Pillar-layered Zn–triazolate–carboxylate frameworks tuned by the bend angles of ditopic ligands

In the utilization of three ditopic ligands with different bend angles as pillars, we reported herein three pillar-layered Zn–triazolate–carboxylate frameworks, namely, [Zn₂(ATRZ)₂(BDC)]_n (1), [Zn₂(ATRZ)₂(TPDC)]_n·2nDMF (2) and [Zn₂(ATRZ)₂(ADDC)]_n (3) (ATRZ = 3-amino-1,2,4-triazole, H₂BDC = 1,4-benzenedicarboxylic acid, H₂TPDC = 2,5-thiophenedicarboxylic acid, and H₂ADDC = 1,3-adamantanedicarboxylic acid). Single crystal structural analyses demonstrate that different geometries of ditopic carboxylate pillars not only result in Zn–ATRZ layers adopting various corrugated configurations, but also give rise to 3,4-connected self-interpenetrated net of 1 and non-interpenetrated nets of 2 and 3. All these compounds exhibit high thermal stability and blue photoluminescence.     

Construction of three new mixed-ligand Zn(II) coordination polymers based on nitrogen-containing heterotopic ligands and carboxylate co-ligands

Reactions of Zn(II) salts, presynthesized 5-(4-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (HIPT) and various carboxylate ligands result to three new coordination polymers (CPs), namely, [Zn₂[(IPT)₂(ox)]}_n (H₂ox = oxalic acid, 1), [Zn₂(IPT)₂(mNBDC)]_n (H₂mNBDC = 5-nitroisophthalic acid, 2), and [Zn₂(IPT)(CA)(H₂O)]_n (H₃CA = citric acid, 3). Compound 1 can be seen as constructed from 2D [Zn(IPT)]_n layers with (6,3) topology and pillared by ox^2 −. It is a 3D (3,4)-connected framework with InS topology. Compound 2 has 2D bilayer structure based on 2D [Zn(IPT)]_n single layer and mNBDC^2 − linkers. Compound 3 is a 3D pillar-layer framework built by Zn–CA bilayers and IPT⁻ pillars. The results showed that the coordination modes, configurations of IPT⁻, and the structure of carboxylate co-ligands have great influence on the structures of the final network. The choice of carboxylate can decide the result of CPs in Zn–IPT chains/net subunits plus carboxyl linkers or Zn–carboxylate chains/net subunits plus IPT⁻ linkers. The thermal stabilities and luminescent properties of selected compounds have also been studied.     

Construction of two-dimensional supramolecular structure containing water tetramer and octamer

The complex [Cd₂(phen)₄(p-phth)(H₂O)₂](p-phth) · 10H₂O (1) has been synthesized by the reaction Cd(NO₃)₂ with phen and p-phth (where phen = 1,10-phenanthroline, p-phth = p-phthalic acid) in a solution of ethanol and distilled water. The crystal structure was characterized by X-ray single-crystal diffraction and infrared spectrum. In 1, a novel 2D supramolecular structure was formed, containing water octamer and tetramer.     

Syntheses,crystal structures and luminescent investigations of cobalt(II) and zinc(II) complexes with 2-propyl-4,5-dicarboxylate-imidazole (H3PIDC)

Presented in this communication are four metal complexes based on 2-propyl-4,5-dicarboxylate-imidazole (H₃PIDC), including two Co(II) coordination compounds, [Co(H₂PIDC)₂(H₂O)₂] · 4H₂O (1) and 2[Co(H₂PIDC)₂(H₂O)₂] · 5H₂O (2), as well as two Zn(II) coordination compounds, [Zn(H₂PIDC)₂(H₂O)₂] · 4H₂O (3) and 2[Zn(H₂PIDC)₂(H₂O)₂] · 7H₂O (4). They contain the same coordinated unit of [M(H₂PIDC)₂(H₂O)₂] (M = Zn or Co). Interestingly, among these four complexes, 1 and 2, or 3 and 4 crystallized in different space group, which may be related with the number of the crystallized H₂O molecules.     

