X-Ray Diffraction Study on Manganese(II) Complexes with Thiophene-2-Carboxylate and Furan-3-Carboxylate Ligands

Abstract

Mn(II) cations in the crystals of trisaquobis(μ-thiophen-2-carboxylato-O,O′)(thiophen-2-carboxylato-O)manganese(II) monohydrate are bridged by oxygen atoms donated by bidentate carboxylic groups of two thiophen-2-carboxylate ligands. In addition, each Mn(II) ion is coordinated by an oxygen atom of a monodentate carboxylic group of this ligand and three oxygen atoms of water molecules. The coordination around the Mn(II) cation is octahedral. The bridging of the ligands results in molecular ribbons propagating in the c-direction of the crystal held together by C?H…O hydrogen bonds. The crystal structure of diaquobis(μ-furan-3-carboxylato-O,O′)di(μ-furan-3-carboxylato-O,O)(μ-aqua-O)manganese(II) consists of dinuclear structural units. In each molecule Mn(II) cations are O,O′ bridged by oxygen atoms of bidentate carboxylic groups of two furan-3-carboxylate ligands and have a water located between the Mn cations. The units are O,O′ bridged to Mn(II) ions located in adjacent units by bidentate oxygen atoms, forming molecular ribbons extending in the c-direction. Octahedral coordination around each Mn(II) ion is completed by two water molecules. The octahedra around two adjacent metal ions in the unit share a common apex - the bridging oxygen atom of the water molecule. The ribbons are held together by C?H…O hydrogen bonds between furan ring oxygen atoms and the carbon atoms of adjacent furan rings.     

Effect of a methyl substituent on the molecular and crystal structure of (2-acetyl-5-nitrofuran)-N-benzoylhydrazone

Conclusions An x-ray diffraction study of (2-acetyl-5-nitrofuran)-N-benzoylhydrazone has shown that the molecules of this compound have a nonplanar structure with syn arrangement of the oxygen and nitrogen atoms of the keto and hydrazone groups and an anti arrangement of the oxygen atom of the furan fragment. With such a conformation, the molecules do not form crystal hydrates; in the crystal, they are connected with one another into chains by intermolecular hydrogen bonds N-H...O 2.26 Å. However, intermolecular N O proton phototransfer does not occur between them.Translated from Izvestiya Akademiii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1319–1322, June, 1988.     

苄醚型树枝化碳水化合物的合成与液晶性

选取3种不同结构的苄醚型树枝状分子为分枝,以N-乙酰氨基葡萄糖为内核,合成出一类树枝化碳水化物;利用DSC、热台偏光显微镜、XRD和CD／UV光谱等手段研究该类化合物的液晶性,并命名为树状碳水化合物液晶。研究表明,连接有楔形树枝状单元的化合物形成手性柱状六方相或者向列相,连接有锥形树枝状单元的化合物未能如预期形成立方相,而仍然形成手性柱状六方相．超分子手性很可能源于树枝状单元与糖内核的协同自组装,使得树状分子沿着柱轴螺旋式堆砌;而糖环内核则对超分子柱的手性起调控作用,从而避免了外消旋的发生．该类化合物为研究碳水化合物诱导手性超分子聚集体提供了新的思路．     

Molecular Chains in the Crystals of a Calcium(II) Complex with Pyridine-3,5-Dicarboxylate (Dinicotinate) and Water Ligands

The crystal of pentaqua (catena-pyridine-3,5-dicarboxylato-O,O) calcium(II) contain zigzag molecular chains composed of Ca ions linked by two bridging oxygen atoms, each donated by one carboxylate group [Ca-O1 2.353(2) Å, Ca-O3^III 2.334(1) Å]. The Ca ions, the ligand molecules and one water oxygen atom coordinated by each metal ion [Ca-O5 2.410(2) Å] are coplanar. The coordination of the Ca ion is completed by four other water oxygen atoms situated above and below the plane of the chain [Ca-O6 2.475(1) Å, Ca-O7 2.371(2) Å]. The coordination number of the calcium(II) ion is seven. The water molecules act as donors in a system of hydrogen bonds.     

Ferroelectrically switchable columnar liquid crystal

The synthesis of a new disc-like mesogenic compound permitted, for the first time, ferroelectric electrooptical switching in a tilted columnar liquid crystal. The spontaneous molecular dipole moment is induced by the bend between the dibenzopyrene core and part of the eight O-hexyllactic acid chains attached to it. Two similar new compounds displayed a weak electrooptical effect in the columnar phase.     

