Cytosinium Isophthalate: Crystal Structure Redetermination and Room Temperature Phosphorescence

The title compound cytosinium isophthalate(C-H_2IA) self-assembly of cytosine(C) and isophthalic acid(H_2IA) in aqueous media has been synthesized and the crystal structure with a reasonable protonation state is redetermined. Single-crystal X-ray diffraction analysis reveals that each asymmetric unit contains one protoned cytosine molecule and one deprotoned isophthalic acid. The proton transferred from carboxylic acid to the pyrimidine ring is disordered across an inversion center with occupancy of 0.5 and the proton located to one of the carboxylate group lies on an inversion center shared by two crystallographically equivalent oxygen atoms. In addition, the cytosine molecules are connected by complementary hydrogen bonds to form a one-dimensional tape structure. The neighboring isophthalic acids are connected via hydrogen bonds between carboxyl groups to form a one-dimensional lattice like tape. Furthermore, the adjacent organic base tapes and organic acid tapes are stacked one with another through π-π stacking interactions to form a three-dimensional supramolecular structure. Interestingly, C-H_2IA displays a green phosphorescence in solid state at room temperature with the lifetime of 0.7 s determined by time resolved studies, indicating that supramolecular C-H_2IA is a potential pure organic phosphorescent luminogens.     

Syntheses,Crystal Structures and Catalytic Properties of Copper(Ⅱ) and Cobalt(Ⅱ) Complexes Containing 5,6-Dimethylbenzimidazole

Two new complexes, [Cu(DMB)2(NAA)2](1) and [Co(DMB)2(NAA)2](2)(DMB = 5,6-dimethylbenzimidazole, HNNA = 1-naphthylacetic acid), were hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TGA, PXRD and single-crystal X-ray diffraction analysis. The coordination geometry of the metal centers is a perfect square plane for 1 and a distorted tetrahedron for 2. In compound 1, the mononuclear units are linked by N–H···O hydrogen bonds to form a 1D chain structure, while mononuclear motifs of 2 are extended via N–H···O hydrogen bonding and π-π stacking interactions into a 2D supramolecular layer. The remarkable catalytic properties of the two complexes for the degradation of Congo red dye have been found.     

The open-close mechanism of M2 channel protein in influenza A virus:A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study,the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues,and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then,quantum chemistry calculations at the MP2/6-311G level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calcula-tion results indicate that the binding strength of the N-H···N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1,and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1(T-shaped interaction) or -12.3 kcal·mol-1(parallel stacking interaction). Thus,the calcu-lated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.     

Unraveling weak interactions in aniline-pyrrole dimer clusters

Weak intermolecular interactions in aniline-pyrrole dimer clusters have been studied by the dispersion-corrected density functional theory(DFT) calculations. Two distinct types of hydrogen bonds are demonstrated with optimized geometric structures and largest interaction energy moduli. Comprehensive spectroscopic analysis is also addressed revealing the orientation-dependent interactions by noting the altered red-shifts of the infrared and Raman activities. Then we employ natural bond orbital(NBO)analysis and atom in molecules(AIM) theory to have determined the origin and relative energetic contributions of the weak interactions in these systems. NBO and AIM calculations confirm the V-shaped dimer cluster is dominated by N.H···N and C.H···π hydrogen bonds, while the J-aggregated isomer is stabilized by N.H···π, n→π* and weak π···π* stacking interactions.The noncovalent interactions are also demonstrated via energy decomposition analysis associated with electrostatic and dispersion contributions.     

