Construction of three low dimensional Zn(II) complexes based on different organic-carboxylic acids

Three new Zn(II) complexes based on different organic-carboxylic acids, [Zn(mba)₂(2,2′-bipy)] (1), [Zn(mpdaH)₂(H₂O)₄] · 4H₂O (2) and [Zn(cda)₂(H₂O)₂]_n (3) (Hmba = 4-methylbenzoic acid, H₂mpda = 2,6-dimethylpyridine-3,5-dicarboxylic acid and H₂cda = chelidonic acid) have been synthesized successfully under hydrothermal conditions. X-ray single crystal diffractions show that compounds 1 and 2 are the mononuclear and 3 is one-dimensional chain, in which the Zn(II) centers have different coordination geometries with octahedron for 1 and 2 and tetrahedron for 3. Through π-π stacking and/or hydrogen bonding (O-H?O and O-H?N) interactions, different supramolecular structures are assembled, namely, 2D supramolecular layer for 1 and 3D supramolecular networks for 2 and 3. Furthermore, the IR, TGA and luminescent properties are also investigated in this work.     

A series of metal-organic frameworks constructed with 2,2′-bipyridine-3,3′-dicarboxylate: Syntheses, structures, and physical properties

To determine the influence of metal ion and the auxiliary ligand on the formation of metal-organic frameworks, six new coordination polymers, {[Mn₂(bpdc)(bpy)₃(H₂O)₂] · 2ClO₄ · H₂O}_n (1), {[Mn(bpdc)(dpe)] · CH₃OH · 2H₂O}_n (2), {[Cu(bpdc)(H₂O)₂]}_n (3), {[Zn(bpdc)(H₂O)₂]}_n (4), {[Cd(bpdc)(H₂O)₃] · 2H₂O}_n (5), and {[Co(bpdc)(H₂O)₃] · 0.5dpe · H₂O}_n (6) (H₂bpdc = 2,2′-bipyridine-3,3′-dicarboxylic acid, bpy = 2,2′-bipyridine, dpe = 1,2-di(4-pyridyl) ethylene), have been synthesized and characterized. Compound 1 forms 1D helical chain structure containing two unique Mn^II ions. In 2, the bridging ligand dpe links Mn-bpdc double zigzag chains to generate a layer possesses rectangular cavities. In 3, bpdc²⁻ ligand connects to three metal centers forming a 2D network. Different from the above compounds, 4 displays a 1D double-wavelike chain. Compound 5 features a helical chain. Compound 6 also displays a helical chain with guest molecule dpe existing in the structure. These diverse structures illustrate rational adjustment of metal ions and the second ligand is a good method for the further design of helical compounds with novel structures and properties. In addition, the magnetic properties of 2, 3 and 6, the thermal stabilities and photoluminescence properties of 4 and 5 were also studied.     

Metal-organic open frameworks with one-dimension channels assembled with pyridine 2,6-dicarboxylic acid and N-containing auxiliary ligands: Syntheses, crystal structures, and physical characterization

Four new complexes, {[Mn(imH)₂(pdc)]·H₂O}_n (1), [Zn₂(pdc)₂(H₂O)₅]·2H₂O (2), [Zn(imH)₂(pdc)]·H₂O (3), {[Zn₂(pdc)₂(bpy)(H₂O)₂]·5H₂O}_n (4) [imH = imidazole pdc = pyridine 2,6-dicarboxylate, bpy = 4,4′-bipyridine] have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, PXRD, single-crystal X-ray diffraction and thermogravimetric analyses. All the four complexes display a three-dimensional (3D) open framework with one-dimensional (1D) channels that are filled with lattice water molecules. Particularly, in 4, the lattice water molecules form an infinite water chain. Both 1 and 4 consist of 1D polymeric chains. While 2 contains a dinuclear Zn(II) unit, and 3 is a mononuclear complex. Further, the result of thermal analysis of 1 and 2 shows the robustness of the overall supramolecular three-dimensional architecture. Complexes 1, 3, and 4 exhibit strong fluorescent emissions in the solid state at room temperature and could be significant in the field of photoactive materials.     

