A comparison of solution and solid state coordination environments for calcium(II), zirconium(IV), cadmium(II) and mercury(II) complexes with dipicolinic acid and methylimidazole derivatives

Four new supramolecular compounds, (2-mimH)[Ca(pydcH)₃][Ca(pydcH₂)(pydc)(H₂O)₂]·4H₂O (1), (1-mimH)₂[Zr(pydc)₃] (2), (2-mimH)₂[Cd(pydc)₂]·8H₂O (3), and (2-mimH)₂[Hg(pydc)₂]·8H₂O (4) [where pydcH₂ = pyridine-2,6-dicarboxylic acid (dipicolinic acid), 1-mim = 1-methylimidazole, and 2-mim = 2-methylimidazole], have been synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–vis, ¹H NMR, and ¹³C NMR), thermal (TG/DTG/DTA) analysis as well as single-crystal X-ray diffraction. All four compounds are proton-transfer salts of the methylimidazolium cations and metal complex anions that crystallized from a solution of pyridine-2,6-dicarboxylic acid, methylimidazole, metal nitrates or chlorides as starting materials. The coordinating dicarboxylic acid is deprotonated at the carboxyl group and methylimidazole is protonated to balance the charge. In the crystal structures of 1–4, hydrogen bonding and π–π stacking play important roles. Water clusters are formed in 1, 3, and 4. The equilibrium constants of dipicolinic acid (pydc) and methylimidazole derivatives (1-mim and 2-mim), pydc-2-mim, pydc-1-mim proton-transfer systems as well as those of their complexes were investigated by a potentiometric pH titration method. The stoichiometries of most of the complex species in solution were very similar to the cited crystalline metal ion complexes.     

Novel Complexes of Gallium(III), Indium(III), and Thallium(III) with Pyridine‐Containing Proton Transfer Ion Pairs Obtained from Dipicolinic Acid – Synthesis,Characterization and X‐ray Crystal Structure

Three new complexes of group thirteen metals, gallium(III), indium(III), and thallium(III) with proton transfer compounds, obtained from 2,6‐pyridinedicarboxylic acid (dipicolinic acid), were synthesized and characterized using elemental analysis, IR, ¹H and ¹³C NMR spectroscopy and single crystal X‐ray diffraction. The gallium(III) and indium(III) complexes were prepared using (pydaH₂)(pydc) (pyda = 2,6‐pyridinediamine, pydcH₂ = dipicolinic acid) and thallium(III) complex was obtained from (creatH)(pydcH) (creat = creatinine). The chemical formulae and space groups of the complexes are (pydaH)[Ga(pydc)₂] · 3.25H₂O · CH₃OH, ( 1 ), [In(pydc)(pydcH)(H₂O)₂] · 5H₂O, Pna2₁ ( 2 ) and [Tl₂(pydcH)₃(pydc)(H₂O)₂], ( 3 ). Non‐covalent interactions such as ion‐pairing, hydrogen bonding and π‐π stacking are discussed. The complexation reactions of pyda, pydc, and pyda + pydc with In³⁺ and Ga³⁺ ions in aqueous solution were investigated by potentiometric pH titrations, and the equilibrium constants for all major complexes formed are described.     

Metal–organic polymers of Sr(II) and Ce(IV): structural studies,supramolecular synthons,and potentiometric measurements

Two metal–organic coordination polymers based on a salt, (pydcH)₃·(pipzH₂)_1.5·(H₂O)_3.7, between pyridine-2,6-dicarboxylic acid, pydcH₂, and piperazine, pipz, formulated as (pipzH₂)[Sr(pydc)₂(H₂O)₂]_n·4H₂O and [Ce(pydc)₂(H₂O)₂]_n·4H₂O were prepared. The synthesis, IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, supramolecular synthons, and potentiometric measurements were investigated. The chemical environment around each Sr(II) or Ce(IV) was a distorted tricapped trigonal prism. The butterfly- and ladder-like structures of these complexes were bridged by oxygens of (pydc)^2– and M–O(pydc)–M bonds. In the crystal structure, intermolecular O–H?O, N–H?O, and C–H?O hydrogen bonds result in the formation of supramolecular structures. The stoichiometry and stability of the pydc–pipz system with Sr(II) in aqueous solution were investigated by potentiometric titration. The stoichiometry of complex species in solution was found to be similar to the cited crystalline metal ion complexes.     

