Metal-organic frameworks constructed from monomeric,dimeric and trimeric phenanthroline citrate zinc building units

Adduct of mononuclear and dinuclear citrate zinc complex [Zn(Hcit)(phen)(H₂O)][Zn₂(Hcit)(phen)₂(H₂O)₃]·13.5H₂O (1) and its aggregate [Zn₃(Hcit)₂(phen)₄]_n·14nH₂O (2) (H₄cit = citric acid, phen = 1,10-phenanthroline) were synthesized in weak acidic solutions. The former was obtained from the reaction of zinc nitrate, citric acid and phenanthroline in a molar ratio of 3:2:3, while a slightly excess of phenanthroline results in the formation of the polymeric product 2 in a molar ratio of 3:2:4. Transformation of 1 to 2 was finished by the reaction of 1 with an equimolar of phenanthroline in 72% yield. Reverse conversion of 2 to 1 is obtained in 77% yield, showing an equilibrium between 1 and 2. Neutral compound 1 consists of one monomeric anionic unit [Zn(Hcit)(phen)(H₂O)]^? and one dimeric cationic unit [Zn₂(Hcit)(phen)₂(H₂O)₃]⁺ that connect each other by strong hydrogen bonds [O6?O4w 2.636(2); O7?O3w 2.630(3) Å]. In 2, the citrate ligand links each trinuclear unit [Zn₃(Hcit)₂(phen)₄] to generate an infinite 1D chain that extents into a 3D supramolecular structure by intra- and inter-molecular hydrogen bonds. Moreover, 1 and 2 exhibit strong fluorescence at room temperature.     

Novel oligonuclear ZnII4, ZnII8 and ZnII2NiII2 complexes with bis(benzoylacetone)-1,3-diiminopropan-2-ol

Reactions of bis(benzoylacetone)-1,3-diiminopropan-2-ol (abbreviated as H₃L) with zinc salts in the presence of triethylamine afforded the compounds [Zn₄(HL)₄]·4CH₃CN (1·4CH₃CN) and [Zn₈L₄(OH)₄]·2CH₃CN (2·2CH₃CN). Further reaction of 1 with Ni(CH₃COO)₂·4H₂O gave the heteronuclear species [Zn₂Ni₂(L)₂(CH₃O)₂(CH₃OH)₂] (3). The crystal structures of 1·4CH₃CN, 2·2CH₃CN and 3 were determined by the X-ray diffraction method.     

Two novel supramolecular isomers based on 2,2′-biimidazole derivative and zinc ions: Syntheses,structures and luminescent properties

Two Zn(II)-2,2′-biimidazole derivative supramolecular isomers 1 and 2 formulated as [Zn(L)] · 2H₂O (H₂L = 4,4′-(1H,1′H-2,2′-biimidazole-1,1′-diylbis(methylene))dibenzoic acid) have been synthesized, and structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography. Complex 1 exhibits a 2D four-connected network with (4³.6³) topology when the zinc center and the L^2? ligand act as four-connected nodes (or a distorted (4,4) grid if the [Zn₂(imidazole)₄] units are considered as four-connected nodes). Complex 2 shows a novel four-connected twofold interpenetrated net with (4².6².8²) topology when the zinc center and the L^2? ligand act as four-connected nodes (or a twofold interpenetrated α-Po topology when [Zn₂(imidazole)₄] units are identified as six-connected nodes). Moreover, complexes 1 and 2 both exhibit strong luminescent properties at room temperature.     

Three New Coordination Polymers Constructed from Mixed Ligands: Syntheses,Luminescence and Magnetism

Three new coordination polymers, namely, {[Cd(H₂bptc)(IP)(H₂O)]·2H₂O} _n (1), {[Mn₂(IP)₂(dstc)]·6H₂O} _n (2) and {[Zn₂(IP)₂(dstc)]·3H₂O} _n (3) (IP = 1H-imidazo[4,5-f][1,10]-phenanthroline, H₄bptc = 3,3′,4,4′-benzophenonetetracarboxylic acid, and H₄dstc = 3,3′,4,4′-diphenylsulfonetetracarboxylic acid) have rationally designed and characterized by single crystal X-ray diffraction. Polymer 1 shows a 1D ribbon-like structure. Although compounds 2 and 3 feature 2D grid networks, the coordinative modes of dstc ligand and the arrangements of IP ligand are very different. Furthermore, the luminescence properties for 1 and 3, as well as the magnetism of 2 are explored in detail.     

