Final R-factor Research Articles

Vanadyl(acetylacetonate)2 mediated hydrolytic splitting of 1,3,5-triazine in a solution of toluene at 130 °C: The crystal structure of its axial formamide adduct

A toluene reaction of vanadyl bis(acetylacetonate) with 1,3,5-triazine produces a symmetrical three-fold hydrolytic cleavage of the triazine, and these three formamide moieties are found in the crystal structure. One of the resulting formamides attaches itself to the sixth (axial) position of the vanadyl complex, producing materials in which the remaining two formamides are trapped in the resulting lattice. Those crystals belong in space group Pca21, Z = 4 and the final R-factor = 0.030 for 3213 data collected at 100 K.

Hydrothermal Synthesis and Crystal Structure of a Novel Bismuth Oxide: (K0.2Sr0.8)(Na0.01Ca0.25Bi0.74)O3.

A novel distorted perovskite-type (K0.2Sr0.8)(Na0.01Ca0.25Bi0.74)O3 was prepared by a hydrothermal method using the starting materials NaBiO3·nH2O, Sr(OH)2·8H2O, Ca(OH)2, and KOH. Single-crystal X-ray diffraction of the novel compound revealed a GdFeO3-related structure belonging to the monoclinic system of the space group Cc with the following cell parameters: a = 11.8927 (17) Å, b = 11.8962 (15) Å, c = 8.4002 (10) Å, and β = 90.116 (9)°. The final R-factors were obtained as R1 = 0.0354 and wR2 = 0.0880 (using all the data). K+ and Sr2+ ions were distributed at four types of A-sites. On the other hand, four Bi5+-sites (Bi1, Bi2, Bi3, and Bi4) were occupied by four Ca2+ ions (Ca1, Ca2, Ca3, and Ca4), and the first three B-sites were occupied predominantly by Bi5+ with Na+ ions. The forth B-site was occupied predominantly by the Ca2+ ion with Bi5+ ions. Two types of B-sites, thus forming tilted distorted (Na/Ca/Bi)O6 and (Bi/Ca)O6 octahedra, have an ordering of 3:1 represented as (K/Sr)4(Na/Ca/Bi)3(Bi/Ca)O12. The distorted (Na/Ca/Bi)O6 and (Ca/Bi)O6 octahedra formed a perovskite-type network by corner sharing with features closely matching those of a GdFeO3-type structure. The novel compound is the first example of a perovskite-type bismuth oxide containing only Bi5+ in a system without a Ba atom and has a unique ordering (3:1) of the B site. The compound showed photocatalytic activity for phenol degradation under visible light irradiation.

The structure of a confiscated street drug: 6-Monoacetyl morphine hydrochloride trihydrate - C19H22NO4Cl·3H2O

Since street drugs are frequently and rapidly modified, in order to circumvent the current laws that make them illicit, it is necessary to fully identify them by single crystal X-ray diffraction; subsequently, ideal powder patterns are computed for rapid identification of additional confiscations, which are mostly available in powder form. Monoacetyl morphine is found in samples of heroin as a by-product of incomplete synthesis, or from degradation of diacetyl morphine caused by heat, humidity, or pH changes. It is formed by the hydrolysis of the acetyl function on the benzene moiety of the morphine ring, thereby inserting an OH moiety at that site. This compound, 6-monoacetyl morphine, is the primary and active metabolite of heroin, rapidly hydrolyzed in the user’s blood. Herein, we describe the structure of 6-monoacetyl morphine, IUPAC name: [(4R,4aR,7S,7aR,12bS)-9-hydroxy-3-methyl-2,4,4a,7,7a,13-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7-yl] acetate (A), as the trihydrated hydrochloride, whose structure has not been described previously. Our crystals belong in space group P212121 with cell parameters of a = 6.9367(2), b = 13.0374(3), c = 21.9856(6) Å, V = 1988.30 (9) Å3; its composition is C19H22NO4Cl·3H2O, and Z = 4.0. A full sphere of data was collected at 100 K using CuKα radiation (λ = 1.54178 Å), yielding 3594 unique reflections measured and a final R-factor = 4.1%, with a Flack parameter = 0.05(1).

