Formation Of Centrosymmetric Dimers Research Articles

N,N′,N′′-Triphenylguanidinium hydrogensulfate

The hydrogensulfate anions of the title compound, C19H18N3+·HSO4−, form centrosymmetric hydrogen-bonded dimers. In the cation, the dihedral angles between the phenyl rings and the plane defined by the central guanidinium fragment are in the range 41.46 (6)–67.11 (5)°.

N-(2-Methylphenyl)methanesulfonamide

The conformation of the N—H bond in the structure of the title compound (2MPMSA), C8H11NO2S, is syn to the ortho-methyl substituent, in contrast with the anti conformation observed for the meta-methyl-substituted compound (3MPMSA). The ortho substitution of the methyl group in N-phenyl­methane­sulfonamde (PMSA) changes its space group from monoclinic P21/c to triclinic P\overline{1}, compared with the change from monoclinic P21/c to ortho­rhom­bic Pccn on meta-substitution. The bond parameters in PMSA, 2MPMSA and 3MPMSA are similar, except for the torsion angles involving the S—N bond. The N—H H atom alone lies on one side of the plane of the phenyl group, while the whole methane­sulfonyl group is on the opposite side of the plane, similar to what was observed in PMSA and 3MPMSA. Thus, the amide H atom is available to a receptor mol­ecule during biological activity. The mol­ecules of the title compound form centrosymmetric dimers via an N—H⋯O(sulfon­yl) hydrogen bond.

5-Phenyl-1,3,4-oxadiazole-2(3H)-thione

In the title compound, C8H6N2OS, the planar oxadiazole ring is effectively coplanar with the phenyl ring. This facilitates the formation of N—H⋯S inter­actions, leading to a thione tautomer in the solid state, and the formation of centrosymmetric dimers.

Design of a depside with a lipophilic adamantane moiety: Synthesis, crystal structure and molecular conformation

New adamantane depsides, ethyl 2-(1-adamantyl)-3- O-[( S)-Boc-Phe]butanoate ( R, R, S)- 1a and ( S, S, S)- 1b were prepared and characterized by spectroscopic data. The crystal structures and the stereochemistry of rac-( R, R, S)- 1a and threo-2-(1-adamantyl)-3-hydroxybutanoic acid rac-( R, R)- 4a were determined by X-ray structure analysis. In the racemic crystal, the molecules of 1a form centrosymmetric dimers through hydrogen bonds involving a double acceptor function of the depside carbonyl oxygen, and donors of the amino group and aromatic C–H atoms. The dimers are connected through an infinite chain of C–H⋯O interactions, where C–H is an aromatic donor and the ester carbonyl oxygen is an acceptor. In the solid state, amphiphilic molecules 1a and 4a exhibit pronounced hydrophilic and hydrophobic bilayers.

Crystal structures of condensation products of 3,5-dibromosalicylic aldehyde with streptocide, norsulfazole, and ethazole

Crystal structures of 4-[(3,5-dibromo-2-hydroxy-benzylidene)-amino]-benzenesulfonamide (I), 4-[(3,5-dibromo-2-hydroxy-benzylidene)-amino]-N-thiazol-2-yl-benzenesulfonamide (II), and 4-[((3,5-dibromo-2-hydroxy-benzylidene)-amino]-N-(5-ethyl-1,3,4-thiadiazol-2-yl)-benzenesulfonamide (III) have been determined. The crystals of I are monoclinic, a = 8.645(2) A, b = 12.622(3) A, c = 14.414(3) A; β = 104.31(3)°, space group P21/n, Z = 4, R = 0.0642. The crystals of II are also monoclinic, a = 10.313(2) A, b = 11.288(2) A, c = 15.766(3) A; α = 99.37(3)°, space group P21/c, Z = 4, R = 0.0635. The crystals of III are triclinic, a = 10.567(2) A, b = 10.849(2) A, c = 18.432(4) A; α = 75.97(3)°, β = 89.71(3)°, γ = 87.33(3)°, space group P-1, Z = 4, R = 0.0644. The asymmetric part of the unit cell of compounds I and II contains a single molecule of the Schiff’s base, while in III two independent azomethine molecules A and B. The studied compounds I–III adopt the E-configuration relatively to the double azomethine bond C=N. Owing to phenolic oxygen together with nitrogen and oxygen atoms of the sulfonamide group, compound I makes in a crystalline state a two-dimensional hydrogen bonded network parallel to the plane (1 0 1). Compound II forms centrosymmetric dimers in the crystals via N-H…N hydrogen bonds. These dimers, in their turn, are connected by hydrogen bonds O-H…O into infinite chains running along the double screw axis b. As in II, molecules and of compound III form centrosymmetric dimers through hydrogen bonding N-H…N. These dimers are linked into infinite chains running along the c axis by hydrogen bonds C-H…O. The π-π-stacking interaction of aromatic rings is observed in all the compounds studied.