[Zn2(H2O)3(2,2′-bipy)2(btc)][Zn(H2O)(2,2′-bipy)(btc)] ·8H2O: a novel zinc–carboxylate complex consisting of independently cationic and anionic chains

A novel zinc complex, [Zn₂(H₂O)₃ (2,2^′-bipy)₂(btc)][Zn(H₂O)(2, 2^′-bipy)(btc)]·8H₂O (1), (H₃btc=1,3,5- benzenetricarboxylic acid, 2,2^′-bipy=2,2^′-bipyridine) has been prepared by hydrothermal reaction of H₃btc, Zn(CH₃CO₂)₂·2H₂O and 2,2^′-bipyridine at 180 °C and characterized by single-crystal X-ray diffraction analysis. Complex 1 consists of independently cationic and anionic chains. The hydrogen bonding interactions between chains extend 1 into a two-dimensional supramolecular architecture.     

Coordination assemblies of CdII/ZnII/CoII with the 3-(pyridin-4-yl) benzoate tecton: Structural diversity and properties

Three novel coordination polymers{[CdL₂(HL)(H₂O)]·(H₂O)}_n (1), [Zn₂(OH)L₃]_n (2) and [CoL₂(H₂O)]_n (3) have been hydrothermally synthesized from M(NO₃)₂·nH₂O (M^II = Cd^II, Zn^II and Co^II) and an unsymmetrical tecton 3-(pyridin-4-yl) benzoic acid (HL). All complexes show interesting structural patterns, namely, unprecedented 1D double-stranded supramolecular clasp for 1, novel (3,5,6)-connected helical tubular double layer for 2, 2-fold interpenetrating cds network for 3. The fluorescent and thermal properties of complexes 1, 2 and/or 3 have also been investigated.     

Ionothermal synthesis of a 3D Zn–BTC metal-organic framework with distorted tetranuclear [Zn4(μ4-O)] subunits

A zinc metal-organic framework (MOF), [Zn₄(BTC)₂(μ₄-O)(H₂O)₂], was synthesized with Zn(NO₃)₂ · 6H₂O and H₃BTC ligand (H₃BTC = 1,3,5-benzenetricarboxylic acid) by ionothermal synthesis in 1-ethyl-3-methylimidazolium bromide ionic liquid as solvent. The compound features a 3-D architecture constructed by linking [Zn₄(μ₄-O)] subunits with BTC³⁻ ligands. They are composed of two five-coordinated and two four-coordinated Zn ions, different from the [Zn₄(μ₄-O)] units of other MOFs. The effect of reaction conditions to the MOF structure is discussed.     

Syntheses and characterizations of two-dimensional polymers based on tetraimidazole tetraphenylethylene ligand with aggregation-induced emission property

Two new coordination polymers [Co(TIPE)(H₂O)₂]·Hbtc·CH₃CN·3H₂O (1) and [Cd(TIPE)_0.5(m-bdc)(H₂O)]·CH₃OH·H₂O (2) (TIPE = tetra(3-imidazoylphenyl)ethylene, H₃btc = 1,3,5-benzenetricarboxylate, m-H₂bdc = 1,3-benzenedicarboxylate) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and PXRD. Furthermore, the luminescent properties of complexes 1, 2 and TIPE ligand have also been investigated in the solid at room temperature.     

Assembly,Fluorescent and Adsorption Properties of Two Cadmium(II)/Cobalt(II) Coordination Complexes Functionalized by the Flexible Bis(Pyridyl)-bis(Amide) Ligand

