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.      

C–H...O,C–H...π and π–π stacking interactions in 3-(2,4-dimethylphenyloxymethyl)-3,4-dihydroisocoumarin

3-(2,4-Dimethylphenyloxymethyl)-3,4-dihydroisocoumarin (C₁₈H₁₈O₃) was prepared by the alkylation of o-lithio N-methyl benzamide with 2-(2,4-dimethylphenoxy)methyl oxirane, followed by alkaline hydrolysis. The compound crystallizes in the orthorhombic space group Pbca with unit cell parameters : a = 8.239(2) Å, b = 14.918(5) Å, c = 24.831(9) Å, Z = 8. The crystal structure was solved by direct methods and refined to R = 0.0514 for 1564 observed reflections. The heterocyclic ring adopts a distorted half-chair conformation. Molecules are connected by π–π interactions between phenyl rings of the isocoumarin nucleus forming dimers. Dimers are connected via C–H...O hydrogen bonds forming chains. Further intermolecular C–H...π hydrogen bonds link the dimer chains to form supramolecular structure.     

7-Hydroxy-2-(2,3,4-trimethoxyphenyl)-4H-1-benzopyran-4-one: (7-hydroxy-2′,3′,4′-trimethoxyflavone)

7-Hydroxy-2,3,4-trimethoxyflavone, (C₁₈H₁₆O₆),M _r =328.32 crystallizes in the orthorhombic system, space groupPbna, with the following crystal data:a=8.853(2),b=12.870(2),c=26.293(3)Å,V=2996(1)ų,Z=8, MoK, =0.67 cm^–1,D _c =1.454 g·cm^–3,F(000)=1376,T=294K. The structure was solved by direct-methods and has been refined by full-matrix least-squares methods to a finalR value (F>(F)) of 0.0496. The molecule is not planar, the dihedral angle between the phenyl ring and the fused ring system is 27.3°. There are no intramolecular hydrogen bonds, but intermolecular short hydrogen contacts exist between hydroxyl hydrogen and carbonyl oxygen atoms.     

Crystal and molecular structure of 2′,4′-dimethoxyflavone

C₁₇H₁₄O₄,M _r =282.3, triclinic,P-1,a=8.469(3),b=8.516(2),c=20.425(8)Å,=84.95(3),=81.98(3), =70.47(2)°,V=1373(13)ų,Z=4,D _x =1.365 g cm^–3, (MoK )=0.71069 Å,=0.91 cm^–1,F(000)=592,T=294K,R=0.038 for 3577 observed reflections (F>3 (F)). The asymmetric unit is composed of two molecules. These two molecules, which are in planar conformations, differ in 4-methoxyl group orientation. Short intramolecular contacts are found between the -benzopyran portion and the dimethoxyphenyl ring.     

Zn(II) and Cd(II) Complexes Extended Structures Sustained by Hydrogen Bonding, π–π and C–H···π Interactions

Abstract  

Two new complexes [Zn(sal)₂(tpt)]·H₂O(1), [Cd(sal)₂(tpt)(H₂O)]·H₂O(2), have been obtained through ligands tpt and Hsal, where Hsal is salicylic acid and tpt is 2,4,6-tripyridyl-1,3,5-triazine, reacting with Zn(II) and Cd(II) salts. Their structures are fully characterized by IR spectroscopy, elemental analysis, single crystal X-ray diffraction. In complex 1, Zn(II) is coordinated by three N atoms and two O atom with a distorted square pyramidal coordination geometry. In 2, Each Cd(II) atom is seven-coordinated with a distorted pentagonal bipyramidal coordination geometry. The structural differences between two complexes show the influence of the coordinating orientation of metal ions. These two mononuclear complexes are further extended into three-dimensional structure via π–π, C–H···π and hydrogen bonding interactions. The solid state luminescent properties of complex 1, 2 are also reported.     