Structure of 2-(1-phenylimidiazolidin-2-ylidene)- malononitrile and 2-(hexahydropyrimidinyl-2-ylidene)- malononitrile

The crystal structure of 2-(1-phenylimidazolidin-2-ylidene)-malononitrile, I, and 2-(hexahydropyrimidin-2-ylidene)-malononitrile, II, were determined with crystal data (I: Monoclinic, P21/n, a=8.116(3) A, b=7.650(3) A, c=17.399(7) A, β=93.065(6)°, R all=0.0980; II: Monoclinic, P21/n, a=9.169(2) A, b=8.103(2) A, c=10.337(3) A, β=99.853(4)°, R all=0.0877). N−H···N hydrogen bonds were responsible for the formation of centrosymmetric dimers of I and one-dimensional zigzag molecular chains of II.

Synthesis, structure and cytotoxic activity of 2‐acetyl‐5‐trimethylsilylthiophene(furan) and their oximes

Abstract5‐Trimethylsilylderivatives of 2‐acetylthiophene and ‐furan have been regioselectively prepared by a one‐pot procedure from the corresponding 2‐acetylfuran or 2‐acetylthiophene using lithium N‐methylpiperazide (LNMP)–butyllithium–trimethylchlorosilane–water as the sequence of reagents. The ketones obtained were converted to the corresponding oximes. The structure of 2‐acetyl‐5‐trimethylsilylthiophene oxime (E‐isomer) has been studied by X‐ray diffraction. Formation of centrosymmetric dimers by means of H‐bonds has been observed. The intermolecular hydrogen bond O9H…N8 length is 2.842(5) Å [H…N8 = 1.87 (6) Å, O9H…N8 = 157(4)°]. Copyright © 2006 John Wiley & Sons, Ltd.

Cis-(6RS,13RS)-3,3,10,10-Tetramethyl-6,13-diphenyl-1,8-dioxa-4,11-diazacyclotetradecane-2,5,9,12-tetraone and two of its precursors

The title macrocycle, C26H30N2O6, (VI), was obtained by ;direct amide cyclization' from the linear precursor 3-hydroxy-N-[1-methyl-1-(N-methyl-N-phenylcarbamoyl)ethyl]-2-phenylpropanamide, the N-methylanilide of rac-2-methyl-2-[(3-hydroxy-2-phenylpropanoyl)amino]propanoic acid, C13H17NO4, (IV). The reaction proceeds via the intermediate rac-2-(2-hydroxy-1-phenylethyl)-4,4-dimethyl-1,3-oxazol-5(4H)-one, C13H15NO3, (V), which was synthesized independently and whose structure was also established. Unlike all previously described analogues, the title macrocycle has the cis-diphenyl configuration. The 14-membered ring has a distorted rectangular diamond-based [3434] configuration and intermolecular N-H...O hydrogen bonds link the molecules into a three-dimensional framework. The propanoic acid precursor forms a complex series of intermolecular hydrogen bonds, each of which involves pairwise association of molecules and which together result in the formation of extended two-dimensional sheets. The oxazole intermediate forms centrosymmetric hydrogen-bonded dimers in the solid state.

