Synthesis, spectral and crystallographic characterization of manganese(II) coordination polymers based on aliphatic dicarboxylate and flexible bis(imidazolyl) derivatives

Two structurally related flexible imidazolyl ligands, bis(N-imidazolyl)methane (L₁) and 1,4-bis(N-imidazolyl)butane (L₂) reacted with Mn(II) salts of aliphatic dicarboxylic acids resulted in the formation of a number of novel metal-organic coordination architectures. All complexes have been structurally characterized by X-ray diffraction analysis. The different coordination modes of dicarboxylate anions due to their chain length, rigidity and diimidazolyl functionality lead to a range of different coordination structures. The coordination polymers exhibit 1D single chain, 2D sheet and 3D network structures. The aliphatic dicarboxylates can adopt chelating μ₂, bridging μ₂, and chelating-bridging μ₃ coordination modes, or act as uncoordinated counter anions. The central metal ions are coordinated in N₂O₄ and N₄O₂ fashions depending on the ancillary ligands. The topology of [Mn(male)(L₁)(H₂O)₂] (1, male = maleate) gives rise to singly bridged 1D chains, whereas compound [Mn(mal)(L₁)(H₂O)] · H₂O (2, mal = malonate) exhibits 2D sheets in which the metal centers are bridged by both imidazolyl ligands and dicarboxylates. Compounds [Mn(L₁)₂(H₂O)₂](suc) · 6H₂O (3, suc = succinate) and [Mn(L₁)₂(H₂O)₂](fum) · 6H₂O (4, fum = fumarate) show doubly bridged 1D chains, and the dicarboxylate groups are not coordinated but form 2D corrugated sheets with water molecules intercalated between the cationic layers. Compound [Mn(suc)(L₂)(H₂O)₂] (5, suc = succinate) was built from very flexible succinate and 1,4-bis(N-imidazolyl)butane which yielded three-dimensional interpenetrate networks, both succinate anion and the imidazolyl ligand act as bidentate bridging.     

Temperature effect on the conversions of phthalato and maleato manganese(II) complexes with diamine ligands

1,10-Phenanthroline hydrogen phthalato manganese(II) dimer [Mn₂(Hphth)₂(phen)₄] · 2Hphth · 6H₂O (1), monomeric phenanthroline phthalato manganese(II) monomer [Mn(phth)(phen)₂(H₂O)] · 2.5H₂O (2), 2,2′-bipyridine phthalato manganese(II) polymer [Mn(phth)(bpy)(H₂O)₂]_n (3) and 1,10-phenanthroline maleato polymer [Mn(male)(phen)(H₂O)₂]_n · 2nH₂O (4) (H₂phth = o-phthalic acid, male = maleic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine) have been synthesized and characterized spectroscopically and structurally. Each Mn(II) atom in dimeric 1 is octahedrally coordinated by two oxygen atoms of phthalate anions and by two cis-phenanthroline ligands. The hydrogen phthalato anion bridges the Mn(II) ions through the deprotonated carboxyl groups, while the carboxylic acid group remains free. In the monomeric 2, the Mn(II) ion is octahedrally surrounded by four nitrogen atoms from two cis-phen ligands, one carboxyl oxygen from a monodentate phth ion, and one coordinated water molecule. The dimeric phthalato complex 1 can be cleaved into monomer 2 under heating with deprotonation, and the course of the reaction can be qualitatively traced by IR spectra. The phthalate group in the complex 3 binds to two manganese atoms through the vicinal carboxyl-oxygen atoms in syn-syn bridging mode. The Mn(II) atoms are linked by the phthalate group to yield a one-dimensional chain running along the a-axis. The coordination polymer 3 can be obtained from the reaction of dichloro dibipyridine manganese with phthalate under heating. In polymer 4, the manganese atom is six-coordinated by two nitrogen atoms from phen, two oxygen atoms from the coordinated water molecules and two oxygen atoms from two different maleate dianions. Each maleato unit links two neighboring manganese atoms to yield one-dimensional chain along b-axis in bis-monodentate mode. The single-chain polymer 4 prepared at low temperature can be converted to double-chain coordination polymer [Mn(male)(phen)]_n · nH₂O (5) with dehydration in warm solution.     

