Two-dimensional Supramolecular Structure Research Articles

The sodium chloride complex catena-poly[[{μ3-2-[bis(2-hydroxyethyl)amino]ethan-1-ol}sodium] chloride], N(CH2CH2OH)3·NaCl

The reaction of sodium chloride with 2-[bis(2-hydroxyethyl)amino]ethan-1-ol results in the formation of the title salt {[Na{N(CH2CH2OH)3}]Cl} n . The polymeric structure is characterized by a sodium cation coordinated by one nitrogen and five oxygen atoms in a distorted octahedral environment. The resulting one-dimensional {—O—Na—O—Na—O}— coordination polymer extends parallel to [010] and is connected through the chloride counter-anion via O—H...Cl hydrogen bonding, giving rise to a two-dimensional supramolecular structure parallel to (001).

Construction of two-dimensional supramolecular nanostructure with aggregation-induced emission effect via host–guest interactions

Formation of fluorescent two-dimensional supramolecular structure based on tetraphenylethene (TPE) derivative and CB[8].

Crystal structure and Hirshfeld surface analysis of (2E)-3-(3-chloro-phen-yl)-1-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one.

In title compound, C17H15ClO3, the dihedral angle between the benzene and chloro-phenyl rings is 18.46 (7)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen contacts, enclosing an R22(14) ring motif, and by a further C-H⋯O hydrogen contact, forming a two-dimensional supra-molecular structure extending along the direction parallel to the ac plane. Hirshfeld surface analysis shows that van der Waals inter-actions constitute the major contribution to the inter-molecular inter-actions, with H⋯H contacts accounting for 36.2% of the surface.

Towards the synthesis of prenylated phloroglucinol derivatives: An X-ray crystallographic and DFT study of unexpected reaction products

Owing to their bioactivity and prevalence in medicinal plant extracts, prenylated phloroglucinols have garnered significant interest. Towards the synthesis of prenylated phloroglucinol derivatives, 2,4,6-trihydroxy-3-(3-methylbut-2-enyl)acetophenone is required as an intermediate. Herein, this was synthesised by a tandem Claisen-Cope rearrangement reaction on 2,4-bis(methoxymethoxy)-6-(3-methylbut-2-enyloxy)acetophenone and a subsequent hydrolysis to remove protecting groups. This reaction yielded the desired product as well as three by-products. Two of these by-products were isomeric chromane derivatives (2 and 3) and the third was a methoxy derivative (4). These compounds have been studied by single crystal X-ray crystallography and DFT methods. Compound (2) crystallised in the P21/c space group with two hydrogen-bonded molecules in the asymmetric unit (Z = 8). Compound (4) crystallised in the Pbca space group with a single molecule in the asymmetric unit (Z = 8). Both compounds formed extensive supramolecular structures supported by hydrogen bonds in the solid state. Compound (2) forms a simple one-dimensional hydrogen-bonded chain co-linear with the a-axis. Compound (4) forms a two-dimensional supramolecular structure comprising “pentameric” hydrogen-bonded motifs linked by additional H-bonds to form the supramolecular structure. Both structures showed intramolecular hydrogen bonds between the acetyl oxygen and adjacent OH group. DFT simulations were used to probe the relative energies of the molecules and hydrogen bonds. These simulations showed that the intramolecular hydrogen bond has a substantial stabilising effect with an interaction strength of 70.64 kJ mol−1. The formation of the hydrogen-bonded dimer of (2) from which the supramolecular structure is formed has a ΔHassoc constant of −42.32 kJ mol−1, illustrating that the formation of the hydrogen-bonded structure is energetically favourable.

Tetra-, Penta- and Hexa-Coordinated Transition Metal Complexes Constructed from Coumarin-Containing N2O2 Ligand

Three newly designed complexes, [Cu(L)]·CHCl3 (1), [Co(L)(MeOH)]·CHCl3 (2) and [{Ni(L)(MeOH)(PhCOO)}2Ni] (3) a coumarin-containing Salamo-type chelating ligand (H2L) have been synthesized and characterized by elemental analyses, IR and UV-VIS spectra, and X-ray crystallography. Complex 1 includes one Cu(II) atom, one completely deprotonated (L)2− unit and one crystalling chloroform molecule, the Cu(II) atom shows a square-planar geometry. Complex 2 includes one Co(II) atom, one completely deprotonated (L)2− unit, one coordinated methanol molecule and one crystalling chloroform molecule. The Co(II) atom is a distorted trigonal-bipyramidal geometry. While complex 3 includes three Ni(II) atoms, two completely deprotonated (L)2− units, two benzoates and two coordinated methanol molecules. The complexes 1 and 2 are both possess three-dimensional supra-molecular structures by abundant noncovalent interactions. But, complex 3 formed a two-dimensional supra-molecular structure by intra-molecular hydrogen bonds. In addition, the antimicrobial and fluorescence properties of H2L and its complexes 1, 2 and 3 were also investigated.

