Construction of three Cd(II) coordination polymers based on extended pyridyl-tetrazolyl-bifunctional ligands: Structures and luminescent properties

Reactions of Cd(II) with three new pyridyl-tetrazole-bifunctional ligands, 3-(4-(1H-tetrazol-5-yl)phenyl)pyridine (HL¹), 4-(3-(1H-tetrazol-5-yl)phenyl)pyridine (HL²), and 3-(3-(1H-tetrazol-5-yl)phenyl)pyridine (HL³) resulted in three Cd(II) coordination polymers (CPs), namely, [CdL¹₂]_n (1), [CdL²₂]_n (2), and [CdL³₂(H₂O)]_n (3). Although the geometry of L¹ and L² is quite different, the coordination modes of Cd(II) ion and ligand, as well as the SBUs in compounds 1 and 2 are quite similar, thus give rise to 3D frameworks with same (3,6)-connected ant topology. Compound 3 is a 3D framework composed of 1D helical chains and features as (3,5)-connected tcj topology. The results showed that the topologies are largely dependent on the coordination angle between two coordination groups. The thermal stabilities and luminescent properties of compounds 1–3 have also been studied.     

Syntheses and structures of a phenoxo-bridged copper(II) distorted cubane and related complexes with 2-hydroxy-N-(2-pyridylalkyl)benzamide ligands

Two new pyridylalkylamide ligands containing phenol groups appended to the amide, 2-hydroxy-N-(2-pyridylmethyl)benzamide (HL^PhOH) and 2-hydroxy-N-(2-pyridylethyl)benzamide (HL^PhOH′), were synthesized. Copper(II) complexes of these ligands were synthesized and characterized by X-ray crystallography, ESI-MS, FTIR, UV/Vis, and EPR spectroscopy. When basic Et₃N was used to deprotonate the ligands, tetracopper(II) [Cu₄(L^PhO)₄] (1) or dicopper(II) [Cu₂(L^PhO′)₂(CH₃OH)₂] (3) were formed. When base was not used, mononuclear [Cu(HL^PhOH)₂Cl₂] (2) resulted. Complex 1 possesses a distorted cubane-like structure, with the ligands bridging via the phenoxo oxygen atoms, and the copper atoms possessing a distorted square planar geometry. The ligands in dimeric complex 3 also bridge between copper(II) atoms via the phenoxo oxygen atoms, and the copper atoms are square pyramidal. Monomeric 2 is a tetragonally distorted six-coordinate species with pyridyl N atoms and chloride ligands in the equatorial plane, and long interactions with the amide carbonyl O atoms in the axial positions.     

Four-, six- and eight-coordinated lead(II) complexes with amine- or amide-type tripodal ligands

Three novel lead(II) complexes, [Pb(L¹)](ClO₄)₂ (1) (L¹ = tris(2-benzylaminoethyl)amine), [Pb(L²)₂](ClO₄)₂ (2) (L² = tris(4-phenyl-3-aza-2-oxobutyl)amine) and [Pb₂(L³)₂](ClO₄)₄ (3) (L³ = tris[3-aza-2-oxo-4-(2-pyridyl)butyl]amine) were synthesized and structurally characterized. All three complexes show different stoichiometries as well as coordination numbers of four in 1, eight in 2 and six in 3, respectively. Complex 1 displays a typical tripodal-type 1:1 (M:L) structure and 2 shows a sandwich-type 1:2 structure. The octa-dentate lead(II) ion in 2 is at the center of a dicapped trigonal prism. Complex 3 is revealed as a unique dinuclear 2:2 complex, in which two hexa-dentate lead(II) ions are linked by two carbonyl μ–O atoms forming a Pb₂(μ–O)₂ parallelogram-type moiety.     

Fixed helical Cd(II) coordination polymers assembled from diastereopure Schiff-base ligands derived from condensation of acetylacetone with 1S,2S- and 1R,2R-cyclohexanediamine

The 1:1 interaction of the diastereopure Schiff bases (1S,2S)-bis(acetylacetone)-cyclohexanediimine (L¹) and (1R,2R)-bis(acetylacetone)cyclohexanediimine (L²) with CdI₂ yields the new helical metal coordination polymers [CdL¹I₂]_n (1) and [CdL²I₂]_n (2). The respective X-ray structures, as expected, confirmed 1 and 2 to be enantiomeric, existing as right-handed (P) and left-handed (M) helical chains in which both L¹ and L² are formally present in their (unusual) uncharged ketoamine form, with the (protonated) amine nitrogens not coordinated. The Cd(II) centres in 1 and 2 display distorted tetrahedral coordination geometries being bound to two iodo ligands and two oxygen donor atoms from individual ketoamine domains belonging to different Schiff base ligands.     

