Crystals of 2-trifluoromethyl-4′-dimethylaminoazobenzene (2-TFMDAB) are orthorhombic, space group Pbca with a =15.625(4), b = 23.028(6), c = 7.685(2)Å, and Z = 8. The structure was solved by direct methods (SIR88) and refined to a final R value of 0.049 for 2536 reflections (I>0.80σ(I)). 2-TFMDAB has a trans geometry about the azo linkage. The bond lengths and angles are similar to those of other azobenzene compounds. The abnormal UV-vis absorption spectrum in an acidic solution can be explained by the existence of the bulky and electronegative CF₃ group at the 2-position, which prevents protonation at the Nβ atom of the azo group in an acidic solution.

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1,2-Bis(formylamino)benzene was crystallized from methanol as chiral crystals belonging to space group P2₁2₁2₁. Both of the formylamide moieties of the compound are almost planar and the configurations are Z. They are located on the same side of the central benzene ring (syn conformation) and tilted in the same direction.

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Crystal structure of 4-N,N-dimethylamino-2,3,5,6-tetrafluorobenzonitrile (4F-DMABN) has been determined by X-ray diffraction. This compound crystallizes in the monoclinic system, space group P2₁/c, with unit cell parameters: a = 4.373(2)Å, b = 10.654(6)Å, c = 20.05(1)Å, β = 92.92(2)°, Z = 4, V = 933.2(9)ų. The crystal structure was solved by direct methods and refined by full-matrix least squares to final values of R = 0.082 and R_w = 0.089 with 1129 reflections (I>1.20σ(I)). The dimethylamino group is out of the aromatic ring plane. The dihedral angle between the least-squares planes of the aromatic ring and the dimethylamino group is 32.73(5)°. The aromatic ring has a significant quinoid nature.

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An X-ray analysis of 7-α-hydroxycholesterol was undertaken in order to determine the inherent conformation and to understand the structure-function relationships. The bond distances and angles are within the expected ranges, except for those of the terminal part of the isoprenoid chain moiety. The A, B, C and D rings in the steroid skeleton take chair, half-chair, chair and envelope conformations, respectively. All rings of the steroid skeleton are trans connected. The isoprenoid chain moiety has an extended conformation.

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Alkylation of calix[4]arene-crown-6 by 2-tert-butoxyethyl bromide with sodium hydride as a base led to 25-(2-tert-butoxyethoxy)-27-hydroxycalix[4]arene-crown-6 in the cone conformation. The conformation of the latter monoalkylated calix[4]arene-crown-6 was established by X-ray crystallography. It crystallizes in the triclinic space group P₁. This monoalkylated calixarene-crown-6 can be used as a synthon useful for the preparation of bisalkylated mixed calix[4]arene-crown-6 atropisomers.

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Crystals of Enoxacin, one of commercial fluoroquinolone antibiotics, were grown from acetonitrile/methanol and the crystal structure was determined. Results show that the unit cell contains two crystallographically independent molecules (A and B), three water and one methanol molecules. The carboxylic group is ionized and the N4 atom from the piperazine ring is protonated, resulting a zwitter ionic structure. The interlayer π–π interactions and the intermolecular hydrogen bonds stabilize the crystal packing.

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The title compound, C₁₄H₁₇N₅, crystallizes in the centrosymmetric space group Pccn with one molecule in the asymmetric unit. The azo group, being coplanar with the attached benzene rings and the -N-C group of the substituent -N(CH₂CH₃)₂ on the phenyl ring, supports extensive delocalization of electron density. The substituent donate electron to the conjugated system via benzene ring into π^* orbital of the azo moiety which, decreases the bond order of the azo leading to a longer bond of 1.283(2) Å.

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(4S,5R)- and (rac)-4-Methyl-5-phenyl-1,3-oxazolidine-2-thione (MPOT) crystallize in the orthorhombic P2₁2₁2 and monoclinic C2/c, respectively, with eight molecules in a unit cell. In (rac)-MPOT crystals, the thioamide groups of the enantiomeric (4S,5R)- and (4R,5S)-MPOT pairs are hydrogen-bonded around a center of symmetry to form a planar cyclic dimer. On the other hand, a cyclic dimer through the hydrogen bonding is formed between the two independent molecules (molecules A and B) and its geometry is considerably distorted in (4S,5R)-MPOT crystals.