Self-assembly of Bis[2-(2-hydroxyphenyl)-pyridine]Copper(Ⅱ) Induced by C-H…π and π…π Stacking Interaction

Introduction The control of molecular assembly in the solid state is an important theme of modern chemistry.It is in this regard that there is an activity in the area of supramolecular structures at present.The self-assembly of molecules can form well-defined supramolecular structures under the influence of drive forces such as hydrogen bonds[1-3],metal-ligand coordination bonds[4-6] and π…π stacking interactions[7-10].Word et al.have described the co-ordination chemistry of polydentate chelating ligands which contain mixed pyridine-phenol donor sets[11].Some unusual structures of transition metal pyridine-phenol complexes have been established in which non-covalent interactions such as hydrogen bonding and π…π stacking appear to play a dominant part.These observations suggest that it might be possible to construct supramolecular structures with a metal pyridine-phenol system.To explore this idea we have begun to investigate the self-assembly properties of metal pyridine-phenol complexes.Herein we present the self-assembly properties of Cu(pp)2[pp=2-(2-hydroxyphenol)-pyridine] under different conditions.     

Two Metal Ion-controlled Zn(Ⅱ)/Cd(Ⅱ) Coordination Polymers Based on 1,3,5-Benzenetricarboxylic Acid

Two new coordination polymers {[Zn(Hbtc)(bpyb)]·H_2O}n(1) and {[Cd(Hbtc)-(bpyb)_(1.5)]·0.5 bpyb}_n(2)(H_3btc = 1,3,5-benzenetricarboxylic acid, bpyb = 1,4-bis(4-pyridyl)benzene) have been synthesized under hydrothermal conditions. The two compounds were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Compound 1 displays a 2-fold interpenetrating 3D supramolecular architecture through O–H···N/O hydrogen bonds and π-π stacking interactions. Compound 2 exhibits a 2D→3D polycatenated structure, which is further stabilized by O–H···N hydrogen bonds. The results indicate that the metal ion has significant effects on the formation and structure of the resulted coordination polymers. Furthermore, thermal stability and photoluminescent properties of 1 and 2 are also discussed in detail.     

Synthesis,Crystal Structure and Antitumor Activity of Tectochrysin-6-sulfonate

In order to enhance water-solubility and biological utilization rate of tectochrysin,sodium 5-hydroxyl-7-methoxyflavone-6-sulfonate(1) was synthesized and its structure was identified on the basis of 1 H NMR,FT-IR and elemental analysis.5-Hydroxyl-7-methoxyflavone-6-sulfonate was assembled with Ni(II) or Mn(II),hexaquanickel(II) bis(5-hydroxyl-7-methoxyflavone-6-sulfonate) tetrahydrate(2) and hexaquamanganese(II) bis(5-hydroxyl-7-methoxyflavone-6-sulfonate) tetrahydrate(3) were obtained and characterized by IR spectroscopy.The crystal structures of 2 and 3 were determined by X-ray single-crystal diffraction analysis.The results showed that 2 and 3 are isomorphous crystals and crystallize in monoclinic crystal system,space group C2/c.In 2 and 3,the supramolecular structures are organized into hydrophilic and hydrophobic regions.Hydrophilic regions are generated by O–H???O hydrogen bonds among sulfonate groups,latticed water molecules and coordinated water molecules.The π-π stacking interactions assemble the flavone skeletons into columns and these columns form hydrophobic regions.The sulfonate groups play an important role as a bridge of the hydrophilic and hydrophobic regions as well as the inorganic and organic components.Three-dimensional networks of 2 and 3 are furnished by extensive array of hydrogen bonds,π-π stacking interactions and electrostatic interactions.The anti-proliferative activities of 1~3 in vitro against human leukemia cells K562 and human lung cancer cells A549 were evaluated by the standard MTT assay.The pharmacological activity results showed that the introduction of sulfonic acid groups enhanced the antitumor activity of tectochrysin.     

Synthesis and Crystal Structure of N-Benzyl-N＇-（2-pyridyl）urea and Its Mononuclear Cu（Ⅱ） Complex

A new ligand of N-benzyl-N＇-（2-pyridyl）urea L and its self-assembly product with CuCl2, [Cu（Ⅱ）LCl2]∞ 1, have been synthesized and structurally characterized by IR, 1H NMR and single-crystal X-ray diffraction analysis. In the structure of L, the urea groups adopt Z,E conformation to form dimers through intermolecular hydrogen bonds; while in complex 1, it assumes Z,Z conformation to fit for the coordination sphere of the Cu（Ⅱ） ions. The coordinated units are connected through intermolecular N-H...Cl hydrogen bonds to form an extended 2D framework. Finally, a 3D structure is obtained via π-π stacking interactions between pyridyl rings     