A one-dimensional Cd(II) coordination polymer with a two-dimensional supramolecular architecture through halogen···halogen interaction

ABSTRACTA new cadmium coordination polymer, formulated as [Cd(L)(phen)]n, were prepared by hydrothermal reactions based on 3,4-dibromothiophene-2,5-dicarboxylic acid (H2L) and 1,10-phenanthroline (phen) mixed organic linkers. In the complex, adjacent Cd2+ ions are linked by L2− anions to form a one-dimensional (1D) [CdL]n chain with [Cd2(COO)2] as the secondary building unit (SBU). These adjacent chains are further stacked together by direct C−Br···Br halogen bonds interactions, generating a two-dimensional (2D) supramolecular structure. From the viewpoint of topology, the 2D supramolecular network can be rationalized to a 3,4-connected 3,4L13 net with {4.62}2{42.62.82} topology.

Polymeric Ni(II) and Cu(II) complexes based on squaric acid and 1-vinylimidazole: Structural studies and hydrogen adsorption properties

[M(sq)(vim)2(H2O)2]n (M: Ni2+ and Cu2+ ions; sq: squarate dianion; vim: 1–vinylimidazole) complexes were crystallized, and characterized by elemental analysis, infrared spectroscopy (IR), thermal analysis, magnetic susceptibility, powder X-ray diffraction (PXRD) and X-ray single crystal techniques. The results of X-ray single crystal analysis demonstrate that both complexes crystallize in the monoclinic system with P21/n space group and have slightly distorted octahedral geometries. In the complexes, the sq ligand behaves as bis(monodentate) via the oxygen atoms in trans-(μ-O1,O3) mode and the vim ligand coordinates to the metal ions via the ring nitrogen atom as monodentate. The complexes have one-dimensional (1D) polymeric chains constructed from the connecting of metal ions to each other by the sq ligands. The linking of 1D polymeric chains with the hydrogen bonds leads to the formation of two-dimensional (2D) supramolecular structures. The π-π interactions also contribute to the formation of three-dimensional (3D) supramolecular structures. The surface areas and hydrogen adsorption properties of the complexes were investigated. The accessible surface areas and free volumes of the complexes were also determined by theoretical calculations in 0.8Å Connolly diameter.

Direct synthesis of CdS nanoparticles via simple one-pot calcination of new two-dimensional Cd(II) coordination polymer

Assembly of quinoxaline with Cd(II) in the presence of SCN− anion produces a new coordination polymer [Cd(Quinoxaline)(SCN)2(CH3CN)] n [Cd(Quinoxaline)2(SCN)2] n (1) and is characterized by IR, 1H NMR and 13C NMR spectroscopy. The single-crystal X-ray data of compound 1 show that this coordination polymer grows in two-dimensional supramolecular structure. In this polymer, the organic ligand chelate through its one nitrogen atom to cadmium(II) atom and thiocyanate anion acts as a bridge to two cadmium(II) atom in the chains. Also, nanoscale of CdS has been synthesized by calcination at 400, 500 and 600 °C under air atmosphere and characterized by scanning electron microscopy, X-ray powder diffraction and energy-dispersive X-ray. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses.

Crystal structure of di-chlorido-{2-methyl-2-[(pyridin-2-ylmeth-yl)amino]-propan-1-ol-κ3N,N',O}copper(II) from synchrotron data.