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N-Allyl-5-hydroxymethyloxazolidin-2-one crystallizes in the triclinic space group P1 with a = 8.059(2), b = 8.531(2), c = 6.481(2)Å, α = 108.77(2)°, β = 111.04(2)°, γ = 89.23(2)°, V = 391.1(2)ų, Z = 2. The oxazolidinone ring is almost planar with a cis geometry of the hydroxymethyl and allyl substituents. A strong intermolecular hydrogen bond of the hydroxy hydrogen in a molecule to the carbonyl oxygen of the oxazolidinone ring in another molecule (1.82 Å) is present to make a stable dimer.

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Tetrathioureacoper(I) chloride was synthesised to study its NLO property. Crystals suitable for single crystal x-ray diffraction studies were grown by evaporation method. The compound crystallizes in the tetragonal system and has been characterized thus: P4₁2₁2, a = 13.4090(5) Å, c = 13.8100(4)Å, V = 2483.1(1)ų, Z = 8, D_c = 1.751 Mg/m³. The compound does not exhibit the NOL property.

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The crystal structure of ciclopirox was determined. The crystal belongs to space group I4₁/a, and the cell dimensions are a = 26.0133(6) and c = 15.8980(8)Å. There are two ciclopirox molecules, of which one is neutral and the other is negatively charged, and one positively charged 2-amino ethanol molecule in an asymmetric unit. The final R-value is 0.068.

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The title compound, C₁₆H₁₇NO₂, was found to crystallize in the triclinic space group P1. The unit cell parameters are: a = 8.279(1)Å, b = 14.843(2)Å, c = 5.959(1)Å, α = 97.02(1)°, β = 102.75(1)°, γ = 100.52(1)°; Z = 2. The molecule is not planar. The ethoxy group is almost coplanar with the ethoxyphenyl ring, the hydroxy group and the central moiety of the molecule are almost in the hydroxyphenyl ring plane. The dihedral angle between the two planes is 65.4(1)°. The crystal structure is stabilized by weak intermolecular interactions of the C-H···O type.

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The crystal structure of ketotifen fumarate was determined. The crystal belongs to space group P1 and there are two molecules in an asymmetric unit. The cell dimensions are a = 10.0901(6), b = 11.7760(7), c = 18.8200(7)Å, α = 74.054(2), β = 81.034(3) and γ = 88.4315(7)°. The final R value is 0.068. The two crystallographically independent ketotifen molecules adopt very similar structures. Their tricyclic systems take a butterfly-shape structure.

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A N3S1-type zinc(II) complex with 6-methylpyridylmethyl and mercaptoethyl groups, chloro{N-mercaptoethyl[bis(6- methyl-2-pyridylmethyl)amine]}zinc(II) complex 2, was synthesized and structurally characterized by X-ray crystallography. Crystallographic studies show that the introduction of 6-methyl group into the pyridine ring changes the geometry from trigonal bipyramid to square pyramid.

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Benzophenone analogue (2) has been synthesized and characterized by X-ray diffraction method. The compound crystallizes in orthorhombic space group Pbca with cell parameters a = 5.8820(5)Å, b = 12.1040(5)Å, c = 30.580(3)Å, Z = 8. The structure exhibits intra and intermolecular hydrogen bonding of the type C-H···O.

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The title compound (C₈H₁₁Cl N₂O) was synthesized by microwave-assisted organic synthesis technique and characterized by X-ray diffraction method. It crystallizes in the monoclinic space group P2₁/c with cell parameters a = 7.251 Å, b = 13.195(1)Å, c = 9.835(1)Å, Z = 4. The final residual factor is R1 = 0.0651 for 1552 reflections with I > 2σ(I). The structure exhibits intermolecular hydrogen bonds.

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The title compound was synthesized by microwave-assisted method and characterized by X-ray diffraction method. It crystallizes in monoclinic space group P2₁/c with cell parameters a = 7.916(1)Å, b = 15.736(2)Å, c = 8.737(8)Å, β = 108.11(6)°, Z = 4. The structure has C-H···O type hydrogen bonds.