Syntheses,Structures and Characterizations of Two New Zinc(Ⅱ) Coordination Polymers Constructed from 3-(1H-Pyrazol-4-yl)-5-(pyridin-2-yl)-1,2,4-triazole and Different Carboxylate Ligands

Two new zinc(Ⅱ) coordination polymers, [Zn(ph)(H2 L)·H_2O]2 n(1) and [Zn(ip)(H2 L)-(H_2O)]n(2)(H2 ph = phthalic acid, H2 ip = isophthalic acid, H2L = 3-(1 H-pyrazol-4-yl)-5-(pyridin-2-yl)-1,2,4-triazole), have been successfully synthesized via hydrothermal reaction. It has been structurally characterized by X-ray single-crystal analysis, IR spectra, fluorescence spectroscopy and thermogravimetry analysis. The single-crystal X-ray diffraction studies reveal that compounds 1 and 2 both exhibit 1D chain structures, and assemble into 2D and 3D supermolecules through hydrogen bonds or π-π interactions. Moreover, the thermal stability and luminescent properties of compounds 1 and 2 were also studied.     

Syntheses,Crystal Structures and Intermolecular Interactions of Cu（II） Complexes with Methyl- benzoic Acid （MBA） and 1,10-Phenanthroline

Two cupric complexes containing methylbenzoic acid have been prepared and crystallized by solvent evaporation method in DMF. The single-crystal X-ray crystallographic analysis reveals that they are dicaryon complexes. Complex I with formula of [Cu2（m- MBA）4DMF2] crystallizes in monoclinic with space group of P21/c and complex 2 with formula of [Cuz（o-MBA）ffo-phen）2]·NO3·H2O crystallizes in triclinic with space group of P I. The weak interactions including C-H...O hydrogen bonds, C-H…π interactions and π-π stacking in the structures of two complexes are observed from the X-ray crystallographic data. In addition, there are still classical hydrogen bonds in 2. The different strength of intermolecular interaction in the structure is reflected on their different thermal stability measured by thermal gravimetric analysis and 2D-1R correlation spectroscopy of two complexes. The study of weak interactions is meaningful to provide supporting data for supramolecular chemistry theory and potential applications in molecular biology.     

Syntheses and Crystal Structures of Two New Metal Phosphonates:[Mn(H_2O)_2(C_(12)H_8N_2)(HO_3PCH_2CH_2CO_2)] and [Co(H_2O)_4(C_(10)H_8N_2)]·(HO_3PCH_2CH_2CO_2)

By the reactions of manganese(II) acetate, 2-sulfoethylphosphonic acid, 1,10-phen (1,10-phen = 1, 10-phenanthroline) or cobalt(II) acetate, 4,4'-bipy and 2-carboxyethylphosphonic acid, two novel compounds of [Mn(H2O)2(C12H8N2)(HO3PCH2CH2CO2)] (1) and[Co(H2O)4 (C10H8N2)]· (HO3PCH2CH2CO2) (2) have been synthesized and characterized by IR spectroscopy, elemental analyses and single-crystal X-ray diffraction. Compound 1 has a 0D structure. Two Mn(II) ions are linked by two 2-carboxyethylphosphonic acid ligands, forming a centrosymmetric dimer. These dimers are further interlinked into a 2D layer structure by π-π stacking interactions and hydrogen bonds. Compound 2 has a 1D chain structure. The 2-carbo- xyethylphosphonic acid remains uncoor- dinated and acts as the organic template. By the bridge of 4,4'-bipy, the [Co(4,4'-bipy)]2+ chains are formed.     