Crystal structure of the gold nanoparticle [N(C8H17)4][Au25(SCH2CH2Ph)18

We report the crystal structure of the thiolate gold nanoparticle [TOA+][Au25(SCH2CH2Ph)18-], where TOA+ = N(C8H17)4+. The crystal structure reveals three types of gold atoms: (a) one central gold atom whose coordination number is 12 (12 bonds to gold atoms); (b) 12 gold atoms that form the vertices of an icosahedron around the central atom, whose coordination number is 6 (five bonds to gold atoms and one to a sulfur atom), and (c) 12 gold atoms that are stellated on 12 of the 20 faces of the Au13 icosahedron. The arrangement of the latter gold atoms may be influenced by aurophilic bonding. Together they form six orthogonal semirings, or staples, of -Au2(SCH2CH2Ph)3- in an octahedral arrangement around the Au13 core.     

Ferroelectrically switchable columnar liquid crystal

Abstract

The synthesis of a new disc-like mesogenic compound permitted, for the first time, ferroelectric electrooptical switching in a tilted columnar liquid crystal. The spontaneous molecular dipole moment is induced by the bend between the dibenzopyrene core and part of the eight O-hexyllactic acid chains attached to it. Two similar new compounds displayed a weak electrooptical effect in the columnar phase.     

A Novel Lead- bis (4-Chloro-2-Methylphenoxy)- Acetate Polymeric Complex

The bis (4-chloro-2-methylphenoxy)acetato lead (II) monohydrate infinite polymer was synthesized and characterized by elemental analysis and infrared spectroscopy. The crystal and molecular structure has been determined and the bond valences were computed. Molecules of the monomer, each occupying an asymmetric unit, are connected by the inversion center and a polymer chain is created by Pb(2O)Pb rings in spiro arrangement. The lead atom is seven coordinate by four oxygen atoms from two chelating carboxyl groups, one water molecule, and two oxygen atoms provided by symmetry generated carboxyl groups. Each carboxyl group acts as a bidentate ligand toward one metal atom and as a monodentate ligand with respect to a second. The lead-oxygen distances are spread over a wide range of values. One molecule of (4-chloro-2-methylphenoxy)acetate in the monomer is close to planarity, and the second is bent. All 4-chloro-2-methylphenoxy groups are almost parallel. The polymer infinite chains are assembled by weak hydrogen bonds to a layered structure.     

Synthesis and Characterization of [Hg(sulfamethoxazolato)2]·2DMSO and[Cu2(μ‐CH3CO2)4(sulfamethoxazole)2]

[Hg(sulfamethoxazolato)₂]·2DMSO ( 1 ) and [Cu₂(CH₃COO)₄(sulfa‐methoxazole)₂] ( 2 ) can be obtained by the reaction of sulfamethoxazole with mercury acetate or copper acetate in methanol. The structures of the two complexes were characterized by single crystal X—ray diffractometry. Compound 1 consists of sulfamethoxazolato ligands bridging the metal ions building an unidimensional chain. Two solvent dimethylsulfoxide molecules are involved via N‐H···O hydrogen bridges. The mercury atom shows a linear primary coordination arrangement formed by two trans deprotonated sulfonamidic nitrogen atoms. The overall coordination around the metal atom may be regarded as a strongly distorted octahedron when the interactions of mercury with four sulfonamidic oxygen atoms [bond distances of 2.761(4) Å—2.971(4) Å] are also considered to build an equatorial plane and the N1 and N1′ atoms [bond distance of 2.037(5) Å] occupy the apical positions. Compound 2 is a dinuclear complex in which the copper ions are bridged by four syn‐syn acetate ligands which are related by a symmetry centre located in the centre of the complex. Each copper atom presents a nearly octahedral coordination where the equatorial plane is formed by four oxygen atoms and an isoxazolic nitrogen atom and the second copper atom occupy the apical positions.     