Synthesis, crystal structure and photoelectric property of Mn(II/IV) coordination complexes

Three novel coordination complexes [Mn(tpha)(phen)]_n (1); [Mn(na)₂(H₂O)₂]_n (2); {[Mn(phen)₂(OH)Cl] · Cl · (OH) · (C₉H₁₁NO₂) · 2H₂O} (3) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction (H₂tpha = terephthalic acid, Hna = nicotinic acid, phen = 1,10-phenanthroline). The tpha groups in complex 1 bridge the Mn(II) ions to an infinite 3D framework. Complex 2 exhibits a 2D network structure in which the Mn(II) ions are linked by nicotinic groups. Complex 3 is connected to a 2D coordination supramolecule by hydrogen bonds. The results of surface photovoltage spectra (SPS) of complexes 1-3 indicate that they all exhibit positive surface photovoltage (SPV) responses in the range of 300-800 nm. However, the intensity, position and numbers of SPV responses are obviously different. The distinctions can be mainly attributed to their structures, valences and coordination environments of the manganese ions in the three complexes. Moreover the external field induced surface photovoltage spectra (FISPS) of the three complexes have been measured.     

Ligand-directed metal(II) coordination polymers: Unusual disorder, and photoluminescence

2,6-Dimethyl-4-phenylpyridine-3,5-dicarboxylic acid (H₂mppdc, H₂L) is firstly employed in coordination chemistry. Two metal-organic coordination polymers with a general formula of M₂L₂(4,4′-bpy)_x(H₂O)_4−2x (M = Zn or Co, x = 1 or 2) are assembled from H₂L, 4,4′-bipyridine, zinc and cobalt salt under hydrothermal conditions, and characterized by single-crystal X-ray diffraction analyses. Of the crystal structures of title compounds, L ligands, limited in the environment from 4,4′-bipyridine, array in head-to-head and head-to-tail modes which are corresponding to the 1D (1) and 3D (2) polymeric structures, respectively. Interesting disorders occur in the crystal lattice of compound 1. And compound 2 has a 3D 4² · 6¹⁰ · 8³ topology. Solid-state H₂L and 1 have expected photoluminescence at room temperature.     

Syntheses, structures, and properties of novel one dimensional copper cyanide coordination polymers

Three new one-dimensional copper coordination polymers have been prepared and fully characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and magnetic susceptibility measurements. The structure of [Cu(CN)₂(bpy)] (1) (bpy = 2,2-bipyridyl) (monoclinic P2₁/c, a = 8.9761(7) Å, b = 16.731(1) Å, c = 8.0224(6) Å, β = 114.437(1)°) consists of Cu(II) metal centers coordinated by three cyanide ligands and chelated by one bpy to form the monomers Cu(CN)₃(bpy) with distorted square pyramidal geometry. Each monomer shares two cyanide ligands with two adjacent monomers to form infinite -Cu(II)-CN-Cu(II)-CN-Cu zigzag chains along the c-axis. The one-dimensional structure of [Cu(CN)(bpy)] (2) (hexagonal P3₂, a = 14.4883(6) Å, b = 12.921(1) Å) is built of tetrahedral Cu(CN)₂bpy metal complexes in which Cu(I) metal centers are coordinated by one nitrogen and one carbon from two different CN ligands, and two nitrogens from one bpy. The two CN ligands act as bridging ligands between adjacent monomers to form helical chains along the 3₂ screw axis. The crystal structure of [Cu₂Cl(CN)(bpy)] (3) (orthorhombic Pbca, a = 17.853(2) Å, b = 6.9724 (9) Å, c = 18.7357 (9) Å) consists of two monomers, CuCl₂(CN) and Cu(bpy)(CN) that share a cyanide ligand to form Cu₂Cl₂(CN)(bpy) dimers. The dimers link to each other by sharing Cl ligands leading to the formation of infinite Cu-Cl-Cu chain decorated by the complex Cu(CN)(bpy). Variable-temperature magnetic measurement shows an overall ferromagnetic behavior for compound 1. The magnetic pathway of compound 1 is through the cyanide bridge connecting apical and equatorial positions of adjacent copper (II) ions.     