Syntheses of crystal structures and in vitro cytotoxic activities of new copper(II) complexes of pyridine-2,6-dicarboxylate

[Cu(pydc)(im)]_n (1), [Cu(pydc)(mim)₃]?2H₂O (2), [Cu(pydc)(ampy)(H₂O)]?H₂O (3), and [Cu(pydc)(phen)][Cu(Hpydc)₂] (4) (H₂pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, im = imidazole, mim = 2-methylimidazole, ampy = 2-amino-4-methylpyridine, and phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, spectroscopic measurements (UV–vis and IR spectra) and single crystal X-ray diffraction. Complexes 1, 2 and 3 were studied by thermogravimetric analysis from ambient temperature to 1100 K under nitrogen and thermal stabilities were investigated. The effects of complexes on proliferation of fibrosarcoma cells were investigated using the Quick Cell Proliferation Assay. The cell viability changes depend on the concentrations and type of complexes. According to cell proliferation/viability data, 4 was determined to be the most cytotoxic.     

A series of 3d–4f heterometallic MOFs: syntheses,structures, optical,and electrochemical properties

Abstract

A series of heterometallic metal-organic frameworks (MOFs) employing pyridine-2,6-dicarboxylate and 1,10-phenanthroline as ligands have been synthesized hydrothermally. In isostructural compounds 1–3 [Ln(pydc)₃Cu₂(phen)₄]·I·× H₂O (Ln?=?La (1), Nd (2), Dy (3); x?=?6, 5, 5), the metalloligand [Ln(pydc)₃] assembles with [Cu(phen)₂] units to construct a dodecanuclear cluster via Cu–O bonds and π–π interactions. The clusters are further stacked into three-dimensional supramolecular frameworks with nano-sized cavities. In [La(Hpydc)(pydc)₂Zn(phen)₃]·3H₂O (4), the metalloligand [Ln(Hpydc)(pydc)₂] assembles with [Zn(phen)₃] units to construct a tetranuclear cluster via electrostatic interaction and π–π interaction. This work reveals that the changes of lanthanide metalloligands and the coordination pattern of 3d transition centers would result in significant variation in the final structures. The thermal, optical, and electrochemical properties have been well investigated.     

A Novel Proton Transfer Compound Containing 2, 6‐Pyridinedicarboxylic Acid and Creatinine and its Zinc(II) Complex — Synthesis,Characterization, Crystal Structure,and Solution Studies

The 1:1 proton transfer compound LH₂, (creatH)⁺ (pydcH)^?, has been prepared from the reaction of creatinine, creat, and dipicolinic acid, pydcH₂, (2, 6‐ pyridinedicarboxylic acid) and characterized using IR, ¹H and ¹³C NMR spectroscopy. The first coordination complex (creatH)[Zn(pydc)(pydcH)]·4H₂O, was prepared using LH₂ and zinc(II) nitrate, and characterized using IR, ¹H and ¹³C NMR spectroscopy and single crystal X‐ray crystallography. The crystal system is triclinic with space group with two molecules per unit cell. The unit cell dimensions are a = 8.085(2) Å, b = 10.802(4) Å, c = 13.632(4) Å, α = 104.98(2)°, β = 90.31(2)° and γ = 92.55(3)°. The structure has been refined to a final value for the crystallographic R factor of 0.0381 based on 3003 reflections. The zinc atom is six‐coordinated with a distorted octahedral geometry. The (pydc)^2? and (pydcH)^? units are almost perpendicular to each other. Extensive hydrogen bondings between carboxylate groups, (creatH)⁺ and water molecules throughout the zinc(II) complex as well as π–π stacking and ion pairing play important roles in stabilizing the corresponding lattices. The protonation constants of the building blocks of the pydcH₂‐creat adduct, the equilibrium constants for the reaction of (pydc)^2? with creat and the stoichiometry and stability of the Zn^II complex with LH₂ in aqueous solution were accomplished by potentiometric pH titration. The solution studies support a self‐associated (creatH)⁺(pydcH)^? as the most abundant species at pH = 3.4. The stoichiometry of the crystalline complex (i.e. (creatH) [Zn(pydc)(pydcH)])and that of the most abundant species detected in solution were found the same.     