含2-苯氧基丙酸根的镍、锌配位聚合物的合成与晶体结构

用溶液法和水热法分别合成了2个含2-苯氧基丙酸配体(HL)的聚合物{[NiL2(H2O)2(bipy)].2H2O}n(1)、{[ZnL2(bipy)].2H2O}n(2)(bipy=4,4′-联吡啶),用元素分析、红外光谱、热重和单晶X-射线衍射对产物进行了表征。在化合物1中,镍原子与2个羧基氧原子、2个配位水氧原子及2个4,4′-联吡啶的2个氮原子配位,配位数为6,镍原子的配位构型为畸变的八面体;而在化合物2中,锌原子与2个羧基氧原子及2个4,4′-联吡啶中的2个氮原子配位,锌原子的配位构型为畸变的四面体。在这2个化合物里,4,4′-联吡啶通过氮原子连接金属原子形成一维链状。链间氢键与π-π堆积作用又将一维链链接成二维层状结构。     

T-shaped ionic liquid crystals based on the imidazolium motif: exploring substitution of the C-2 imidazolium carbon atom

In this contribution the first examples of so‐called rigid‐core, T‐shaped imidazolium ionic liquid crystals, in which the C‐2 atom of the imidazolium ring is substituted with an aryl moiety decorated with one or two alkoxy chains, are described. The length of the alkoxy chain(s) was varied from six to eighteen carbon atoms (n=6, 10, 14–18). Whereas the compounds with one long alkoxy chain display only smectic A phases, the salts containing two alkoxy chains exhibit smectic A, multicontinuous cubic, as well as hexagonal columnar phases, as evidenced by polarising optical microscopy, differential scanning calorimetry, and powder X‐ray diffraction. Structural models are proposed for the self‐assembly of the molecules within the mesophases. The imidazolium head groups and the iodide counterions were found to adopt a peculiar orientation in the central part of the columns of the hexagonal columnar phases. The enantiotropic cubic phase shown by the 1,3‐dimethyl‐2‐[3,4‐bis(pentadecyloxy)phenyl]imidazolium iodide salt has a multicontinuous Pm$\bar 3In this contribution the first examples of so-called rigid-core, T-shaped imidazolium ionic liquid crystals, in which the C-2 atom of the imidazolium ring is substituted with an aryl moiety decorated with one or two alkoxy chains, are described. The length of the alkoxy chain(s) was varied from six to eighteen carbon atoms (n=6, 10, 14-18). Whereas the compounds with one long alkoxy chain display only smectic A phases, the salts containing two alkoxy chains exhibit smectic A, multicontinuous cubic, as well as hexagonal columnar phases, as evidenced by polarising optical microscopy, differential scanning calorimetry, and powder X-ray diffraction. Structural models are proposed for the self-assembly of the molecules within the mesophases. The imidazolium head groups and the iodide counterions were found to adopt a peculiar orientation in the central part of the columns of the hexagonal columnar phases. The enantiotropic cubic phase shown by the 1,3-dimethyl-2-[3,4-bis(pentadecyloxy)phenyl]imidazolium iodide salt has a multicontinuous Pm ?3m structure. To the best of our knowledge, this is the first example of a thermotropic cubic mesophase of this symmetry.     

Two-dimensional self-assembly of linear molecular rods at the liquid/solid interface

We report on the synthesis and scanning tunneling microscopy (STM) studies of a series of linear molecular rods (1-5) comprising different numbers and/or spatial arrangements of perfluorinated benzene and benzene subunits interlinked with diacetylenes in the para position and decorated with or without terminal dodecyl chains. The molecules organize themselves into well-ordered 2D crystal structures at the liquid/solid interface through intermolecular and molecule-substrate interactions. Whereas the molecules substituted by dodecyl chains form the lamellar structures with alternating rigid core rows and alkyl chain rows, the unsubstituted ones change the orientation of the rigid backbones with respect to the lamellar axis. The molecular arrangement is not influenced by fluoro substituents on any phenyl ring of the backbone, which suggests that the interactions between the π-conjugated backbones are dominated by close packing rather than by the dipole moments of the rods or fluorine-based intermolecular interactions.     

Scanning tunnelling microscopic study of the interfacial order in a ferroelectric liquid crystal

We present scanning tunnelling microscopy images of a ferroelectric liquid crystal in its chiral smectic C phase. These images show evidence of pronounced interaction between the adjacent lateral dipoles located near the chiral centres of neighbouring molecules. The two dimensional structure at the graphite—liquid crystal interface is found to be highly ordered. Features of this crystal-like order are the pronounced dimer arrangement within a layer and a kinked conformation in which the aromatic core is tilted with respect to the chains. The core axis is tilted at 30° with respect to the layer normal in the plane of the interface. This tilt is very similar to the tilt angle of the bulk material.     