Hydrothermal Synthesis and Crystal Structure of a Mixed-Valence Bismuthate, Na3Bi3O8.

Four types of bismuth oxides, Na3Bi3O8, NaBiO3, α-Bi2O3, and ε-Bi2O3, were obtained by hydrothermal reactions using NaBiO3·nH2O in NaOH solution. The crystal structure of a new phase (Na3 Bi3+)Bi25+O8 ((Na0.75Bi0.25)2BiO4) was determined by using single crystal X-ray diffraction data, and this compound was found to show a Na2MnCl4-related structure with a monoclinic system (space group, Pm) with the following lattice parameters: a = 5.990 (2) Å, b = 3.335 (2) Å, c = 10.108 (2) Å, and β = 91.08 (3)°. The final R-factors R1 and wR2 were 0.041 and 0.090 (all data), respectively. The new phase was composed of mixed valence states of Bi (Bi3+ and Bi5+, with a mean Bi valence of 4.30) with five distinct Bi sites, where two Bi5+ (Bi1 and Bi2) fully occupied the distorted octahedral sites and three Bi3+ (Bi3, Bi4, and Bi5) were statistically distributed at the split sites with Na+ (Na3, Na4, and Na5). The Na6 site is fully occupied. The distorted Bi5+O6 octahedra formed one-dimensional chains via edge-sharing along the b-axis, with the chains held by Bi3+/Na+ split sites. The structural feature except for the split distribution of Bi3+/Na+ was classified as a Na2MnCl4-type structure. DFT calculations based on a model discounting the split distribution of Bi3+/Na+ indicated that Bi 6s and O 2p orbitals form sp hybridization at the conduction band. This new mixed valence bismuth oxide exhibited photocatalytic activity for phenol degradation under visible light irradiation. In addition to Na3Bi3O8, the hydrothermal reaction using NaBiO3·nH2O in NaOH solution yielded micrometer-sized single crystals of an ilmenite-type NaBiO3 and two polymorphs of bismuth oxides with monoclinic (α-Bi2O3) and orthorhombic (ε-Bi2O3) structures, depending on the reaction temperature and NaOH concentration.

Hydrothermal synthesis and crystal structure of a fluorite-type Pb0.35Bi0.65O1.59 compound with photocatalytic activity

A fluorite-type compound, Pb0.35Bi0.65O1.59, was synthesized by a hydrothermal reaction. The crystal structure of the compound was refined using synchrotron powder X-ray diffraction data; the cubic cell dimensions were a = 5.4864 (1) Å and the space group was Fm3-m (No. 225). The final R-factors were Rwp = 5.76% and Rp = 4.36%. The band gap of this compound was estimated to be 0.98 eV from the UV–vis spectrum. This compound comprised mixed-valence states Bi3+ and Bi5+ with an average Bi valence of 3.83. This compound exhibited photocatalytic activity for phenol degradation and was thermally stable up to 380 °C.

Synthesis, structure and molecular docking analysis of an anticancer drug of N-(2-aminophenyl)-2-(2-isopropylphenoxy) acetamide

N-(2-aminophenyl)-2-(2-isopropylphenoxy) acetamide(3) has been synthesized in good yield by stirring compound ethyl 2-(2-isopropylphenoxy) acetic acid(1), with, 2-diaminobenzene (2), in dry dichloromethane followed by the addition of lutidine, and TBTU in cooled condition. The crude product (3) was recrystallized and elucidated by elemental analyses and spectroscopic techniques (HNMR, LC-MS). The anticancer activity was confirmed by in silico modeling study which targets the VEGFr receptor. The compound crystallizes in the orthorhombic crystal system with space group Pbca with unit cell parameters: a = 7.4250 (4) Å, b = 14.9753 (7) Å, c = 27.5656 (14) Å and Z = 4. The crystal structure has been solved by using direct methods and refined by full matrix least-squares procédures to a final R-factor of 0.042 for 2158 observed reflections. The structure exhibits intermolecular H-bonds of the type N–H⋅⋅⋅O. In addition, two intramolecular interactions N1-H1…O2 and N2-H2B…N1 were also observed.

