Syntheses and characterizations of two lanthanide(III)-copper(II) coordination polymers constructed by pyridine-2,6-dicarboxylic acid

The hydrothermal reaction of La₂O₃ and Pr₂O₃ with pyridine-2,6-dicarboxylic acid (H₂pydc), CuO, and H₂O with a mole ratio of 1:2:4:300 resulted in the formation of two polymeric Cu(II)-Ln(III) complexes, [{Ln₄Cu₂(pydc)₈(H₂O)₈} · 18H₂O]_n (Ln = La (1); Pr (2)). 1 and 2 are isomorphous and crystallize in monoclinic space group C2/c. Complexes 1 and 2 have one-dimensional infinite chains with “∞” shape. The 1D chains are linked by the hydrogen bonds and π?π stacking interactions to form layer structures which are further linked by the hydrogen bonds and π?π stacking interactions to form the three-dimensional (3D) structures with nanoscale porosities. Temperature-dependent magnetic susceptibilities and the thermal stabilities of complexes 1 and 2 were studied.     

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.     

Synthesis, characterization and preliminary cytotoxicity evaluation of five lanthanide(III)-plumbagin complexes

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone, H-PLN) was isolated from Plumbago zeylanica, the anticancer traditional Chinese medicine (TCM). Five new lanthanide(III) complexes of deprotonated plumbagin: [Y(PLN)₃(H₂O)₂] (1), [La(PLN)₃(H₂O)₂] (2), [Sm(PLN)₃(H₂O)₂]⋅H₂O (3), [Gd(PLN)₃(H₂O)₂] (4), and [Dy(PLN)₃(H₂O)₂] (5) were synthesized by the reaction of plumbagin with the corresponding lanthanide salts, in amounts equal to ligand/metal molar ratio of 3:1. The PLN-lanthanide(III) complexes were characterized by different physicochemical methods: elemental analyses, UV-visible, IR and ¹H NMR and ESI-MS (electrospray ionization mass spectrum) as well as TGA (thermogravimetric analysis). The plumbagin and its lanthanide(III) complexes 1-5, were tested for their in vitro cytotoxicity against BEL7404 (liver cancer) cell lines by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The five PLN-lanthanide (III) complexes 1-5 effectively inhibited BEL7404 cell lines growth with IC₅₀ values of 11.0 ± 3.5, 5.1 ± 1.3, 6.1 ± 1.1, 6.4 ± 1.3, and 9.8 ± 1.5 μM, respectively, and exhibited a significantly enhanced cytotoxicity compared to plumbagin and the corresponding lanthanide salts, suggesting a synergistic effect upon plumbagin coordination to the Ln(III) ion. The lanthanide complexes under investigation also exerted dose- and time-dependent cytotoxic activity. [La(PLN)₃(H₂O)₂] (2) and plumbagin interact with calf thymus DNA (ct-DNA) mainly via intercalation mode, but for [La(PLN)₃(H₂O)₂] (2), the electrostatic interaction should not be excluded; the binding affinity of [La(PLN)₃(H₂O)₂] (2) to DNA is stronger than that of free plumbagin, which may correlate with the enhanced cytotoxicity of the PLN-lanthanide(III) complexes.     

Gadolinium(III) and europium(III) l-glutamates: Synthesis and characterization

Two lanthanide(III) complexes with l-glutamate ligands [{Ln₂(l-Glu)₂(H₂O)₈} · 4(ClO₄) · 2.5H₂O]_n (Ln = Gd (1), Eu (2)) have been prepared and characterized by single-crystal X-ray diffraction. The compounds are isomorphous with infinite cationic 2D layers stacked together by secondary bonds. The building blocks are slightly different non-centrosymmetric dinuclear units placed in alternating layers, the resulting structures thus containing four non-equivalent Ln metal sites. The dinuclear units contain a fourfold bridge, two in the η¹:η¹:μ₂ and two in the η²:η¹:μ₂ modes, from two α- and two γ-carboxylates of four different l-Glu residues, respectively.     

Europium (III) complexes derived from carboxylic-substituted polychlorotriphenylmethyl radicals

Two europium (III) complexes (3 and 4) have been obtained reacting europium (III) nitrate and two polychlorotriphenylmethyl radicals properly functionalized with one (PTMMC⁻, 1) and six (PTMHC⁶⁻, 2) carboxylate groups, respectively. While complex 3 reveals a lamellar polar-apolar separated ion pair structure alternating PTM-based bilayers with nonaaquaeuropium cations ([Eu(H₂O)₉](PTMMC)₃(PTMMCH)₃ · 7H₂O · 6EtOH), complex 4 shows a one-dimensional chain-like structure with formula [Eu₂(PTMHC)(H₂O)₁₃] · 16H₂O · EtOH. Magnetic properties of both complexes were studied in the 2-300 K range, and show the presence of weak inter-radical antiferromagnetic interactions below 5 K.     