(2E)-2-(3,5-Dimethoxyphenyl)-3-(4-ethoxy-3-iodophenyl)acrylic acid

The X-ray analysis of the title compound, C19H19IO5, shows that the orientation of the two benzene rings is cis and confirms the E configuration of the mol­ecule. The occurrence of O—H⋯O hydrogen-bonding inter­actions results in the formation of centrosymmetric dimers.

9-(2-Acetoxyethoxymethyl)-2-formamido-6-(p-tolylsulfonyloxy)purine

The title compound, C18H19N5O7S, can be considered as a synthetic analogue of nucleosides. The mol­ecule displays an anti conformation. The occurrence of N—H⋯O hydrogen bonds results in the formation of centrosymmetric dimers. The crystal packing is characterized by π–π stacking inter­actions between the purine systems.

Erythro-2-(2,6-Dimethoxy-4-methylphenoxy)-1-(4-hydroxy-3,5-dimethoxyphenyl)propane-1,3-diol

In the title compound, C20H26O8, the mol­ecules adopt a conformation in which the torsion angle C(aryl)—C—C—O(aryl­oxy) is −70.8 (2)° and the torsion angle C(aryl)—O—C—C(benzyl­ic) is −152.71 (18)°, leading to a C(aryl)⋯C(aryl) distance of 4.426 (3) Å. This distance is identical, within experimental error, to the calculated maximum value obtained when the torsion angle C(aryl)—O—C—C(benzyl­ic) is varied and the torsion angle C(aryl)—C—C—O(aryl­oxy) is kept constant. The angle between the aromatic ring planes is 64.13 (7)°. The conformation is compared with those of related lignin model compounds. The hydrogen-bonding pattern reveals intramolecular interactions, and the formation of centrosymmetric dimers and chains of mol­ecules by intermolecular interactions.

Synthesis and structural characterization of ferrocene-based bis(pyrazol-1-yl)borate ligands: FcB(Me)pz 2K, Fc 2Bpz 2K, and 1,1′-fc[B(Me)pz 2] 2K 2 (Fc: ferrocenyl, fc: ferrocenylene, pz: pyrazolyl)

Reaction of the ferrocenyl(dimethylamino)boranes FcB(Me)NMe 2, Fc 2BNMe 2, and 1,1′-fc[B(Me)NMe 2] 2 with 1:1 mixtures of pyrazole and potassium pyrazolide in refluxing THF gave the potassium salts of the ferrocene-based bis(pyrazol-1-yl)borate ligands FcB(Me)pz 2K, Fc 2Bpz 2K, and 1,1′-fc[B(Me)pz 2] 2K 2 in good yield (Fc: ferrocenyl, fc: ferrocenylene, pz: pyrazolyl). In the solid state, FcB(Me)pz 2K and Fc 2Bpz 2K form centrosymmetric dimers with short K⋯Cp contacts suggesting an η 5 coordination mode of the potassium ion. The crystal lattice of the ditopic ligand 1,1′-fc[B(Me)pz 2] 2K 2 consists of coordination polymer strands featuring essentially the same structural motif that has been observed for the monotopic derivatives. All three scorpionate ligands are thus promising building blocks for the preparation of ferrocene-containing multiple-decker sandwich complexes.

Crystal Structure of a New Modification of cis-Bis(pivalyltrifluoroacetonato)copper(II)

Powder and single-crystal X-ray diffraction study of cis-bis(pivalyltrifluoro-acetonato)copper(II) has been performed (Bruker AXS P4 automatic diffractometer, MoKβ radiation, t = −25°C). Crystal data for C16H20CuF6O4: a= 9.980(7) A, b = 19.236(13) A, c = 20. 771(14) A, space group Pbca, V = 3987(5) A3, Z = 8, dcalc = 1.512 g/cm3. The square-planar environment of the Cu atom (Cu-Oav 1.904 A, =O-Cu-Oav 92.4°) is completed to bipyramidal by the atoms of the neighboring molecules, Cu...F 2.78 A and Cu...Cγ 3.30 A. The complex forms centrosymmetric pseudo dimers with Cu...Cu distances of 4.59 A.