Pyridine-2,5-dicarboxylic acid complexes of nickel(II) with 2,2′-bipyridine and 1,10-phenanthroline coligands; syntheses,crystal structures,spectroscopic and thermal studies

Two pyridine-2,5-dicarboxylic acid (pydcH₂) complexes of nickel(II) with 2,2′-bipyridine and 1,10-phenanthroline were synthesized and characterized by elemental, spectroscopic, thermal analysis, magnetic measurements and single crystal X-ray diffraction techniques. Both [Ni(pydc)(bipy)₂]·7H₂O and [Ni(pydc)(phen)₂]·6.5H₂O crystallize in the monoclinic system and P2₁/c space group. The Ni(II) ions are coordinated by two bidentate bipy or phen ligands and one pydc dianion in a distorted octahedral geometry. The pydc ligand is coordinated through the pyridine nitrogen atom and oxygen atom of carboxyl group as a bidentate ligand. Both carboxylate groups of pydc are deprotonated but only the 2-carboxylate is coordinated to the metal. Thermal decompositions of the complexes have been studied over the range 30–600 °C on heating in a static air atmosphere.     

Piperazinediium,Zr(IV) and Ce(IV) pyridine-2,6-dicarboxylates: Syntheses,characterizations, crystal structures, ab initio HF,DFT calculations and solution studies

The novel title compounds, (pipzH₂)_1.5(pydcH)₃·3.7H₂O, 1, (pipzH₂)[Zr(pydc)₃]·8H₂O, 2 and (pipzH₂)[Ce(pydc)₃]·8H₂O, 3 in which pydcH₂ is pyridine-2,6-dicarboxylic acid and pipz is piperazine were obtained in aqueous solution. The compounds were characterized by IR, ¹H NMR and ¹³C NMR spectroscopy, elemental analyses, and X-ray crystallography. Compound 1 is resulted from proton transfer between pydcH₂ and pipz. However, compounds 2 and 3 are resulted from complexation of 1 and corresponding metallic salts. Both compounds 2 and 3 contain three pyridine-2,6-dicarboxylate species as tridentate ligands, one piperazinediium as counter ion, and eight-uncoordinated water molecules in the asymmetric unit. In both structures each M(IV) is coordinated in a distorted tricapped trigonal prism geometry by three nitrogen and six oxygen atoms of carboxylate groups of three (pydc)²⁻ fragments. In the crystal structures of 1, 2 and 3, extensive O–H···O, N–H···O and C–H···O hydrogen bonds as well as electrostatic forces, C–H···π, C–O···π and π–π stacking play important roles in stabilizing structures. The geometrical parameters of the [M(pydc)₃]²⁻ anionic complexes, where M = Ce(IV), Zr(IV) have been optimized with the B3LYP method of density functional theory (DFT) and ab initio Hartree–Fock (HF) methods for comparison. In addition, we have studied the structures of (pydc)²⁻ anion and its mono and doubly protonated forms, (pydcH)⁻ and pydcH₂. The electronic properties of the anionic complexes and ligands have been investigated based on the natural bond orbital (NBO) analysis at the B3LYP method which verifies that the synergistic effect has been occurred in the title complexes. In solution study of 2, the stoichiometry and stability constant of complexation of pipz, pydc, pydc–pipz proton transfer system and Zr(IV) ion in aqueous solution were investigated by potentiometric method.     