Structural analysis of chalcone derivative: 2‐{4‐[(2E)‐3‐(4‐fluorophenyl)prop‐2‐enoyl]phenoxy}acetic acid hydrate

The crystal structure of the title compound has been determined from X-ray diffraction studies. The compound crystallizes from methanol in the monoclinic system with space group P21/c with unit cell parameters: a = 10.647 (8), b = 8.494 (6), c = 16.743 (12) A, β = 92.731 (13)°, Z = 4, V = 1512.4(19) A3. The structure was determined by direct methods and refined to a final R-factor of 0.06. The two six-membered rings, A and B are planar with RMS deviation of fitted atoms is 0.0041 A and the structure is stabilized by strong Osingle bondH..O, weak Csingle bondH…O, and Csingle bondH…F interactions.

SYNTHESIS AND CRYSTAL STRUCTURE OF (E)-3-(4-BUTOXYPHENYL)-1-(NAPHTHALEN-1-YL)PROP-2-EN-1-ONE

Chalcone derivative ( E )-3-(4-Butoxyphenyl)-1-(naphthalen-1-yl)prop-2-en-1-one (C23 H22 O2) crystallizes in monoclinic system with space group 'P 2 1 /c ' and unit cell parameters: a = 15.1595(14) A, b = 7.6644(7) A, c = 15.8634(15) A, b = 96.942(7) o . The crystal structure was solved using direct methods and refined by full matrix least squares procedures to a final R-factor of 0.0911 for 1591 observed reflections. The enone moiety adopts E conformation with respect to C12=C13 bond.The molecules in the unit cell are linked by weak C–H⋅⋅⋅O and π-π interactions. The molecule contains two C–H⋅⋅⋅O intramolecular interactions which stabilizes the crystal structure

Production in Pichia pastoris, antifungal activity and crystal structure of a class I chitinase from cowpea (Vigna unguiculata): Insights into sugar binding mode and hydrolytic action

A cowpea class I chitinase (VuChiI) was expressed in the methylotrophic yeast P. pastoris. The recombinant protein was secreted into the culture medium and purified by affinity chromatography on a chitin matrix. The purified chitinase migrated on SDS-polyacrylamide gel electrophoresis as two closely-related bands with apparent molecular masses of 34 and 37 kDa. The identity of these bands as VuChiI was demonstrated by mass spectrometry analysis of tryptic peptides and N-terminal amino acid sequencing. The recombinant chitinase was able to hydrolyze colloidal chitin but did not exhibit enzymatic activity toward synthetic substrates. The highest hydrolytic activity of the cowpea chitinase toward colloidal chitin was observed at pH 5.0. Furthermore, most VuChiI activity (approximately 92%) was retained after heating to 50 °C for 30 min, whereas treatment with 5 mM Cu2+ caused a reduction of 67% in the enzyme's chitinolytic activity. The recombinant protein had antifungal activity as revealed by its ability to inhibit the spore germination and mycelial growth of Penicillium herquei. The three-dimensional structure of VuChiI was resolved at a resolution of 1.55 Å by molecular replacement. The refined model had 245 amino acid residues and 381 water molecules, and the final R-factor and Rfree values were 14.78 and 17.22%, respectively. The catalytic domain of VuChiI adopts an α-helix-rich fold, stabilized by 3 disulfide bridges and possessing a wide catalytic cleft. Analysis of the crystallographic model and molecular docking calculations using chito-oligosaccharides provided evidences about the VuChiI residues involved in sugar binding and catalysis, and a possible mechanism of antifungal action is suggested.