A new cadmium(II) and a new cobalt(II) coordination complexes [Cd₅(BTB)₄(HL)₂]·2H₂O (1) and [Co(HBTB)(L)]·2H₂O (2) [H₃BTB?=?1,3,5-tri(4-carboxylphenyl)benzene, L?=?N,N′-bis(3-pyridyl)octandiamide] were prepared under the solvothermal conditions by the assembly of cadmium(II)/cobalt(II) chloride, the flexible bis(pyridyl)-bis(amide) ligand L and the aromatic tricarboxylic acid H₃BTB. The structures of complexes 1–2 have been characterized by X-ray single crystal diffraction analyses, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complex 1 is a 3D metal–organic network with the penta-nodal (2,4,4,5,6)-connected {4·6³·8·10}₂{4²·6⁵·8³}₂{4³·6³}₂{4⁶·8⁹}{6}₂ topology constructed from the 3D [Cd₅(BTB)₄]_n^2n? coordiantion framework and the protonated HL ligands. Complex 2 displays a binodal (4,4)-connected {6⁴·8·10}{6} topological 2D layered architecture based on the 1D [Co(HBTB)]_n chains and the 1D [CoL]_n chains, which are further linked by hydrogen bonding interactions to form a 3D supramolecular network. Moreover, the fluorescent properties of the cadmium(II) complex and the dyes adsorption performances of complexes 1–2 have been studied.     

A novel Zn6Co3 cluster-based heterometallic coordination polymer with PMG3 − linker formed via in situ decarboxylation from H4PMIDA

A novel Zn₆Co₃ cluster-based heterometallic coordination polymer, [Zn₆Co₃(PMG)₆(H₂O)₄]·12H₂O (1), has been hydrothermally synthesized, in which the PMG^3 − (N-(phosphonomethyl)glycinate) as a multifunctional ligand was firstly formed via in situ decarboxylation from original ligand N-(phosphonomethyl)imino-diacetic acid during the hydrothermal reaction. The complex was characterized by elemental analysis, FT-IR, powder X-ray diffraction, thermal analysis and single-crystal X-ray diffraction techniques. Its structure features a 2D framework constructed by [Zn₆Co₃(PMG)₆(H₂O)₄] pinwheel-like heteronuclear clusters, which contains rings with two tropisms. Through extensive O–H⋯O hydrogen bondings, the adjacent 2D layered structure further extends into a 3D supramolecular network. Moreover, the solid-state fluorescence property of this complex has also been investigated at room temperature, which exhibits a good fluorescent emission.     

A tetranuclear [Zn4(L)2(OAc)3(OH)] complex based on the Salen-type Schiff-base ligand H2L for effective bulk solvent-free melt ring-opening polymerization (ROP) of l-lactide

Through the self-assembly of the typical Salen-type Schiff-base ligand H₂L (H₂L = N,N′-bis(salicylidene)cyclohexane-1,2-diamine) and an excess of Zn(OAc)₂·2H₂O in the presence of Et₃N, a new tetranuclear complex [Zn₄(L)₂(OAc)₃(OH)] (1) with multiple active species and self-owned normal initiators was obtained and shown to efficiently catalyze the bulk solvent-free melt ring-opening polymerization (ROP) of l-lactide, giving the uniformly isotactic poly-l-lactides (PLLAs).     

Structures and photoluminescence of coordination polymers assembled from bifunctional ligand containing both tetrazole and imidazole groups

Three new coordination polymers, namely, {[Cu₂(IPT)(SO₄)(OH)(H₂O)]·H₂O}_n (HIPT = 5-(4-(1H-imidazol-1-yl)phenyl)- 1H-tetrazolate, 1), {[Cd₂(IPT)(NPA)(OH)]·H₂O}_n (H₂NPA = 5-nitroisophthalic acid, 2), and {[Zn₂(IPT)(IDC)(H₂O)]·3H₂O}_n (H₃IDC = 1H-imidazole-4,5-dicarboxylic acid, 3), were assembled from a bifunctional organic ligand containing both tetrazole and imidazole groups with/without the aid of carboxylate coligands. Compound 1 possesses 2D structure built by 1D [Cu₂(IPT)(SO₄)(OH)]_n secondary building blocks and IPT⁻ linkers. The 2D networks are linked into 3D supramolecular framework via water chains in helical conformation. Compound 2 displays 3D pillar-layer framework with 2D layers based on tetranuclear Cd(II) SBUs and NPA^2 − pillars. Compound 3 exhibits a 3D framework constructed from the interconnection of 1D [Zn-IDC]_n chains and binuclear Zn₂(IPT)₂ rings. The thermal stabilities of porous compound 3 and luminescent properties of compounds 2 and 3 have also been studied in detail. They exhibit intense solid-state fluorescent emissions at room temperature.     