Hydrogen-bonding Networks in Cocrystal of Melamine and 4-Fluoro-benzoic Acid

A novel interpenetrating structure [(HMA + )(FB – )]·2H 2 O of melamine(MA) with 4-fluoro-benzoic acid (HFB) was synthesized. It crystallized in the monoclinic system with space group P2 1 /c. The complex has a interpenetrating 2D structure with hydrogen-bonded grid networks. Carboxylic acid to melamine proton transfer occurs in the complex. The adjacent HMA + cations related by an inverse center form cationic [HMA + ] ∞ ribbons via a pair of N―H···N hydrogen bonds. Adjacent FB – anions are paired by C―H···F hydrogen bonds to form dimers, which are connected to [HMA + ] ∞ ribbons through N―H···O interactions. The supramolecular features in the complex are guided by control of strong N―H···N, N―H···O and O―H···O hydrogen bonds, as well as highly directional weak C―H···F interactions and aromatic π···π stacking interactions.     

Synthesis and Crystal Structure of a Complex of Melamine with Benzoic Acid

A new complex of melamine（MA） with benzoic acid（HBA） was prepared, affording [（HMA＋）（BA-）]-2H2O. Each HBA molecule is deprotonated and one triazine nitrogen atom of MA is protonated. The adjacent HMA＋ cations are related via an inverse center to form ribbons with a pair of N--H…N hydrogen bonds. COO- groups of BA- anions are hydrogen bonded to alternate sides of the （HMA＋）∞ ribbons to generate indention ID tapes, which are extended into a 3D structure via N--H…O- and N--H…OW hydrogen bonds and π-π stacking interactions. Predominant patterns of the hydrogen bond present in the complex are anion/water and amino/water tape structures. The hydrogen-bonding patterns consist of alternate 6, 10-membered rings sharing two edges. Infrared（IR） spectroscopy conforms that proton transfer has taken place in the complex.     

Thiourea Based Tweezer Anion Receptors for Selective Sensing of Fluoride Ions

Three 3,3＇-di（4-substituted-phenyl）-1,1＇-isophthaloylbis（thiourea） compounds were designed as novel neutral anion receptors, and synthesized by simple steps in good yields. The single crystal structure of receptor 1 shows that a solvent molecule was captured by the host molecule through intermolecular hydrogen bonding. Moreover, it was self-assembled as a supramolecular system for the presence of abundant inter- and intramolecular hydrogen bonding and π-π interactions between phenyl groups. Their application as anion receptors has been examined by UV-Vis and ^1H NMR spectroscopy, showing that they had a higher selectivity for fluoride than other halides. The host and guest formed a 1 ： 1 stoichiometry complex through hydrogen bonding interactions in the first step, then following a process of deprotonation in presence of an excess of F^- in the solvent of DMF.     

Hydrothermal Syntheses,Crystal Structures and Fluorescence of a Copper(I) Polymer and a Salt with H_2SO_4 Based on a Pyrimidine Building Block

Based on the building block of 2-phenyl-4,6-di(pyridin-2-yl)pyrimidine(L = C20H14N4), a Cu(I) polymer [(Cu C20H14N4)(Cu Cl2)]∞ and a salt with H2SO4 [(C20H16N4)(HSO4)2] have been synthesized by hydrothermal method and characterized by X-ray single-crystal diffraction. In the Cu(I) polymer, although the central metal ions of Cu(I) directly coordinate with the building block L, they still do not assembly expected grid-type complexes and there exists a one-dimensional chain constructed through coordinate bonds. In the salt, hydrogen bonds along with two kinds of π···π supramoleuclar interactions fabricate two-dimensional(2D) networks which further generate a 3D supramolecular architecture via interlayer π···π interactions. Fluorescent spectra show that the L emits blue fluorescence and its Cu(I) polymer and salt decrease the fluorescent intensity.     