The title compound, [CuCl2(C10H16N2O)], has been synthesized and characterized by synchrotron single-crystal X-ray diffraction and FT-IR spectroscopy. The 2-methyl-2-[(pyridin-2-ylmeth-yl)amino]-propan-1-ol (mpmapOH) ligand, including pyridine, amine and hy-droxy groups, was synthesized by the reaction of 2-amino-2-methyl-propan-1-ol with pyridine-2-carbaldehyde and was characterized by NMR spectroscopy. In its CuII complex, the metal ion has a distorted square-pyramidal coordination geometry with two N and one O atom of the mpmapOH ligand and one chloride anion in the equatorial plane, and the second chloride in an axial position. The bond lengths involving the CuII ion range from 1.9881 (10) to 2.0409 (9) for the Cu-N and Cu-O bonds, and from 2.2448 (5) to 2.5014 (6) Å for the equatorial and axial Cu-Cl bonds, respectively. Inter-molecular hydrogen bonds (N-H⋯Cl and O-H⋯Cl) and face-to-face π-π inter-actions stabilize the mol-ecular structure and give rise to a two-dimensional supra-molecular structure extending parallel to (101).

Stereochemical Recognition of Helicenes on Metal Surfaces.

The chiral recognition among biomolecules is fundamentally important for many processes of life, including the stereochemistry of evolution. Of special interest is chiral recognition during crystallization of racemates, when either homochiral recognition leads to a conglomerate of homochiral crystals or heterochiral recognition dominates resulting in a racemic compound. The complex nature of molecular recognition at the level of nucleation and crystal growth renders it difficult to understand and calls for manageable model systems. Notably, the approach of studying aggregation of molecules at surfaces under well-defined conditions includes the benefit of the availability of a multitude of highly sensitive investigation methods, of which scanning tunneling microscopy (STM) with its submolecular resolution is tremendously valuable. Heterogeneous nucleation at surfaces is strongly favored over homogeneous nucleation in solution; hence, surfaces are significantly involved in stereochemical recognition during crystallization. Helicenes are a fascinating class of chiral compounds with outstanding optical activity. These π-conjugated, ortho-fused, aromatic hydrocarbons are promising candidates for organic electronic devices such as sensors, circular dichroic photonics, liquid crystal displays or spin filters. But in particular the defined footprint of their terminal benzo rings on a surface makes them interesting for studying stereochemical recognition with different single crystalline surfaces and the impact this has, in turn, on intermolecular recognition. In this Account, we describe the self-assembly of helicenes on metal surfaces with the focus on stereochemical recognition in two-dimensional structures. Using the isomeric all-carbon helicenes, heptahelicene and dibenzohelicene as examples, different aggregation phenomena on different surfaces of single crystalline copper, silver, and gold are investigated. By means of STM different modes of transmission of molecular handedness from single molecules into extended two-dimensional supramolecular structures are identified. For the problem of racemate versus conglomerate crystallization, the impact of surface and molecular structure and their interplay are analyzed. This leads to detailed conclusions about the importance of the match of molecular and surface binding sites for long-range self-assembly. The absence of polar groups puts emphasis on van der Waals interaction and their maximization by steric overlap of molecular parts in enantiomeric and diastereomeric interactions. With STM as a manipulation tool, dimers are manually separated in order to analyze their chiral composition. And finally, new nonlinear cooperative effects induced by small enantiospecific bias are discovered that lead to single enantiomorphism in two-dimensional racemate crystals as well as in racemic multilayered films. By means of these model studies many details that govern chiral recognition at surfaces are rationalized.

Extended structures of two coordination polymers based on 1,10-phenanthroline derivatives: Preparation, structural characterization and properties

In this paper, we report two coordination polymers, [Cd(Medpq)(SO4) (H2O)2]n (1) and {[Mn(Medpq)(QUI)H2O] ⋅ H2O} n (2) (H2QUI = 2,3-pyridinedicarboxylic acid, Medpq = 2-methyldipyrido[3,2-f:2,3-h]quinoxaline) by hydrothermal processing and structural characterization by elemental analysis, thermogravimetric analysis and single-crystal X-ray diffraction. The coordination polymers 1 and 2 have 1D chains formed via coordination bonds, and unique two-dimensional supramolecular structures are further formed due to π- π stacking interactions. The results reveal that the coordination preferences of metal ions play a critical role in the framework construction of the two coordination polymers. Meanwhile, natural bond orbital (NBO) analysis was performed by the PBE0/LANL2DZ method in Gaussian 09 program. The calculated results show the obvious covalent interaction between the coordinated atoms and metal ions.

Assembly of Zn(II) and Cd(II) coordination polymers based on a flexible multicarboxylate ligand and nitrogen-containing auxiliary ligands through a mixed-ligand synthetic strategy: syntheses, structures and fluorescence properties.