Interaction of copper(II) with N-substituted bis(2-pyridylmethyl)amine derivatives: New discrete and 1-D polymeric complex systems — The latter displaying ferromagnetic behaviour

Interaction of copper(II) with the N-substituted bis(2-pyridylmethyl)amine derivatives, (R)-N¹,N¹-bis(pyridine-2-ylmethyl)butane-1,2-diamine (L¹) and (R)-2-(bis(pyridin-2-ylmethyl)amino)butan-1-ol (L²), has led to isolation of optically active [Cu(L¹)Cl]PF₆ (1) and [Cu(L²)Cl]ClO₄ (2), respectively. The X-ray structures of (1) and (2) show that the copper is bound to all four heteroatoms of the respective ligands as well as to a chlorine atom in a distorted square pyramidal arrangement in which the three nitrogens of L¹ or L² occupy three positions of each basal plane while the fourth position is occupied by the chloro ligand; apical sites in each case are filled by the amine donor from the NH₂-substituted butane arm in L¹ or the (protonated) alcohol oxygen of the 2-aminobutane-1-ol substituent in L². To a first approximation the coordination geometry in 2 is distorted square pyramidal; however, the remaining (axial) site on each copper centre is involved in a long contact (2.96 Å) with a bound chloro ligand from an adjacent complex which connects individual complex units in a zigzag 1-D polymeric chain, so that the coordination geometry could also be seen as pseudo-octahedral. A temperature-dependent magnetic study revealed the presence of ferromagnetic exchange coupling between copper centres in the chain reflecting the orthogonal structure between the chloro-bridged copper(II) ions; in contrast, and as expected, the discrete complex 1 is magnetically dilute.     

Three hydrogen-bonded nanotubular zinc(II) complexes of N-(9-anthracenyl)-N′-(4-pyridyl)-urea

Three hydrogen-bonded nanotubular zinc(II) complexes of a monodentate ligand N-(9-anthracenyl)-N′-(4-pyridyl)urea (L), [Zn(OAc)₂L₂]?H₂O (1), [ZnBr(OAc)L₂]?H₂O (2) and [ZnCl(OAc)L₂]?4H₂O (3), were synthesized and structurally characterized. In the complexes, the central metal ion is tetrahedrally coordinated by the pyridyl nitrogen atoms of two ligands and different anions, while the urea groups of the ligands self-associate into the typical urea tape through R₂¹(6) hydrogen bonds, which are essential for the formation of the nanotubes. The fluorescence properties of ligand L and the complexes were studied in the solid state at room temperature.     

Zirconium complexes of amino(polyphenolic) ligands and their hydrolytic stability

Three amino(polyphenolic) ligands, N,N′-bis(5-tert-butyl-2-hydroxybenzyl)-1,2-diaminoethane 1, tris(5-tert-butyl-2-hydroxy-3-methylbenzyl)amine 3, its 3-chloro analogue 4 and their Zr^IV complexes have been synthesised. The crystal structure of the Zr^IV complex of tris(5-tert-butyl-3-chloro-2-hydroxybenzyl)amine, shows this to be [Zr(4-2H)₂] in which both ligands exists in a zwitterionic form with one alkylammonium and three phenolate groups. The complexes are stable in a two phase, chloroform/water, system at high pH, but the zirconium is stripped at pH < 2.5. The pH value needed to strip 50% of the Zr^IV from the complex [Zr(1-4H)] of the tetraphenolic ligand is ∼2.0 whilst the complexes [Zr(3-2H)₂] and [Zr(4-2H)₂] of the triphenolic ligands are slightly more stable with pH_1/2 values of ∼1.4. We were unable to use the ligands to extract zirconium from low pH aqueous zirconium oxychloride solutions into an organic phase under a variety of conditions.     

Toward chiral iron(II) spin-crossover grafted resins with imidazole Schiff-base ligands

Using chiral imidazole Schiff-base as ligands, two couples of mononuclear iron(II) enantiomeric complexes fac-Λ-[Fe(R-L)₃](ClO₄)₂·H₂O (1), fac-Δ-[Fe(S-L)₃](ClO₄)₂·H₂O (2), fac-Λ-[Fe(R-L)₃](BF₄)₂·H₂O (3), fac-Δ-[Fe(S-L)₃](BF₄)₂·H₂O (4) (L = 1-(2-naphthyl)-N-((1-methyl-imidazol-2-yl)methylene)ethanamine) have been successfully synthesized and characterized. The CD spectra of 1 and 2, 3 and 4, were basically mirror images confirming their enantiomers. X-ray crystallography revealed that complexes 1–4 all crystallized in the chiral space group P2₁3 with the iron(II) center surrounded by three bidentate ligands. Magnetic measurements revealed incomplete spin transition for 1, and gradual spin crossover (T_1/2 = 150 K) for 3. However, the spin-crossover behaviors were vanished after grafting 1–4 to the Merrifield's peptide resin, and the iron(II) centers in the resin remained in a high-spin state in the temperature range of 2–300 K.     