A New Cadmium(Ⅱ) Coordination Polymer Extended through Hydrogen Bonds and π-π Stacking Interactions: Synthesis and Photoluminescence Property

A new coordination polymer, {[Cd(OPY)_2(tdc)(H_2O)]·H2 O}n(OPY = 4,4?-(oxybis(4,1-phenylene))dipyridine, H2 tdc = thiophene-2,5-dicarboxylic acid), has been synthesized hydrothermally based on a V-shaped ligand OPY. The structure was fully characterized by elemental analysis, FT-IR spectroscopy, and X-ray single-crystal diffraction analysis. In1, two OPY ligands and one water molecule acted as terminal ligands coordinating to Cd~(2+) cation to form [Cd(OPY)_2 H_2O]~(2+) units, which are then linked by tdc2-ligands to generate a one-dimensional chain. Every two adjacent chains linked by extensive O–H···O hydrogen bonds constitute one-dimensional double-chains, and such chains are extended into two-dimensional layers via O–H···N hydrogen bonds. These layers are further connected to form a three-dimensional supramolecular architecture via π-π stacking interactions. In addition, the thermal stability and solid state fluorescence property of 1 were also investigated.     

Syntheses,Structures,and Properties of Three New Polymers Based on Flexible and Rigid Ligands

Three new supramolecular polymers, [(IP)(H_2SO_4)(H_2O)](1), [(H_2SDC)(BPA)](2) and [Mn(SDC)(IP)_2]_n (3), have been constructed by three modes(rigid IP, rigid SDC + flexible BPA, rigid IP + rigid SDC). Polymers 1 and 2 are supramolecular structures, assembled by hydrogen bonds and π···π interactions. X-ray structure analysis of 3 shows waved 1D chains which form a 3D supramolecular network by hydrogen bonds and π···π interactions. Solid-state properties of thermal stability, luminescent properties, and X-ray powder diffractions for these crystalline materials have also been investigated, and polymer 3 is considered to be a good stable luminescence material.     

Synthesis and Crystal Structure of a 1-D Copper(Ⅱ) Polymer with 1-Hexylimidazole and Oxalate

A novel Cu(Ⅱ) complex has been prepared by means of self-assembly of CuCl2,1-hexylimidazole L and oxalic acid(H2OX) in the presence of triethylamine,and structurally characterized by X-ray diffraction analysis.In complex 1,1-D polymer chains are formed through pentacoordinated Cu(Ⅱ),oxalate and bridging chlorine atoms.In the crystal packing of 1,the imidazole ring head-to-tail π-π stacking interactions exist between 1-D polymer chains and extend the 1-D polymer chains into 2-D supramolecular layers.The fluorescence emission spectra of L and 1 were described.     

Synthesis of a new macrocyclic compound and its self-assembly

A new macrocyclic compound has been synthesized by condensation of pyridine-1-oxide-2,6-dialdehyde with diethylenetria-mine. The self-assemly behaviours were studied by X-ray diffraction. The results show that the self-assembly were controlled by intermolecular hydrogen bonds and π-π stacking effects.     

Syntheses and Crystal Structures of Two New Metal Phosphonates： [Mn（H2O）2（C12H8N2） （HO3PCH2CH2CO2） ] and [Co（H2O）4（C10H8N2）]-（HOaPCH2CH2CO2）

By the reactions of manganese（if） acetate, 2-sulfoethylphosphonic acid, 1,10-phen （1,10-phen = 1, 10-phenanthroline） or cobalt（Ⅱ） acetate, 4,4＇-bipy and 2-carboxyethylphosphonic acid, two novel compounds of [Mn（H2O）2（C12H8N2） （HO3PCH2CH2CO2） ] （1） and[Co（H2O）4（C10H8N2）]-（HOaPCH2CH2CO2） （2） have been synthesized and characterized by IR spectroscopy, elemental analyses and single-crystal X-ray diffraction. Compound 1 has a 0D structure. Two Mn（ii） ions are linked by two 2-carboxyethylphosphonic acid ligands, forming a centrosymmetric dimer. These dimers are further interlinked into a 2D layer structure by π-π stacking interactions and hydrogen bonds. Compound 2 has a 1D chain structure. The 2-carboxyethylphosphonic acid remains uncoordinated and acts as the organic template. By the bridge of 4,4＇-bipy, the [Co（4,4＇-bipy）]^2＋ chains are formed.