Crystal and Molecular Structure of 4-Arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine-1,3-dione Derivatives

The X-ray crystal structure determination of 4-(2-methylphenyl)hexahydro-1H,3H-pyrido[ 1,2-c]pyrimidine-1,3-dione (2) and 4-(3-methylphenyl)hexahydro-1H,3H-pyrido[1,2-c]- pyrimidine-1,3-dione (3) is reported. The crystal structures show the formation of centrosymmetric dimers via intermolecular N-H···O hydrogen bonds. The saturated ring adopts a slightly distorted halfchair conformation in both 2 and 3. In either compound the planar phenyl ring is twisted with respect to the pyrimidine-1,3-dione fragment.

Crystal structure of 2-benzoyl-3,4,5,6-tetrachlorobenzoic acid.

intermediates in the synthesis of a variety of phthaleins and fluorans. Besides their importance in synthetic chemistry, this class of compounds also furnishes interesting research topics in structural chemistry. Lalancette et al.1 studied the X-ray structure of the simplest acid, 2-benzoylbenzoic acid (BBA). They demonstrated that BBA crystallizes in dimorphic (anhydrous and hydrated) forms, where BBA molecules take the open conformation as shown in Fig. 1(a), and form centrosymmetric dimers through intermolecular hydrogen bonds between carboxylic acid groups. This type of intermolecular hydrogen bonding is normally seen in carboxylic acids. Recently we have analyzed the X-ray structure of o-(p-N,Ndimethylaminobenzoyl)benzoic acid (DMABBA) and pointed out that intermolecular hydrogen bonds are formed between the carboxyl OH and the ketone oxygen of adjacent DMABBA molecules to form catemeric chains.2 In solution, 2benzoylbenzoic acids also exist as the lactone form (Fig. 1(b)) as well as the open form. Bhatt et al. investigated the effect of the benzene ring substitution on the tautomeric equilibrium between the open and the lactone form.3 Interestingly, he suggested that 2-benzoyl-3,4,5,6-tetrachlorobenzoic acid (TCBBA) takes the lactone form in the crystalline state. In this work, we have undertaken the X-ray analysis of TCBBA in order to clarify the crystal and molecular characteristics of 2-benzoylbenzoic acids having a typical lactone form. The title compound was prepared as follows. Anhydrous aluminum(III) chloride (2.320 g:8.1 mmol) was added portionwise to tetrachlorophthalic anhydride (2.160 g:16.2 mmol) in benzene (20 ml). The mixture was refluxed for 20 h. The reaction was stopped by adding 1 M HCl (10 ml) and the raw product was extracted with ethyl acetate. After evaporation of the extract in vacuo, the residue was purified by column chromatography (hexane/ethyl acetate = 1/3). Colorless crystals suitable for X-ray diffraction analysis were obtained by crystallization from aqueous acetone solution at room temperature (m.p. 196.0 C). All the non-hydrogen atoms were refined anisotropically. The hydrogen atoms were located by a difference Fourier synthesis and a geometrical calculation, with the parameters of H atom bonded to O3 also being refined. The crystal and experimental data are listed in Table 1. The final fractional atomic coordinates and equivalent isotropic thermal parameters for non-hydrogen atoms are given in Table 2. Selected bond 615 ANALYTICAL SCIENCES MAY 2002, VOL. 18 2002 © The Japan Society for Analytical Chemistry

The influence of charges and hydrogen bond on the conformation of zwitterionic 3-(2-hydroxyalkyl-pyridinium)-propionates and their hydrobromides