Synthesis,Characterization, and Crystal Structure of a Chromium(III)‐Complex Containing 2,6‐Pyridinedicarboxylic Acid and 1,10‐Phenanthroline

The reaction of solution 2,6‐pyridinedicarboxylic acid and 1,10‐phenanthroline ( 1 ) with CrCl₃·6H₂O led to the complex [Cr(phen)(pydc)(H₂O)][Cr(pydc)₂]·4H₂O ( 2 ) (phen is 1,10‐phenanthroline and pydcH₂ is 2,6‐pyridinedicarboxylic acid). 2 was characterized by elemental analysis, IR spectroscopy and single‐crystal structure determination. Crystal data for 2 at ?80 °C: triclinic, space group , a = 818.5(1), b = 1492.2(1), c = 1533.6(2) pm, α = 76.45(1)°, β = 84.22(1)°, γ = 77.99(1)°, Z = 2, R₁ = 0.0416.     

Two supramolecular complexes of gallium(III) with different adduct ion pairs containing pyridine-2,6-dicarboxylic acid: Syntheses,characterization, crystal structures and computational study

Two complexes of gallium(III) with adduct ion pair compounds containing pyridine-2,6-dicarboxylic acid and two different Lewis bases are synthesized. The chemical formulae are (dmpH)[Ga(pydc)₂]·2H₂O, (1) and (bpyH₂)_1/2(pydcH₂)_1/2[Ga(pydc)₂]·4H₂O, (2) where pydc, dmp, and bpy are pyridine-2,6-dicarboxylate, 2,9-dimethyl-1,10-phenanthroline, and 4,4′-bipyridine respectively. The two crystal structures illustrate that the Ga^III ion is six-coordinated by two pyridine-2,6-dicarboxylates. Hydrogen bonds as well as other noncovalent interactions such as ion-pairing, C-O...π, C-H...π, and π...π stacking play an important role in the formation of supramolecular systems. Particular attention is given to the molecular geometries and NMR properties of the complexes from the computational point of view. The electronic properties of the complexes are analysed using the parameters derived from the atoms in molecules (AIM) and natural bond orbital (NBO) methodologies at the B3LYP/6-311++G(2d,2p) computational level.     

Chromium(III) and Calcium(II) complexes obtained from dipicolinic acid: Synthesis, characterization, X-Ray crystal structure and solution studies

The Cr(III) and Ca(II) complexes (dmpH)[Cr(pydc)₂]?H₂O (1) and [Ca₂(pydc)₂(H₂O)₆].2pydcH₂ (2) were synthesized by reaction of 2,9-dimethyl-1,10-phenanthroline (dmp) and pyridine-2,6-dicarboxylic acid (pydcH₂) with Cr(NO₃)₃ and Ca(NO₃)₂, respectively, and characterized using IR spectroscopy, single crystal X-ray diffraction method and solution studies. The space group and crystal system of these two compounds are P2 ₁/c and monoclinic. The crystal dimensions are a = 9.785(3) Å, b = 25.671(4) Å, c = 9.3402(16) Å, β = 90.790(17)° for (1) and a = 9.1319(4) Å, b = 14.8430(8) Å, c = 12.2449(7) Å, β = 98.227(5)° for (2). In complex (1), a water molecule presents in the crystal packing, linking the anionic and cationic fragments together by hydrogen bonding and thus increases the stabilization of crystal lattices. In complex (2), the coordinated water molecules relate each dimer to adjacent dimers forming infinite molecular ribbons by strong hydrogen bondings. Hydrogen bonding and ion pairing play an important role in stabilizing these crystals. The complexation reactions of pydc, dmp and pydc+dmp with Cr³⁺ and Ca²⁺ ions in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed were evaluated.     

Syntheses,crystal, molecular structures,and solution studies of Cu(II), Co(II), and Zn(II) coordination compounds containing pyridine-2,6-dicarboxylic acid and 1,4-pyrazine-2,3-dicarboxylic acid: comparative computational studies of Cu(II) and Zn(II) complexes

Structural Chemistry - Three new coordination compounds of Cu(II), Co(II), and Zn(II) based on different dicarboxylic acids formulated as (AcrH)[Cu(pydc)(pydcH)]·5H2O (1)...     