Synthesis and crystal structures of four pH-dependent Pb(II) and Cd(II) phosphonates based on a novel ligand, 3-phosphono-benzoic acid

Four metal phosphonate hybrid compounds, [Pb(Hpbc)] (1), [Pb₃(pbc)₂(H₂O)₂] (2), [Cd(H₂pbc)₂(H₂O)₂] (3) and [Cd_1.5(pbc)(H₂O)_1.5] · 0.5H₂O (4) (H₃pbc = 3-phosphono-benzoic acid) were successfully synthesized by the hydrothermal/solvothermal reaction of metal acetate and 3-phosphono-benzoic acid. Compounds 1-4 were pH-dependent products and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra and single-crystal X-ray diffraction studies. Compound 1 is a two-dimensional (2D) structure constructed by inorganic layer and organic pendant. With the increase of pH value, structure 2 shows 3D inorganic framework with distributing organic moieties in the channels. In 3, the Cd₂O₁₀ dimers are linked by alternating terminal and bridging ligands, resulting in 1D chain structure. Compound 4 is a 2D structure where the 1D inorganic chains are connected by the organic moieties of the ligands.     

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.     

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.     

Syntheses, structures, and magnetic properties of 3d-4f heterometallic complexes constructed from pyrazole-bridged CuLn dinuclear units

A series of pyrazole-bridged heterometallic 3d-4f complexes, [CuDy(ipdc)₂(H₂O)₄] · (2H₂O)(H₃O⁺) (1) and [CuLn(pdc)(ipdc)(H₂O)₄] · H₃O⁺ (Ln = Ho (2), Er (3), Yb (4); H₃ipdc = 4-iodo-3,5-pyrazoledicarboxylic acid; H₃pdc = 3,5-pyrazoledicarboxylic acid), {[Cu₃Ln₄(ipdc)₆(H₂O)₁₆] · xH₂O}_n (Ln = Sm (5), x = 8.5; Ln = Eu (6), x = 7; Ln = Gd (7), Tb (8), x = 9), have been synthesized and structurally characterized. Ligand H₃ipdc was in situ obtained by iodination of ligand H₃pdc. Complexes 1-4 are pyrazole-bridged heterometallic dinuclear complexes, and 2-4 are isostructural. Complexes 5-8 are isostructural and comprised of an unusual infinite one-dimensional tape-like chain based on pyrazole-bridged heterometallic dinuclear units. The magnetic properties of compounds 1-4, 7 and 8 have been investigated through the magnetic measurement over the temperature range of 1.8-300 K.     

Imidazole derivatives of binuclear copper (II) and nickel (II) complexes incorporating bis(1,4,7-triazacyclononan-1-yl) ligands

A series of new binuclear copper (II) and nickel (II) complexes of the macrocyclic ligands bis(1,4,7-triazacyclononan-1-yl)butane (L^but) and bis(1,4,7-triazacyclononan-1-yl)-m-xylene (L^mx) have been synthesized: [Cu₂L^butBr₄] (1), [Cu₂L^but(imidazole)₂Br₂](ClO₄)₂ (2), [Cu₂L^mx(μ-OH)(imidazole)₂](ClO₄)₃ (3), [Cu₂L^but(imidazole)₄](ClO₄)₄ · H₂O (4), [Cu₂L^mx(imidazole)₄](ClO₄)₄ (5), [Ni₂ L^but(H₂O)₆](ClO₄)₄ · 2H₂O (6), [Ni₂L^but(imidazole)₆](ClO₄)₄ · 2H₂O (7) and [Ni₂L^mx (imidazole)₄(H₂O)₂](ClO₄)₄ · 3H₂O (8). Complexes 1, 2, 7 and 8 have been characterized by single crystal X-ray studies. In each of the complexes, the two tridentate 1,4,7-triazacyclononane rings of the ligand facially coordinate to separate metal centres. The distorted square-pyramidal coordination sphere of the copper (II) centres is completed by bromide anions in the case of 1 and/or monodentate imidazole ligands in complexes 2, 4 and 5. Complex 3 has been formulated as a monohydroxo-bridged complex featuring two terminal imidazole ligands. Complexes 6-8 feature distorted octahedral nickel (II) centres with water and/or monodentate imidazole ligands occupying the remaining coordination sites. Within the crystal structures, the ligands adopt trans conformations, with the two metal binding compartments widely separated, perhaps as a consequence of electrostatic repulsion between the cationic metal centres. The imidazole-bearing complexes may be viewed as simple models for the coordinative interaction of the binuclear complexes of bis (tacn) ligands with protein molecules bearing multiple surface-exposed histidine residues.     