Synthesis, crystal structures, and fluorescence properties of six complexes with thiophene derivative carboxylic acid ligand

The crystallization of 2,3-dihydro-thieno[3,4-b][1,4] dioxine-5,7-dicarboxylic acid (H₂tddc) with divalent transitional metal (Co, Ni, Zn, Cd) or with tervalent lanthanide metal (Sm) and with mixed ligand 4,4′-bipyridine (4,4′-bipy) or 1,10-phenanthroline (1,10-phen) formed six new complexes: [Co(C₈H₄O₆S) · 3H₂O] (1), [Co(C₈H₄O₆)(1,10-phen)(H₂O)] · H₂O (2), [Ni(C₈H₄O₆S)(4,4′-bipy)(H₂O)] · 3H₂O (3) [Sm(C₈H₄O₆S)(NO₃)(H₂O)₄] · 2H₂O (4), [Zn(C₈H₄O₆S)(H₂O)₃] (5), and [Cd₂(C₈H₄O₆S)₂(4,4′-bipy)₂] (6). The structures of these six crystals have been characterized by single-crystal X-ray diffraction analyses, which revealed that complexes 1, 4, 5 are all one-dimensional chain structures and they self-assemble into three-dimensional super-molecules via the hydrogen bond interactions and π-π stacking interactions, 2 is also a one-dimensional chain structure but still self-assembles into one-dimensional double-chains, the complex 3 has two-dimensional undulating parallelogram grid structure extended along the bc-plane, the crystal of 6 is a 3D threefold interpenetration topology framework with 4⁶6³8 nodes. The photoluminescent properties of the H₂tddc ligand and the six compounds have been measured in the solid state at room temperature. Free ligand has no luminescence, while its complexes 1, 4, and 6 all exhibit intense photoluminescence which implies that these complexes may be excellent candidates for potential photoactive materials.     

pH-value-controlled assembly of photoluminescent zinc coordination polymers

By pH-value adjustment, the reactions of zinc salt, 1,3,5-benzenetricarboxylic acid (H₃btc) and 4,4′-bipyridine (bpy) yield three coordination polymers, formulated as [Zn₃(btc)₂(bpy)(H₂O)₂]_n (1), [Zn(Hbtc)(bpy)(H₂O)]_n · 3nH₂O (2) and [Zn(Hbtc)(bpy)(H₂O)]_n · 4nH₂O (3), respectively. The structure of 1 is a 3D network containing channels filled with bpy ligands. Compound 2 consists of twofold interpenetrating (10,3)-b networks, while compound 3 is a 2D layer structure. The fluorescent studies reveal that they exhibit intense violet luminescence in solid state.     

In situ hydrothermal syntheses, crystal structures and luminescent properties of two novel zinc(II) coordination polymers based on tetrapyridyl ligand

Two novel Zn(II) coordination polymers, [Zn(2-pytpy)(fum)]_n·nH₂O (1) and [Zn₆(4-pytpy)₃(mal)₄]_n·5n(H₂O) (2), (2-pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, 4-pytpy = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H₂fum = fumaric acid and H₂mal = malic acid) have been hydrothermally synthesized and structurally characterized. Notably, in situ ligand reactions occur in the formation of complexes 1 and 2, in which maleic acid is converted into fumaric acid and malic acid, respectively. Complex 1 is a 1D infinite chain structure, which is extended into a supramolecular layer by intermolecular π…π stacking interactions. Complex 2 is a 3D network structure, in which the bidentate-bridging 4-pytpy ligands link the layers based on the tetranuclear Zn(II) subunits to form the (4,10)-connected network. The luminescent properties of 1 and 2 have been investigated with emission spectra and UV-Vis diffuse reflectance spectra in the solid state. Additionally, these two complexes possess great thermal stabilities.     