Supramolecular networks constructed by cationic copper(II) complexes incorporating hybrid water–anionic polymeric assemblies

Two complexes, [Cu₂(TFSA)(2,2′-bpy)₄]?·?TFSA?·?8H₂O (1) and {[Cu(4,4′-bpy)(H₂O)₂]?·?TFSA?·?6H₂O} _n (2) (H₂TFSA?=?tetrafluorosuccinic acid, 2,2′-bpy?=?2,2′-bipyridine, and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized and structurally characterized by X-ray structural analyses. Complex 1 is a binuclear molecule bridged by TFSA ligands; 2 is a 1-D chain bridged by 4,4′-bpy ligands. The asymmetric units of the two complexes are composed of cationic complexes [Cu₂(TFSA)(2,2′-bpy)₄]²⁺ (1) and [Cu(4,4′-bpy)(H₂O)₂]²⁺ (2), free TFSA anion, and independent crystallization water molecules. A unique 2-D hybrid water–TFSA anionic layer by linkage of {[(H₂O)₈(TFSA)]^2?} _n fragments consisting of 1-D T6(0)A2 water tape and TFSA anionic units by hydrogen bonds in 1 was observed. Unique 2-D hybrid water–TFSA anionic layer generated by the linkage of {[(H₂O)₆(TFSA)]^2?} _n fragments consisting of cyclic water tetramers with appended water molecules and TFSA anionic units, and 1-D metal–water tape [Cu–H₂O?···?(H₂O)₆?···?H₂O^?] _n in 2 were found. 3-D supramolecular networks of the two complexes consist of cationic complexes and water–TFSA anionic assemblies connected by hydrogen bonds.     

Synthesis,spectroscopic, and thermal analyses of trinuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with some sulfa derivatives

New bi- and trihomonuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with sulfa-guanidine Schiff bases have been synthesized for potential chemotherapeutic use. The complexes are characterized using elemental and thermal (TGA) analyses, mass spectra (MS), molar conductance, IR, ¹H-NMR, UV-Vis, and electron spin resonance (ESR) spectra as well as magnetic moment measurements. The low molar conductance values denote non-electrolytes. The thermal behavior of these chelates shows that the hydrated complexes lose water of hydration in the first step followed by loss of coordinated water followed immediately by decomposition of the anions and ligands in subsequent steps. IR and ¹H-NMR data reveal that ligands are coordinated to the metal ions by two or three bidentate centers via the enol form of the carbonyl C=O group, enolic sulfonamide S(O)OH, and the nitrogen of azomethine. The UV-Vis and ESR spectra as well as magnetic moment data reveal that formation of octahedral [Mn₂L¹(AcO)₂(H₂O)₆] (1), [Co₂(L¹)₂(H₂O)₈] (2), [Ni₂L¹(AcO)₂(H₂O)₆] (3), [Mn₃L²(AcO)₃(H₂O)₉] (5), [Co₃L²(AcO)₃(H₂O)₉] · 4H₂O (6), [Ni₃L²(AcO)₃(H₂O)₉] · 7H₂O (7), [Mn₃L³(AcO)₃(H₂O)₆] (9), [Co₂(HL³)₂(H₂O)₈] · 4H₂O (10), [Ni₃L³(AcO)₃(H₂O)₉] (11), [Mn₃L⁴(AcO)₃(H₂O)₉] · H₂O (13), [Co₂(HL⁴)₂(H₂O)₈] · 5H₂O (14), and [Ni₃L⁴(AcO)₃(H₂O)₉] (15) while [Zn₂L¹(AcO)₂(H₂O)₂] (4), [Zn₃L²(AcO)₃(H₂O)₃] · 2H₂O (8), [Zn₃L³(AcO)₃(H₂O)₃] · 3H₂O (12), and [Zn₃L⁴(AcO)₃(H₂O)₃] · 2H₂O (16) are tetrahedral. The electron spray ionization (ESI) MS of the complexes showed isotope ion peaks of [M]⁺ and fragments supporting the formulation.     

