Self-assembly of 1-D and 3-D transition-metal coordination polymers based on 4-(1H-l,3-benzimidazol-2-yl)pyridine 1-oxide

Three metal-organic coordination polymers based on 4-(1H-l,3-benzimidazol-2-yl)pyridine 1-oxide (BImPyO) with the molecular structures [Cu₂(C₁₂H₈N₃O)₂]_n (1), [Cu(C₁₂H₈N₃O)]_n (2), and [Zn(C₁₂H₈N₃O)Cl]_n (3) were synthesized under hydrothermal conditions. They showed diverse coordination modes and were further characterized by elemental analysis, infrared spectroscopy, and single crystal X-ray structure analysis, respectively. In 1 and 2, BImPyO generated a 1-D chain by adopting μ₂-kN?:?kN′ coordination to bridge two Cu(II) ions with bis-N-chelation. In 3, by adopting μ₃-kN?:?kN′:kO coordination, BImPyO bridged three crystallographically independent Zn(II) ions to form a 3-D framework; 3 exhibits strong fluorescent emission in the solid state at room temperature.     

Self-assembly of 1-D, 2-D,and 3-D transition-metal coordination polymers based on a T-shaped tripodal ligand 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine 1-oxide

Three coordination polymers, {[Co(C₁₀H₅N₃O₅)(H₂O)₂]·H₂O}_n (1), {[Mn₃(C₁₀H₅N₃O₅)₂Cl₂(H₂O)₆]·2H₂O}_n (2), and {[Cu₃(C₁₀H₄N₃O₅)₂(H₂O)₃]·4H₂O}_n (3), based on a T-shaped tripodal ligand 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine 1-oxide (H₃DCImPyO), were synthesized under hydrothermal conditions. The polymers showed diverse coordination modes, being characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray structure analysis. In 1, the HDCImPyO^2? generated a 1-D chain by adopting a μ₂-kN, O : kN′, O′ coordination mode to bridge two Co(II) ions in two bis-N,O-chelating modes. In 2, the HDCImPyO^2? adopted a μ₃-kN, O : kO′, O′′ : O′′′ coordination mode to bridge two crystallographically independent Mn(II) ions, forming a 2-D hcb network with {6³} topology. In 3, by adopting μ₄-kN, O : kO′, O′′ : kN′′, O′′′ : O′′′′ coordination, DCImPyO^3? bridged three crystallographically independent Cu(II) ions to form a 3-D framework having the stb topology.     

Transformation of 1-D Chiral-chained Titanium Phosphate to 2-D Layer Structure Through a 1-D Zigzag Chain

The transformation of titanium phosphate from 1-D chiral- chain(JTP-A) to 2-D layer( TP-J1 ) has been carefully investigated. Through a hydrolysis-condensation self-assembly pathway, the crystals of TP-J1 can be obtained from the JTP-A phase under hydrothermal conditions. An intermediate material with zigzag chain during the transformation was observed by XRD characterization. A hypothesis of the transformation mechanism is also described in this article. It is noteworthy that ethylenediamine plays an important role in the transformation.     

Construction of 1-D 4f and 3d-4f coordination polymers with flexible Schiff base ligands

Three new lanthanide 1-D coordination polymers ({[Ln(2)(H(2)L)(OAc)(6)]·EtOH·2H(2)O}(n) (Ln = Eu (1), Er (2)) and {YbNiLCl(OAc)(2)(H(2)O)}(n) (3)) and a heterobinuclear complex [YbNiLCl(3)(H(2)O)(3)] (4) are reported which are formed from salen type Schiff-base ligands H(2)L (H(2)L = N,N'-bis(3-methoxysalicylidene)butane-1,4-diamine). The polymeric structures are formed by bridging H(2)L units in the case of 1 and 2, and by acetate groups in 3. The structures of 1-4 were determined by single crystal X-ray crystallographic studies and their luminescence properties in MeCN solution were determined.     

Structural Assignment of Side Chain Liquid Crystalline Monomer and Polymer by 1-D and 2-D Solution NMR Studies

In the present study, the synthesis and characterization of a methacrylic-based side chain liquid crystalline monomer and its polymer were investigated with the aid of both 1-D and 2-D nuclear magnetic resonance (NMR) techniques. The mesophase characteristics of the monomer and polymer were determined by hot-stage optical polarized microscopy (HOPM). The nematic and smectic phases were observed for the monomer and polymer. Furthermore, ¹³C spin-lattice relaxation time measurements were performed on the above systems in order to monitor molecular dynamics. The present study provides an opportunity to carry out a systematic comparison of the evolution of structural as well as dynamical changes of the monomer and the polymer.     