Three Mn(II) supramolecular coordination complexes containing carboxylate-tetrazolate ligands

Three novel complexes [Mn(atza)₂(H₂O)₄] (1), [Mn(nptza)₂(CH₃OH)₄] (2), and [Mn(a4-ptz)₂(H₂O)₂]_n · 2nH₂O] (3) [atza = 5-aminotetrazole-1-acetato, nptza = 5-[(4-nitryl)phenyl] tetrazole-1-acetato, a4-ptz = 5-[N-acetato(4-pyridyl)] tetrazole] containing carboxylate-tetrazolate ligands have been synthesized and characterized by element analysis. X-ray crystallography shows that complexes 1 and 2 both contain mononuclear structure. The complex 3 is a 1D polymeric chain structure. Compounds 1-3 are self-assembled to form supramolecular structures through hydrogen bonds interactions.     

One-dimensional chain structures constructed from tetra(acetamidato)dirhodium(II,III) complexes and square planar platinum and palladium complexes

The reaction of [Rh₂(acam)₄(H₂O)₂]ClO₄ (1) (Hacam = acetamide) with K₂PtCl₄ in aqueous solution gave crystals of [Rh₂(acam)₄(H₂O)₂][Rh₂(acam)₄{(μ-Cl)₂PtCl₂}] · 2H₂O (2). The reaction of 1 with K₂PdCl₄ produced the palladium analog [Rh₂(acam)₄(H₂O)₂][Rh₂(acam)₄{(μ-Cl)₂PdCl₂}] · 2H₂O (3) and a small amount of an aquated palladium complex [Rh₂(acam)₄{(μ-Cl)₂PdCl(H₂O)}] · H₂O (4). Complexes 2 and 3 have anionic chains of [Rh₂(acam)₄{(μ-Cl)₂MCl₂}]⁻ (M = Pt, Pd), while 4 includes neutral chains of [Rh₂(acam)₄{(μ-Cl)₂PdCl(H₂O)}]. Although all of the structures include infinite chains of (-Rh-Rh-Cl-M-Cl-)_n (M = Pt, Pd), the chain structures are different; zigzag for 2 and 3 and helical for 4. In the structures of 2 and 3, the counter cation [Rh₂(acam)₄(H₂O)₂]⁺ made a hydrogen-bonded chain with the crystallization water molecules. The cationic chains and the anionic chains are connected with hydrogen bonds. In the structure of 4, the chains are also linked together by direct hydrogen bonds between the chains and those with the crystallization water molecules. ESR spectra of the powdered samples of 2 and 3 at 77 K were consistent with a rhombic structure: for 2, g₁ = 2.111, g₂ = 2.054, g₃ = 2.004; for 3, g₁ = 2.115, g₂ = 2.057, g₃ = 2.007. These results indicate that there is a spin flip-flop exchange between the cations, [Rh₂(acam)₄(H₂O)₂]⁺, and the units in the anionic chains. The electrical conductivities of 2 and 3 were in the order of 10⁻⁷ S cm⁻¹ at room temperature.     

Three zinc(II) complexes constructed from aromatic dicarboxylate and 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene: Syntheses, crystal structures and luminescent properties

To investigate the effect of organic anions on the coordination frameworks, we synthesized three new complexes, namely, Zn(DPA)(bpimb)_0.5(H₂O) (1), Zn(BDC)(bpimb)_0.5 (2) and Zn₂(SDBA)₂(bpimb)·H₂O (3) (H₂DPA = diphenic acid; H₂BDC = isophthalic acid; H₂SDBA = 4,4′-dicarboxybiphenylsulfone), which were obtained by the reactions of 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene (bpimb) as main ligand, and several aromatic polycarboxylate as organic anions with Zn(NO₃)₂·6H₂O. Single-crystal structure analysis shows that complex 1 is a one-dimensional chain structure, which is further interlinked into a higher-dimensional supramolecular framework by hydrogen-bonding interactions. In 2, BDC bridge Zn(II) atoms to give dimeric units, which are further linked by bpimb ligands to form sql nets. In 3, SDBA ligands and bpimb ligands connect Zn(II) ions into catenane-like two-dimensional layers. These catenane-like two-dimensional layers stack in an ABAB fashion to form a 3D supramolecular network. The distinct structures indicate three kinds of carboxylic ligands with different lengths and angles play fundamental roles in the formation of the final products. In addition, the luminescence measurements reveal that three complexes exhibit strong fluorescent emissions in the solid state at room temperature.     