Hydrothermal synthesis and crystal structure of a new lithium copper bismuth oxide, LiCuBiO4

A new lithium copper bismuth oxide, LiCuBiO4 was prepared by hydrothermal reaction using NaBiO30.1*4H2O. The crystal structural model of this compound was refined by using synchrotron X-ray powder diffraction data. This bismuthate has the LiCuSbO4 related structure with the orthorhombic cell (Space group: Pnma) of a=10.9096(9), b=5.8113(5) and c=5.0073(4)Å, and the final R-factors were Rwp=4.84 and Rp=3.58%. This compound is the first example of a lithium copper bismuthate containing Bi5+. An antiferromagnetic ordering of Cu2+ moment was observed at 6K.

Crystal structure of an antifungal osmotin-like protein from Calotropis procera and its effects on Fusarium solani spores, as revealed by atomic force microscopy: Insights into the mechanism of action

CpOsm is an antifungal osmotin/thaumatin-like protein purified from the latex of Calotropis procera. The protein is relatively thermostable and retains its antifungal activity over a wide pH range; therefore, it may be useful in the development of new antifungal drugs or transgenic crops with enhanced resistance to phytopathogenic fungi. To gain further insight into the mechanism of action of CpOsm, its three-dimensional structure was determined, and the effects of the protein on Fusarium solani spores were investigated by atomic force microscopy (AFM). The atomic structure of CpOsm was solved at a resolution of 1.61Å, and it contained 205 amino acid residues and 192 water molecules, with a final R-factor of 18.12% and an Rfree of 21.59%. The CpOsm structure belongs to the thaumatin superfamily fold and is characterized by three domains stabilized by eight disulfide bonds and a prominent charged cleft, which runs the length of the front side of the molecule. Similarly to other antifungal thaumatin-like proteins, the cleft of CpOsm is predominantly acidic. AFM images of F. solani spores treated with CpOsm resulted in striking morphological changes being induced by the protein. Spores treated with CpOsm were wrinkled, and the volume of these cells was reduced by approximately 80%. Treated cells were covered by a shell of CpOsm molecules, and the leakage of cytoplasmic content from these cells was also observed. Based on the structural features of CpOsm and the effects that the protein produces on F. solani spores, a possible mechanism of action is suggested and discussed.

Impact of Aromatic Ring Count on the Ability to Participate in Attractive Interactions. Crystal Structure (X-ray) and Solid State Computational (DFT/QTAIM/RDS/Hirshfeld-surfaces) Study of 1,4-di(2-phenyl-1H-imidazol-4-yl)benzene. A Potential Nanotechnology Intrinsic Component

The crystal structure of 1,4-di(2-phenyl-1H-imidazol-4-yl)benzene (DPI4B) is determined by X-ray diffraction with a final R-factor of 6.42% at room temperature. It crystallizes with a space group P21/c, Z = 4, a = 5.01790(10), b = 28.8971(6), and c = 12.9362(3) A; β = 98.757(2)°. Two 4-phenyl-1H-imidazole (4PI) fragments are related by inversion symmetry and each makes a dihedral angle of 0° with the benzene rings. Despite the presence of a total number of five homo- and heterocyclic rings in the DPI4B molecule, similarly to 2-phenyl-1H-imidazole (2PI) but in contrast to 1,4-di(1H-imidazol-4-yl)benzene (DI4B) and 4-phenyl-1H-imidazole (4PI), it is almost planar. Each plane containing a terminal phenyl ring makes a small dihedral angle of about 3° with the central benzene ring plane. The average twisting angle of the whole molecule is equal to 7°. The ordering of compounds studied according to the decreasing twisting angle is 4PI > DI4B > DPI4B > 2PI and is the same as that according to hydrogen bond lengt...