Ionothermal syntheses and characterization of 2-D coordination polymers with 4-(1H-imidazol-1-yl) benzoic acid

4-(1H-imidazol-1-yl) benzoic acid and its coordination polymers [M(IBA)Cl] _n (M?=?Zn (1) and Co (2)) have been synthesized. Compounds 1 and 2 were obtained under ionothermal conditions and possess a 2-D laminar [M(IBA)] _n layer based on M₂(CO₂)₂ building blocks with coordinated chloride completing tetrahedral coordination of the metal. Compound 1 exhibits two photoluminescence emission peaks at 410 and 510?nm. The low-energy emission can be attributed to ligand-centered transition and the high-energy band can be assigned to ligand-to-metal charge transfer between the aromatic systems of the organic ligands and the 4s orbitals of Zn(II). The role of the ionic liquid in ionothermal synthesis and crystallization of 1 and 2 are briefly discussed.     

Allylstannation: VII. Preparation of carboxylic acid 1-alkene-4-yl and 1-alkyne-4-yl esters by transalkoxylation of 4-n-dibutylchlorostannoxy-1-alkenes and 4-n-dibutylchlorostannoxy-1-alkynes with acyl chlorides

Carboxylic acid 1-alkene-4-yl and 1-alkyne-4-yl, esters (RCH(CH₂CHCH₂)OCOR′ ad RCH(CH₂CCH)OCOR′, R = R′ or R ≠ R′ = alkyl or alkenyl group) can be readily prepared in high yields by transalkoxylation reactions between 4-n-dibutylchlorostannoxy-1-alkenes or 4-n-dibutylchlorostannoxy-1-alkynes with acyl chlorides. This represents a general route for preparation of esters containing allyl or propargyl groups.     

The 1-D hindered rotor approximation

We offer an overview of the popular one- dimensional (1-D) hindered rotor model that is often used for quantum mechanical treatment of internal rotation. This model is put in context with other methods used for treating anharmonic motions. The 1-D hindered rotor scheme is general for tops of any symmetry and has been used to provide accurate treatment of hindered rotors in a wide range of systems. One obstacle preventing wider use of the model is its lack of incorporation into common electronic structure codes. We have developed an algorithm for consistently treating all tops in a molecule, and we present simple codes which interface with electronic structure codes to provide thermochemical properties (S, C _p , H) of individual species and reactions that have been corrected for internal rotations. Finally, we use this approach to give sensible advice about how the model can be used best. We show that dramatic changes in the reduced moment of inertia do not necessarily cause comparable changes in the properties of individual hindered rotors. We demonstrate that the rotational hindrance potential can be accurately determined using relatively coarse step sizes. Finally, we show that internal rotation in transition states can be treated using a “frozen transition state” approximation at a significant computational savings. We also discuss the relationship between calculated properties of hindered rotors and the choice of method and basis set used. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Self-assembly of 1-D organic semiconductor nanostructures

This review focuses on the molecular design and self-assembly of a new class of crowded aromatics that form 1-D nanostructures via hydrogen bonding and pi-pi interactions. These molecules have a permanent dipole moment that sums as the subunits self assemble into molecular stacks. The assembly of these molecular stacks can be directed with electric fields. Depending on the nature of the side-chains, molecules can obtain the face-on or edge-on orientation upon the deposition onto a surface via spin cast technique. Site-selective steady state fluorescence, time-resolved fluorescence, and various types of scanning probe microscopy measurements detail the intermolecular interactions that drive the aromatic molecules to self-assemble in solution to form well-ordered columnar stacks. These nanostructures, formed in solution, vary in their number, size, and structure depending on the functional groups, solvent, and concentration used. Thus, the substituents/side-groups and the proper choice of the solvent can be used to tune the intermolecular interactions. The 1-D stacks and their aggregates can be easily transferred by solution casting, thus allowing a simple preparation of molecular nanostructures on different surfaces.     

1-D nanochannels fabricated in polyimide

A simple method using spin-deposition and sacrificial layer etching is used to fabricate all-polyimide nanochannels (100 and 500 nm channel height). Channels are characterized using spontaneous capillary filling with water, ethanol and isopropanol, and with electroosmotic flow. The channels can be produced with simple cleanroom equipment, namely spinning and metal deposition facilities. Polyimide is an excellent material for micro- and nanofluidic channels due to its favourable electrical and mechanical properties and its biocompatibility.     