Two New Zn(II) Coordination Polymers Constructed from Asymmetric Biphenyl-Dicarboxylate and Imidazole-Containing Ligands: Structures and Photoluminescent Properties

Two new coordination polymers, [Zn(2,4′-bpdc) (L₁)_0.5·(H₂O)] _n (1) and {[Zn(3,4′-bpdc) (L₁)]·(H₂O)} _n (2), have been obtained from hydrothermal reactions of zinc (II) nitrate with the ligands 1,4-bis(imidazol-1-yl)benzene (L) and two asymmetric biphenyl-dicarboxylate [biphenyl-2,4′-dicarboxylate (2,4′-bpdc) and biphenyl-3,4′-dicarboxylate (3,4′-bpdc)]. Single-crystal X-ray diffraction analysis the two coordination polymer show different structures due to the different dicarboxylate ligands. Complex 1 features a 3D mab topological net. Complex 2 is unusual case that has 3D frameworks constructed from 2D 4⁴-sql layers by parallel polycatenation. The photoluminescent properties of 1 and 2 have also been investigated.     

A new family of trinuclear Ru(II) polypyridyl complexes acting as pH-induced fluorescence switch

Tripodal ligands 1,3,5-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)methyl}-2,4,6-trimethylbenzene (L¹), 1,1,1-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)methyl}propane (L²), 2,2′,2′′-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)ethyl}amine (L³), and corresponding Ru(II) complexes [(bpy)₆L^1–3(Ru^II)₃](PF₆)₆, shortly called (Ru–L^1–3), have been synthesized. UV–vis absorption and fluorescence spectra of these complexes are both strongly dependent on the pH of the buffer solution. These complexes act as pH-induced off–on–off fluorescence switch through protonation and deprotonation of the imidazole-containing ligands.     

Preparation,photophysical, and electrochemical properties of three novel trinuclear Ru(II) polypyridyl complexes based on diazafluorenes

Three tripodal ligands 2,2′,2″-tris[(4,5-diazafluoren-9-ylimino)phenoxyethyl]amine (L¹), 1,3,5-tris[(4,5-diazafluoren-9-ylimino)phenoxymethyl]-2,4,6-trimethylbenzene (L²), 1,1′,1″-tris[(4,5-diazafluoren-9-ylimino)phenoxymethyl]-1″′-(p-tosyloxymethyl)-methane (L³), and corresponding Ru(II) complexes [(bpy)₆L^1–3(Ru^II)₃](PF₆)₆ (Ru-L^1–3) have been prepared. Cyclic voltammetry of the three complexes are consistent with one Ru(II)-centered quasi-reversible oxidation and three ligand-centered reductions. Photophysical behaviors are investigated by UV–Vis absorption and fluorescence spectrometry. The three complexes display metal-to-ligand charge transfer absorption at 445 nm and emission at 578 nm.     

Construction of two mercury(II) coordination frameworks involving in situ tetrazole ligand synthesis

Two novel mercury(II)-organic polymeric complexes [HgCl(pzta)]_n (1) and [Hg₃Cl₂(pzta)₄(H₂O)₂]_n (2) [pzta = pyrazinyl tetrazolate] were obtained by in situ synthesis of pyrazinyl tetrazolate from the reaction of pyrazinecarbonitrile with sodium azide in the presence of mercury(II) salts. Complex 1 is a 3D coordination polymer with a 3,5-connected hms [(6³)(6⁹ · 8)] net consisting of mildly undulate (6, 3) sheets and bridging chlorine ligands; while complex 2 is also a 3D supramolecular network built from 2D layers with the 4-connected sql {4⁴ · 6²} net that are assembled via hydrogen bonds and π?π stacking interactions. Last but not least, photofluorescent properties of the two complexes have also been investigated.     