Topological diversity in copper aromatic meta-dicarboxylate coordination polymers with bis(pyridylformyl)piperazine coligands

Hydrothermal synthesis has afforded divalent copper coordination polymers containing bis(4-pyridylformyl)piperazine (4-bpfp) tethers and aromatic meta-dicarboxylate ligands. {[Cu(ip)(4-bpfp)]·2H₂O}_n (1, ip = isophthalate) possesses a (4, 4) rectangular grid structure with an unusual ABCD stacking pattern along a 4₁ screw axis. Sterically bulky substituents in the 5-position of the isophthalate ligands reduced the coordination polymer dimensionality, with [Cu₂(tBuip)₂(4-bpfp)(H₂O)₂]_n (2, tBuip = 5-tert-butylisophthalate) and {[Cu(MeOip)(HMeOip)₂(4-bpfp)]·3H₂O}_n (3, MeOip = 5-methoxyisophthalate) displaying 1D polymeric ladder and chain motifs, respectively. Compound 3 possesses a rare twofold interpenetrated binodal supramolecular hms net with (6³)(6⁹8) topology. Longer meta-disposed acetate pendant arms induced a doubly interpenetrated 3D primitive cubic topology in {[Cu₂(1,3-phda)₂(H₂O)₂(4-bpfp)]}_n (4, 1,3-phda = 1,3-phenylenediacetate), which possesses antiferromagnetically coupled {Cu₂O₂} kernels (J = −6.14(8) cm⁻¹).     

Iron(III), chromium(III) and cobalt(II) complexes with squarate: Synthesis, crystal structure and magnetic properties

The preparation and variable temperature-magnetic investigation of three squarate-containing complexes of formula [Fe₂(OH)₂(C₄O₄)₂(H₂O)₄]·2H₂O (1) [Cr₂(OH)₂(C₄O₄)₂(H₂O)₄]·2H₂O (2) and [Co(C₄O₄)(H₂O)₄]_n (3) [H₂C₄O₄ = 3.4-dihydroxycyclobutene-1,2-dione (squaric acid)] together with the crystal structures of 1 and 3 are reported. Complex 1 contains discrete centrosymmetric [Fe₂(OH)₂(C₄O₄)₂(H₂O)₄] diiron(II) units where the iron pairs are joined by a di-μ-hydroxo bridge and two squarate ligands acting as bridging groups through adjacent oxygen atoms. Two coordinated water molecules in cis position complete the octahedral environment at each iron atom in 1. The iron-iron distance with the dinuclear unit is 3.0722(6) Å and the angle at the hydroxo bridge is 99.99(7)°, values which compare well with the corresponding ones in the isostructural compound 2 (2.998 Å and 99.47°) whose structure was reported previously. The crystal structure of 3 contains neutral chains of squarato-O¹,O³-bridged cobalt(II) ions where four coordinated water molecules complete the six-coordination at each cobalt atom. The cobalt-cobalt separation across the squarate bridge is 8.0595(4) Å. A relatively important intramolecular antiferromagnetic coupling occurs in 1 whereas it is very weak in 2, the exchange pathway being the same [J = −14.4 (1) and −0.07 cm⁻¹ (2), the spin Hamiltonian being defined as ]. A weak intrachain antiferromagnetic interaction between the high-spin cobalt(II) ions occurs in 3 (J = −0.30 cm⁻¹). The magnitude and nature of these magnetic interactions are discussed in the light of their respective structures and they are compared with those reported for related systems.     

Supramolecular isomers of lanthanides(III): Synthesis, crystal structures and luminescent properties

Six lanthanide coordination polymers La₂(1,4-BDOA)₂(OX)(H₂O) (1), Ln₂(1,4-BDOA)₂(OX)(H₂O) [Ln = La (2); Ln = Pr (3); Ln = Sm (4); Ln = Eu (5); Ln = Tb (6)], [BDOA = benzene-1,4-dioxydiacetate; OX = oxalate] had been prepared under hydrothermal conditions, which were characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Compounds 1-6 crystallize in a triclinic system, space group ; compounds 1 and 2 are true structural supramolecular isomers based on BDOA ligands constructed from different acid effects; compounds 2-5 are isostructural and exhibit new 3D 12-connected topological networks, which are the same as the topological structure of 6, while 1 shows another 3D 11-connected topological architecture. Furthermore, the luminescent properties of 5 and 6 were studied.     