Intracomplex π-π stacking interaction between adjacent phenanthroline molecules in complexes with rare-earth nitrates: Crystal and molecular structures of bis(1,10-Phenanthroline)trinitratoytterbium and bis(1,10-Phenanthroline)trinitratolanthanum

Crystals of the compounds Yb(NO₃)₃(Phen)₂ and La(NO₃)₃(Phen)₂ (Phen = 1,10-phenanthroline) are investigated using X-ray diffraction. It is established that there exist two different crystalline modifications: the main modification (phase 1) is characteristic of all members of the isostructural series, and the second modification (phase 2) is observed only for the Eu, Er, and Yb elements. It is assumed that the stability and universality of main phase 1 are associated with the occurrence of the nonbonded π-π stacking interactions between the adjacent phenanthroline ligands in the complexes. The indication of the interactions is a distortion of the planar shape of the Phen molecule (the folding of the metallocycle along the N?N line with a folding angle of 11°–13° and its “boomerang” distortion). The assumption regarding the π-π stacking interaction is very consistent with the shape of the ellipsoids of atomic thermal vibrations, as well as with the data obtained from thermography and IR spectroscopy. An analysis of the structures of a number of rare-earth compounds has demonstrated that the intracomplex π-π stacking interactions directly contribute to the formation of supramolecular associates in the crystals, such as molecular dimers, supramolecules, chain and layered ensembles, and framework systems.     

Bis[aqua(2,5-bis(4-pyridyl)-1,3,4-oxadiazole)thiocyanate] cadmium(II): A three-dimensional framework built from hydrogen bonds and π-π stacking interactions

A three-dimensional (3D) network complex [Cd(L)₂(NCS)₂(H₂O)₂], L being 2,5-bis(4-pyridyl)-1,3,4-oxadiazole, has been synthesized and structurally determined by X-ray diffraction analysis: triclinic, space group P-1 with a = 7.8863(9) Å, b = 8.6287(10) Å, c = 11.4696(12) Å, = 94.346(2)°, = 109.331(2)°, = 94.354(2)°, Mr = 713.04, V = 730.13(14) ų, Z = 1. The crystal structure of the title complex reveals that it is a neutral molecule and the Cd(II) ion is at the center of symmetry. Each Cd(II) is six-coordinated and the CdN₄O₂ coordination sphere can be considered as an octahedron. The most striking feature of this complex resides in the formation of a 3D network through hydrogen bonds and - stacking interactions.     

Synthesis and crystal structure of 7-ethoxyl-4′-hydroxyisoflavone

7-Ethoxyl-4-hydroxyisoflavone was prepared and its crystal structure was examined by X-ray diffraction. Crystallization of the title compound occurs in the monoclinic, space group P2(1)/c with a = 11.144(2) Å, b = 10.209(1) Å, c = 13.191(2) Å, = 113.43(1) and Z = 4. The molecular structure of title compound consists of a benzopyranone moiety, a phenyl moiety, a hydroxyl and an ethoxyl group. The benzopyranone ring is not coplanar with the phenyl ring, the dihedral angle being 46.75. The ethoxyl group is nearly coplanar with its corresponding ring with the torsion angle 175.23(2). Three kinds of hydrogen bond and two kinds of aromatic stacking interaction link the title compounds into a three-dimensional networking structure.     

Anticancer agent development: X-ray crystal structure and keto-enol tautomerism of dimethyl 1-hydroxy-6,7-methylenedioxy-4-(3′,4′,5′-trimethoxyphenyl-trans-3,4-dihydronaphthalene-2,3-dicarboxylate

Structural and conformational information obtained from the crystal structure and solution¹H nmr investigations of the title compound are compared. The 4-aryltetralone, C₂₄H₂₄O₁₀, crystallizes as a chloroform solvate in the monoclinic space group, P2₁/n, witha=12.519(4),b=17.938(6),c=12.534(9)Å,=111.90(5)°, and D_calc=1.51 g cm^–3 forZ=4. The data for this compound were collected at –150°C. Least-squares refinement of 2796 observed [F _o5(F _o)] reflections led to the final agreement index ofR=0.062. A threefold static disorder was observed for one of the carboxyl groups. The second carboxyl group participates in an intramolecular hydrogen bond and is thus ordered. The¹H nmr spectrum revealed the title compound to exist as a keto-enol tautomeric mixture in solution. Vicinal hydrogen coupling constant analysis proved reliable in ascertaining B-ring stereochemistry of 2,3-disubstituted-4-aryltetralones.     