Cd(II)-NCS/NCO complexes of 1-alkyl-2-(arylazo)imidazole: Single crystal X-ray structure of [Cd(HaaiMe)2(SCN)2]

The reaction of Cd(OAc)₂ · 4H₂O and 1-alkyl-2-(arylazo)imidazole [RaaiR′ where R = H (a), Me (b); R′ = Me (1/3/5), Et (2/4/6)] and NH₄NCS/NaNCO in methanol in 1:2:2 mole ratio has afforded [Cd(RaaiR′)₂(NCS)₂] (3, 4) and [Cd(RaaiR′)₂(NCO)₂] (5, 6) complexes. The complexes are characterized by different physicochemical methods and in one case, the structure was confirmed by single crystal X-ray diffraction study for title compounds.     

Self-assembly of four three-dimensional reduced molybdenum(V) phosphates decorated with transitional metal complexes

Four new three-dimensional materials built from reduced molybdenum(V) phosphates as building blocks and transitional metal (Co, Zn and Cd) complexes as linkers, (Hbpy)₂[Co(bpy)(H₂O)]₂[Co(H₂PO₄)₂ (HPO₄)₆(MoO₂)₁₂(OH)₆] (1), [Co(H₂O)₄]₂[Co(Hbpy)(H₂O)]₂[Co(bpy)][Co(HPO₄)₄(PO₄)₄(MoO₂)₁₂(OH)₆] · 6H₂O (2), Na₂[Zn(Hbpy)(H₂O)₂]₂[Zn(Hbpy)]₂[Zn(HPO₄)₂(PO₄)₆(MoO₂)₁₂(OH)₆] · 4H₂O (3), (H₂bpy)₂[Cd(bpy)(H₂O)]₂[Cd(bpy)(H₂O)₂]₂[Cd(HPO₄)₄(PO₄)₄(MoO₂)₁₂(OH)₆] · 2H₂O (4) (bpy = 4,4′-bipyridine), have been synthesized and characterized by elemental analyses, IR, TG, and single crystal X-ray diffraction. The 3-D framework of 1 is constructed from Co[P₄Mo₆]₂ dimers bonded together with [Co(bpy)]_n coordination polymer chains. In compound 2, the Co[P₄Mo₆]₂ dimers are linked by both [Co(bpy)] complex chains and the cobalt dimers to form a 3-D framework. Compounds 1 and 2 represent the first examples of reduced molybdenum(V) phosphates decorated with transition metal complexes chains. The 3-D framework of 3 is constructed from Zn[P₄Mo₆]₂ dimers bonded together with [Zn(bpy)] coordination complexes and [Zn(bpy)(H₂O)₂] complexes. In compound 4, the Cd[P₄Mo₆]₂ dimers are coordinated with [Cd(bpy)(H₂O)] and [Cd(bpy)(H₂O)₂] complexes to construct a 3-D structure. To our best knowledge, it is the first time that linear ligand 4,4′-bpy molecules have been grafted into the backbone of reduced molybdenum phosphates. Furthermore, the magnetic properties of compounds 1 and 2 are reported.     

Properties of homo- and heteronuclear mixed biscarbene complexes with conjugated bithiophene units