Hetero-trinuclear near-infrared (NIR) luminescent ZnLn2 (Ln = Nd,Yb or Er) complexes based on monomer ZnL Schiff-base precursor and o-vanillin

With the monomer [Zn(L¹)(H₂O)] (1) complex in situ formed by the deprotonated hexadentate Salen-type Schiff-base ligand H₂L¹ (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) and Zn(NO₃)₂ as the precursor, series of the hetero-trinuclear ZnLn₂ complexes [ZnLn₂(L¹)₂(L²)(NO₃)₂Cl] (Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained from the further reaction with LnCl₃ (Ln = Nd, Yb Er or Gd) and the second o-vanillin (HL²) ligand, respectively. The photophysical properties of complexes 2–4 showed that the characteristic near-infrared (NIR) luminescence of Ln^3 + ions with two emission centers and emissive lifetimes in microsecond ranges, was sensitized from the excited state (both ¹LC and ³LC) of mixed H₂L¹–HL² ligands.     

Reactions of benzophenone imine complex [Tp(NH═CPh2)(PPh3)Ru–Cl] with alkyne and dimerization of terminal alkynes in the presence of Et3N

Treatment of benzophenone imine complex [Tp(PPh₃)(NH═CPh₂)Ru–Cl] (1) {Tp═HB(pz)₃, pz = pyrazolyl} with 4-Ethynyltoluene in the presence of H₂O in distilled ethanol afforded the chelate alkenyl ketone complex [Tp(PPh₃)RuCCH₂(p-MeC₆H₄)═CHC(O)(p-MeC₆H₄)] (2). On the other hand, reaction of 1 with HC≡C(O)OR₁ in R₂OH produced the chelate vinyl ether complexes [Tp(PPh₃)Ru–C(OR₂)═CHC(O)OR₁] (3a, R₁ = Me, R₂ = Me; 3b, R₁ = Et, R₂ = Me; 3c, R₁ = Et, R₂ = Et; 3d, R₁ = Me, R₂ = Et), respectively. Preliminary results on the catalytic activity of 1 are also presented. Intriguingly, complex 1 is found to catalyze the dimerization of terminal alkynes HC≡CR (R = p-MeC₆H₄, C(O)OCH₃) in the presence of Et₃N to give eynes. The structures of 3c and 3d have been determined by X-ray diffraction analysis.     

A novel supramolecular adduct formed by CB[6]-based pseudo-rotaxane and hydrated Zn(II) ion

A novel supramolecular adduct of [C6N2(CB[6])]₃ · [Zn(H₂O)₆]Cl₂ · 14H₂O (1) is reported, where C6N2 = N,N′-bis(2-pyridylmethyl)-1,6-diaminohexane, CB[6] = Cucurbit[6]uril. It consists of a CB[6]-based pseudo-rotaxane and a six-hydrated Zn(II) ion, and forms an infinite 2D network and 3D spatial structure by hydrogen bonding interactions.     

Synthesis,luminescence, and structural characterization of Zn and Cd coordination polymers of flexible bis(imidazolyl) derivatives

Coordination polymers [Zn(imc)(L¹)] · H₂O, (1, imc = iminodiacetate, L¹ = bis(N-imidazolyl)methane) [Zn(hba)₂(L²)]₂ · EtOH · 3H₂O, (2, hba = p-hydroxybenzoate, L² = bis(N-benzimidazolyl)methane), [Cd(mal)(H₂O)(L³)](3, L³ = 1,4-bis(N-imidazolyl)butane, mal = maleate) have been prepared and structurally characterized. Complex 1 consists of hexa-coordinated central Zn ions and exhibits 2D network structure. The Zn atoms in 2 have tetrahedral coordination geometry, and are linked by bis(imidazolyl) ligands into 1D chain structure. The cadmium ions in 3 are hepta-coordinated with pentagonal bipyramidal geometry. Complex 3 displays 2D grid structure. The TGA showed that the coordination polymers are stable up to 200 °C. All the three complexes are emissive at room temperature in their solid state.     

