Three inorganic–organic hybrid compounds based on Keggin polyoxometalate and transition metal complexes: crystal structures and electrochemical properties

Polyoxometalate (POM)-based coordination polymers, [Cu(L)₂][SiW₁₂O₄₀]·4py·H₂O (1), [Ag(py)₂]₄[SiW₁₂O₄₀] (2) and [Co(L)₃]₂[SiW₁₂O₄₀]·py·7H₂O (3) (L?=?pyridine-2-carboxylic acid, py?=?pyridine), have been obtained hydrothermally and characterized by elemental analyses, IR and single-crystal X-ray diffraction analyses. Electrochemical properties are also investigated.     

Investigation of inorganic–organic hybrid materials containing polyoxometalate cluster anions and organic dye cations

Two new ionic-pair salts containing an organic dye cation, i.e. New Fuchsin or Pararosaniline cation, with Keggin-type POMs, [SiW₁₂O₄₀]^4? and [BW₁₂O₄₀]^6?, have been isolated under hydrothermal conditions. [(C₂₂H₂₄N₃)₄][SiW₁₂O₄₀] (1) and [(C₁₉H₁₈N₃)₆][BW₁₂O₄₀] (2) have been characterized by elemental analyses, FT-IR and single crystal X-ray crystallography. Both of these complexes have strong absorption in the visible-light range due to the involvement of the organic dye and both show weak fluorescence emission.     

Copper(I) and copper(II) complexes with pyrazine-containing pyridylalkylamide ligands N-(pyridin-2-ylmethyl)pyrazine-2-carboxamide and N-(2-(pyridin-2-yl)ethyl)pyrazine-2-carboxamide

Four copper(II) complexes and one copper(I) complex with pyridine-containing pyridylalkylamide ligands N-(pyridin-2-ylmethyl)pyrazine-2-carboxamide (HL^pz) and N-(2-(pyridin-2-yl)ethyl)pyrazine-2-carboxamide (HL^pz?) were synthesized and characterized. The X-ray crystal structures of [Cu₂(L^pz)₂(4,4?-bipy)(OTf)₂] (1, OTf?=?trifluoromethanesulfonate, 4,4?-bipy?=?4,4?-bipyridine) and [Cu(L^pz)(py)₂]OTf·H₂O (2, py?=?pyridine) revealed binuclear and mononuclear molecular species, respectively, while [Cu(L^pz)(μ₂-1,1-N₃)]_n (3), [Cu(L^pz?)(μ₂-1,3-N₃)]_n (4), and [Cu(HL^pz)Cl]_n (5) are coordination polymer 1-D chains in the solid state.     

Synthesis,crystal structure,and fluorescence of an unexpected dialkoxo-bridged dinuclear copper(II) complex with bis(salen)-type tetraoxime

An unexpected dinuclear Cu(II) complex, [Cu₂(L²)₂] (H₂L^2?=?3-methoxysalicylaldehyde O-(2-hydroxyethyl)oxime), has been synthesized via complexation of Cu(II) acetate monohydrate with H₄L¹. Catalysis by Cu(II) results in unexpected cleavage of two N–O bonds in H₄L¹, giving a dialkoxo-bridged dinuclear Cu(II) complex possessing a Cu–O–Cu–O four-membered ring core instead of the usual bis(salen)-type tetraoxime Cu₃–N₄O₄ complex. Every complex links six other molecules into an infinite-layered supramolecular structure via 12 intermolecular C–H?···?O hydrogen bonds. Furthermore, Cu(II) complex exhibits purple emission with maximum emission wavelength λ_max?=?417?nm when excited with 312?nm.     

Synthesis,crystal structure and magnetic properties of a new complex containing Cu(I) and radicals, [Cu(imme2py)2](ClO4)

A new complex, [Cu(imme2py)₂](ClO₄) (imme2py?=?2-(2′-(6′-methylpyridyl))-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxyl) has been synthesized and structurally characterized by X-ray diffraction methods. It crystallizes in the orthorhombic crystal system, space group P ₂₁₂₁₂₁ . The structure consists of [Cu(imme2py)₂]⁺ cations and chloride anions. The coordination geometry about Cu(I) is tetrahedral with the four coordination sites being occupied by four nitrogen atoms. Magnetic measurements show intramolecular antiferromagnetic interactions between the imino nitroxides.     