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The title compound, C₆H₆N₂Cl₂O₄S₂, is one of the carbonic anhydrase inhibitors and can be clinically applied for the treatment of glaucoma. The crystal belongs to space group C2/c with the cell dimensions a = 17.216(1), b = 7.9030(5), c = 16.457(2)Å and β = 94.671(3)°. The final R value is 0.037. Two amino groups are on the same side of the phenyl rings. Although all nitrogen and oxygen atoms are involved in hydrogen bonds, chlorine atoms are not involved.

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The crystal of the title compound belongs to space group P2₁, and the cell dimensions are a = 7.6961(3), b = 14.6036(5), c = 10.4355(5)Å and β = 95.739(2)°. The final R is 0.038. In the pregna-1,4-diene-3-one skeleton, rings A, B, C and D adopt planar, chair, chair and envelope conformations, respectively. There are seven intramolecular C-H···acceptor interactions.

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The crystal structure of (2,2′-bipyridine-N,N′)(diphenyl-2-phosphinopyridine-P)-chloro(dicarbonyl)ruthenium(II) hexafluorophosphate ([Ru(bpy)(dppy)(CO)₂Cl]PF₆; bpy = 2,2′-bipyridine, dppy = diphenyl-2-phosphinopyridine) has been determined by X-ray diffraction. This compound crystallizes in a monoclinic system, space group P2₁/n, with the following unit cell parameters: a = 10.237(1), b = 18.754(2), c = 16.566(2)Å, β = 106.257(4)°, Z = 4, V = 3053.3(5)ų. The crystal structure was solved by the Patterson method and refined on F² by full-matrix least squares to final values of R = 0.046 and R_w = 0.079 with 6879 reflections (all data). The dppy ligand coordinates only to the ruthenium center through the phosphorus atom. The pyridyl ring in the three aromatic rings of the dppy directs toward the plane including the terminal carbonyl ligands.

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4-(2-Aminothiazol-4-yl)-4-(hydroxyimino)acetic ester crystallizes in monoclinic form, space group P2₁/c with a =10.2822(17), b = 10.9006(18), c = 8.8072(15)Å, and Z = 4. The structure was solved by direct methods (SHELXS97) and refined by full-matrix least squares to a final value of R1 = 0.0501 for 2207 reflections [I > 2σ(I)]. The C5 atom and O1 atom are in cis conformation with regard to the C4-N3 double bond. There is an intra molecular hydrogen bond between O1-H1A···O2, and different molecules are associated to each other to form the whole by three kinds of intermolecular hydrogen bonds and van der Waals force.

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Crystallization from an equimolar acetonitrile solution of 4-(3-chlorobenzyloxy)-6-methyl-2-pyrone (1) and maleimide (2) gave a 1:1 complex crystal (1·2). X-ray diffraction showed four types of intermolecular hydrogen bondings (C2-H···O4^*, N1^*-H^*···O2, C4-H···O5^*, and C16^*-H^*···O3) between 1 and 2. The crystal afforded a single [2+2] cycloadduct by photoirradiation owing to the packing structure.

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A microbicide, 5-chloro-2-methyl-4-isothiazoline-3-one (1), makes a host-guest complex with a host molecule of 4,4′-ethylidenebisphenol (2). The crystal structure, analyzed by X-rays, revealed that one of the two OH groups of 2 make a strong hydrogen bond with the carbonyl group of 1. The O···O distance is 2.627(3)Å. The other OH group of 2 makes an intermolecular hydrogen bond to the OH group of the adjacent 2 forming a linear chain along the c axis. The O···O distance is 2.765(3)Å.

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A microbicide, 5-chloro-2-methyl-4-isothiazoline-3-one (1), makes a host-guest complex with a host molecule of gallic acid methyl ester (2). The crystal structure, analyzed by X-rays, revealed that one of the three OH groups of 2 makes a hydrogen bond with the oxygen atom of 1. The O···O distance is 2.671(2)Å. The other two OH groups of 2 participate in the intra-molecular hydrogen bonds with the neighboring OH groups in the benzene ring.

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A dinuclear 1,2-bis(diphenylphosphinooxide)ethane-bridged (6,8,15,17-tetra-methyldibenzo[b,i][1,4,8,11]tetraazacyclo-tetradecinato) zinc(II) complex was synthesized and its crystal structure was determined by a single-crystal X-ray diffractometry. The crystal system is monoclinic with the space group of P2₁/n(#14) and Z = 2. The unit cell dimensions are a = 15.456(3)Å, b = 9.993(2)Å and c = 21.691(2)Å with β = 103.23(1)°, V = 3261(1)ų. Each zinc(II) ion is coordinated through four nitrogen atoms of the macrocyclic ligand and one oxygen atom of 1,2- bis(diphenylphosphinooxide)ethane to form a five-coordinated dinuclear complex of square-pyramidal geometry.