The syntheses and structures of homo- and heteronuclear biscarbene complexes with bithiophene spacers were investigated. The complexes were synthesized by lithiation of bithiophene followed by metallation using combinations of the metal precursors MnMeCp(CO)₃, W(CO)₆, Mo(CO)₆ and Cr(CO)₆, after which the reaction was quenched with triethyloxonium tetrafluoroborate. This classical Fischer method yielded monocarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₃S], ([ML_n] = Cr(CO)₅1a, W(CO)₅2a or MnMeCp(CO)₂3a), homonuclear biscarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₂SC(OEt)ML_n], ([ML_n] = Cr(CO)₅1b, W(CO)₅2b or MnMeCp(CO)₂3b) and heteronuclear biscarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₂SC(OEt)M′L_n] (1d: [ML_n] = Cr(CO)₅ and [M′L_n] = W(CO)₅; 1e: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = Cr(CO)₅; 1f: [ML_n] = Cr(CO)₅ and [M′] = Mo(CO)₅); 2d: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = W(CO)₅; 3c: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = Mo(CO)₅). Electron density calculations with the gaussian03 software package of 1e revealed a polar rod with the negative pole towards the chromium carbene side, whereas the biscarbenes 1d and 1b showed very little polarity. By-products resulting from activation of the carbene moieties in homonuclear biscarbene complexes included (i) ester-type complexes of the form [ML_nC(OEt)C₄H₂S-C₄H₂SC(O)OEt], ([ML_n] = Cr(CO)₅1c or W(CO)₅2c), formed in situ in the reaction of 1b and 2b, (ii) the organic bis-ester compound [EtOC(O)C₄H₂S-C₄H₂SC(O)OEt] 4, where both metal moieties had been substituted by oxygen and (iii) the carbon-carbon coupled dimeric bithienyl compound [C₄H₃S-C₄H₂SC(O)C(O)C₄H₂S-C₄H₃S] 5. By-products obtained from heteronuclear biscarbene reactions contain the former diketo compound (or a derivative) as spacer between two metal carbonyl fragments and have the general formula [ML_nC(OEt)C₄H₂S-C₄H₂SCR-CR′C₄H₂S-C₄H₂SC(OEt)ML_n] (5a: [M] = Cr(CO)₅, R = OH, R′ = OEt; 5b: [M] = W(CO)₅, R = R′ = O; 5c: [M] = Mo(CO)₅, R = R′ = O). Reaction of 1d, 1e and 1f with hex-3-yne resulted in the formation of benzannulated products 6a, 6b and 6c. All novel complexes were fully characterized using various spectroscopic techniques. The crystal structures of 1b, 2a and 5 are reported.     

Supramolecular assembly driven by hydrogen-bonding and π-π stacking interactions based on copper(II)-terpyridyl complexes

Six 2D and 3D supramolecular complexes [Cu(L1)(O₂CCH₃)₂] · H₂O (1), [Cu₂(L2)₂(μ₂-O₂CCH₃)₂](BF₄)₂ (2), [Cu₂(L1)₂(BDC)(NO₃)₂] · 0.5H₂O (3) [Cu₂(L2)₂(BDC)(NO₃)₂] (4), [Cu₂(L3)₂(BDC)(NO₃)₂] · 0.5H₂O (5) and [Cu₂(L2)₂(BDC)(H₂O)₂](BDC) · 8H₂O (6) (L1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine, L3 = 4′-phenyl-2,2′:6′,2″-terpyridine, BDC = 1,4-benzenedicarboxylate), have been prepared and structurally characterized by X-ray diffraction crystallography. In complexes 1, 3, and 4, 1D channels are formed through C-H?O and C-H?N hydrogen-bonding interactions, and further linked into 3D structure via C-H?O and O-H?O interactions. Complex 2 is a 2D layer constructed from intermolecular C-H?F and π-π stacking interactions. In the structure of 6, the BDC²⁻ ions and solvent water molecules form a novel 2D layer containing left- and right-handed helical chains via hydrogen-bonds, and an unusual discrete water octamer is formed within the layer. In 2, 4, 6 and [Ag₂(L2)₂](PF₆)₂ (7) the bonding types of pendent pyridines of L2 depending on the twist about central pyridines are involved in intramolecular (2 and 4), intermolecular (6) or coordination bonds (7) in-twist-order of 5.8°, 3.7°, 28.2° and 38.0°, respectively. Differently, the pendent pyridines of L1 in 1 and 3 form intermolecular hydrogen bonds despite of distinct corresponding twist angles of 25.1° (1) and 42.6°(3). Meanwhile, π-π stacking interactions are present in 1-6 and responsible for the stabilization of these complexes.     