Synthesis and Structural Characterization of (2,4-Diamino-5-(3′,4′,5′-Trimethoxybenzyl)Pyrimidine Copper (II)) Complex

Abstract  The reaction of Cu(OOCCH₃)₂·H₂O with (2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl) pyrimidine (trimethoprim) in ethanolic solution at 80 °C affords the title complex which has been characterized by elemental, IR, and NMR (¹H and ¹³C).The crystal structure has been determined by single crystal X-ray diffraction. Compound 1 (C₃₆H₄₈Cu₂N₈O₁₄) is triclinic, space group P-1 with a = 7.2676(4) ?, b = 11.6721(7) ?, c = 12.8279(8) ?, α = 95.839(1)°, β = 93.456(1)°, γ = 105.541(1)°, Z = 1. Two copper atoms are coordinated directly to each other as well as are held together by four bridging aceto groups. Each copper atom is also bonded opposite the Cu–Cu vector to a trimethoprim molecule through the N(1) atom of the pyrimidine ring. Trimethoprim acts as a monodentate ligand through the pyrimidine nitrogen N(1) atom. The complex was screened for the activity against several bacteria, showing more activity against bacteria as compared to trimethoprim. Graphical Abstract  To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria was analyzed.      

Hydrogen in Cu?Ti and Ni?Ti Metallic Glasses

The hydrogen solubility and its effect on the crystallization of Cu Ti and Ni Ti glasses were studied by differential scanning calorimetry, thermogravimetry, and X-ray diffraction. Dependence of the crystallization products of the hydrogenated Ti-based alloys on the hydrogen content was found. Whereas in Cu-Ti alloys hydrogenation leads to drastic decreasing in the thermal stability due to phase separation in the amorphous state and to formation of microcrystalline structure during crystallization, in Ni Ti system hydrogen produces hydrides with Ni as well with Ti, which after heat treatment decompose, and finally the same crystalline phases as in unhydrogenated alloy are formed. The isothermal crystallization kinetics of the maximum hydrogenated Cu₅₀Ti₅₀ amorphous alloy was also investigated to obtain additional information about this transformation leading to nano-crystalline material.     

Crystal and molecular structure of chloramphenicol analog: 2-amino-4-methoxy-2′,2′-dichloroacetophenone

The crystal and molecular structure of the title compound has been determined from diffractometric data usingMo K radiation. The crystals are orthorhombic, space groupP2₁2₁2₁, witha=12.052(3),b=11.901(2),c=6.976(1) Å andZ=4. The structure was solved by the heavy-atom method and refined by full-matrix least-squares to a finalR value of 0.039 with 1096 observed reflections. The molecule is is almost planar. The acetyl group and the phenyl ring are strongly conjugated, the corresponding dihedral angle being 3.3(2)°. The structure is stabilized by an intramolecular N(1)-H(N)1O(l) hydrogen bond.     

Polymorphic–polytypic transition induced in crystals by interaction of spirals and 2D growth mechanisms

The relationship between crystal polymorphism and polytypism can be revealed by surface patterns through the interlacing of the growth spirals. Simple high-symmetry structures as SiC, ZnS, CdI2 and more complex low-symmetry layered structures as n-paraffins, n-alcohols and micas are concerned with polymorphic–polytypic transition. In this paper, we will show for the first time, through in situ AFM observations and X-ray diffractometry, that a protein polymorph (P2₁2₁2₁α-amylase) locally changes, during growth, to a monoclinic P2₁ polytype, thanks to the screw dislocation activity. The interplay between spiral steps and 2D nuclei of the polytypes coexisting in the same crystalline individual allows to foresee the consequences on the crystal quality. The discussion is extended to other mineral and biological molecules and a new general rule is proposed to explain the interactions between surface patterns and the bulk crystal structure.     