Assembly of two new polyoxometalate-templated supramolecular compounds by utilizing flexible 1,4-bis(pyrazol-1-ylmethyl)benzene ligand

Two new polyoxometalate-templated supramolecular compounds, [Cu^I₄(bpmb)₄][PMo^VI₁₁Mo^VO₄₀] (1) and [Cu^I₄(bpmb)₄SiW₁₂O₄₀] (2) (bpmb = 1,4-bis(pyrazol-1-ylmethyl)benzene), have been synthesized under hydrothermal conditions and characterized by routine methods. Structural analysis shows that in 1, there exist crown-like [Cu^I₄(bpmb)₄] coordination macrocycles, and the Keggin polyanions [PMo ^VI₁₁Mo^VO₄₀]^4? (abbr. as PMo₁₂), which direct the crown-like macrocycle to form a 3-D supramolecular framework. In 2, there exist unusual meso-helix chains, and these chains are mutually interlaced in a wave–trough pattern, but without intersection resulting in a multi-cavity layer, in which the [SiW₁₂O₄₀]^4? (abbr. as SiW₁₂) clusters as guest molecules occupy the cavities of the layers. The distinct structural features of the two compounds suggest that Keggin polyanions should play a significant role in the process of assembly. Electrocatalytic properties of 1 and 2 were investigated.     

Ionothermal synthesis and characterization of two new heteropolytungstates with 1-ethyl-3-methylimidazolium bromide ionic liquid as solvent

In this article, we have synthesized two new heteropolytungstate-based compounds [EMIM]₄[SiW₁₂O₄₀] (1) and [EMIM]₆[P₂W₁₈O₆₂] · 4H₂O (2) using the ionic liquid (IL) [EMIM]Br (EMIM = 1-ethyl-3-methylimidazolium) as a solvent and characterized them by infrared (IR) and ultraviolet (UV) spectra, thermogravimetric (TG) and elemental analyses, electrochemistry, and single-crystal X-ray analyses. Compound 1 is constructed from one [SiW₁₂O₄₀]^4? and four [EMIM]⁺. In the structure, [SiW₁₂O₄₀]^4? and [EMIM]⁺ are connected by hydrogen bonds with the surface oxygens of the polyoxoanion to form a 3-D supramolecular framework. The heteropolyanion of 2 is a classical Dawson-type structure [P₂W₁₈O₆₂]^6? and connected with six cations through hydrogen bonds. The structures of these two heteropolyanions are consistent with those synthesized by traditional methods, indicating that ionothermal synthesis is an effective method for the preparation of heteropolyoxometalates. The photocatalytic properties of these compounds have also been investigated.     

pH-dependent assembly of saturated to dilacunary Keggin-based silicotungstate: [Cu(en)2(H2O)][H2en]{γ-SiW10O36[Cu(en)2(H2O)]2}·7.5H2O

By controlling the pH of the reaction system, a dilacunary γ-Keggin silicotungstate [Cu(en)₂(H₂O)][H₂en]{γ-SiW₁₀O₃₆[Cu(en)₂(H₂O)]₂}·7.5H₂O (1) (en?=?ethylenediamine) has been hydrothermally synthesized by the reaction of CuCl₂ with α-H₄SiW₁₂O₄₀ and characterized by IR spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. The product is prepared in the pH range 7.9–8.2, which reveals that pH plays a key role in the assembly of saturated α-H₄SiW₁₂O₄₀ to dilacunary [γ-SiW₁₀O₃₆]^8? polyoxometalate. The polyoxoanion {γ-SiW₁₀O₃₆[Cu(en)₂(H₂O)]₂]}^4? of 1 presents a rare [γ-SiW₁₀O₃₆]^8?-retaining structure, in which two lacunary sites of [γ-SiW₁₀O₃₆]^8? are unoccupied, meanwhile, two [Cu(en)₂(H₂O)]²⁺ groups are grafted on either side of the [γ-SiW₁₀O₃₆]^8? unit by Cu–O–W bond.     