Binuclear copper and zinc complexes based on polypyridyl ligand 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz): Synthesis, spectral and structural characterization

The reaction of MCl₂ · 2H₂O (M = Cu, Zn) with 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) (referred hereafter as L) in 2:1 molar ratio in acetonitrile at room temperature afforded binuclear complexes [M₂(κ³-L)Cl₄] [Cu (1), Zn (2)] where the ligand is bis-tridentate manner. The complexes have been characterized by elemental analyses, FAB-MS, IR, EPR, NMR and electronic spectral studies. Solid state structures of both the [Cu₂(κ³-L)Cl₄] · 5H₂O (1), [Zn₂(κ³-L)Cl₄] · H₂O (2) have been determined by single crystal X-ray analyses. A well-resolved uudd cyclic water tetramer and water monomer were reported in the crystal host of [Cu₂(κ³-L)Cl₄] · 5H₂O (1) and [Zn₂(κ³-L)Cl₄] · H₂O (2) showing the contribution of the water cluster to the stability of the crystal host 1 and 2.     

Four coordination polymers constructed from a multicarboxylate ligand and metal centers various from Ba, Cu, Zn to Gd: Syntheses, crystal structures and properties

Hydrothermal reactions between H₄ODPA (2,2′,3,3′-oxydiphthalic acid) and metal ion salts of Ba²⁺, Cu²⁺, Zn²⁺ and Gd³⁺ afford four novel coordination polymers [Ba(H₂ODPA)(H₂O)₄] · H₂O (1), [Cu₂(ODPA)(H₂O)₃] · H₂O (2), Zn₂(ODPA)(H₂O)₂ (3) and [Gd(HODPA)(H₂O)_3.5] · H₂O (4), accordingly. These polymers show great differences in regard to their structures and properties originated from the variation of size and coordination geometry of the metal ions. Compound 1 presents puckered achiral layer structure with (4.8²) topology with helices, 2 has a 6³ topology with copper tetramer as SBUs, 3 has chiral layer with two kinds of helices built up from Zn-binuclear “paddle-wheel” like SBUs, and 4 features a simple 1D helix with opposite chirality. Compound 3 shows obvious fluorescent emissions upon excitation. Compound 2 shows ferromagnetic interactions between Cu^II centers bridged by carboxylate groups, whereas compound 4 presents weak ferromagnetic interaction between Gd^III ions.     

Synthesis, structures and magnetic properties of four new oxamidato-bridged heterobimetallic complexes

Four new heterobimetallic coordination polymers, namely, {[Cu(aeoe)M(H₂O)₃ · 2H₂O]₂}_n (M = Mn(II) (1), Co(II) (2), Ni(II) (3)) and [Cu(aeoe)Ni(H₂O)₃]₂ (4) (H₄aeoe = N′-(2-aminoterephthalic acid)-N′′-(ethylenediamine)oxamidato) have been synthesized and characterized structurally. Complexes 1-3 are allomerism and feature 1-D ladder-like chain structure constructed from neutral tetranuclear complex units through the syn-anti carboxylate bridges, whereas complex 4 is a cyclic neutral tetranuclear complex unit. Their magnetic properties are also investigated based on their structures.     