Crystal Structures and Solution Studies of Two Novel Zinc(II) Complexes of a Proton Transfer Compound Obtained from 2, 6‐Pyridinedicarboxylic Acid and 1, 10‐Phenanthroline: Observation of Strong Intermolecular Hydrogen Bonds

The proton transfer compound LH₂ , (phenH⁺)₂(pydc^2—), has been prepared from 1, 10‐phenanthroline, phen, and 2, 6‐pyridinedicarboxylic acid, (dipicolinic acid), pydcH₂. Characterization was performed using solution and solid phase CP/MAS ¹³C NMR and IR spectroscopy. The reactions of this adduct with ZnSO₄·7H₂O and Zn(NO₃)₂·4H₂O give the complexes, [Zn(pydc)₂][Zn(phen)₂(H₂O)₂]·7H₂O (1) and [Zn(phen)₃]₄(H(Hpydc)₂)(NO₃)₇·26H₂O (2) , respectively. These complexes were characterized by ¹H and ¹³C NMR spectroscopy and single crystal X‐ray analysis. The complexes crystallize in the triclinic space group P1 with Z = 2. The unit cell dimensions for complex 1 and 2 are: a = 9.9838(9) Å, b = 14.7483(13) Å, c = 14.8365(13) Å and a = 12.640(4) Å, b = 15.855(5) Å, c = 21.830(7) Å, respectively. In complex 1 (pydc^2—) and phen, are tri‐ and bidentate ligands, respectively, and an anionic [Zn(pydc)₂]^2— and cationic [Zn(phen)₂(H₂O)₂]²⁺ complex are formed simultaneously. In complex 2 , three phen participate in complexation leaving hydrogen‐bis(pyridine‐2‐carboxylate), (H(Hpydc)₂)^— as a supramolecular anion. The fragments (H(Hpydc)₂)^—, 7 NO₃^—, and 26 H₂O in complex 2 are joined together by extensive and strong H‐bonding; therefore, the structure is composed of [Zn(phen)₃]₄⁸⁺, and an anionic hydrogen bond supramolecular assembly with the formula, {(H(Hpydc)₂(NO₃)₇)^8— · 26H₂O}_n. The anionic species (H(Hpydc)₂)^— has a special position at the inversion center, as well as one of the NO₃^— anions, which is disordered over the inversion center. Most of the hydrogen bonds in complex 2 represent strong H‐bonding. The protonation constants of the building blocks of the pydc‐phen adduct, the equilibrium constants for the reaction of (pydc^2—) with phenanthroline and the stoichiometry and stability of the Zn^II complex with LH₂ on aqueous solution were determined by potentiometric pH titration. The solution study results support self‐association between (pydc^2—) and (phenH⁺) with a stoichiometry for the Zn(II) complex similar to that observed for the isolated crystalline complex.     

Novel platinum(II) and (IV) complexes of naphthaldimine schiff bases

Naphthaldimines containing N₂O₂ donor centers react with platinum(II) and (IV) chlorides to give two types of complexes depending on the valence of the platinum ion. For [Pt(II)], the ligand is neutral, [(H₂L¹)PtCl₂]·3H₂O (1) and [(H₂L³)₂Pt₂Cl₄]·5H₂O (3), or monobasic [(HL²)₂Pt₂Cl₂]·2H₂O (2) and [(HL⁴)₂Pt]·2H₂O (4). These complexes are all diamagnetic having square-planar geometry. For [Pt(IV)], the ligand is dibasic, [(L¹)Pt₂Cl₄(OH)₂]·2H₂O (5), [(L²)Pt₃Cl₁₀]·3H₂O (6), [(L³)Pt₂Cl₄(OH)₂]·C₂H₅OH (7) and [(L⁴)Pt₂Cl₆]·H₂O (8). The Pt(IV) complexes are diamagnetic and exhibit octahedral configuration around the platinum ion. The complexes were characterized by elemental analysis, UV-Vis and IR spectra, electrical conductivity and thermal analyses (DTA and TGA). The molar conductances in DMF solutions indicate that the complexes are non-ionic. The complexes were tested for their catalytic activities towards cathodic reduction of oxygen.     