Manganese(II) and zinc(II) compounds via amino acid derivatives: Effects of temperature and solvents

To investigate the influence of temperature and the ratios of solvents on the design and synthesis of metal-organic frameworks (MOFs), we have synthesized and structurally characterized a series of supramolecular assemblies based on different amino acid derivatives and nitrogen-containing heterocyclic ligands, namely [Mn(phen)₂(phth)(H₂O)]·4H₂O (1), [Mn(phen)₂(HL1)₂]·3.5H₂O (2), [Zn(bpp)₂(L-Me)₂] (3), and [Zn(bpp)(L-Me)₂] (4) (H₂phth = phthalic acid, H₂L¹ = phthalyl-l-valine, H₂L = (+)-N-tosyl-l-glutamic acid, phen = 1,10-phenanthroline, bpp = 1,3-bis(4-pyridyl)propane, and L-Me = C₁₂H₁₃NO₆S-CH₃). Compounds 1 and 2, which are assembled through noncovalent interactions, were obtained by controlling the temperature. In 1, π-π stacking and hydrogen-bonding interactions lead to stacking in a 3D supramolecular network, while in 2, π-π stacking interactions form 1D chains that extend along the c-axis. Depending on the solvents employed, compounds 3 and 4 could be generated, with a 1D bpp-connected Zn-bpp-Zn double chain that is further hydrogen-bonded into a 2D network that extends parallel to the ac plane in 3, and a single chain in 4.     

One-dimensional ladder like and two-dimensional polymorphs of heterometallic thiocyanate bridged copper(II) and mercury(II) coordination polymer: Syntheses, structural, vibration, luminescence and EPR studies

The 1D triclinic {CuHg(en)(μ-NCS-N,S)₄}_n (1) and 2D monoclinic {CuHg(en)(μ-NCS-N,S)₃(SCN)}_n (2) (en = ethylenediamine) heterometallic coordination polymers, as the two polymorphs of the {CuHg(en)(NCS)₄}_n, were synthesized at room temperature by the reaction of mercuric thiocyanate, potassium thiocyanate, copper(II) malonate and ethylenediamine using different reagent ratios. XRD on single crystals shows that the compound 1 consists of 1D ladder like zigzag ribbons extended along the b axis, whereas compound 2 shows a 2D wavy polymeric structure running parallel to the ab plane. In the crystal packing of the both polymorphs, the polymeric structures are further interlinked to each other via weak interactions and hydrogen bonding to afford a 3D network. Diagnostic ligand and metal-ligand bands in the IR, far-IR and Raman spectra are assigned for the studied compounds. While compound 1 shows no significant emission upon excitation at any wavelength in the UV-Vis region, compound 2 exhibits intense emission at around 410 nm. Moreover, the room temperature X-band EPR spectrum of a powdered sample of 1, shows a signal of rhombic symmetry with g₁ = 2.2637, g₂ = 2.0765 and g₃ = 2.0483. In contrast to this, 2 reveals an axial signal with g_⊥ = 2.0742; however, the g_|| is unresolved.     

A dicarboxylate with asymmetric coordination ability: Characterization of a two dimensional coordination polymer of copper(II) exhibiting spin canting

A copper(II) coordination polymer {[Cu₂(cpa)₂]}_n (1) (cpaH₂ = 4-carboxyphenoxyacetic acid) has been synthesized by hydrothermal technique. The X-ray structure of the compound shows that it is a 2D coordination polymer where Cu(II) ions are pentacoordinated in a square pyramidal fashion. The magnetic measurement of 1 in different magnetic fields suggest a weak ferromagnetic ordering taking place below 20 K, arising from spin canting phenomenon due to the non-coplanar basal planes of copper ions.     

Sonochemical syntheses and characterization of a new nano-structured one-dimensional lead(II) coordination polymer with 4,4,4-trifluoro-1-phenyl-1,3-butandione

A new nano-sized lead(II) one-dimensional coordination polymer with Pb?F interactions, [Pb(μ-TFPB)₂]_n (1) [TFPB⁻ = 4,4,4-trifluoro-1-phenyl-1,3-butandionate], has been synthesized and characterized by SEM, X-ray powder diffraction, IR spectroscopy and elemental analyses. The single-crystal X-ray data of compound 1 show that the Pb(II) atoms have a hemidirected coordination sphere with an environment of PbO₆F₂. The presence of a stereo-chemically active lone pair of the lead atom is apparently the reason that the neighboring bridging bond relative to gap of coordination sphere are so long. Therefore arrangement of “TFPB⁻” ligands suggests a gap or hole in coordination geometry around the lead(II) ions. PbO nanoparticles were obtained by calcination of the nano-sized compound 1 at 600 °C.     