Syntheses,structures and photoluminescence properties of two 2D Cd(II) coordination polymers based on a semirigid tridentate N-donor ligand

The assembly of a semirigid tridentate N-donor ligand with Cd(II) ions afforded two novel coordination polymers, [Cd(tipa)(H₂O)₂·2NO₃·2DMF·H₂O]_n (1), [Cd₂(tipa)₂Cl₄·2DMF·6H₂O]_n (2), where tipa = tris(4-(1H-imidazol-1-yl)phenyl) amine. Structural analyses indicate that the two compounds feature 2D layered networks. A 3-connected uninodal net with point symbol of (8²·10) is constructed in compound 1 by the connection of tipa and metal ions, in which the terminally coordinated water molecules prevent further extension of the layer. Compound 2 features [Cd₂Cl₄] motifs, which are bridged by tridentate tipa ligands into a 2D (3,6)-connected layer. The results show that tipa with different dihedral angles between benzene ring and terminal imidazole groups can act as versatile building blocks for the generation of various networks. Moreover, the photoluminescence properties of 1 and 2 in the solid state at room temperature have been investigated.     

A novel pentanuclear Zn(II) coordination polymer with double helices: Synthesis,structure and luminescent property

A novel 3D coordination polymer, [Zn₅(hqc)₄(μ₃-OH)₂]_n (1), has been prepared by hydrothermal reaction and characterized by elemental analyses, TGA, and single-crystal X-ray diffraction analysis. Compound 1 is built by hqc²⁻ ligands bridging pentanuclear Zn(II) SBUs, [Zn₅(μ₃-OH)₂], and there is coexistence of left-, and right-handed double helical chains in the 3D network. It represents the first pentanuclear Zn(II) coordination polymers with double helices constructed from quinoline-based carboxylic acid. In addition, the fluorescent property of compound 1 was also determined, which exhibits blue fluorescence at 441 nm in the solid-state upon excitation at 330 nm.     

Crystal structures and photoluminescence of the Zn(II) and Cd(II) complexes of N-methylpyrazinium obtained by a less hazardous approach

Compared to previously reported methods, a less hazardous approach has been used to synthesize N-methylpyrazinium cation (mpz⁺) by the reaction of pyrazine and ClCH₂COONa. Although a few mpz⁺-containing complexes have been documented, there is no example of mpz⁺-containing group IIB metal complexes. Three novel complexes containing mpz⁺, (mpz)ZnI₃ (1), [(mpz)CdCl₃]_n (2), and [(mpz)CdBr₃]_n (3), have been successfully obtained via a solution or hydrothermal method by reactions of ZnI₂, CdCl₂·2.5H₂O, and CdBr₂·4H₂O with the mpz⁺ ligand, respectively. Complex 1 features an isolated structure, with each zinc atom coordinated by one mpz⁺ ligand and three terminal iodine atoms. The CD spectra of 1 reveal that it exhibits spontaneous resolution. Complexes 2 and 3 are isotypic, and exhibit chain structures made by linear arrays of Cd(II) bridged by halogen atoms. Photoluminescent analyses reveal that complexes 1–3 exhibit strong blue emissions originating from intra-ligand π–π¹ transition of the mpz⁺ ligand.     

Nickel(II) thiolates derived from transmetallation reaction of [Zn(Tab)4](PF6)2 with Ni(II) ions and their catalytic activity toward the CN coupling reactions

Reactions of NiCl₂·6H₂O or Ni(ClO₄)₂·6H₂O with 2,2′-bipyridine (2,2′-bipy), or 2-bis(diphenylphosphino)ethane (dppe) or 1,4-bis(diphenylphosphino)butane (dppb) followed by addition of [Zn(Tab)₄](PF₆)₂ (1) resulted in the formation of one trinuclear cationic complex [(2,2′-bipy)₄Ni₃(μ-Tab)₄]Cl_0.5(PF₆)_5.5 (2), one mononuclear cationic complex [Ni(Tab)₂(dppe)](PF₆)₂ (3), and one dinuclear cationic complex [Ni₂(dppb)(μ-Tab)₂(Tab)₂](PF₆)₂(ClO₄)₂ (4). Complexes 2–4 were characterized by elemental analysis, IR, UV–vis, ¹H and ³¹P NMR, and single-crystal X-ray diffraction. In the [(2,2′-bipy)₄Ni₃(μ-Tab)₄]^6 + hexacation of 2, the central Ni(II) atom is connected to two [Ni(2,2′-bipy)₂]^2 + fragments by two pairs of μ-Tab ligands, forming a linear trinuclear cationic structure. The Ni(II) center of the dication of 3 is tetrahedrally coordinated by two S atoms from two Tab ligands and two P atoms of one dppe ligand. Complex 4 has a dimeric cationic structure in which two [(Tab)Ni]^2 + species are linked by a pair of μ-Tab ligands and one dppb ligand. Complexes 2–4 displayed high catalytic activity toward the cross-coupling reactions of arylboronic acids and amines to produce N-arylated amines.     