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 new multidimensional organic-inorganic hybrids based on polyoxometalates and copper coordination polymers with 4,4′-bipyridine ligands

Three new organic-inorganic hybrid materials with 4,4′-bipy ligands and copper cations as linkers, [Cu^II(H₂O)(4,4′-bipy)₂][Cu^II(H₂O)(4,4′-bpy)₂]₂H[Cu^IIP₈Mo₁₂O₆₂H₁₂] · 5H₂O (1), [Cu^I(4,4′-bipy)][Cu^II(4,4′-bipy)]₂ (BW₁₂O₄₀) · (4,4′-bipy) · 2H₂O (2) and [Cu^I (4,4′-bipy)]₃ (PMo₁₂O₄₀) · (pip) · 2H₂O (3) (pip = piperazine; 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. The single X-ray structural analysis reveals that the structure of 1 is constructed from [Cu(H₂O)(4,4′-bipy)₂] complexes into a novel, three-dimensional supermolecular network with 1-D channels in which Cu[P₄Mo₆]₂ dimer clusters reside. To the best of our knowledge, compound 1 is the first complex in which the [P₄Mo₆] clusters have been used as a non-coordinating anionic template for the construction of a novel, three-dimensional supermolecular network. Compound 2 is constructed from the six-supported [BW₁₂O₄₀]⁵⁻ polyoxoanions and [Cu^I(4,4′-bipy)] and [Cu^II(4,4′-bipy)] groups into a novel, 3-D network. Compound 3 exhibits unusual 3-D supramolecular frameworks, which are constructed from tetrasupporting [PMo₁₂O₄₀]³⁻ clusters and [Cu^I (4,4′-bipy)_n] coordination polymer chains. The electrochemical properties of 2 and 3 have been investigated in detail.     

Hydrogen-bonded copper(II) and nickel(II) complexes and coordination polymeric structures containing reduced Schiff base ligands

Complexes [Cu(HSas)(H₂O)] · 2H₂O (H₃Sas = N-(2-hydroxybenzyl)-l-aspartic acid) (1), [Cu(HMeSglu)(H₂O)] · 2H₂O (H₃MeSglu = (N-(2-hydroxy-5-methylbenzyl)-l-glutamic acid) (2), [Cu₂(Smet)₂] (H₂Smet = (N-(2-hydroxybenzyl)-l-methionine) (3), [Ni(HSas)(H₂O)] (4), [Ni₂(Smet)₂(H₂O)₂] (5), and [Ni(HSapg)₂] (H₂Sapg = (N-(2-hydroxybenzyl)-l-aspargine) (6) have been synthesized and characterized by chemical and spectroscopic methods. Structural determination by single crystal X-ray diffraction studies revealed 1D coordination polymeric structures in 2 and 4, and hydrogen-bonded network structure in 5 and 6. In contrast to previously reported coordination compounds with similar ligands, the phenol remains protonated and bonded to the metal ions in 2 and 4, and also probably in 1. However, the phenolic group is non-bonded in 6.     

Organic-inorganic hybrid materials: Ligand influences on the structural chemistry of copper-vanadates

Hydrothermal reactions were used in the preparation of a series of bimetallic organic-inorganic hybrid materials of the M(II)/V_xO_y/organonitrogen ligand class. Compound 1, [{Cu₂(bpa)₂(C₂O₄)}₂V₄O₁₂]·H₂O, is molecular, while [{Cu(terpy)}₂V₆O₁₇] (2), [Cu₂(bpyrm)V₄O₁₂] (4) and [{Cu(phen)(H₂O)₂}VOF₄(H₂O)]·2H₂O (5) are two-dimensional, three-dimensional and one-dimensional, respectively (bpa = 2,2′-bipyridylamine; terpy = 2,2′:6,2″-terpyridine; bpyrm = 2,2′-bipyrimidine; phen = 1,10-phenanthroline). In contrast to the 2-D structure of 2, the Ni(II) analogue [{Ni(terpy)}₂V₄O₁₂]·2H₂O (3) is one-dimensional. The {V₄O₁₂}⁴⁻ cluster is a building block of structures 1, 3, and 4 while 2 is constructed from {V₆O₁₇}⁴⁻ rings.     