Synthesis, structures, and luminescence properties of mixed ligand Cd(II) and Zn(II) coordination compounds mediated by 1,2-bis(4-pyridyl)ethane

Interaction of cadmium(II) or zinc(II) acetate with 1,2-bis(4-pyridyl)ethane (bpe) in the presence of dioxime(1,2-cyclohexanedionedioxime = NioxH₂ or diphenylglyoxime = dpgH₂) resulted in three complexes with the compositions [Cd₂(CH₃COO)₄(NioxH₂)₂(bpe)(H₂O)₂] (1), [Cd(CH₃COO)₂(bpe)(H₂O)]_n (2) and [Zn(CH₃COO)₂(NioxH₂)(bpe)(H₂O)]_n (3), which were characterized by single-crystal X-ray diffraction, elemental analysis, IR, and luminescence spectroscopy. Dioxime-containing binuclear molecule 1 and 1D linear polymer 3 possess moderate luminescence properties, while the dioxime-free 1D polymer 2 demonstrates strong blue luminescence.     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

A series of 1-D to 3-D metal-organic coordination architectures assembled with V-shaped bis(pyridyl)thiadiazole under co-ligand intervention

Six new coordination polymers based on V-shaped linkage 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and transition metal ions, [Co(bpt)(pm)_0.5(H₂O)]_n · 3nH₂O (1), [Cu₂(bpt)(pm)(H₂O)₄]_n (2), [Co(bpt)(pydc)]_n · 2nCHCl₃ · nH₂O (3), [Cu₂(bpt)(pydc)₂(H₂O)₂]_n (4), [Cu₂(bpt)(pydco)₂(H₂O)₂]_n · nH₂O (5) and [Cd(bpt)(pydco)]_n (6) (H₄pm = pyromellitic acid, H₂pydc = pyridine-2,6-dicarboxylic acid, H₂pydco = pyridine-2,6-dicarboxylic acid N-oxide), have been synthesized under the intervention of various polycarboxylate ligands. Complex 1 exhibits a 3-D 4-connected structure with 1-D nanosized open channels encapsulated lots of water molecules. Complex 2 represents a 2-D grid containing two types of rectangular windows. When pydc and pydco instead of pm, complexes 3 and 6 were obtained with highly undulated 2-D layers. The interlayers of 3 are filled with two kinds of solvent molecules, whereas 6 is a double-layered framework without free molecules. Complexes 4 and 5 consist of two distinct 1-D infinite chains held together to form different 2-D supramolecular networks. Importantly, bpt spacer shows changeful conformational geometries and generates complicated crystalline architectures with the introduction of polycarboxylate ligands. Additionally, thermal stability of complexes 1, 3 and 5, fluorescent properties of 6 and X-ray powder diffraction of 1 have also been investigated.     

Structural change of supramolecular coordination polymers of itaconic acid and 1,10-phenanthroline along lanthanide series

Five new supramolecular lanthanide coordination polymers with three different structures, {[La₂(IA)₃(phen)₂] · 2H₂O}_n (1), {[Ln(IA)_1.5(phen)] · xH₂O}_n [x = 1, Ln = Eu (2); x = 0.25, Ln = Dy (3)], and [Ln(IA)_1.5(phen)]_n [Ln = Er (4); Yb (5)], were prepared by hydro- and solvothermal reactions of lanthanide chlorides with itaconic acid (H₂IA) and 1,10-phenanthroline (phen), and structurally characterized by single crystal X-ray diffraction. 1 Comprises 1-D double-chains that are further assembled to a 3-D supramolecular structure via hydrogen bonds and π-π stacks between phen molecules. 2 and 3 have 2-D infinite networks which are further constructed to form 3-D supramolecular architectures with 1-D channels by π-π aromatic interactions. 4 and 5 have 2-D layer structures consisting of three types of rings which are further architectured to form 3-D supramolecular structures by C-H?O hydrogen bonds. The H₂IA ligands are all completely deprotonated and exhibit tetra-, penta-, and hexadentate coordination modes in the titled complexes. The high-resolution emission spectrum of 2 shows only one Eu³⁺ ion site in 2, which is in agreement with the result of X-ray diffraction. And the magnetic property and the thermal stability of 2 were also investigated.