Polynuclear copper(II) carboxylates with 2,2′-bipyridine or 1,10-phenanthroline: Synthesis,characterization, X-ray structures and magnetism

[Cu₂(phen)₂(μ-O₂CH)₂(O₂CH)₂]_n (1) and [Cu₆(bpy)₆(μ-O₂CC₂H₅)₇(H₂O)₂)](PF₆)₅ · 2H₂O (2) were synthesized and characterized by elemental analyses, electronic and EPR spectra and X-ray structure analyses. Compound 1 consists of four independent polymeric chains of dinuclear [Cu₂(phen)₂(μ-O₂CH)₂(O₂CH)₂] subunits with the asymmetric bidentate bridging formato groups linking Cu atoms in an anti–anti configuration. All Cu(II) ions are in a distorted square-pyramidal geometry. The hexanuclear copper(II) molecule of compound 2 is constructed from three different dinuclear units connected to each other via two syn–anti-μ₃-η¹;η² carboxylato bridges. All copper(II) ions are in the distorted square-pyramidal geometry. Two terminal dinuclear units are similar in structure in which both Cu(II) ions are doubly bridged by the syn–syn carboxylato anions, while those of the central dinuclear entity are triply bridged by two μ₃-η¹;η² carboxylato anions via monoatomic bridging fashion and one syn–syn carboxylato anion. The magnetic susceptibility (5–350 K) of compound 2 was measured and agree with a weak antiferromagnetic interaction between the Cu(II) centers.     

Highly selective luminescent sensing of xylene isomers by a water stable Zn-organic framework

A new Zn(II) metal-organic framework was synthesized with 5-nitro-1,2,3-benzenetricarboxylic acid and auxiliary triazole ligand via hydrothermal method, namely, {[Zn_2.5(nbta)(trz)₂(H₂O)]·3H₂O}_n (1), where H₃nbta = 5-nitro-1,2,3-benzenetricarboxylic acid and Htrz = 1H-1,2,4-triazole. 1 shows high thermal stability up to 150 °C under air atmosphere and water stability with the pH range from 1 to 12. Luminescent study shows that 1 displays a high-sensitivity sensing function for p-xylene in the three kinds of xylene isomers.     

Syntheses and structures of cadmium(II) and cobalt(II) coordination polymers based on 1,1′-(2,2′-oxybis(ethane-2,1-diyl))bis(1H-imidazole) and carboxylate ligands

Two novel coordination polymers containing Cd(II) and Co(II) metals, connected via 1,1′-(2,2′-oxybis(ethane-2,1-diyl))bis(1H-imidazole) (L) ligand, have been synthesized. Compound [Cd(L)₂(p-BDC)] · 2H₂O (1) (p-BDC = 1,4-benzenedicarboxylate anion) is a three-dimensional interdigitated supramolecular architecture. Compound [Co(L)(BTCA)_0.5] (2) (BTCA = 1,2,3,4-butanetetracarboxylate anion) possesses a unique (3,4)-connected 3D framework with (8³)₂(8⁵ · 10) topology.     

A metal–organic framework containing meso-helical chains: Synthesis,characterization and luminescent property

A new metal–organic frameworks (MOFs), [Cd₃(pmb)₂(bpdc)₂] 2H₂O (1) (pmb = 3,5-bis(4-pyridylmethylenoxyl)benzoate, bpdc = 2,2′-biphenyldicarboxylate), has been synthesized by hydrothermal method and structurally characterized through IR, TG and single-crystal X-ray analysis. The infinite wave-like 1D metal–oxygen chains made by Cd₃N₄O₁₂ clusters in 1 bridged by the carboxylate of bpdc ligand, construct a 2D framework in which interesting meso-helical chains are constructed by metal centers and pmb ligands. Solid state luminescent spectrum of 1 also has been investigated at room temperature.     