Five-, seven-, and eight-coordinate Cd(II) coordination polymers built by anthranilic acid derivatives: Synthesis, structures and photoluminescence

Two novel Cd(II) coordination polymers, [(CH₃)₂NH₂]₂[Cd(cma)₂](H₂O) (1) and [Cd₃(bcma)₂(H₂O)](H₂O) (2) (H₂cma = N-(carboxymethyl)-anthranilic acid, H₃bcma = N,N′-bis-(carboxymethyl)-anthranilic acid), have been synthesized under hydrothermal conditions and characterized by X-ray single crystal analysis, IR spectra and TGA. Compound 1 possesses 1D double-stranded chain, which further packs into square channels. Compound 2 consists of a novel 3D framework, which not only possesses unique meniscus-like channels but also contains infinite helical chains. Compound 2 is the first example of Cd(II)-aminopolycarboxylate coordination polymers containing three crystallographically independent Cd(II) centres, in which Cd(1), Cd(2), and Cd(3) present distorted pentagonal bipyramidal, tetragonal antiprismatic, and trigonal bipyramidal coordination geometry, respectively. Both compounds display intense room temperature photoluminescence in the solid state.     

Synthesis, characterization, and luminescence properties of magnesium coordination networks using a thiophene-based linker

By varying the solvents and temperatures under solvothermal conditions, two new magnesium based coordination networks were synthesized using 2,5-thiophenedicarbxoylate as a linker. Mg₃(TDC)₃(DMF)₃ [1; TDC = 2,5 thiophenedicarboxylate; space group P2₁/c, a = 17.747(4) Å, b = 9.805(2) Å, c = 21.359(4) Å, β = 103.13(3)°] is constructed by a combination of magnesium polyhedral trimers, which are connected by the TDC²⁻ linkers to form a 3-D network. Coordinated DMF molecules are present within the channels. Mg(TDC)(H₂O)₂ [2; space group Pnma, a = 7.296(4) Å, b = 17.760(4) Å, c = 6.6631(3) Å] is formed by 1-D chains of magnesium octahedra connected by the TDC²⁻ linker. Water molecules are coordinated at the axial positions of the magnesium octahedra. Compound 1 is formed using DMF as the synthesis solvent at 180 °C, while compound 2 is formed using ethanol as the synthesis solvent at 100 °C. Both compounds show enhanced photoluminescence intensity when excited at 397 nm compared to the free TDC ligand, suggesting a charge transfer between the ligand and the magnesium metal center.     

A series of d transition metal coordination complexes: Structures and comparative study of surface electron behaviors (n = 9, 8, 7, 6, 5)

Ten transition metal coordination complexes [Cu₂(phen)(p-tpha)(μ-O)]_n1, [Cu(m-tpha)(imH)₂]_n2, [Ni(5-Haipa)₂(H₂O)₂]_n3, [Ni(phen)₂(H₂O)₂]·btc·[Ni(H₂O)₆]_0.5·9H₂O 4, [Co(2,5-pdc)(H₂O)₂]_n·nH₂O 5, [Co₂(2,5-pdc)₂(H₂O)₆]_n·2nH₂O 6, [Fe(2,5-Hpdc)₂(H₂O)₂]·H₂O 7, [Co(C₆H₄NO₂)₃]·H₂O 8, [Fe₂(μ₂-btec)(μ₂-H₂btec)(bipy)₂(H₂O)₂]_n9, [Mn(phen)(2,5-pdc)(H₂O)₂]·H₂O 10 (H₄btec = 1,2,4,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline, 2,5-H₂pdc = 2,5-pyridine-dicarboxylic acid, p-tpha = p-phthalic acid, m-tpha = m-phthalic acid, bipy = 2,2′-bipyridine, 5-H₂aipa = 5-aminoisophthalic acid, imH = imidazole, H₃btc = 1,3,5-benzenetricarboxylic acid) were synthesized through hydrothermal method. They were characterized by UV-Vis absorption spectra, single-crystal X-ray diffraction and surface photovoltage spectra (SPS). Structural analysis indicated that the complexes 1, 2, 3, 5, 6 and 9 were linked into infinite structures bridged by organic acid ligands. The other four complexes were molecular complexes and further connected to 2D or 3D structures by the hydrogen bonds. The SPS of complexes 1-10 indicate that there are positive response bands in the range of 300-800 nm showing different levels of photo-electric conversion properties. The intensity, position, shape and the number of the response bands in SPS are obviously different since the structure, species, valence, dⁿ electrons configuration and coordinated environment of the center metals are different. There are good relationships between SPS and UV-Vis spectra.     