Ancillary Ligand-Mediated Syntheses,Structures and Fluorescence of Three Zn/Cd(II) Coordination Polymers Based on Nitrobenzene Dicarboxylate

The Zn/Cd(II)-nbdc carboxylate motifs mediated by various dipyridyl-typed ligands afforded three new coordination compounds, namely, [Zn(nbdc)(bpa)_0.5(H₂O)]·H₂O (1), [Zn₂(nbdc)₂(bpp)₂]·H₂O (2), and [Cd(nbdc)(bpe)_0.5(H₂O)₂] (3) (H₂nbdc = 4-nitrobenzene-1,2-dicarboxylic acid, bpa = 1,2-bi(4-pyridyl)ethane, bpe = 1,2-di(4-pyridyl)ethylene, and bpp = 1,3-bis(4-pyridyl)propane), which were synthesized by hydrothermal reaction and characterized by elemental analysis, IR, thermal analysis (TGA), and fluorescent analysis. The single-crystal X-ray diffractions reveal that three complexes display a diverse range of connectivity topology from 1D to 3D, which is dependent on the type of dipyridyl-typed ligands and metal centers. Complex 1 is the 1D chain featuring Zn-carboxylate binuclears extended further by bpa coligands. Complex 2 is the 2D thick-layer containing double-stranded chains cross-linked further by bpp coligands. Complex 3 is the 3D framework with (6³)(6⁵.8) ins topology featuring Cd-carboxylate chiral layers pillared by bpe coligands. The thermal stabilities and fluorescence properties for complexes 1–3 are investigated.     

Three New Metal(II) Complexes with Unusual 2D Hydrogen Bond Network Based on <Emphasis Type="Italic">N</Emphasis>-methylimidazole

Three new metal(II) complexes based on N-methylimidazole, [ML₆]·(SH)₂·(H₂O)_2, (M = Ni(II) (1), Co(II) (2), Cu(II) (3), L=N-methylimidazole), have been synthesized and characterized. The single crystal X-ray structural analyses show that complexes 1, 2, and 3 have isomorphous structures and crystallize in monoclinic system with space group P2₁/c. The complexes containing isolated SH^? anions, which may come from the thermochemical sulfate reduction, are located in the gap with lattice water molecules and provide multiple intermolecular hydrogen bonds to form 2D layers. Topology analyses show a 2D hydrogen bond network, which can be regarded as an unprecedented trinodal (3,4,6)-connected topology with Schläfli symbol (3.4.5³.6)₂(3.4.5)₂(3²;5⁴;6⁴;8²;9³). Cyclic voltammetry and UV–vis spectra were studied.     

Temperature/anion-dependent self-assembly of Co(II) coordination polymers based on a heterotopic imidazole-tetrazole-bifunctional ligand: Structures and magnetic properties

Reactions of Co(II) with 5-(3-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (HIPT) resulted in three Co(II) coordination polymers (CPs), namely, {[Co(IPT)₂(H₂O)₂]·2H₂O}_n (1), [Co(IPT)₂]_n (2), and {[Co₃(IPT)₂(CH₃COO)₂(OH)₂(H₂O)₂]·2H₂O}_n (3). Compound 1 that obtained from CoCl₂·6H₂O at 120 °C is a 2D network based on Co(II) ions and μ₂-IPT⁻ ligands. Compound 2 that obtained from CoCl₂·6H₂O at 170 °C exhibits a 3D framework based on linear trinuclear Co(II) SBUs and features a pcu network topology. Compound 3, which obtained by using Co(Ac)₂ as salt, displays a 2D network based on 1D SBUs. The structures of compounds 1–3 are dependent on the temperatures and inorganic anions. The magnetic properties of compounds 2–3 were also explored.     

Hydrothermal synthesis and structural characterization of one-dimensional coordination polymers of cobalt(II) and nickel(II) with 1,3,5-benzenetriacetic acid

Transition metal complexes [M(Hbta)(H₂O)₄] [M=Co(II) (1), Ni(II) (2), H₃bta=1,3,5-benzenetriacetic acid] have been prepared by reaction of H₃bta with the M(OH)₂ in water by hydrothermal method. The complexes were characterized by X-ray crystallography and electrospray mass spectrometry. The coordination geometries around Co(II) and Ni(II) atoms are both distorted octahedral with O₆ donor set. And the conformation of flexible triacid is cis, trans, trans in the title complexes.