Coordination compounds of tetrazolate-5-carboxylate with cobalt(II): Synthesis, structure and magnetic properties

Four coordination compounds of tetrazolate-5-carboxylate (tzc) with cobalt(II), [Co₂(tzc)₂(H₂O)₆]·2H₂O (1), [Co₂(tzc)₂(phen)₂(H₂O)₂]·2H₂O (2), [Co₂(tzc)₂(2,2′-bpy)₂(H₂O)₂]·H₂O (3), and [Co(tzc)(4,4′-bpy)] (4), where phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridyl, and 4,4′-bpy = 4,4′-bipyridyl, have been synthesized by the hydrothermal methods involving the in situ generation of the ligand from sodium ethyl tetrazolate-5-carboxylate. Compounds 1, 2 and 3 all contain dinuclear molecules in which metal ions are linked by the double N-N bridges from two tzc ligands in the μ₂-N₁,O₁:N₂ mode, and the dinuclear molecules are associated into 3D architecture through extensive hydrogen bonding and π-π stacking interactions in various fashions. Compound 4 exhibits a two-dimensional layer structure in which Co(tzc) chains with μ₃-N₁,O₁:O₁:N₂ tzc are cross-linked by 4,4′-bpy. Magnetic investigations on 1-3 revealed intramolecular ferromagnetic coupling through the double N-N bridges with intermolecular ferromagnetic or antiferromagnetic interactions. The interaction through the mixed N-N and μ₂-O_carboxylate bridges in 4 is antiferromagnetic.     

Syntheses, crystal structures and properties of Cd(II) and Co(II) complexes with 4,4′-dipyridylsulfide ligand

Two new coordination polymers [Cd(dps)₂Cl₂] (1) and [Co(dps)₂(H₂O)₂]·(abs)₂(H₂O)₂ (2) (dps = 4, 4′-dipyridylsulfide, Habs = 4-amino benzenesulfonic acid) have been synthesized under similar conditions and characterized by elemental analysis, fluorescence spectra and single crystal X-ray diffraction. Compound 1 displays a dps-bridged 2D puckered, grid-like layer, which is further linked by C-H?Cl hydrogen bonds to form a 3D supramolecular architecture. Compound 2 shows a dps-bridged double-stranded chain structure, which is extended by N-H?O and O-H?O hydrogen bonds generating a 3D network. Solid-state fluorescence results reveal that both complexes can emit strong emission bands, at 467 nm and 518 nm for 1 and 344 nm for 2, respectively. Magnetic measurements show that there are weak antiferromagnetic interactions between the adjacent Co(II) ions in 2.     

Photoluminescent coordination polymers of d metals with 4,4′-dipyridylsulfide (dps)

Reactions of AgClO₄, Zn(CH₃COO)₂ · H₂O and CuI with the ligand 4,4′-dipyridylsulfide (dps) in 1:1 ratio give rise to coordination polymers 1-3 and 5, the structures of which were characterized by X-ray crystallography. Polymers [Ag₂(dps)₂](ClO₄)₂ · MeCN (1) and [Ag₂(dps)₂(μ₂-MeCN)(MeCN)](ClO₄)₂ · MeCN · H₂O (2) are pseudo-supramolecular isomers, differing from each other in the coordination geometry of silver atom and the packing pattern. Both 1 and 2 are zigzag coordination polymers bridged by weak Ag?Ag, Ag?S or Ag?NC-CH₃ interactions to form double stranded coordination polymers. While [Zn(dps)(CH₃COO)₂] (3) is a zigzag single stranded coordination polymer, [Zn(dps)₂(H₂O)₂](ClO₄)₂ · H₂O (4) is an unusual mononuclear complex with a box-like structure. Interesting intermolecular hydrogen bonding present in the compounds 3 and 4 leads to 3D hydrogen-bonded network structure.Coordination polymer [Cu₂I₂(dps)₂] (5) is a non-interpenetrating (4,4) net. Photoluminescence properties of the compounds 1-5 have been examined in solid states at room temperature. These compounds have been found to exhibit yellow and blue photoluminescence.