Bond Valence Sum Calculations Research Articles

Solvothermal preparation of nano cobalt sulfide from tris (cyclohexylpiperazinedithiocarbamato)cobalt(III) and characterization, single crystal X-ray crystal structure of the precursor

Solvothermal formation of CoS nano particles is reported with a cobalt(III) dithiocarbamate as a single source precursor. Morphology and composition of the nano product have been characterized by PXRD and EDX analysis. Four unsymmetrically substituted tris cobalt(III) compounds, [Co(chmdtc)3] (1), [Co(chedtc)3] (2), [Co(achdtc)3] (3), and [Co(chpdtc)3] (4) (where chmdtc = cyclohexylmethylcarbodithioate, chedtc = cyclohexylethylcarbodithioate, achdtc = allylcyclohexylcarbodithioate and chpdtc = cyclohexylpiperazinecarbodithioate) were synthesized and characterized. Compounds (1)– (4) show bands at 634, 642, 635, and 643 nm respectively, due to d-d transitions. One electron quasi reversible reductions due to Co(III)/Co(II) redox process are observed in CV. In the 13C NMR spectra of the complexes, the thioureide (N13CS2) carbons resonate between 203.8 and 205.7 ppm. The observed deshielding of the –CH2 protons in 1H NMR of the compounds is attributed to the shift of electron density on the sulfur (or the metal) through the thioureide π system. TGA supported the proposed formulas of the compounds. Single crystal X-ray structure of [Co(chpdtc)3] (4) shows that the cobalt is in a distorted octahedral environment. Bond Valence Sum (BVS) calculations confirmed the formal oxidation state of cobalt as +3.

STUDY ON THE STABILITY OF TRIVALENT CATIONS GADOLINIUM (Gd) DOPED FERRIC OXIDE (Fe2O3) THROUGH ATOMISTIC MODELING

This research is aimed to study the stability of the structure Fe 2 O 3 doped with trivalent cations Gadolinium (Gd) into compound Fe 1-x Gd x O 2 -δ through atomistic modeling and Bond Valence Sum (BVS) calculations. Short range potential used in this study was Buckingham potential. Result of geometry optimization at constant pressure shown the more of the concentration and the size of substituting dopant of ferric oxide (Fe 2 O 3 )increase, the more positive the lattice energy of the doped structure is, so that the stability of the doped Fe 2 O 3 structure decreases.

Zero-thermal-quenching and improved chemical stability of a UCr4C4-type phosphor via crystal site engineering

• CsNa 2 K(Li 3 SiO 4 ) 4 :Ce 3+ phosphor was synthesized with 80% quantum efficiency. • First zero-thermal-quenching phosphor among other Ce 3+ -doped phosphors. • Upon Ce 3+ doping in host shows excellent chemical stability than Eu 2+ doping. • CsNa 2 K(Li 3 SiO 4 ) 4 :Ce 3+ shows high color rendering index value of 95 at 1000 mA. Europium-doped UCr 4 C 4 cuboid phosphors with narrow and tunable emission show promise for application in designing light-emitting diodes with high color purity and thermal stability. Nevertheless, their poor chemical stability bottlenecks their use in lighting applications. Herein, a dual narrow-band blue-emitting Ce 3+ -doped CsNa 2 K(Li 3 SiO 4 ) 4 (CNKLSO) cuboid phosphor with a quantum yield of 80% is synthesized. The dual-band emission is attributed to the occupation of Ce 3+ at two distinct sites of CNKLSO, which is consistent with the density functional theory outcomes. Ce 3+ doping produces stable emission characteristics, in contrast to Eu 2+ incorporation, because of the improved site stability, as realized from bond valence sum calculations. Remarkably, no drop in the emission intensity is observed even at 200 °C, making CNKLSO:Ce 3+ the first Ce 3+ -based zero-thermal-quenching phosphor. A CNKLSO:Ce 3+ -based white light-emitting diode displays an excellent color rendering index (~95) at a high flux current of 1000 mA. The proposed study indicates that Ce 3+ doping in other UCr 4 C 4 - type oxide phosphors may improve the site stability, which in turn the chemical stability of the phosphor materials can be boosted.