Hydrothermal Syntheses and Crystal Structures of Three Zn(II) Coordination Compounds Constructed with 3,5-Pyrazoledicarboxylic Acid

Three novel metal–organic coordination compounds, [Zn(Hdcp)(H₂O)₄]·1.5H₂O (1), [Zn(Hdcp)(H₂O)₂]_∞ (2) and [Zn₃(dcp)₂(H₂O)₅]_∞ (3) with the ligand 3,5-pyrazoledicarboxylic acid were prepared by the hydrothermal method. The complexes were structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Compound 1 is a mononuclear molecule that is linked into a 3D supramolecular framework via N–H···O and O–H···O hydrogen bonds. In 2, two types of carboxylic bridges were found between Zn^II ions to form a 1D double-chain. The 1D chains were further construct into a 3D structure by hydrogen bonds. Trinuclear 3 consists of 1D bi-infinite parallelogram chains of [Zn₃(dcp)₂(H₂O)₃] trimers. In the basic trinuclear unit a further bridging mode of the ligand is seen where two dcp^3? ligands chelate three Zn^II ions by utilizing five donors of the dcp^3? ligand. The photoluminescent properties of 1, 2 and 3 were investigated.     

Three New Metal–Organic Polymers Based on Flexible 3-(4-(Carboxymethoxy) Phenyl) Propanoic Acid: Crystal Structures, Luminescent and Magnetic Properties

Three new metal–organic coordination complexes, [Zn₂L(bpp)₂Cl₂] _n (1), [ZnL(bipy)] _n (2), [NiL(bipy)(H₂O)] _n (3), have been synthesized through hydrothermal reactions of flexible 3-(4-(carboxymethoxy)phenyl) propanoic acid(H₂L) with different pyridyl-containing 1,3-bis(4-pyridyl)propane(bpp) or 4,4′-bipyridine(bipy) ligand, and they are characterized by elemetal analysis and single-crystal X-ray diffraction techniques. Complex 1 has a 2-D layer supramolecular network composed of 1-D distorted trapezoidal chains via C–H···π stacking interactions. Complex 2 displays a 2-D lattice-shaped layer structure. Complex 3 has three kinds of O–H···O intermolecular hydrogen bonds, exhibiting a 3-D supramolecular framework. The luminescent properties of complex 1 and 2 have indicated the mixture characteristic of intraligand and ligand-to-ligand charge transition. The magnetic property of 3 has shown the ferromagnetic coupling between Ni²⁺ ions.     

New dinuclear cobalt (ΙΙ, ΙΙΙ) and tetranuclear manganese (ΙΙΙ) complexes assembled by a polydentate Schiff-base ligand: synthesis,structure and magnetic properties

The reactions of 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H₄L) and Mn(ClO₄)₂·6H₂O or Co(SCN)₂·3H₂O in the presence of triethylamine in methanol led to the formation of two new complexes [Mn^ΙΙΙ₄(HL)₂(H₂L)₂(CH₃OH)₄]·4CH₃OH·(ClO₄)₂ (1) and [Co^ΙΙCo^ΙΙΙ(H₂L)₂(CH₃OH)(SCN)]·1.5CH₃OH·1.5H₂O (2), respectively. According to structural data and magnetic properties tetranuclear complex 1 contains four homo-valence manganese (ΙΙΙ) atoms, while in the binuclear complex 2 composed of hetero-valence bi- and trivalent cobalt (ΙΙ, ΙΙΙ) atoms. Weak antiferromagnetic exchange interactions between neighboring manganese ions in 1 have place. χ_MT for 2 was fitted using a model of isolated cobalt (ΙΙ) ion with zero-field splitting parameters and the study confirms its mixed valence Co^ΙΙ/Co^ΙΙΙ nature. No slow magnetic relaxation effects were observed for both complexes in the absence of an applied dc magnetic field.     

Six- and five-coordinated complexes of Co(II) with 2-(2′-pyridyl)quinoxaline. Crystal structures of the complexes [CoLCl2(DMF)] and [CoL2(H2O)2](ClO4)2·H2O·2CH3OH

Reaction of Co(II) perchlorate hexahydrate and anhydrous Co(II) chloride with the ligand 2-(2′-pyridyl)quinoxaline (L) leads to the formation of the novel five- and six-coordinated complexes CoLCl₂(DMF) (1) and [CoL₂(H₂O)₂](ClO₄)₂·H₂O·2CH₃OH (2), correspondingly. The crystal structures of the above complexes show a trigonal bipyramidal geometry around the metal atom for complex 1 and a distorted octahedral geometry for complex 2.     