Three dimensional metal-malonate frameworks with pillared layered architecture: Unusual role of metal-chelate as pillar

One hetero-bimetallic Cu(II)/Cd(II) compound, [Cd^II(H₂O)₂][Cu^II(mal)₂(H₂O)₂]_n (1) (H₂mal = malonic acid) has been synthesized and characterized using single crystal X-ray crystallography, thermogravimetric (TG) studies and X-ray powder diffraction (XRPD) measurements. The compound crystallizes in orthorhombic Pbcn space group having cell dimensions a = 6.6260(12) Å, b = 13.958(2) Å and c = 13.052(2) Å. The solid state structure of compound 1 demonstrates a 3D pillared layered coordination network generated through the simultaneous bridging as well as chelating mode of malonate towards the Cd(II) and Cu(II), respectively. TG analysis reveals relatively high thermal stability for the compound (decomposition temperature ∼320 °C). The thermal study also reveals that the coordinated waters attached to both the metal centers (Cd(II) and Cu(II)) are reversibly lost and gained and this behavior is also corroborated by XRPD studies.     

Synthesis and structures of three d metal coordination polymers constructed from flexible polycarboxylate and 1,10-phenanthroline ligands

Three novel d¹⁰ metal coordination polymers, {[Cd(H₂odpa)(phen)₂]·H₂O}_n (1), [Cd₂(odpa)(phen)(H₂O)₂]_n (2), {[Zn₄(odpa)₂(phen)₂(H₂O)₂]·H₂O}_n (3), (H₄odpa = 4,4′-oxydiphthalic acid, phen = 1,10-phenanthroline) were obtained with different metal/ligand ratios through hydrothermal method and characterized. Compound 1 forms a one dimensional zigzag chain, in which two phen ligands chelate to one cadmium atom. Compound 2 shows a three dimensional network structure comprised of new tetranuclear cadmium clusters as the nodes and (odpa)⁴⁻ anions as the linkers, exhibits an unusual topological structure. Compound 3 is an unprecedented three dimensional polymer based on octanuclear zinc clusters cross-linked by (odpa)⁴⁻ anions. In 1-3, central Cd^II/Zn^II ions and (odpa)⁴⁻ ligand display completely different coordination modes and conformations. In addition, the thermal stabilities and photoluminescence properties of 1-3 were also studied.     

A copper(II) coordination polymer with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges

A new one-dimensional (1D) copper(II) complex, [Cu₂(dpk · CH₂O)(N₃)₃]_n (dpk · CH₂OH = unimethylated diol of di-2-pyridyl ketone) (1), has been synthesized and characterized. X-ray crystal structure study reveals that 1 is composed of 1D copper(II) chain with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges. The magnetic determination indicates that ferromagnetic interaction dominates in this new 1D S = 1/2 system.     

A family of lanthanide-containing molecular open frameworks with high porosity: [Ln(abdc)(Habdc), nH2O]∞ with Ln = La-Eu and 8 ? n ? 11

Reactions in water between the di-sodium salt of amino terepthalic acid (C₈H₃NO₄Na₂) and a lanthanide chloride lead to a family of 3D-coordination polymers with general chemical formula [Ln(C₈H₃NO₄)(C₈H₄NO₄), O]_∞ where Ln = La-Eu (except Pm) and 8 ? n ? 11. All these compounds are isostructural. High quality single crystals of [Ln(C₈H₃NO₄)(C₈H₄NO₄), nH₂O]_∞ with Ln = La-Sm (except Pm) and 8 ? n ? 11 have been obtained by slow diffusion in agar-agar gels. The crystal structure has been solved for the Nd-containing compound. This compound crystallizes in the cubic system, space group Ia-3 (no. 206) with a = 26.8056(5) Å. The crystal structure can be described as the juxtaposition of large channels with square cross-section.The channels are filled by highly disordered crystallization water molecules. The dehydration of the compounds by freeze-drying is possible and most of the crystallization water molecules can be removed without destruction of the molecular skeleton. The partially dehydrated compounds have general chemical formula [Ln(abdc)(Habdc), 2H₂O]_∞ with Ln = La-Eu except Pm. The porosity of the Nd-containing compound has been estimated by computational methods to 2170 m² g⁻¹. This dehydrated compound reversibly binds water when exposed to wet atmosphere restoring the initial hydrated phase.     

