Abstract

Abstract

Abstract

Abstract

Abstract

Three new coordination polymers, namely {[Cu₂(bptc)(4,4′-bpy)(H₂O)₂]·2H₂O}_n (1), {Cu₂(bptc)(bpe)(H₂O)₆}_n (2), and {[Mn(H₂bptc)(H₂O)₄]·2bpe}_n (3) [H₄bptc = 3,3′,4,4′-biphenyltetracarboxylic acid, 4,4′-bpy = 4,4′-bipyridine, bpe = trans-1,2-bis(4-pyridyl)ethene], were rationally designed and hydrothermally synthesized at different pH values. Their structures were determined by X-ray diffraction on single crystals. Compound 1 exhibits a 3D network with 1D open channels that contain free solvent water molecules, and two kinds of chiral, helical, hydrogen-bonded chains exist in the neighboring holes. Both compounds 2 and 3 show a 3D supramolecular network that is connected through hydrogen bonds. Compound 2 also shows weak Cu···O semicoordinated interactions that are based on 1D chains. Importantly, bptc reveals three different coordination modes in these compounds: the four carboxylic groups combine with metal ions by bis(monodentate) and bis(chelate) fashions in 1, whereas only two carboxylic groups are bis(monodentate) in 2 and 3, respectively, and the 4,4′-carboxylic groups are protonated in 3. The elemental analysis, IR spectra, UV/Vis spectra, and TG analysis for compounds 1, 2, and 3 are discussed. Additionally, the XRPD is also studied for compound 1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A new V-shaped bis-monodentate ligand L (L = 2,3′-dipyridylamine) (1) has been designed and synthesized by alkylation reaction of pyridylamine. An investigation of the charge distributions of the coordination atoms and single-point energy calculations of four conformers of ligand L based on the geometry of conformers optimized by the DFT (density functional theory) method was carried out. The results show that the four conformers of ligand L take on two stable and two less stable configurations. Theory forecasts that two relatively stable configurations present in complexes as probable coordination motifs of the ligand, and that steric hindrance of pyridine nitrogen atoms in isomers will affect its coordination ability together with the electronic factor. This forecast has been demonstrated by the coordination chemistry of ligand L, that is, configuration (a) and (b) of the ligand occur in the following reported complexes, which combines with Ag^I or Cu^II through two coordination modes (bidentate bridging or a monodentate mode) resulting in coordination polymers {[Ag (L)₂]NO₃}_n (2), [Cu₂(L)₂(maa)₄]_n (maa = methacrylic acid) (3), and the mononuclear molecule [Cu(L)₄](ClO₄)₂·2CH₃CH₂OH (4). The ligand assumes different coordination modes in the three complexes because of different levels of steric hindrance of the pyridine nitrogen atoms in the conformers. Interestingly, polymers 2 and 3 assume a 1D helical structure and a linear framework, respectively, and 4 has a 2D supramolecular architecture induced from hydrogen bond interactions. In addition, the magnetic properties of 3 have been explored, which shows a strong antiferromagnetic interaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Two novel supramolecular complexes [Cu(bpapa)(dhbd)]·CH₃OH (1) and [Cu(bpapa)(ma)]·ma (2) (bpapa=bis[6-(2-pyridylamino)pyrid-2-yl]amine, dhbd=2,3-dihydroxybutanedioate dianion, ma=α-methacrylate) were rationally designed, synthesized and characterized by single crystal X-ray diffraction, IR, electronic spectroscopy and thermogravimetric analyses. Complex 1 was the first oligo-α-pyridylamino complex based on hydroxypolycarboxylate and self-assembled into a 3D honeycomb configuration network with open channels and tubes containing 1D ladder-shaped double chains formed by hydrogen bonds and aromatic π-π stacking interactions. Complex 2 constructed a 2D supramolecular network extended by 1D chains from dimeric supramolecular synthon through noncovalent supramolecular interactions. In the two complexes, the chelating monohelical ligand adopted all-anti configuration. Density functional theory calculations were applied to 1 and 2.