The effects of intra- and intermolecular electrostatic interactions and hydrogen bonding on the conformation of 3-(2-hydroxymethyl-pyridinium)-propionic acid bromide (1) and 3-(2-hydroxyethyl-pyridinium)-propionic acid bromide (2) have been studied. In 1, the molecules are linked by Br− ion to form two intermolecular hydrogen bonds COOH⋯Br⋯HOCH2 (O(1)⋯Br=3.175(3) and O(3)⋯Br=3.305(3)Å) yielding chains. The molecules of 2 form centrosymmetric dimers connected by a pair of H-bonds between COOH and CH2OH groups (O(1)⋯O(3)=2.674(3)Å), and the H-bonded CH2OH group further interacts with the Br− ion (O(3)⋯Br=3.166(5)Å). In both the compounds, the Br− ion additionally interacts electrostatically with the positively charged nitrogen atom. To analyse these interactions theoretically, the structures of 3-(2-hydroxy-alkyl)pyridinium propionates (betaines) and their hydrogen bromides as monomers and dimers in various configurations are analysed by PM3 and B3LYP/6-31G(d,p) calculations. Although both electrostatic interactions and H-bonds strongly affect the conformation of the investigated compounds, the former effect seems to be dominant. FTIR spectra of 1 and 2 in the solid state are analysed.

X-Ray Structure of 6(E)-[2(Z)-(Hydroxyimino)-2-phenylethyIidene]- 7,7,8,8,9,9-hexamethyl-3-phenyl-1,2-oxazaspiro[4.4]non-2-ene

Abstract The X-ray crystallographic structure of the title compound, a product of a 1,3-dipolar cy­ cloaddition reaction of benzonitrile oxide to 3,3,4,4,5,5-hexamethyl-1,2-bis(methylene)cyclopentane, has been determined. Colourless plates crystallize in the orthorhombic space group Pbca with cell dimensions a = 13.698(2), b = 11.836(2), c = 29.157(4) Å, V= 4727.2(1.2)Å3, Z = 8, 3736 reflections, final R(F) = 0.063 and wR(F2) = 0.166. The crystals are racemic, the molecules of opposite chirality form centrosymmetric dimers via intermolecular hydro­ gen bonds O-H···N between their oxime groups. The molecules are highly strained and the geometrical consequences of the steric strain are discussed.

Crystalline Inclusion Compounds Derived from Derivatives of Mandelic Acid. Host Synthesis, Inclusion Formation, and X-Ray Structures of a Free Host Compound and of DMSO Inclusion Complexes in Both Racemic and Optically Resolved Forms

New chiral host compounds based on mandelic acid derivatives having methyl (6a, b and 8a, b) or bromo substituents (7a, b) attached to the phenyl ring of mandelic acid and involving additional aromatic groups were synthesized. The inclusion properties of both the racemic and the optically resolved host species are reported, including solvent co-crystallization as well as chiroselective and vapour sorptive inclusion. The structures of the free racemic host compound 6b and of the DMSO inclusion compounds of optically resolved and racemic 8 (8a and 8b, respectively) have been determined by X-ray analysis. Enantiomeric pairs of molecules in 6b form centro-symmetric dimers by mutual hydrogen bonding of one hydroxyl group while the other is involved in O-–H ... π interactions. The guest molecules in the DMSO complexes of 8a and 8b are bound via hydrogen bonds to two host molecules related by translation along crystallographic axes. Parallels to previous hosts of this type are drawn.