Solvent coordination in changing dimensionality of lead benzoate coordination polymers

The reaction of lead (II) nitrate with sodium benzoate at low temperature gives one dimensional coordination polymer with composition [Pb(Ben)₂(MeOH)₂]_n (where Ben = benzoate, MeOH = methanol). This one dimensional polymer on heating in aqueous solution results in the formation of a two dimensional polymer having composition [Pb(Ben)₂(H₂O)]_n. Similar reaction of lead (II) nitrate with 2-methylbenzoic acid in the presence of sodium hydroxide in methanol at low temperature gives a coordination polymer having composition [Pb(o-TOL)₂(MeOH)₂]_n (where o-TOL = 2-methylbenzoate); which on re-dissolution in aqueous methanol or keeping in water, at room temperature leads to another coordination polymer having a composition of [Pb(o-TOL)₂(H₂O)]_n.     

Synthesis and characterization of new coordination polymers generated from oxadiazole-containing ligands and IIB metal ions

The coordination chemistry of the oxadiazole-containing rigid bidentate ligands 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (L1) and 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L2) with inorganic IIB metal salts have been investigated. Five new coordination polymers (1-5) were prepared by solution reactions and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Cd(L1)₂(CH₃CN)₂](ClO₄)₂ · (CH₃CN)₂ (1) crystallized in the monoclinic space group P2₁/c, a = 8.4028(5) Å, b = 21.3726(13) Å, c = 10.5617(7) Å, β = 95.1200(10)°, and Z = 2. In the solid state, it adopts an infinite two-dimensional polymeric structural motif with effective cross section of ca. 14.31 × 14.31 Å. Cd(L2)(H₂O)(NO₃)₂ (2) crystallized in the monoclinic space group Ia, a = 7.1203(5) Å, b = 22.2475(15) Å, c = 20.2652(16) Å, β = 90.6080(10)°, and Z = 8. In the solid state, the two Cd(II) centers are connected to each other by L2 ligands and bridging nitrates into a two-dimensional network. [ZnCl₂(L1)] (3) and [HgI₂(L1)] · CH₃CN (4) crystallized in the monoclinic crystal system (3: P2₁/c, a = 5.3702(3) Å, b = 20.4800(11) Å, c = 12.4093(7) Å, β = 94.7930(10)°, and Z = 4; 4: P2/n, a = 17.2733(11) Å, b = 5.2173(3) Å, c = 20.4069(13) Å, β = 102.8690(10)°, and Z = 4). In the solid state, Zn(II) and Hg(II) metal centers are connected to each other by L1 ligands into a zigzag chain motif. Compound 5 (HgBr₂(L2) is different from 3 and 4, monoclinic, P2(1)/n, a = 5.470(4) Å, b = 16.271(13) Å, c = 16.486(12) Å, β = 93.197(15)°, and Z = 4) adopts a novel one-dimensional helical chain motif which resulted from the relative different coordinated orientation of the two N-donors on L2 ligand.     

Syntheses, crystal structures and magnetic properties of 1D and 2D cobaltous coordination polymers with mixed ligands

Two new Co(II) coordination polymers with mixed ligands, {[Co(BTA)_0.5(DBI)₂]·DBI·H₂O}_n (1) and [Co(PDA)(DBI)(H₂O)]_n (2) (H₄BTA = benzene-1,2,4,5-tetracarboxylic acid; H₂PDA = 2,2′-(1,2-phenylene)diacetic acid; DBI = 5,6-dimethyl-1H-benzoimidazole) have been synthesized under hydrothermal conditions, respectively. Both of them are characterized by elemental analyses, powder X-ray diffraction, thermogravimetric analysis, single-crystal X-ray diffraction, and magnetic susceptibilities. In 1, the Co(II) ions are four-coordinated and lie in distorted tetrahedron coordination environment. 1D ladder-like chain structure is formed by the bridging BTA⁴⁻ ligand. In 2, the Co(II) ions are in slightly distorted octahedral coordination geometry, and linked by PDA²⁻ ligand exhibiting a 2D layer structure. Temperature-dependent magnetic susceptibility measurements of 1 and 2 revealed that there are antiferromagnetic interactions between Co(II) ions.     

Self-assembly of two 3D coordination polymers based on Ni/Co-terephthalic 1D blocks

Two 3D coordination polymers, {Ni^II(tp)(OHCH₃)}_n (1), and {Co^II(tp)(phen)(H₂O)}_n (2) (tp = terephthalic dianion, phen = 1,10-phenanthroline), have been synthesized by self-assembly. The structure analyses show that both of the two complexes are formed by one-dimensional infinite chains through non-covalent interactions, but 1 is formed by one-dimensional straightforward chains, while 2 is based on one-dimensional zigzag ones. The photoluminescent study of the two complexes shows that they exhibit fluorescent emission bands at ca. 374 nm and 392 nm, respectively.