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A metabolite of thalidomide, 5′-hydroxythalidomide (1), was crystallized from acetonitrile solution. The angle between the least-square planes of the glutarimide ring and the phthalimide plane was 83.52(6)°. This conformation was similar to that of thalidomide and the thalidomide structure was not significantly affected by the hydroxylation of the glutarimide ring.

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A thermal rearrangement reaction of (R)-1-bromo-2-benzylaminobutane hydrobromide gave 3-bromo-1-benzylaminobutane hydrobromide. The process was confirmed by formation of a four-membered cyclic amine, the azetidine. After optical resolution of the racemic azetidine obtained, the compound was analyzed by its hydrobromide. The absolute configuration was unambiguously determined as S. The azetidine ring is bent to have a dihedral angle of 153° at the diagonal through non-N atoms.

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The title compound was synthesized by the Hantzch method and characterized by the X-ray diffraction method. It crystallizes in monoclinic space group P2₁/c with cell parameters a = 8.722(7)Å, b = 11.420(1)Å, c = 13.307(1)Å and Z = 4. The structure has N-H···N type intermolecular hydrogen bonds and exhibits a flattened boat conformation.

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Benzophenone analogue (3) has been synthesized and characterized by X-ray diffraction method. The compound crystallizes in monoclinic space group P2₁/a with cell parameters a = 10.9500(7)Å, b = 10.9670(7)Å, c = 11.0740(7)Å and Z = 4. The structure exhibits intermolecular hydrogen bonding of the type C-H···O. The dimer structure is observed in the molecular packing diagram. The methoxy and chloro substituents play an important role for their biological activity.

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The crystal structure of 4-(1-phenyl-1-methylcyclobutyl-3-yl)-2-aminothiazole (C₁₄H₁₆N₂S) has been determined by X-ray analysis. It crystallizes in the triclinic space group P1, with unit cell parameters: a = 10.4686(16), b = 11.9543(16), c = 5.9271(16)Å, α = 102.365(16), β = 92.120(16), γ = 65.302(15)°, V = 657.1(2)ų, D_c = 1.235 g/cm³, and Z = 2. The crystal structure was solved by direct methods and refined by full-matrix least squares to a final R-value of 0.041 for 2561 observed reflections. In the thiazole ring, N2=C1 and C1-S1 bond distances are 1.304(2) and 1.7415(16)Å, respectively.

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The crystal structure of 1-(4-methylphenylamino)-2-phenyl-1,2-ethandione-1-oxime (C₁₅H₁₄N₂O₂) has been determined by X-ray analysis. It crystallizes in the orthorhombic space group Pna2₁, with unit cell parameters: a = 23.516(3), b = 5.364(3), c = 21.872(3)Å, V = 2758.7(17)ų, D_c = 1.224 g/cm³, and Z = 8. The crystal structure was solved by direct methods and refined by full-matrix least squares to a final R-value of 0.041 for 2204 observed reflections. There are two independent molecules, A and B. These molecules are linked by intermolecular O-H···N hydrogen bonds.

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The crystal structure of capillarisin, which is one of the constituents of Artemisia capillaries, has been determined. The chromone ring system is nearly planar stabilized by an intramolecular hydrogen bond; the dihedral angle between the chromone and p-hydroxybenzyl moieties is 61.57(4)°. There are intermolecular π-π stacking interactions between the ring moieties correlated with symmetrical operations. The crystal structure is also stabilized by intermolecular hydrogen bonds.

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The title compounds are produced when L-ascorbic acid and its diastereomer, D-isoascorbic acid (Erythorbic acid), react with amino acids in the browning process of vegetables and fruits. The proton of the hydroxyl group at C3 in each molecule is transferred to the amino group at C2, showing the amphoteric ion.