Study of the Phase Situation in 4-n-pentylphenyl-4′-n-heptyloxythiobenzoate (7S5)

Results of measurements of the specific heat of 4-n-pentylphenyl-4′-n-heptyloxythiobenzoate in the temperature range from about 90 K to about 370 K are presented. They were carried out with an adiabatic calorimeter, a differential scanning calorimeter and a polarizing microscope. Adiabatic calorimetry revealed four anomalies in the specific heat vs. temperature curve viz., two associated with transitions in the solid phase, one with melting and one with the liquid-crystalline nematic-to-isotropic phase transition. Also, two modifications of the solid, stable and metastable, were found to exist. In addition, the DSC method applied in the 285 K to 370 K range revealed a smectic C phase, but only when the sample is being cooled. The polarizing microscope showed the structural polymorphism of the solid phase in the 297 K to 327 K range to be more complex than would stem from adiabatic calorimetry and DSC measurements alone. It also confirmed the occurence of the S_c phase on cooling as ascertained by the DSC method.     

Oxidation–reduction processes upon interaction of aluminum oxide melt with molybdenum and tungsten in a hydrogen-containing atmosphere

A thermodynamic analysis of the processes occurring in the Мо–W–Al₂O₃ system at T = 2400 K and a total pressure of 1 bar, set by controlled reducing Ar + H₂ atmosphere, has been performed. It is found that the basic components of the system do not interact directly, although may be actively involved in chemical reactions with participation of other components to undergo numerous cyclic oxidation–reduction processes. Particular attention is paid to the processes involving such chemically active reagents as Н₂O₂, HO₂, H₂ (H), gaseous Al, and its hydrides (AlH, AlH₂, AlH₃).

     

Orientational Distribution Function and Order Parameters of Two 4′-Alkoxy-4-Cyanobiphenyls in Mesomorphic Phase

X-ray diffraction studies on samples of 4′-Pentyloxy-4-Cyanobiphenyl and 4′-Octyloxy-4-Cyanobiphenyl over the entire mesomorphic range are reported in this paper. A magnetic field was used to align samples. The orientational distribution functions f(β) have been calculated from the angular distribution of X-ray intensities. Orientational order parameters ( P ₂) and ( P ₄) have been calculated and compared with Maier-Saupe theoretical values. Expressions for the angular part of the pseudopotentials have been obtained from the temperature variation of f(β). The intermolecular distances D have been calculated from the experimental data and it is found that D is significantly smaller for well aligned samples. The apparent molecular length in the nematic phase and the layer thickness in the smectic phase have also been determined and are found to be about 1.4 times larger than the true molecular length in the fully extended form. This is in accordance with the findings from other cyano compounds.     

Structure of two 1,3-dioxane derivatives from 4′, 5′-dimethylfurocoumarins: 4a, 11a-dihydro-4a, 11a-dimethyl-8H-pyrano[3′,2′∶5,6]benzofuro[3,2-e]-1, 3-dioxan-8-one and 7a,11a-dihydro-7a,11a-dimethyl-2H-pyrano[2′, 3′∶4,5]benzofuro[3,2-d] (1,3) dioxan-2-one

Treatment of dimethylated psoralen and angelicin in the 4, 5-position leads to the formation of 1,3-dioxane derivatives, resulting from the condensation of an 1,3-dioxane ring to the 4, 5-positions of the dihydrofurocoumarin moiety. The structures of these new compounds, 4a, 1 1a-dihydro-4a, 11a-dimethyl-8H-pyrano [3, 25,6]benzofuro[3,2-e]-1, 3-dioxan-8-one (C₁₅H₁₄O₅) (1) and 7a, 11a-dihydro-7a, 11a-dimethyl-2H-pyrano[2, 34, 5]benzofuro[3, 2-d](1, 3)dioxan-2-one (C₁₅H₁₄O₅) (2) have been assigned by¹H and¹³C NMR measurements, mass spectrometry results, and X-ray analysis. Compound (1): triclinic,P¯1,a=9.847(2),b=8.927(2),c=8.334(2) Å,=95.98(2),=108.81(3), =106.73(3)°; compound (2): triclinic,P¯1,a=7.296(4),b=7.481(2),c=11.812(4) Å,=91.67(2),=95.97(4), =94.20(3)°. The structures were solved by direct methods and refined by full-matrix least squares toR=0.050 (1) and 0.056 (2). In both compounds the coumarin rings can be regarded as coplanar, while the five-membered ring adopts an envelope conformation and the 1,3-dioxane ring a chair conformation.