Influence of mesogenic core polarity and position of chains attachment on columnar phase stability

Series of new Ni(II) metalomesogens of triangular molecular shape and forming Col_h liquid crystalline (LC) phase were synthesised and described. Using in the molecular core the barbituric moieties that contain carbonyl or thiocarbonyl groups causes strong polarisation of the molecules and creates a permanent dipole moment μ, which was confirmed by quantum mechanical calculations. The relationship between molecular dipole moment and self-organisation of molecules into the columnar phase was considered. The position of alkyl and alkoxy chains substituted at phenyl ring that affects LC phase formation seems to be connected with planar conformation of the attached chains. These can broaden the mesogenic core and stabilise the Col_h mesophase.     

Ionic hexagonal columnar metallomesogens derived from tetrabenzo[b,f,j,n] [1,5,9,13]tetraazacyclohexadecine

A series of transition metal (Ni, Cu, Pd) complexes derived from macrocyclic tetrabenzo[b,f,j,n] [1,5,9,13]tetraazacyclohexadecine (TAAB) was synthesized and their mesomorphic properties studied by differential scanning calorimetry, polarized optical microscopy and X-ray powder diffraction (XRD). These compounds have eight alkoxy side chains attached around the central molecular core and form disc-like molecules. All the derivatives exhibited columnar mesophases over a wide range of temperature. The mesomorphic behaviour was found to be dependent on the incorporated metal and the carbon length of the alkoxy side chains. The clearing temperatures decreased in the order M = Ni > Pd > Cu; this decrease was probably due to the size of the metal ions. Some derivatives with shorter side chains (n = 10, 12) were room temperature liquid crystals. All compounds were found to exhibit hexagonal columnar (Col_h) phases which were confirmed by powder XRD.     

Polycatenar Mesogens with Various Degree of Flexibility of Molecular Structure

A series of newly synthesised rod‐like polycatenar mesogens forms columnar phases, with the number of molecules in the column cross section depending on the core rigidity. For non‐symmetric molecules, an additional density modulation, namely helical arrangement of molecules with a periodicity of approximately 10 molecular distances develops along the columns. For one of the compounds, a new type of columnar liquid crystal phase with 3D positional order is observed. Introducing a stilbene unit in the mesogenic core enhances the fluorescent properties of the compounds. In the hexagonal columnar phase, polarised light emission is observed.     

Effect of Atomic‐Scale Differences on the Self‐Assembly of Thiophene‐based Polycatenars in Liquid Crystalline and Organogel States

Two series of polycatenars are reported that contain a central thiophene moiety connected to two substituted oxadiazole or thiadiazole units. The number, position, and length of the peripheral chains connected to these molecules were varied. The oxadiazole‐based polycatenars exhibited columnar phases with rectangular and hexagonal or oblique symmetry, whereas the thiadiazole‐based polycatenars exhibited columnar phases with rectangular and/or hexagonal symmetry. All of the compounds exhibited bright emission in the solution and thin‐film states. Two oxadiazole‐based molecules and one thiadiazole‐based molecule exhibited supergelation ability in hydrocarbon solvents, which is mainly supported by attractive π–π interactions. These gels showed aggregation‐induced enhanced emission, which is of high technological importance for applications in solid‐state emissive displays. X‐ray diffraction studies of the xerogel fibers of oxadiazole‐based polycatenars revealed a columnar rectangular organization, whereas a hexagonal columnar arrangement was observed for thiadiazole‐based polycatenars. Rheological measurements carried out on the samples quantitatively confirmed the formation of gels and showed that these gels are mechanically robust. The impact of an atomic‐scale difference (oxygen to sulfur, <2 % of the molecular weight) on the self‐assembly and the macroscopic properties of those self‐assembled structures are clearly visualized.     