Structural diversity controlled by alkali/alkaline earth metals for heterometallic AeI/AeII-ZnII coordination polymers based on 4-nitrobenzene-1,2-dicarboxylate

Six heterometallic Zn(II) coordination polymers, Zn(H₂O)₃(FNA) (1), [NH₄]₂[Zn(H₂O)₂(FNA)₂] (2), [ZnNa₂(FNA)₂]·3H₂O (3), [ZnK₂(FNA)₂]·H₂O (4), [ZnRb₂(FNA)₂]·2H₂O (5) and [ZnMg(FNA)₂]·4H₂O (6) (H₂FNA = 4-nitrobenzene-1,2-dicarboxylic acid), were synthesised by introducing different alkali/alkaline earth (Ae^I/Ae^II) metals. These complexes exhibit diverse structures with the different Ae^I/Ae^II metals used and distinct ligand coordination modes the ions provide. For 1 and 2, the Zn(II) centres with distorted octahedra are connected by FNA to form 1-D chain structures. The Zn(II) centres in 3–6 with distorted tetrahedra are linked by FNA to form 2-D anionic grid layers. For 3–5, these 2-D anionic grid layers are connected by alkali metal (Na, K and Rb) with the O–Ae^I–O connectivity to exhibit 3-D framework structures, while 6 features a 2-D Zn–Mg network. Luminescence properties of 1–6 have been investigated.     

Hexaaquacobalt(II) and hexaaquanickel(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate

The title complexes, hexaaquacobalt(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate, [Co(H₂O)₆][Bi₂(C₇H₄NO₄)₄]·2H₂O, (I), and hexaaquanickel(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate, [Ni(H₂O)₆][Bi₂(C₇H₄NO₄)₄]·2H₂O, (II), are isomorphous and crystallize in the triclinic space group P. The transition metal ions are located on the inversion centre and adopt slightly distorted MO₆ (M = Co or Ni) octahedral geometries. Two [Bi(pydc)₂]⁻ units (pydc is pyridine‐2,6‐dicarboxylate) are linked via bridging carboxylate groups into centrosymmetric [Bi₂(pydc)₄]²⁻ dianions. The crystal packing reveals that the [M(H₂O)₆]²⁺ cations, [Bi₂(pydc)₄]²⁻ anions and solvent water molecules form multiple hydrogen bonds to generate a supramolecular three‐dimensional network. The formation of secondary Bi...O bonds between adjacent [Bi₂(pydc)₄]²⁻ dimers provides an additional supramolecular synthon that directs and facilitates the crystal packing of both (I) and (II).     

Synthesis,crystal structures,and fluorescence properties of (RS)-2-methylglutarato Zn(II), Cd(II) complexes

Reactions of fresh M(OH)₂ (M = Zn²⁺, Cd²⁺) precipitate and (RS)-2-methylglutaric acid (H₂MGL), 2,2′-bipyridine (bipy), or 1,10-phenanthroline (phen) in aqueous solution at 50°C afforded four new metal–organic complexes [Zn₂(bipy)₂(H₂O)₂(MGL)₂] (1), [Zn₂(phen)₂(H₂O)(MGL)₂] (2), [Cd(bipy)(H₂O)(MGL)] · 3H₂O (3), and [Cd(phen)(H₂O)(MGL)] · 2H₂O (4), which were characterized by single crystal X-ray diffraction, IR spectra, TG/DTA analysis as well as fluorescence spectra. In 1, the [Zn(bipy)(H₂O)]²⁺ moieties are linked by R- and S-2-methylglutarate anions to build up the centrosymmetric dinuclear [Zn₂(bipy)₂(H₂O)₂(MGL)₂] molecules. In 2, the 1-D ribbon-like chains [Zn₂(phen)₂(H₂O)(MGL)₂] _n can be visualized as from centrosymmetric dinuclear [Zn₂(phen)₂(H₂O)₂(MGL)₂] units sharing common aqua ligands. Both 3 and 4 exhibit 1-D chains resulting from [Cd(bipy)(H₂O)]²⁺ and [Cd(phen)(H₂O)]²⁺, respectively, bridged alternately by R- and S-2-methylglutarate anions in bis-chelating fashion. The intermolecular and interchain π···π stacking interactions form supramolecular assemblies in 1 and 1-D chains in 2–4 into 2-D layers. The hydrogen bonded lattice H₂O molecules are sandwiched between 2-D layers in 3 and 4. Fluorescence spectra of 1–4 exhibit LLCT π → π* transitions.