Solvothermal syntheses,characterizations and properties of two new NiII-PMIDA phosphonates

Two new nickel(II) phosphonates (H₄PMIDA = N-(phosphonomethyl)iminodiacetic acid, H₄L), one-dimensional zigzag chain (NH₄)₂[Ni(PMIDA)(H₂O)] (1) and tetramer (H₃O)₈[Ni₄O₂(HPMIDA)₄(H₂O)₂] (2), have been solvothermally synthesized and characterized by elemental analyses, IR, TGA and X-ray single-crystal diffraction, and their magnetic and fluorescent properties are also reported.Compound 1 is the first chain phosphonate linked by carboxyl group in anti–anti mode based on Ni(II) and H₄PMIDA ligand, and compound 2 with tetranuclear units is the first example of showing the spin-canting antiferromagnetic coupling between Ni(II) centers.     

Polycatenation and photoluminescence of two zinc coordination polymers based on arched and linear mixed ligands

Two polycatenated coordination polymers, {[Zn₃(adc)₃(bpp)₄]₂ · 3H₂O}_n (1) and [Zn(adc)(bphy)]_n (2) (adc = azobenzene-4,4′- dicarboxylate, bpp = 1,3-bis(4-pyridyl)propane, bphy = 1,2-bis(4-pyridyl)hydrazine), have been obtained from Zn(NO₃)₂∙ 6H₂O, linear H₂adc ligand and arched bpp/azpy (azpy = 4,4′-azobispyridine) ligands by hydro(solvo)thermal reactions. Compound 1 presents a 2-D structure catenated from 1-D double ladders (1-D → 2-D polycatenation), while compound 2 displays a 3-D structure catenated from 2-D (4,4) stair-stepping layers (2-D → 3-D polycatenation). Luminescence properties of 1 and 2 have been explored, together with study of photoluminescent mechanism by density of states (DOS) calculation.     

A novel three-dimensional 3d–4f heterometallic coordination polymer with unique (3,4)-connected topology and helical units: Synthesis,crystal structure and photoluminescence property

One new three-dimensional 3d–4f heterometallic coordination polymer, namely, {[EuZn₂(imdc)₂(C₂O₄)_0.5(H₂O)₄]·2H₂O}_n (1) (H₃imdc = imidazole-4,5-dicarboxylic acid), has been successfully synthesized by the hydrothermal reactions of Eu₂O₃, Zn(NO₃)₂·6H₂O, H₃imdc, H₂C₂O₄·2H₂O and H₂O. Single-crystal X-ray diffraction analysis reveals that complex 1 possesses 3D heterometallic framework containing 2D layer based on L–Zn2–L (L = imdc) helical chains and L–EuZn1–L chains. Complex 1 exhibits unprecedented (3,4)-connected four-nodal topology with Schläfli symbol (6·7·8) (6·7·9) (6·7²·8²·10) (7·8²). Moreover, the photoluminescence property of 1 was investigated in the solid-state at room temperature.     

1D Zn(II) coordination polymer of arylhydrazone of 5,5-dimethylcyclohexane-1,3-dione as a pre-catalyst for the Henry reaction

Reaction of a new hydrazone of β-diketone, 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)isophthalic acid (H₃L), with zinc(II) nitrate hexahydrate in a mixture of DMF and water (1:1) under hydrothermal conditions affords the 1D coordination polymer [Zn(μ₃-HL)(H₂O)₂]_n ∙ nH₂O (1), where one of the carboxylic groups links two Zn(II) centers in a bridging bidentate (syn-syn-type) mode and the remaining one ligates a third metal cation in a monodentate fashion. It was characterized by IR and NMR spectroscopies, ESI-MS, elemental and single-crystal X-ray crystal structural analyses. 1 acts as an efficient pre-catalyst for the Henry reaction at 40 °C in aqueous medium, providing β-nitroalcohols with good yields (67–86%) and diastereoselectivities (syn:anti 77:23–69:31).     

