One-dimensional Helical Polymer Research Articles

Cadmium halide coordination complexes of serpentine pentadentate ligands

A series of morphologically distinct cadmium halide complexes were obtained from potentially pentadentate, serpentine ligands 2,6-bis([(2-pyridylmethyl)oxy]methyl)-pyridine (L) and 2,6-bis([(2-pyridylmethyl)thio]methyl)pyridine (L*). Methods were developed to isolate crystalline materials ranging from mononuclear [CdLCl2] (1) to zig-zag one-dimensional polymer {[CdL(μ-Cl)]2(CdCl4)}n·n(CH3CN) (2) for L and from one-dimensional helical polymers [CdL*Cl2]n (3) and [CdL*Br2]n (4) to dinuclear [CdL*(μ-Br)(CdBr3)]2 (toluene solvate 5a, ether solvate 5b) or three-dimensional polymer [((Cd(μ-Cl)2)2L*)2]n (6) for L*. Compounds 1 and 2 had pentagonal bipyramidal metal centers with L in a pseudo-planar spiral, pentadentate mode. In contrast, the complexes of L* had octahedral metal centers with a bis-N,S metal-bridging ligand binding mode linking Cd(halogen)2 units in polymeric complexes 3, 4, and 6, but a pentadentate Λ2/Δ2 ligand conformation in dinuclear complexes 5a and 5b. Interactions involved in supramolecular aggregation included offset π-π stacking interactions and edge-to-face σ-π interactions, as well as anion-π(pyridine) interactions, chalcogen–chalcogen interactions, halogen-chalcogen interactions and CH⋯X–Cd halide hydrogen bonds. Additional characterizations of the complexes included elemental analysis, solution 1H NMR spectroscopy, FTIR, TGA and PXRD.

Structure of the mercury(II) mixed-halide (Br/Cl) complex of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzo[d]imidazole).

The mercury(II) complex of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benz-imidazole), namely catena-poly[[dihalogenido-mercury(II)]-μ-2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzimidazole)-κ2N3:N3'], [HgBr1.52Cl0.48(C34H42N4)], 2, has a polymeric structure bridging via the N atoms from the benzimidazole moieties of the ligand. The compound crystallizes in the ortho-rhom-bic space group Pca21 and is a racemic twin [BASF = 0.402 (9)]. The geometry around the HgII atom is distorted tetra-hedral, with the HgII atom coordinated to two N atoms, one Br atom, and a fourth coordination site is occupied by a mixed halide (Br/Cl). For the two ligands in the asymmetric unit, there is disorder with one of the two tert-butyl groups and benzimidazole moieties showing twofold disorder, with occupancy factors of 0.57 (2):0.43 (2) for the tert-butyl group and 0.73 (3):0.27 (3) for the benzimidazole group. In addition, there is threefold disorder for two of the four n-pentyl groups, with occupancy factors of 0.669 (4):0.177 (4):0.154 (4) and 0.662 (4):0.224 (4):0.154 (4), respectively. The mol-ecules form a one-dimensional helical polymer propagating in the b-axis direction. The helices are held together by intra-strand C-H⋯Br and C-H⋯Cl inter-actions. Each strand is further linked by inter-strand C-H⋯Br and C-H⋯Cl inter-actions. In addition, there are weak C-H⋯N inter-strand inter-actions which further stabilize the structural arrangement.

Metal-Directed Formation of Molecular Helix, Cage, and Grid Using an Asymmetric Pyridine-Pyrazole Based Bis-Chelating Ligand and Properties

The present work reports the construction and self-assembly studies of molecular helix and polyhedral coordination cages using a pyridine-pyrazole based asymmetric ligand. Employment of different metals has resulted in different architectures ranging from a one-dimensional helical polymer, [2 × 2] grid to a pentanuclear cage. For all the structures, hydrogen bonding and π–π stacking were found to be instrumental in bringing additional stability to the polymeric networks. Furthermore, chirality and magnetic properties of cobalt and copper complexes have also been investigated.

Dimeric and polymeric silver(I) saccharinato complexes of two bis(pyridine) ligands: Synthesis, structural, spectroscopic, fluorescent and thermal properties

The reaction of silver(I) with 1,2-bis[1-(pyridin-2-yl)ethylidene]hydrazine (bpeh) and N, N-bis(pyridin-2-ylmethyl)amine (bpma) in the presence of Na(sac) (sac = saccharinate) yielded [Ag 2(sac) 2(bpeh)] ( 1) and [Ag(sac)(bpma)] n ( 2) with conformational chirality. Both complexes have been characterized by elemental analysis, IR, thermal analysis and X-ray single crystal diffraction. Complex 1 displays a binuclear composition, in which each silver(I) ion is bound to one monodentate sac ligand and one of the bidentate pyridylimino groups of the bpeh ligand in a distorted trigonal coordination geometry. Complex 2 is a one-dimensional helical polymer, in which silver(I) centers are bridged by tridentate bpma ligands, and each silver(I) ion is coordinated in a distorted tetrahedral geometry by one monodentate sac ligand, a bidentate pyridylamine group of one bpma ligand, and a py group of another bpma ligand. Weak intermolecular C–H⋯O hydrogen bonds and C–H⋯π interactions lead to assembly of 1 and 2 into three-dimensional supramolecular frameworks. Spectral and thermal analysis data for 1 and 2 are in agreement with the crystal structures. In addition, both complexes in the solid state display intraligand π–π∗ fluorescence.

Catena-Poly[[aquabarium(II)]-μ-aqua-bis(μ-2′-carboxybiphenyl-2-carboxylato)

In the title compound, [Ba{HOOC(C(6)H(4))(2)CO(2)}(2)(H(2)O)(2)] or [Ba(C(14)H(9)O(4))(2)(H(2)O)(2)], the Ba atoms are coordinated by nine O atoms, six from two 2'-carboxybiphenyl-2-carboxylate (Hbpdc(-)) ligands and three from three coordinated water molecules, resulting in the formation of face-sharing distorted monocapped square antiprisms. The Hbpdc(-) ligands bridge the Ba atoms to form a one-dimensional helical polymer, with a Ba...Ba distance across the chain of 4.1386 (17) A. Adjacent chains are parallel to each other. The two independent ligands are tetradentate and have the same coordination mode, exhibiting mu-oxo bridges and eta(8)-chelation. The crystal structure is further stabilized by hydrogen bonds within each chain.

Synthesis of functionalised (triorganostannyl)tetrazoles: supramolecular structures of n-[2-(triorganostannyl)tetrazol-5-yl]pyridine (n = 2, 3 or 4)†

Six pyridine-substituted triorganostannyltetrazoles, n-[2-(triorganostannyl)tetrazol-5-yl]pyridine (n = 2, 3 or 4; R = Et or Bu), have been synthesized by a cycloaddition method involving R3SnN3 and n-cyanopyridine. 1,7-Bis[2-{(triorganostannyl)tetrazol-5-yl}phenyl]-1,4,7-trioxaheptane has been synthesized by the cycloaddition of tributyltin azide and 1,7-di(2-cyanophenyl)-1,4,7-trioxaheptane. The crystal structures of 3-(Et3SnN4C)C5H4N·H2O, 4-(Et3SnN4C)C5H4N and 4-(Bu3SnN4C)C5H4N·2H2O, have been determined. While the first and third are three-dimensional arrays held together by hydrogen bonds, the supramolecular structure of the anhydrous second consists of one-dimensional helical polymers.