Ag/CuI-Mischbesetzung in den Kristallstrukturen der Kupfer(II)-cyanoargentate Cu(NH3)(py)Ag3-xCux(CN)5 · py

Ag/Cu^I Mixed Occupancy in the Crystal Structures of the Copper(II) Cyanoargentates Cu(NH₃)(py)Ag_3?xCu_x(CN)₅ · py From pyridine and ammonia containing Cu^II solutions, to which K[Ag(CN)₂] and in part KCu(CN)₂/KCN has been added, we obtained single crystals of mixed-valent copper compounds of variable composition Cu(NH₃)-(py)Ag_3-xCu_x(CN)₅ · py. The phases corresponding to x = 0.39(1) ( I ) and to x = 1.243(6) ( II ) were characterized by X-ray structure analysis. They are isomorphous and crystallize with Z = 4 in the monoclinic space group P2₁/c. The lattice constants for I [and II , resp.] are: a = 923.8(2) [901.4(2)], b = 1226.8(2) [1227.3(2)], c = 1809.8(4) [1783.5(2)] pm, β = 91.41(3) [91.02(1)]°. The Cu^II cation shows trigonal bipyramidal [CuN₅] coordination, with the neutral ligands in axial positions (mean value Cu? N for II : 201 pm), three N atoms of cyano bridges in equatorial ones (Cu? N: 206 pm). One of these bridges stems from a trigonal unit [AgCN(NC)₂], the central atom of which is substituted by Cu^I to an extent of 39% in I , and completely in II . The two other bridges originate from two [Ag(CN)₂]^? groups, of which the more bent one may be partially occupied by Cu^I as well (24% in II ). The units mentioned are connected into meshes of elongated hexagons and further into puckered layers within the (010) plane, interpenetrating each other in pairs. A threedimensional linking of layers occurs by the trigonal Ag/Cu^I species forming centrosymmetric dimers, in which the metal coordination is completed to tetrahedral by a C-atom of the corresponding neighbouring group and short metal-metal distances of 279.1(3) pm in I and 264.1(1) pm in II appear. Details and relations are discussed.     

pH-controlled assembly of two new supramolecular hybrid compounds based on Keggin polyoxotungstates

Two supramolecular compounds based on Keggin polyoxotungstates, (4,4′-H₂bpy){[Cu(4,4′-bpy)]₂[SiW₁₂O₄₀]} (1) and (4,4′-H₂bpy)₂[SiW₁₂O₄₀]·2H₂O (2) have been synthesized and characterized by elemental analyses, IR, UV, XPS spectra, TG analyses, and single crystal X-ray diffraction analyses. Compound 1 exhibits an infinite 1-D ladder like structure, which is further interconnected into a 3-D supramolecular framework via hydrogen bonding interactions. Compound 2 contains 4,4′-bipyridine (4,4′-bpy), pseudo-Keggin polyoxoanions [SiW₁₂O₄₀]^4?, and water molecules. Polyoxoanions together with water molecules in 2 construct a 3-D inorganic supramolecular network through O···O and O···Ow(1) interactions. The electrochemical behaviors and photocatalytic properties of 1 and 2 have been investigated.     

A series of new organic–inorganic compounds templated by the [SiW12O40]4− polyanion

Two couples of new compounds templated by the polyanion [SiW₁₂O₄₀]^4?,[Hbix][Cu^I(bix)]₃[SiW₁₂O₄₀]·4H₂O (1) and [Cu^II(H₂O)(Hbix)₂(bix)]₂[Cu^II(H₂O)₂(Hbix)₂(bix)][SiW₁₂O₄₀]₃·4H₂O (2) (bix = 1,4-Bis(imidazol-1-ylmethyl)benzene), [Cu^I(bbi)]₄[SiW₁₂O₄₀]·2H₂O (3) and [Cu^II(bbi₂)]₂[SiW₁₂O₄₀] (4) (bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) were hydrothermally synthesized, and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses and single X-ray diffraction. Compounds 1 and 2 were synthesized from the same reactants but exhibited distinct structures which could be ascribed to the different ratios of the reactant bix to Cu^II. In compound 1, the higher ratio of bix results in the transformation of the Cu^II to Cu^I, the [SiW₁₂O₄₀]^4? templates direct the Cu^I–bix coordination polymers to form a 3D supramolecular framework with grid-like channels along two directions. The [SiW₁₂O₄₀]^4? templates in compound 2 locate in the voids of the 3D supramolecular network constructed by Cu^II–bix coordination polymers, which exhibits the interdigitation fashion in both the formation of the 2D layer and the 3D framework. Compounds 3 and 4 were synthesized similar to 1 and 2, except for the change of bix to bbi. In compound 3, the Cu^I–bbi polymers form a supramolecular metal–organic host framework with rhombic channels in which the SiW₁₂ templates reside. Compound 4 shows a framework with hexagonal channels constructed by Cu^II–bbi coordination polymers which accommodated the SiW₁₂ templates.     