Hydrothermal synthesis and crystal structure analysis of two new cadmium bismuthates, CdBi2O6 and Cd0.37Bi0.63O1.79

Two new cadmium bismuthates, CdBi2O6 and Cd0.37Bi0.63O1.79, were prepared by hydrothermal reaction using NaBiO3·nH2O as one of the starting compounds. The crystal structures of these compounds were refined by using synchrotron X-ray powder diffraction data. The former bismuthate has a MnSb2O6-type structure with a hexagonal cell (space group: P321); the cell parameters were a = 9.3641(7) and c = 4.9523(3) Å, and the final R-factors were Rwp = 4.59% and Rp = 3.04%. The latter bismuthate has a fluorite-type structure with a cubic cell (space group: ) of a = 5.4110(4) Å, and the final R-factors were Rwp = 4.79% and Rp = 3.57%. These new bismuthates exhibit no photocatalytic activity under visible light.

Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry.

The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(O(i)Pr)2}9], was determined by single-crystal neutron diffraction. The Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5](3-) ion with an exceptionally short Cu-Cu distance. The 11 hydrides in the cluster display three different coordination modes to the Cu atoms: six μ3-hydrides in a pyramidal geometry, two μ4-hydrides in a tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected for 7 days on a small crystal with dimensions of 0.20 mm × 0.50 mm × 0.65 mm using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at Oak Ridge National Laboratory. The final R-factor was 8.63% for 16,014 reflections.

Crystal structures of a pentavalent bismuthate, SrBi2O6 and a lead bismuth oxide (Pb1/3Bi2/3)O1.4

The crystal structures of a pentavalent bismuthate, SrBi2O6 with the PbSb2O6-type structure and a lead bismuth oxide, (Pb1/3Bi2/3)O1.4 with the fluorite-type structure were refined by using neutron diffraction data. The final R-factors were Rwp = 4.49, Rp = 3.46, RI = 4.50 and RF = 1.70% for SrBi2O6 and Rwp = 5.04, Rp = 3.93, RI = 5.47 and RF = 4.26% for (Pb1/3Bi2/3)O1.4. SrBi2O6 prepared from NaBiO3·1.4H2O is the first example of the bismuthate with the PbSb2O6-type structure. The fluorite-type lead bismuth oxide, (Pb1/3Bi2/3)O1.4 was obtained by heating the PbSb2O6-type lead bismuthate, PbBi2O5.9·H2O which was prepared also from NaBiO3·1.4H2O.

Quantum-Chemical Insight into Structure–Reactivity Relationship in 4,5,6,7-Tetrahalogeno-1H-benzimidazoles: A Combined X-ray, DSC, DFT/QTAIM, Hirshfeld Surface-Based, and Molecular Docking Approach

The weak interaction patterns in 4,5,6,7-tetrahalogeno-1H-benzimidazoles, protein kinase CK2 inhibitors, in solid state are studied by the X-ray method and quantum chemistry calculations. The crystal structures of 4,5,6,7-tetrachloro- and 4,5,6,7-tetrabromo-1H-benzimidazole are determined by X-ray diffraction and refined to a final R-factor of 3.07 and 3.03%, respectively, at room temperature. The compound 4,5,6,7-tetrabromo-1H-benzimidazole, which crystallizes in the I41/a space group, is found to be isostructural with previously studied 4,5,6,7-tetraiodo-1H-benzimidazole in contrast to 4,5,6,7-tetrachloro-1H-benzimidazole, which crystallizes as triclinic P1̅ with 4 molecules in elementary unit. For 4,5,6,7-tetrachloro-1H-benzimidazole, differential scanning calorimetry (DSC) revealed a second order glassy phase transition at Tg = 95°/106° (heating/cooling), an indication of frozen disorder. The lack of 3D isostructurality found in all 4,5,6,7-tetrahalogeno-1H-benzimidazoles is elucidated on the basis of the intra- and intermolecular interactions (hydrogen bonding, van der Waals contacts, and C-H···π interactions). The topological Bader's Quantum Theory of Atoms in Molecules (QTAIM) and Spackman's Hirshfeld surface-based approaches reveal equilibration of electrostatic matching and dispersion van der Waals interactions between molecules consistent with the crystal site-symmetry. The weakening of van der Waals forces accompanied by increasing strength of the hydrogen bond (N-H···N) result in a decrease in the crystal site-symmetry and a change in molecular packing in the crystalline state. Crystal packing motifs were investigated with the aid of Hirshfeld surface fingerprint plots. The ordering 4,5,6,7-tetraiodo > 4,5,6,7-tetrabromo > 4,5,6,7-tetrachloro > 4,5,6,7-tetrafluoro reflects not only a decrease in crystal symmetry but also increase in chemical reactivity (electronic activation), which could explain some changes in biological activity of compounds from the 4,5,6,7-tetrahalogeno-1H-benzimidazole series. The ability of formation of a given type of bonds by 4,5,6,7-tetrahalogeno-1H-benzimidazole molecules is the same in the crystal and in CK2. Analysis of the interactions in the crystal permits drawing conclusions on the character (the way) of connections between a given 4,5,6,7-tetrahalogeno-1H-benzimidazole as a ligand with CK2 protein to make a protein-ligand complex.