The synthesis and structures of six compounds prepared in two different systems have been explored with the purpose of isolating coordination polymers with interlaced triple-stranded molecular braid architectures. The dinuclear paddle-wheel units of [Cu₂(maa)₄⋅2 H₂O] can be rationally tuned to form three classes of isomorphous compounds, namely [Cu₂(maa)₄(bpp)] (1) (bpp=1,3-bis(4-pyridyl)propane, Hmaa=2-methylacrylic acid), [Cu₃(maa)₆(bpp)₂] (2), and[Cu₄(maa)₈(bpp)₄(H₂O)₂]⋅2 H₂O (3), with a bridging bpp ligand, at controlled ligand-to-metal molar ratios, and lead to three coordination polymers having similar one-dimensional characteristics but different mono- and dinuclear nodes. Compound 1, with a bpp:[Cu₂(maa)₄⋅2 H₂O] stoichiometry of 1:1, contains a zigzag chain containing dinuclear nodes, whereas polymer 2, with a bpp:[Cu₂(maa)₄⋅2 H₂O] stoichiometry of 1.5:1, also adopts the topology of a zigzag chain but with both mono- and dinuclear nodes. Compound 3, with a bpp:[Cu₂(maa)₄⋅2 H₂O] stoichiometry of 2:1, contains a neutral, interlaced, triple-stranded molecular braid, which is interwoven by three single-stranded meso-helical chains that contain only a mononuclear node. With the three aromatic chelating terminal ligands 2,2′:6′,2′′-terpyridine (tpy), 1,10-phenanthroline (phen), and di(2-pyridyl)amine (dpa) we have also prepared three neutral complexes containing the linear, rigid bridging ligand biphenyl-4,4′-dicarboxylate (bpdc), namely [Cd(bpdc)(tpy)]⋅H₂O (4), [Cu(bpdc)(phen)₂]⋅4.25 H₂O (5), and [Cu(bpdc)(dpa)] (6). An infinite meso-helix is formed initially in 4, and then three of these chains assemble into a triple-stranded braid similar to that of 3. Complexes 5 and 6 have a mononuclear and a looped dinuclear structure, respectively. Compounds 3 and 4 are unusual examples of triple-stranded molecular braid coordination frameworks based on different types of co-ligands.

Two novel 1-D coordination polymers, {[Cu(Hhbd)(bpy)]·3H₂O}_n (1) and {[Cu(Hhbd)(phen)]·H₂O·MeOH}_n(2) [Hhbd = α-hydroxybutanedioicate dianion, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline], were rationally designed and synthesized with an identical construction strategy, using Hhbd ligands as bridges and chelating aromatic ligands as terminal ligands. Interestingly, the chelating aromatic ligand and the –OH groups of the Hhbd ligand play an important role in the self-assembly of the polymeric coordination chain by providing potential supramolecular recognition sites for π–π aromatic stacking and hydrogen-bond interactions, resulting in the self-assembly of the molecular double chains to give a 3-D supramolecular framework with 1-D open channels. More significantly, in 1 the host framework encapsulates unprecedented centrosymmetric cyclic (H₂O)₈ clusters that have a chair conformation and are connected into 1-D arrays by supramolecular association along the 1-D open channels. In contrast, the channels of 2 contain lattice water and disordered methanol molecules. TGA and XRPD show that the host frameworks of 1 and 2 are stable when the guest solvent molecules are removed from the channels. Variable-temperature magnetic susceptibility measurements for both complexes indicate the presence of weak antiferromagnetic exchange interactions between adjacent copper(II) ions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Two novel supramolecular complexes, [Cu(bpapa)(mal)]·H₂O·CH₃OH (1) and {[Cu(bpapap)](Hmal)₂}·2H₂O (2) [bpapa=bis-[6-(2-pyridylamino)pyrid-2-yl]amine, bpapap=2,6-bis-[6-(pyrid-2-ylamino)pyrid-2-ylamino]-pyridine, mal=maleate dianion] were rationally designed and synthesized based on flexible multidentate ligands and copper(II) maleate. Complexes 1 and 2 were all characterized by elemental analysis, spectroscopic techniques, thermal analysis and single crystal X-ray diffraction analysis. Complex 1 is of an infinite 3-D supramolecular framework constructed by 2-D sheets to contain 1-D helical chains formed by intermolecular hydrogen bond interactions between the non-coordinated oxygen atoms from maleate and nitrogen atoms from amino groups of bpapa. Complex 2 also takes a 3-D supramolecular structure, which is built from 2-D rhombic sheets produced by sequential dimer units. Interestingly, three pairs of symmetrical hydrogen bonds generate these dimer units.

A methanol solution of 4,4′-bipyridine reacts with Cu₂A₄(H₂O)₂ to yield coordination polymers of general formula: [Cu₂A₄(bipy)]_n [A: CH₂C(Me)CO₂⁻ (1), CH₂CHCO₂⁻ (2); bipy: 4,4′-bipyridine]. They were characterized by elemental analyses, IR spectra and thermal analyses. The X-ray structure analyses of 1 show a one-dimensional chain structure where the binuclear structural units Cu₂[CH₂C(Me)CO₂]₄ are bridged by 4,4′-bipyridine molecules. Furthermore, the binuclear units between adjacent layers can form micropores. The temperature-dependent magnetic susceptibility of 1 indicates that the strong antiferromagnetic interaction exists between copper(II) atoms in the binuclear units.

Molecular weaving: Mixing a Cu^II complex having a paddle-wheel structure with a highly flexible neutral 1,3-bis(4-pyridyl)propane ligand (1:2 ratio) gives an interlaced braid which looks just like a hair plait (see X-ray crystallographic structure). The three strands are held together through hydrogen-bonding interactions.

Molekulares Weben: Beim Mischen eines Cu^II-Komplexes mit Schaufelrad-Struktur mit einem hochflexiblen, neutralen 1,3-Bis(4-pyridyl)propan-Liganden im Verhältnis 1:2 entsteht ein verkettetes Gebilde, das genau wie ein Haarzopf aussieht (siehe Strukturbild). Die drei Stränge werden durch Wasserstoffbrücken zusammengehalten.