Polysulfonylamine. LXXXIV [1]. Zur Isotypie in den Dimesylamid-Komplexreihen [M(H2O)4{(CH3SO2)2N}2] (MMg,Ca, Ni,Cu, Zn,Cd) und [M(py)4{(CH3SO2)2N}2] (MNi,Cu, Zn,Cd)

Polysulfonylamines. LXXXIV. Isotypic Structures in the Dimesylamide Complex Series [M(H₂O)₄{(CH₃SO₂)₂N}₂] (M?Mg, Ca, Ni, Cu, Zn, Cd) and [M(py)₄{(CH₃SO₂)₂N}₂] (M?Ni, Cu, Zn, Cd) The crystal structures of the trans-octahedral complexes [M(H₂O)₄{(CH₃SO₂)₂N}₂] (M?Ca, Cd), in which the dimesylamide anion acts as a monodentate O-ligand and a tetrafunctional hydrogen bond acceptor, were determined by low-temperature X-ray diffraction. Both belong to an isotypic series (triclinic, space group P1 , Z = 1) that had previously been characterized for M?Mg, Ni, Cu and Zn (Z. Anorg. Allg. Chem. 1996 , 622, 1065). In this structure there exists an extended network of strong hydrogen bonds which is probably the underlying reason why the structure type surprisingly persists across the whole series. To support this explanation by indirect evidence from comparison with suitable structures devoid of strong hydrogen bonding, the analogous trans-octahedral complexes [M(py)₄{(CH₃SO₂)₂N}₂] (M?Mn, Co, Ni, Cu, Zn, Cd) were prepared by treating M[(CH₃SO₂)₂N]₂ with pyridine, and the crystal structures of the Ni, Cu, Zn and Cd compounds were studied by low-temperature X-ray crystallography. As anticipated, the four pyridine complexes do not form an isotypic series but instead two isotypic pairs consisting of the Ni and Zn compounds (monoclinic, space group P2₁/n, Z =2) and of the Cu and Cd complexes (triclinic, space group P1, Z = 1). All molecules of the aqua and the pyridine complexes display crystallographic centrosymmetry. In the hydrates, the mean M? OH₂ and the M? O(anion) distances are 232.6 and 232.7 pm for M ? Ca, 225.5 and 230.3 pm für M ? Cd. The mean M? N and the M? O(anion) bond lengths of the pyridine species amount to 211.8 and 213.1 pm for M ? Ni, 217.0 and 218.5 pm for M ? Zn, 232.8 and 234.4 pm for M ? Cd; the corresponding values for the severely Jahn-Teller distorted Cu complex are 203.6 and 254.5 pm. In the crystals of the pyridine complexes, each methyl group is connected through a weak C? H…?O bond to a sulfonyl oxygen atom of an adjacent molecule.     

Metal–oxo cluster-supported transition metal complexes: hydrothermal synthesis and characterization of [{Cu(phen)2}2SiW12O40]

A new neutral α-Keggin polyoxometalate, [{Cu(phen)₂}₂SiW₁₂O₄₀] (1) (phen?=?1,10-phenanthroline) was hydrothermally synthesized and characterized by IR, TG and single-crystal X-ray diffraction. The compound is monoclinic, space group P2₁/c with a?=?26.065(5), b?=?11.867(2), c?=?23.385(5)?Å, β?=?113.78(3)°, V?=?6619?ų, Z?=?4. X-ray analysis showed that both [Cu(phen)₂]²⁺ units are supported on the α-Keggin polyoxoanion [SiW₁₂O₄₀]^4? via the surface bridging and terminal oxygen atoms of two non-adjacent WO6 octahedra; these show unusual coordination environments. One Cu ion displays distorted trigonal bipyramidal geometry and the other square pyramidal. The unusual coexistence of complexes with different geometries is most likely caused by steric effects involving surface oxygen atoms of the heteropolytungstate and phen, which prevent the presence of a sixth coordinating atom. Weak π–π stacking interactions between phen groups give a 1D chain-like structure and hydrogen bonds are responsible for extended 2D and 3D motifs in the crystal.     