Benzylgallium-Verbindungen. Die Kristallstrukturen von [Mg3Br2,4Cl1,6(OEt2)6][Ga(CH2Ph)4]2 · 0,5 Toluol und [(3,5-Me2C6H3CH2)2GaBr]2 / Benzylgallium Compounds. The Crystal Structures of [Mg3Br2,4Cl1,6(OEt2)6][Ga(CH2Ph)4]2 · 0.5 Toluene and [(3,5-Me2C6H3CH2)2GaBr]2

Abstract [Mg3Br2.4Cl1.6(OEt2)6][Ga(CH2Ph)4]2 · 0.5 toluene (1) can be obtained by the reaction of one equivalent of GaCl3 with four equivalents of PhCH2MgBr in Et2O. Recrystallization of the crude product from toluene at 60°C gives colorless crystals of 1. Treatment of GaCl3 with two equivalents 3,5-Me2C6H3CH2MgBr in Et2O gives after recrystallization from toluene the diorganogallium bromide [(3,5-Me2C6H3CH2)2GaBr]2 (2). 1 and 2 were characterized by NMR, IR and MS techniques as well as by X-ray structure analyses. 1 consists in the dication [Mg3Br2.4C1.6(OEt2)6]2+, two gallate units [Ga(CH2Ph)4]- and a toluene molecule, disordered around a center of inversion. 2 forms centrosymmetric dimers [(3,5-Me2C6H3CH2)2GaBr]2.

Symmetrisation, isomerism and structural studies on novel phenylmercury(II) thiosemicarbazonates: correlation of the energy barrier to rotation of the amino group with the bonding parameters of the thioamide group

The reactions of phenylmercury(II) acetate with a series of alkyl, aryl and heterocyclic thiosemicarbazones in ethanol formed novel phenylmercury(II) derivatives of stoichiometry [HgPhL] [HL = RN3N2HC1(S)N1H2 = cyclopentanone 1, cyclohexanone 2, benzaldehyde 3, 2-hydroxybenzaldehyde 4, 4-methoxybenzaldehyde 5, pyrrole-2-carbaldehyde 6, thiophene-2-carbaldehyde 7 or furan-2-carbaldehyde 8 thiosemicarbazone], characterised with the help of analytical data, physical properties, IR, far-IR, multinuclear NMR (1H, 13C, 199Hg) spectroscopy and X-ray crystallography of complexes 1, 5 and 6. The 1H and 13C NMR data suggest that the N2H group is deprotonated during reaction with phenylmercury(II) acetate and co-ordination occurs via the N3,S atoms in a chelating mode. The 199Hg NMR data suggest symmetrisation phenomenon for complexes 3 and 5, 2[HgPhL] ⇌ HgPh2 + [HgL], which is supported also by 1H and 13C NMR data. The δ(Hg) values reveal that shielding of Hg with the change of organic group in the thiosemicarbazones decreases in the order: 2-hydroxybenzene ⋙ furan > benzene > 4-methoxybenzene thiophene ≈ cyclohexanone ≈ cyclopentanone > pyrrole and the Lewis basicity of the thiosemicarbazones varies in the opposite order. The 1H and 13C NMR data reveal that 7 and 8 show isomerism. There are two strong [Hg–C 2.063(7) 1, 2.069(10) 5, 2.049(11) 6; Hg–S 2.382(2) 1, 2.357(3) 5, 2.377(3) A 6] and one weak bond [Hg–N3 2.489(6) 1, 2.611(7) 5, 2.492(9) A 6], with CPh–Hg–S bond angles of 162.9(2), 174.2(3), 165.8(3)° respectively. The weak intermolecular interactions via Hg · · · N2 [3.001(6) A] in 1 and via Hg · · · S in 5 [3.518(3) A] and 6 [3.528(3) A] form centrosymmetric dimers and Hg formally acquires four-co-ordination with two strong (Hg–C, Hg–S), one weak (Hg · · · N3) and one secondary (Hg · · · N2 or S) bonds. The preferred dimer formation via N2 nitrogen in 1, rather than via sulfur atoms (5 and 6) despite Hg · · · S affinity represents an unusual bonding mode. From the low-temperature 1H NMR studies of some selected complexes, the energy barrier (ΔGTc*, Tc is coalescence temperature) to rotation of the amino group about the C1–N1 bond was calculated and correlated with bonding parameters of the thioamide group in the solid state.