetate

The crystal and molecular structure of the title compound has been determined by X-ray analysis. 4-(3,5-Dimethylpyrazol-l-yl)benzoic acid trifluoroacetate crystallizes in the 12/a space group witha=20.6584(13),b=9.9068(3),c=14.9467(6) , =106.195(4),V=2937.6(2) ų, Dc=1.494 g/cm³ andZ=8. The ions pack in chains parallel to thea axis through O–HO and N–HO hydrogen bond interactions. Solid-state¹³C CPMASNMR spectroscopy has been used to compare the structure of the trifluoracetate with that of the neutral molecule [4-(3,5-dimethylpyrazol-l-yl)benzoic acid].     

Nuclear magnetic resonance: a powerful tool to study liquid crystals

Nuclear magnetic resonance (NMR) is a spectroscopic technique widely used to investigate materials and soft matter in particular. In this brief review, the main uses of NMR techniques to investigate different aspects of liquid crystals, such as the orientational and dynamic properties, the supramolecular structure and average molecular conformations, are described. In the second part of the paper, the case study of a ‘de Vries’ liquid crystal is reported and the main results obtained by combining different NMR techniques are discussed.     

Synthesis and Crystal Structure of 4-Methyl-6H-pyrido[3,2,1-<Emphasis Type="Italic">jk</Emphasis>]carbazol-6-one

Abstract  The synthesis, NMR and X-ray structure of 4-methyl-6H-pyrido[3,2,1-jk]carbazol-6-one—a potential DNA intercalator are reported. The compound crystallizes in the orthorhombic Pbca space group with unit cell parameters: a = 7.775(8), b = 15.113(7), c = 19.849(7) ?, V = 2332.8(3) ?³, Mr = 233.26 and Z = 8. In the three-dimensional arrangement of the molecules no classical hydrogen bonds were found; weak π···π and C–H···O interactions are responsible for the packing of the molecules in the crystal structure. Index Abstract  In the three-dimensional arrangement of the title compound no classical hydrogen bonds were found; weak π···π and C–H···O interactions are responsible for the packing of the molecules in the crystal structure.