Syntheses,spectroscopic characterization,thermal behavior,electrochemistry and crystal structures of two novel pyridine metatungstates

Two novel metatungstate compounds [Hdmpy]₄H₂[H₂W₁₂O₄₀]·4H₂O (dmpy?=?2,6-dimethyl pyridine) (1) and [Hpy]₄H₂[H₂W₁₂O₄₀] (py?=?pyridine) (2) have been synthesized by rational reaction, rather than hydrothermal or electrosynthetic reaction, of sodium tungstate dihydrate with 2,6-dimethyl pyridine and pyridine, respectively and characterized by IR and electronic spectroscopies, thermal behavior and electrochemistry. X-ray single-crystal structural analyses indicate that both structures consist of close-packed arrangements of the almost spherical Keggin-type anion [H₂W₁₂O₄₀]^6? with protonated 2,6-dimethyl pyridine or pyridine molecules filling the gap of the polyanions and interacting with the metatungstate anions in the mode of W-O···H-N or W-O···H-C, giving a two-dimensional network structure. The TG-DTA curves of 1 show that weight loss is divided into two stages, and reveal that the framework of the polyanion in 1 begins to decompose at 613°C. Electrochemical study shows that Compound 1 exhibits two chemically quasi-reversible one-electron reduction processes in aqueous solution (0.5?M NaCl?+?HCl) in the pH range 4–7.     

Syntheses, structures and properties of 3D inorganic-organic hybrid frameworks constructed from lanthanide polymer and Keggin-type tungstosilicate

Inorganic-organic hybrid frameworks, namely [Ce(H₂O)₃(pdc)]₄[SiW₁₂O₄₀]·6H₂O 1, [M(H₂O)₄(pdc)]₄[SiW₁₂O₄₀]·2H₂O (M=Ce for 2a, La for 2b, Nd for 2c; H₂pdc=pyridine-2,6-dicarboxylic acid) were assembled through incorporation of Keggin-type heteropolyanion [SiW₁₂O₄₀]⁴⁻ within the voids of lanthanides-pdc network as pillars or guests under hydrothermal condition. Single-crystal X-ray analyses of these crystals reveal that compound 1 presents 3D pillar-layered framework with the [SiW₁₂O₄₀]⁴⁻ anions located on the square voids of the two-dimensional Ce-pdc bilayer. Compounds 2a-c are isostructural and constructed from 3D Ln-pdc-based metal-organic framework (MOF) incorporating noncoordinating guests Keggin structure [SiW₁₂O₄₀]⁴⁻. Solid-state properties of compounds 1 and 2a-c such as thermal stability and photoluminescence have been further investigated.     

Rhenium(I) Polypyridine Diamine Complexes as Intracellular Phosphorogenic Sensors: Synthesis,Characterization, Emissive Behavior,Biological Properties,and Nitric Oxide Sensing

We report the development of a series of rhenium(I) polypyridine complexes appended with an electron‐rich diaminoaromatic moiety as phosphorogenic sensors for nitric oxide (NO). The diamine complexes [Re(N^N)(CO)₃(py‐DA)][PF₆] (py‐DA=3‐(N‐(2‐amino‐5‐methoxyphenyl)aminomethyl)pyridine; N^N=1,10‐phenanthroline (phen) ( 1 a ), 3,4,7,8‐tetramethyl‐1,10‐phenanthroline (Me₄‐phen) ( 2 a ), 4,7‐diphenyl‐1,10‐phenanthroline (Ph₂‐phen) ( 3 a )) have been synthesized and characterized. In contrast to common rhenium(I) diimines, these diamine complexes were very weakly emissive due to quenching of the triplet metal‐to‐ligand charge‐transfer (³MLCT) emission by the diaminoaromatic moiety through photoinduced electron transfer (PET). Upon treatment with NO, the complexes were converted into the triazole derivatives [Re(N^N)(CO)₃(py‐triazole)][PF₆] (py‐triazole=3‐((6‐methoxybenzotriazol‐1‐yl)methyl)pyridine; N^N=phen ( 1 b ), Me₄‐phen ( 2 b ), Ph₂‐phen ( 3 b )), resulting in significant emission enhancement (I/I₀≈60). The diamine complexes exhibited high reaction selectivity to NO, and their emission intensity was found to be independent on pH. Also, these complexes were effectively internalized by HeLa cells and RAW264.7 macrophages with negligible cytotoxicity. Additionally, the use of complex 3 a as an intracellular phosphorogenic sensor for NO has been demonstrated.     