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A cyclic hexamer of 4-(methylamino)benzoic acid was crystallized from dichloromethane-ethyl acetate to give colorless prisms, which belonged to space group P₁ with a = 12.441(1)Å, b = 16.003(1)Å, c = 11.7479(9)Å α = 94.421(7)°, β = 117.911(5)°, γ = 100.205(7)°, V = 1999.5(3)ų, and Z = 2. The compound adopted a folded conformation with all six N-methylamides having a cis (E) conformation; four intermolecular CH/n contacts were observed in the crystal.

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The crystal structure of 1,4-dimethoxyanthracene (DMA) was determined by a single-crystal X-ray diffraction method. DMA crystallized in the orthorhombic system, space group Pbca, with unit cell parameters: a = 6.3805(5)Å, b = 15.624(1)Å, c = 24.778(2)Å, V = 2470.0(4)ų, Z = 8. The crystal structure was solved by direct methods and refined by full-matrix least squares to a final R value of 0.071 for 2779 reflections (I > 2.00σ(I)). Two methoxy groups on DMA had a syn-geometry and lay in the anthracene plane.

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The crystal structure of [Sn(pydc)(OH)(H₂O)(μ-OH)]₂·4H₂O, (pydc = 2,6-pyridinedicarboxylate), has been determined by the X-ray diffraction method. This compound crystallizes in the triclinic system, space group P₁, with two molecules per unit cell. The unit cell dimensions are a = 6.5534(13)Å, b = 7.4907(15)Å, c = 12.030(2)Å, with α = 85.42(3)°, β = 82.92(3)° and γ = 74.83(3)°. The final R value is 0.0528 for 3258 reflections measured. The complex is binuclear with two bridging OH groups. Each of the two Sn atoms is also coordinated by the chelate [pydc]^2- ligand and one terminal OH group as well as by one terminal water molecule.

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The crystal structure of 3-amino-1,2,4-triazine was determined with single-crystal XRD data. The double bond sites are at C(2)-N(2) and C(3)-N(3) positions. The 3-amino group donates the unpaired electrons and resonates through C(1)-N(1) with the 1,2,4-triazine ring. There are two intermolecular hydrogen bonds stabilizing the crystal structure.

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2-Amino-3-(N-O-chlorophenylcarboxamido)-3,4-dimethylthiophene has been characterized by the X-ray diffraction method. The compound crystallizes in monoclinic space group P2₁/c with cell parameters a = 8.4740(6)Å, b = 7.5780(6)Å, c = 20.5860(10)Å, β = 100.27(4)° and Z = 4. The molecules appeared stacked. The crystal structure is stabilized by the intermolecular hydrogen bonds. 2-Amino-3-(N-O-chlorophenylcarboxamido)-3,4-dimethylthiophene has been characterized by the X-ray diffraction method. The compound crystallizes in monoclinic space group P2₁/c with cell parameters a = 8.4740(6)Å, b = 7.5780(6)Å, c = 20.5860(10)Å, β = 100.27(4)° and Z = 4. The molecules appeared stacked. The crystal structure is stabilized by the intermolecular hydrogen bonds. 2-Amino-3-(N-O-chlorophenylcarboxamido)-3,4-dimethylthiophene has been characterized by the X-ray diffraction method. The compound crystallizes in monoclinic space group P2₁/c with cell parameters a = 8.4740(6)Å, b = 7.5780(6)Å, c = 20.5860(10)Å, β = 100.27(4)° and Z = 4. The molecules appeared stacked. The crystal structure is stabilized by the intermolecular hydrogen bonds.

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The crystal belongs to space group P2₁2₁2₁, and the cell dimensions are a = 8.5300(5), b = 11.4516(9) and c = 23.893(1)Å. The final R value is 0.047. There are two crystallographically independent molecules in an asymmetric unit. The pyranose rings in both molecules take chair conformations. The nitrosourea moieties are planar. There is an extensive hydrogen network in the crystal.

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C₂₈H₃₁FO₄ is monoclinic, P2₁. The unit-cell dimensions at 293 K are a = 12.4629(10), b = 6.1705(5), c = 15.5815(13)Å, β = 102.243(2)°, V = 1171.00(17)ų, D_x = 1.278 g/cm³ and Z = 2. The R value is R = 0.048 for 4105 reflections. The A, B, C and D rings occur in half chair, distorted chair, distorted chair, and distorted envelope conformations. The molecules in the crystal are packed at the normal van der Waals distances.

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