Crystal structure of putative CbiT from Methanocaldococcus jannaschii: an intermediate enzyme activity in cobalamin (vitamin B12) biosynthesis

BackgroundIn the anaerobic pathway of cobalamin (vitamin B12) synthesis, the CbiT enzyme plays two roles, as a cobalt-precorrin-7 C15-methyltransferase and a C12-decarboxylase, to produce the intermediate, cobalt-precorrin 8.ResultsThe primary structure of the hypothetical protein MJ0391, from Methanocaldococcus jannaschii, suggested that MJ0391 is a putative CbiT. Here, we report the crystal structure of MJ0391, solved by the MAD procedure and refined to final R-factor and R-free values of 19.8 & 27.3%, respectively, at 2.3 Å resolution. The asymmetric unit contains two NCS molecules, and the intact tetramer generated by crystallographic symmetry may be functionally important. The overall tertiary structure and the tetrameric arrangements are highly homologous to those found in MT0146/CbiT from Methanobacterium thermoautotrophicum.ConclusionsThe conservation of functional residues in the binding site for the co-factor, AdoMet, and in the putative precorrin-7 binding pocket suggested that MJ0391 may also possess CbiT activity. The putative function of MJ0391 is discussed, based on structural homology.

Temperature Variation of Ultralow Frequency Modes and Mean Square Displacements in Solid Lasamide (Diuretic Drug) Studied by 35Cl-NQR, X-ray and DFT/QTAIM

The application of combined (35)Cl-NQR/X-ray/DFT/QTAIM methods to study the temperature variation of anisotropic displacement parameters and ultralow frequency modes of anharmonic torsional vibrations in the solid state is illustrated on the example of 2,4-dichloro-5-sulfamolybenzoic acid (lasamide, DSBA) which is a diuretic and an intermediate in the synthesis of furosemide and thus its common impurity. The crystallographic structure of lasamide is solved by X-ray diffraction and refined to a final R-factor of 3.06% at room temperature. Lasamide is found to crystallize in the triclinic space group P-1, with two equivalent molecules in the unit cell a = 7.5984(3) Å, b = 8.3158(3) Å, c = 8.6892(3) Å; α = 81.212(3)°, β = 73.799(3)°, γ = 67.599(3)°. Its molecules form symmetric dimers linked by two short and linear intermolecular hydrogen bonds O-H···O (O-H···O = 2.648 Å and ∠OHO = 171.5°), which are further linked by weaker and longer intermolecular hydrogen bonds N-H···O (N-H···O = 2.965 Å and ∠NHO = 166.4°). Two (35)Cl-NQR resonance frequencies, 36.899 and 37.129 MHz, revealed at room temperature are assigned to chlorine sites at the ortho and para positions, relative to the carboxyl functional group, respectively. The difference in C-Cl(1) and C-Cl(2) bond lengths only slightly affects the value of (35)Cl-NQR frequencies, which results mainly from chemical inequivalence of chlorine atoms but also involvement in different intermolecular interactions pattern. The smooth decrease in both (35)Cl-NQR frequencies with increasing temperature in the range of 77-300 K testifies to the averaging of EFG tensor at each chlorine site due to anharmonic torsional vibrations. Lasamide is thermally stable; no temperature-induced release of chlorine or decomposition of this compound is detected. The temperature dependence of ultralow frequency modes of anharmonic small-angle internal torsional vibrations averaging EFG tensor and mean square angle displacements at both chlorine sites is derived from the (35)Cl-NQR temperature dependence. The frequencies of torsional vibrations higher for the para site than the ortho site are in good agreement with those obtained from thermal parameters obtained from X-ray studies. The mean square angle displacements are in good agreement with those estimated from X-ray data with the use of the TLS model. The detailed DFT/QTAIM analysis suggests that the interplay between different hydrogen bonds in adjacent molecules forming dimers is responsible for the differences in flexibility of the carboxyl and sulphonamide substituents as well as both C-Cl(1) and C-Cl(2) bonds. Three ultralow wavenumber modes of internal vibrations in Raman and IR spectra obtained at the B3LYP/6-311++G(d,p) level close to those obtained within the TLS model suggest that internal and external modes of vibrations are not well separated.