Two supramolecular structures constructed from Keggin-type polyoxometalates and 4,4′-bipyridine

Two supramolecular compounds based on Keggin-type polyoxometalates (POMs), (4,4′-H₂bpy)(4,4′-Hbpy)[PMo₁₂O₄₀] (1) and (4,4′-H₂bpy)(4,4′-Hbpy)₂[SiW₁₂O₄₀]?·?4H₂O (2), have been synthesized hydrothermally and characterized by elemental analyses, IR, UV-Vis, XPS spectra, thermogravimetric analyses, and single-crystal X-ray diffraction analyses. The two compounds consist of 4,4′-bipyridine (4,4′-bpy) ligands and different Keggin-type POMs which are [PMo₁₂O₄₀]^3? for 1 and [SiW₁₂O₄₀]^4? for 2. There are hydrogen-bonding interactions between the POMs, 4,4′-bipyridine, and/or water in 1 and 2. In addition, 2 contains an uncommon (H₂O)₂ water cluster.     

Synthesis, structures and properties of new hybrid solids containing ruthenium complexes and polyoxometalates

Two new organic-inorganic hybrid solids containing Keggin ions and ruthenium complexes have been synthesized and characterized by FT-IR, UV-vis, luminescence, X-ray, and TG analysis. In KNa[Ru(bpy)₃]₂[H₂W₁₂O₄₀]·8H₂O (1), the [Ru(bpy)₃]²⁺ (bpy=2,2′-bipyridine) complex ions are located in between the infinite one-dimensional double-chains formed by adjacent Keggin anions [H₂W₁₂O₄₀]⁶⁻ linked through {KO₇} and {NaO₆} polyhedra, while in K₆[Ru(pzc)₃]₂[SiW₁₂O₄₀]•12H₂O (2), the [Ru(pzc)₃]⁻ (pzc=pyrazine-2-carboxylate) complex anions are confined by layered networks of the [SiW₁₂O₄₀]⁴⁻ clusters connected by potassium ions. Both compounds exhibit three-dimensional frameworks through noncovalent interactions such as hydrogen bonds and anion?π interactions. Additionally, compound 1 shows strong luminescence at 604 nm in solid state at room temperature.     

Assembly of a new Keggin polyoxometalate-templated complex using flexible 1,2-bis(imidazol-1′-yl)ethane ligand

A new compound, [{Cu^I(bim)}₄{SiW₁₂O₄₀}] (1) (bim?=?1,2-bis(imidazol-1′-yl)ethane), was hydrothermally synthesized and characterized by elemental analyses, IR, TG, and single-crystal X-ray diffraction. Compound 1 is an infinite 1-D chain composed of Cu-bim coordination polymers and [α-SiW₁₂O₄₀]^4? polyanions. The electrochemical and electrocatalytic behaviors of 1-modified carbon paste electrode (1-CPE) have been studied.     

A Novel Keggin Units-Supported Complex: Synthesis,Characterization and Crystal Structure of [(CH3)2NH2]6[Cu(DMF)4(GeW12O40)2] · 2DMF

A novel hybrid compound, [(CH₃)₂NH₂]₆[Cu(DMF)₄(GeW₁₂O₄₀ ^4-)₂] [sdot] 2DMF, has been synthesized from H₄GeW₁₂O₄₀ [sdot] n H₂O, CuCl₂ and N, N -dimethylformamide (DMF) in aqueous solution and characterized by elemental analysis, UV and IR spectra. Single crystal X-ray structure analysis shows that the crystal consists of a α-Keggin heteropolyanion-supported anion [Cu(DMF)₄(GeW₁₂O₄₀ ^4-)₂], two free N, N-dimethylformamide molecules, six protonated dimethylamine (DMA) molecules, and that the coordinating atoms of DMF are the oxygen atoms of C=O group. Thermal analysis indicates that the thermal stability of the GeW₁₂O₄₀ ^4- anion in the title compound is stronger than that in acid.