A Novel Aqua Ligand Assisted Water Octamer Confinement in the Hydrophilic Channels of a Zn(II) Supramolecular Architecture

A new two-dimensional polymeric [Zn₂(4-pzpt)(btc)(H₂O)₂·3H₂O] (1) (4-Hpzpt = 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole, H₃btc = 1,2,3-benzenetricarboxylate), has been synthesized and structurally characterized and features a 3D supramolecular framework with 1D hydrophilic channels formed by the interlayer hydrogen bonds. An unprecedented aqua ligand assisted octameric water cluster consisting of a quasiplanar cyclic hexameric core and two dangling water molecules is captured in 1. The thermal stability and solid state fluorescent property of 1 are discussed.     

Conformational isomerism of a flexible fluorinated bis-pyridinecarboxamide ligand in the structural direction of two distinct layered CuII coordination polymers

Reaction of a flexible pyridinecarboxamide ligand N,N′-[(2,3,5,6-tetrafluoro-1,4-phenylene) bis(methylene)]bis(pyridine-4-carboxamide) (H₂tfpbbp) with Cu^II chloride or perchlorate affords two coordination polymers {[Cu(H₂tfpbbp)(tfpbbp)(H₂O)] · 2DMF · 4H₂O}_n (1) and {[Cu(H₂tfpbbp)₂(ClO₄)₂] · 3H₂O}_n (2). Both complexes have 2-D (4,4) layered networks extended by the exo-bidentate bridging ligands, which however consist of distinct [Cu–ligand]₄ meshes owing to the conformational difference of ligands. Their spectroscopic, thermal, and fluorescence properties have also been investigated.     

Tracking the Transformation Process of a Pair of Zn(II) Coordination Clusters: Crystallography and Mass Spectrometry

Two zinc clusters Zn₄(H₃L)₄(NO₃)₄?5H₂O ( Zn₄ , H₄L=(1,2‐bis(1H‐benzo[d]imidazol‐2‐yl)ethane‐1,2‐diol) and [Zn₅(H₂L′)₆](NO₃)₄]?8H₂O?2CH₃OH ( Zn₅ , H₃L′=(1,2‐bis(benzo[d] imidazol‐2‐yl)‐ethenol) have been obtained by the reaction of Zn(NO₃)₂?6H₂O with H₄L at 80 °C or 140 °C under solvothermal condition. Powder X‐ray Diffraction (PXRD) of precipitate and Electrospray Ionization Mass Spectrometry (ESI‐MS) of reaction solution revealed the existence of transformation behavior from Zn₄ to Zn₅ by increasing the temperature from 80 °C to 140 °C, or directly heating Zn₄ at 140 °C via solvothermal reaction. Here we proposed a possible mechanism involves split process of Zn₄ and reassembly to form Zn_{5 .} ESI‐MS for single crystals revealed [Zn₄(H₃L)₄?3H]⁺ splits to [Zn(H₃L)]⁺ via [Zn₂(H₃L)₂?H]⁺. Time dependent ESI‐MS of reaction solution revealed the [Zn(H₂L′)]⁺→[Zn₂(H₂L′)₂?H]⁺→[Zn₅(H₂L′)₆?H]³⁺ stepwise assembly. It also has been captured the in situ reaction mainly occurs in the step of [Zn(H₃L)]⁺ to [Zn(H₂L′)]⁺.     

Amino acid template-synthesis and characterization of three-dimensional metal phosphate/phosphite networks

In this contribution, two novel metal phosphate/phosphate, namely [Zn₂(HPO₃)₂(H₂O)₄]·H₂O (1) and Cd₅(HPO₄)₂(PO₄)₂(H₂O)₄ (2), were obtained by amino acid template-synthesis under mild hydrothermal conditions. X-ray crystallographic studies show that the inorganic network of 1 contains binuclear zinc building units with large 16-ring channels along [1 0 0] directions. The structure of 2 consists of asymmetric pentanuclear chiral motifs. It is notable that two centered pentanuclear cadmium structure motifs form a mesomeric unit, which is linked by bridging oxygen atoms to construct 3D inorganic network.