Hydrothermal synthesis,crystal structure and magnetic properties of a novel nickel carboxylate–phosphonate with a layered structure

Hydrothermal reactions of N-(phosphonomethyl)proline (H₃L) with nickel sulfate hexahydrate resulted in a novel nickel carboxylate–phosphonate: |H₂O|[Ni₃(O₃PCH₂–NC₄H₇–CO₂)₂(H₂O)₄] (complex 1). Single-crystal X-ray diffraction analysis revealed that complex 1 crystallizes in the triclinic space group P-1 (No. 2), with lattice parameters of a = 10.0167(5) Å, b = 10.3882(5) Å, c = 11.9528(5) Å, α = 90.132(3)°, β = 107.246(3)°, γ = 111.158(3)°, V = 1099.39(9) Å³, and Z = 2. Complex 1 features a 2D layered structure. The structure contains alternating Ni-centered octahedra (Ni(1)O₆, Ni(2)O₅N and Ni(3)O₅N) and O₃PC tetrahedra linked to construct a layer with rhombohedral 12-MRs holes. The cyclopentylamine moieties of H₃L were grafted onto the layer through coordination of CPO₃, CO₂ and (CH₂)₂NCH₂ with central nickel atoms. These layers are stacked in an AA sequence, which results in a one-dimensional channel in the [001] direction. Water molecules are located in these channels. Magnetic studies showed that complex 1 exhibits predominantly paramagnetic behavior.     

Microporous metal–organic frameworks constructed by Cu(I)/Zn(II), Tpt and 1,4-benzenedicarboxylate

Two novel metal–organic frameworks, [Cu(tpt)(bdc)_1/2]_n · nH₂O (1) and [Zn(tpt)(bdc)_1/2I]_n (2) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine, H₂bdc = 1,4-benzenedicarboxylic acid), have been prepared by hydrothermal reactions. In complex 1, Cu(I) center is in a trigonal coordination environment with bidentate tpt coordinating Cu(I) atoms to form 1D zigzag chains, and bdc ligand links the zigzag chains to form a 2D layered structure. In complex 2, Zn(II) center is in a trigonal–pyramidal environment with bidentate tpt coordinating Zn(II) atoms to form zigzag chains, and bdc links the zigzag chains to form metal–organic framework which contains interesting hexagonal nano-channels.     

A novel transition-metal-linked hexaniobate cluster with photocatalytic H2 evolution activity

A novel transition-metal (TM) complex based on Lindqvist polyoxoniobate K₁₀[(Nb₆O₁₉)Cr^III(H₂O)₂]₂·28H₂O (1) has been synthesized by a new two-pot synthesis strategy and structurally characterized by single crystal X-ray diffraction analysis, IR spectrum, UV–vis spectroscopy, XRPD and TG analysis. Compound 1 crystallizes in the C2/m space group with a = 32.143(19) Å, b = 10.030(6) Å, c = 12.878(8) Å, β = 110.611(9)°, and V = 3886(4) ų. X-ray structure analysis reveals that polyanion [(Nb₆O₁₉)Cr^III(H₂O)₂]₂^10 − (1a) represents the first example of two nuclear dimeric polyoxoniobate, in which two Lindqvist anions [Nb₆O₁₉]⁸ are sandwiched by two {Cr^III(H₂O)₂} groups. Further, 1 exhibits photocatalytic H₂ evolution activity.     

Co-existence of heterometallic Zn2Er and ZnEr arrayed chromophores for the sensitization of near-infrared (NIR) luminescence

With the Zn-Schiff-base [ZnL(Py)] from the simple Salen-type Schiff-base ligand H₂L (H₂L = N,N′-bis(salicylidene)ethylene-1,2-diamine) as the precursor, two co-crystallized heterometallic (Zn₂Ln and ZnLn array) complexes [Zn₂Ln(L)₂(Py)₂(NO₃)₂]·[ZnLn(L)(Py)(NO₃)₃(H₂O)]·NO₃·mMeOH·nS (Ln = Er(1), S = CH₃CN, m = 2, n = 1 or Gd(2), S = H₂O, m = 1, n = 3) were obtained by the further reaction with Ln(NO₃)₃·6H₂O, respectively. The result of their photophysical properties shows the intramolecular effective energy transfer has been demonstrated in the Zn₂Er and ZnEr arrayed complex 1, and the co-existence of different chromophores should be a potentially new way to the fine-tuning properties of NIR luminescence from Er³⁺ ions.