The structures of coordination polymers are strongly influenced by the organic ligands and metal ions used for their construction, so it is important to choose suitable ligands and metal ions and appropriate synthetic processes. Two novel d(10) coordination polymers, namely poly[[diaquabis(2,2'-bipyridine)[μ4-4,4'-(1,4-phenylenedioxy)bis(benzene-1,2-dicarboxylato)]dizinc(II)] dihydrate], {[Zn2(C22H10O10)(C10H8N2)2(H2O)2]·2H2O}n, (1), and poly[[diaquabis(1,10-phenanthroline)[μ4-4,4'-(1,4-phenylenedioxy)bis(benzene-1,2-dicarboxylato)]dicadmium(II)] dimethylformamide disolvate], {[Cd2(C22H10O10)(C12H8N2)2(H2O)2]·2C3H7NO}n, (2), have been synthesized from 4,4'-(1,4-phenylenedioxy)bis(benzene-1,2-dicarboxylic acid) (H4L) and two different N-containing auxiliary ligands through a mixed-ligand synthetic strategy under a solvothermal environment. The structures were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis and IR spectroscopy. Compounds (1) and (2) both present one-dimensional chain structures and two-dimensional supramolecular layer structures constructed by weak hydrogen bonds. It is interesting to note that the carboxylate ligands reveal stable trans configurations in both compounds. The fluorescence properties of (1) and (2) in the solid state were also investigated.

Crystal structure of bis-(acetyl-acetonato-κ(2) O,O')(tetra-hydro-furan-κO)(tri-fluoro-methane-sulfonato-κO)iron(III).

The mononuclear title complex, [Fe(CF3O3S)(C5H7O2)2(C4H8O)] or [Fe(acac)2(OTf)(THF)] (acac = acetyl-acetonate; OTf = tri-fluoro-methane-sulfon-ate; THF = tetrahydrofuran), (I), consists of one six-coordinate Fe(3+) atom in a slightly distorted octa-hedral environment [Fe-O bond-length range = 1.9517 (11)-2.0781 (11) Å]. The triflate ligand was found to be disordered over two sets of sites, with a site-occupancy ratio of 0.622 (16):0.378 (16). Weak inter-molecular C-H⋯O and C-H⋯F hydrogen-bonding inter-actions generate a two-dimensional supra-molecular structure lying parallel to (100). This is only the second crystal structure reported of a mononuclear bis-(acetyl-acetonato)iron(III) complex.

Crystal structure of the bis-(cyclo-hexyl-ammonium) succinate succinic acid salt adduct.

The crystal structure of the title salt adduct, 2C6H14N(+)·C4H4O4 (2-)·C4H6O4, consists of two cyclo-hexyl-ammonium cations, one succcinate dianion and one neutral succinic acid mol-ecule. Succinate dianions and succinic acid mol-ecules are self-assembled head-to-tail through O-H⋯O hydrogen bonds and adopt a syn-syn configuration, leading to a strand-like arrangement along [101]. The cyclo-hexyl-ammonium cations have a chair conformation and act as multidentate hydrogen-bond donors linking adjacent strands through inter-molecular N-H⋯O inter-actions to both the succinate and the succinic acid components. This results in two-dimensional supra-molecular layered structures lying parallel to (010).

Crystal structure of the co-crystalline adduct 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD)-4-bromo-phenol (1/2).

The structure of the 1:2 co-crystalline adduct C8H16N4·2C6H5BrO, (I), from the solid-state reaction of 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD) and 4-bromo-phenol, has been determined. The asymmetric unit of the title co-crystalline adduct comprises a half mol-ecule of aminal cage polyamine plus a 4-bromo-phenol mol-ecule. A twofold rotation axis generates the other half of the adduct. The primary inter-species association in the title compound is through two inter-molecular O-H⋯N hydrogen bonds. In the crystal, the adducts are linked by weak non-conventional C-H⋯O and C-H⋯Br hydrogen bonds, giving a two-dimensional supra-molecular structure parallel to the bc plane.