Conformations and intermolecular interactions pattern in solid chloroxylenol and triclosan (API of anti-infective agents and drugs). A 35Cl NQR, 1H-14 N NQDR, X-ray and DFT/QTAIM study

Two antibacterial and antifungal agents, chloroxylenol (4-chloro-3,5-dimethyl-phenol) and triclosan (5-chloro-2-(2',4'-dichlorophenoxy)-phenol), were studied experimentally in solid state with an X-ray, (35)Cl-nuclear quadrupole resonance (NQR) and (17)O-nuclear quadrupole double resonance (NQDR) spectroscopies and, theoretically, with the density functional theory/quantum theory of atoms in molecules (DFT/QTAIM). The crystallographic structure of triclosan, which crystallises in space group P31 with one molecule in the asymmetric unit [a = 12.64100(10), b = 12.64100(10), c = 6.71630(10) Å], was solved with an X-ray and refined to a final R-factor of 2.81% at room temperature. The NQR frequencies of (35)Cl and (17)O were detected with the help of the density functional theory (DFT) assigned to particular chlorine and oxygen sites in the molecules of both compounds. The NQR frequencies at (35)Cl sites in chloroxylenol and triclosan were found to be more differentiated than frequencies at the (17)O site. The former better describes the substituent withdrawing effects connected to π-electron delocalization within the benzene rings and the influence of temperature; whereas, those at the (17)O site provide more information on O-H bond and intermolecular interactions pattern. The conformation adopted by diphenyl ether of triclosan in solid state was found to be typical of diphenyl ethers, but the opposite to those adopted when it was bound to different inhibitors. According to an X-ray study, temperature had no effect on the conformation of the diphenyl ring of triclosan, which was the same at 90 K and at room temperature (RT). The scattering of NQR frequencies reproduced by the DFT under assumption of the X-ray data at 90 K and RT is found to be a good indicator of the quality of resolution of the crystallographic structure.

X-ray structure analysis of 3-chloro-7-hydroxy-4- methyl-chroman-2-one

The title compound crystallizes in the monoclinic space group P21/c, with unit cell parameters a=7.7203(3), b=14.0481(4), c=8.9066(3) Å, â=112.858(5)º, V= 890.11(5) Å3 and Z = 4. The structure has been solved by direct methods and the final R-factor is 0.0433 for 2832 unique reflections. The molecule, as such, is planar and the planarity is confirmed by the magnitude of dihedral angles between the two rings. Extensive Hydrogen-bonding has been observed and chlorine atom is responsible for the formation of trifurcated hydrogen-bond. Trifurcated hydrogen-bond plays a significant role in the design and synthesis of molecules having drug implications.