Syntheses and structures of dimesitylbismuth(III) bromide, Mes2BiBr, and bis(diphenyldithiophosphinato)mesitylbismuth(III), MesBi(S2PPh2)2

Addition of BiBr₃ to Mes₃Bi (Mes = 2, 4, 6-Me₃C₆H₂) in Et₂O gives 86% of Mes₂BiBr (1) as yellow crystals. Reaction of 1 with Ph₂PS₂NH₄ in a 1 : 1 molar ratio gives a quantitative yield of MesBi(S₂PPh₂)₂ (2) rather than the expected dimesitylbismuth compound. The crystal and molecular structures of 1 and 2 were determined at 153 K and 173 K, respectively. They contain Mes₂BiBr molecules with trigonal pyramidal coordination around Bi. The mean Bi---C bond distance is 2.27 Å and the Bi---Br bond distance is 2.690(2) Å. The angles around Bi vary between 89.4 and 106.4°. Intermolecular Bi…Br contacts of 3.795 Å, indicating weak secondary bonding, give rise to zig-zag shaped (Bi---Br)_x chains. In the polymeric chain the coordination geometry around bismuth atoms can be described as pseudo-trigonal bipyramidal. The crystals of 2 consist of discrete monomeric MesBi(S₂PPh₂)₂ molecules with a symmetry plane containing the metal atom and the aromatic ring of the attached mesityl group. The dithiophosphinato ligands exhibit an anisobidentate coordination pattern with long and short phosphorus—sulfur bonds, i.e. P(1)---S(1) 2.051(31) Å and P(1)---S(2) 1.980(3) Å, related to short and long bismuth—sulfur distances, respectively, i.e. Bi---S(1) 2.662(2) Å and Bi---S(2) 3.123(3) Å. This leads to a square-pyramidal geometry around the bismuth atom, with the metal lying 0.33 Å above the basal plane formed by the four sulfur atoms.     

Supramolecular networks of polymethylphosphonic acid groups bonded to aromatic platforms: biphenyldiyl-2,2'-bis(methylphosphonic acid) and benzenetriyl-1,3,5-tris(methylphosphonic acid)

Biphenyldiyl-2,2'-bis(methylphosphonic acid) (BBMP) and benzenetriyl-1,3,5-tris(methylphosphonic acid) (BTMP) as ligands have been synthesized from diphenic acid and trimesic acid, respectively. Cu, Mn and Co complexes of BBMP have been prepared but similar complexes of BTMP did not crystallize. However, a copper compound with added 4,4'-bipyridyl was obtained. This copper complex is dimeric in which the dimers are linked into a supramolecular compound through the bipyridyl groups. Interestingly, the structure was solved in P1 with an unusual correlation between the ligand oxygen bond distances and the copper bond distances to water molecules. The Mn and Co BBMP complexes are isostructural in which the BBMP ligands phenyl groups rotate around each other to bridge the metal atoms forming 1:1 linear chains. There are four water molecules bonded to Co that can be removed reversibly. In the case of the Cu compound, one Cu is square planar bonded to four phosphonate oxygen atoms from two BBMP molecules. The second copper is six coordinate adding two water molecules in the axial positions. The two copper ions alternate forming a one dimensional chain but with ligands bonding the chain on both sides. The four coordinate copper atoms are chelated by two BBMP ligands utilizing one oxygen atom from the two phosphonate groups of each ligand and a second oxygen atom from these groups that bridge across the Cu atoms to bond to the six coordinate copper ion. A detailed synthetic procedure for each of the two ligands is supplied as ESI.     

The Crystal and Molecular Structure of a New Calcium(II) Complex with Pyridine-2,6-DiCarboxylate,Water and Nitrate Ligands

Crystals of {catena-[μ-aqua-O]bis[μ-pyridine-2,6-dicarboxylato-O,N-O']} {[monoaqua-nitrato, O-calcium(II)] [diaqua-calcium(II)]} contain dimeric units composed of two calcium(II) ions and two ligand molecules, in which the calcium ions are bridged by two bidentate oxygen atoms, each donated by one carboxylic group of the ligand. The Ca(II) ion is also coordinated by one oxygen atom of the second carboxylate group and the hetero-ring nitrogen atom belonging to the same ligand molecule. The dimers form molecular chains through protons situated at the symmetry centers halfway between the non-bridging carboxylate oxygen atoms. In addition, both calcium ions in the dimer are bridged to calcium ions in adjacent dimers - each by a pair water oxygen molecules giving rise to two-dimensional molecular sheets. Coordination of the Ca ion in the dimer is completed either by two water oxygen atoms or by one water oxygen atom and an oxygen atom donated by a nitrate group. The molecular sheets are held together by an extended system of hydrogen bonds.