On-Surface Construction of Network Structures by the tert-Butyl-Substituted Organic Molecules

On-surface formation of two-dimensional supramolecular network structures using molecular self-assembly has been an efficient and the most widely employed method. Through delicate modifying the molecular candidates with specific substituents, it is possible to build on-surface nanostructures according to one’s will. Here, from the interplay of high-resolution STM imaging and DFT calculations we have investigated role of the tert-butyl substituent in the formation of self-assembled network structures by planar aromatic molecules on metal surfaces. Our results demonstrate that the tert-butyl groups can change adsorption geometry of molecule from entirely flat-lying to a bit of upright-standing and vary the intermolecular interactions, which resulted in the formation of two-dimensional supramolecular network structures on both Au(111) and Ag(110). These findings further present that tert-butyl substituent could be a good candidate for fabricating on-surface self-assembled nanostructures from more general aromatic molecules.

Palladium(II) complexes of 2-pyridylmethylamine and 8-aminoquinoline: A crystallographic and DFT study

Two nominally square planar palladium(II) chelates: dichloro-(2-aminomethylpyridine-N,N′)-palladium(II) ([Pd(L1)Cl2]) and dichloro-(8-aminoquinoline)-palladium(II) ([Pd(L2)Cl2]) have been synthesised and studied by X-ray crystallography and DFT methods. [Pd(L1)Cl2] crystallised in the monoclinic space group C2/c. In the solid state this compound exists as a one-dimensional supramolecular structure supported by NH⋯Cl hydrogen bonds and metallophilic Pd⋯Pd interactions. The same hydrogen bonding motif leads to a two-dimensional supramolecular structure in the case of [Pd(L2)Cl2]; this structure is devoid of metallophilic interactions. DFT simulations show that the planar geometry of [Pd(L1)Cl2] in the solid state is not the lowest energy conformation. An out-of-plane distortion of the methylene group leads to a structure ca. 11kJmol−1 lower in energy. The NBO partial charges provide insight into the stability of the hydrogen bonding motif. TD-DFT calculations were used to delineate the experimental UV–visible spectra.

Synthesis and Structure of a Ternary Copper(II) Complex with Mixed Ligands of Diethylenetriamine and Picrate: DNA/Protein-Binding Property and In Vitro Anticancer Activity Studies.

Based on the importance of the design and synthesis of transition metal complexes with noncovalent DNA/protein-binding abilities in the field of metallo pharmaceuticals, a new mononuclear ternary copper(II) complex with mixed ligands of diethylenetriamine (dien) and picrate anion (pic), identified as [Cu(dien)(pic)](pic), was synthesized and characterized by elemental analysis, molar conductivity measurement, infrared spectrum, electronic spectral studies, and single-crystal X-ray diffractometry. The structure analysis reveals that the copper(II) complex crystallizes in the monoclinic space group P21 /c, and the copper(II) ion has a distorted square pyramidal coordination geometry. A two-dimensional supramolecular structure is formed through hydrogen bonds. The DNA/bovine serum albumin (BSA)-binding properties of the complex are explored, indicating that the complex can interact with herring sperm DNA via intercalation mode and bind to BSA responsible for quenching of tryptophan fluorescence by static quenching mechanism. The in vitro anticancer activity shows that the copper(II) complex is active against the selected tumor cell lines.

A Two-Dimensional Supramolecular Layered Structure Constructed from Pyridine Carboxamide Molecule of 6-Bromo-N-(2-hydroxyphenyl)picolinamide

A Two-Dimensional Supramolecular Layered Structure Constructed from Pyridine Carboxamide Molecule of 6-Bromo-N-(2-hydroxyphenyl)picolinamide

Synthesis and Crystal Structure of a New Aluminum(III) Oxalate Complex, (C2H10N2)2 [Al2(μ-O2)(C2O4)4].2H2O

A new Al(III) oxalate complex, (C2H10N2)2.[Al2(μ-O2)(C2O4)4]·2H2O (1), has been synthesized by hydrothermal technique. Single-crystal X-ray diffraction analysis reveals that the compound crystallizes in triclinic space group P-1 (2) with cell parameters a = 7.5297 (5) Å, b = 8.1418 (6) Å, c = 9.8279 (8) Å, α = 107.48 (1)°, β = 99.96 (1)°, γ = 95.09 (1)°. Four oxalate ligands binds with two metal centers in bidentate fashion and creates a rare μ-oxo bridged Al(III) dimer. Further, these dinuclear subunits, [Al2(μ-O2)(C2O4)4]4−, are linked by ethylene diamine [(NH3CH2CH2NH3)2+] and water molecules via hydrogen bonding through ab-planes making a two-dimensional supramolecular layered structure.