1-D infinite array of metalloporphyrin cages

The reaction of Co(II) with 5,15-dipyridyl-10,20-diphenylporphyrin (H(2)DPyP) produces the first metal-organic coordination polymer supported by a trans meso-bifunctional porphyrin ligand. Formulated empirically as [Co(3)(DPyP)(3)] x 4DMF, this compound exhibits a ribbonlike coordination network consisting of tetranuclear metalloporphyrin cages. The DMF guest molecules fill the intra-ribbon cages as well as the inter-ribbon space. Evacuation of [Co(3)(DPyP)(3)] x 4DMF at 130 degrees C generates [Co(3)(DPyP)(3)] that retains crystallinity, as shown by its powder X-ray diffraction pattern, which is consistent with that of [Co(3)(DPyP)(3)] x 4DMF.     

Self-assembly of three Cd(II) complexes: 0-D, 1-D,and 3-D structures based on 2-(1H-imidazol-1-methyl)-1 H-benzimidazole

Three new complexes, [Cd(L)I₂]₂ (1), {[Cd(L)I₂]?·?DMF} _n (2), and [Cd₂(L)₄(μ ₂-I)I(H₂O)] _n (3), have been obtained through self-assembly of an unsymmetrical ligand 2-(1H-imidazol-1-methyl)-1H-benzimidazole (L) with Cd(II) salts. Single-crystal X-ray diffraction shows that 1 displays a dimeric structure in which two Cd(II) ions are bridged by two bidentate bridging L. Complex 2 exhibits a 1-D chain structure (···Cd–L–Cd–L···) constructed by L bridging Cd(II) ions. In 3, the Cd(II) ions are five-connected nodes and linked by L and iodide leading to the 3-D network. Complexes 2 and 3 are synthesized maintaining the same solvents and stoichiometric ratio of metal and ligand at different reaction temperature. The different structures of the complexes indicate that the temperature plays a significant role in construction of the complexes. Luminescent properties of 1–3 have been investigated in the solid state at room temperature.     

Hydrothermal synthesis and structural characterization of two 1-D and 2-D Dawson-based phosphotungstates

Two new Dawson-based phosphotungstates (H₂en)_0.5H[Cu(en)₂(H₂O)]₂{[Cu(en)₂](α₁-P₂W₁₇CuO₆₁)}·8H₂O (1) (en=ethylenediamine) and [4,4′-H₂bpy]₂{[Cu(4,4′-bpy)₃][Cu(4,4′-bpy)₄(H₂O)₂]₂[Cu(4,4′-bpy)][α-P₂W₁₈O₆₂]₂}·6H₂O (2) (4,4′-bpy=4,4′-bipyridine) have been hydrothermally synthesized and structurally characterized. 1 crystallizes in the triclinic space group P−1 with a=11.7626(17), b=13.246(2), c=29.350(5) Å, α=87.355(5), β=79.583(5), γ=66.993(3)°, V=4138.3(11) Å³, Z=2, GOF=1.089, R₁=0.0563 and wR₂=0.1505, whereas 2 belongs to the orthorhombic space group Iba2 with a=22.277(8), b=47.04(2), c=22.153(8) Å, V=23215(17) Å³, Z=4, GOF=1.051, R₁=0.0627 and wR₂=0.1477. 1 consists of a 1-D linear chain structure constructed from monocopper^II-substituted Dawson polyoxoanions, while 2 represents the first 2-D sheet-like structure with a (4,4)-connected topological net built up from plenary Dawson-type polyoxoanions and Cu^II-4,4′-bpy complex cations in polyoxometalate chemistry.     

Quantum-chemical Investigations of Pyrimidinones-4. 1. Tautomerism of 2-Oxopyrimidinones-4

Semiempirical quantum-chemical calculations have been carried out of the molecules of 2-oxopyrimidinones-4. The geometry and electronic structures and the stabilities of the tautomeric forms have been analyzed.     

Three 4-connected nickel coordination polymers affording a 3-D CdSO4 network and two 2-D (4,4) networks

The self-assembly reaction of 1,4-bis(1,2,4-triazol-1-yl)butane (btb) and Ni(II) salts gives three coordination polymers {[Ni(btb)₂(NCS)₂]?·?H₂O} _n (1), [Ni(btb)₂(NCO)₂] _n (2), and [Ni(btb)₂Cl₂] _n (3). Compound 1 is comprised of a twofold interpenetrating 4-connected 6⁵?·?8-CdSO₄ 3-D coordination network. Compounds 2 and 3 are neutral 2-D (4,4) networks with the ABAB?···?and ABCABC?···?stacking modes, respectively. The thermal stabilities of 1–3 were investigated.     

Cu(pyrazine-2-carboxylate)2]2Cd4I8: unprecedented 1-D serpentine inorganic chains and regular 2-D metal-organic square grids in a 3-D framework

A novel three-dimensional coordination polymer containing an unprecedented one-dimensional serpentine motif conjoined with a two-dimensional square grid motif is presented.