Synthesis, structure, third-order nonlinear optical properties and Hirshfeld surface analysis of tetrakis(azepanium) hexachlorostannate(IV) dichloride and tetrakis(azepanium) hexabromostannate(IV) dibromide

The new organic-inorganic hybrids of tetrakis(azepanium) hexachlorostannate(IV) dichloride (1) and tetrakis(azepanium) hexabromostannate(IV) dibromide (2) crystals have been grown after slow evaporation of the solvent and characterized through single-crystal X-ray diffraction analysis. The characteristic functional groups present in the compounds are confirmed by FT-IR analysis. The direct band gap values for the compounds are estimated by the application of Kubelka-Munk function. Photoluminescence studies exhibit fluorescent emission of both the compounds in the solid-state at room temperature. TG/DTA analysis reveals the thermal pattern of the compounds. Bond valence sum (BVS) calculation confirmed the formal oxidation state of tin to be +4. Z-scan studies very much reveal that both the compounds exhibit significant third-order nonlinear optical response. Investigation of the intermolecular interactions and crystal packing using Hirshfeld surface analysis, derived by single-crystal XRD data, reveals the close contacts associated with strong interactions.

Ring-Shaped Polyoxometalate Built by {Mn 4 PW 9 } and PO 4 Units for Efficient Visible-Light-Driven Hydrogen Evolution

A novel mixed-valence, ring-shaped multinuclear Mn-containing polyoxometalate, [H2N(CH3)2]15NaH8-[MnIII3MnIV(μ3-O)3(OAc)PO4(B-α-PW9O34)]4·36H2O (1) was made and systematically characterized using v...

Quadruple perovskite oxide LaCu3Co2Re2O12: A ferrimagnetic half metal with nearly 100% B-site degree of order

An A- and B-site ordered quadruple perovskite oxide LaCu3Co2Re2O12 was synthesized at 9 GPa and 1323 K. The compound possesses a Pn-3 space group, where both A and B sites are orderly occupied by different cations with a nearly 100% degree of order. Bond valence sum calculations and x-ray absorption spectroscopy confirm the charge distribution to be LaCu2+3Co2+2Re5.5+2O12. A ferrimagnetic phase transition is found to occur around 150 K due to the Cu2+(↑)-Co2+(↑)-Re5.5+(↓) spin coupling found by x-ray magnetic circular dichroism at Cu-, Co-, and Re-L2,3 edges. The magnetoresistance effects as well as the first-principle calculations indicate the half-metallic nature for LaCu3Co2Re2O12 with a wider energy gap at the up-spin channel and a conducting band at the down-spin channel.

U(H2O)2]{[(UO2)10O10(OH)2][(UO4)(H2O)2]}: A Mixed-Valence Uranium Oxide Hydrate Framework

A uranium oxide hydrate framework, [U(H2O)2]{[(UO2)10O10(OH)2][(UO4)(H2O)2]} (UOF1), was synthesized hydrothermally using schoepite as a uranium precursor. The crystal strucutre of UOF1 was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron miscroscopy. The typical uranyl oxide hydroxide layers similar to those in β-U3O8 are further connected via double-pentagonal-bipyramidal uranium polyhedra to form a three-dimensional (3D) framework structure with tetravalent uranium species inside the channels. The presence of mixed-valence uranium was investigated with a combination of X-ray absorption near-edge structure and diffuse reflectance spectroscopy. Apart from the major hexavalent uranium, evidence for tetravalent uranium was also found, consistent with the bond valence sum calculations. The successful preparation of UOF1 as the first pure uranium oxide hydrate framework sheds light on the structural understanding of the alteration of UO2+x as either a mineral or spent nuclear fuel.

Synthesis, structure, and properties of the multinuclear cobalt core POM Na14[Co3O(H2O)(A-α-PW9O34)2]·~29.5H2O

A new trimeric Co(II) containing Keggin trilacunary polyoxometalate (POM) sandwich complex, Na14[Co3O(H2O)(A-α-PW9O34)2]·~29·.5H2O (Na14-1) was synthesized by the reaction of [Co2(μ- OH2)(O2CCMe3)4(HO2CCMe3)4] and Na9[A-α-PW9O34]·7H2O. The compound has been characterized by elemental analysis, FTIR, TGA and single crystal XRD (Triclinic space group P- 1, a = 12.2204(8) Å, b = 16.7035(11) Å, c = 23.3466(16) Å, α = 78.448(2)°, β = 80.551(2)°, γ = 78.448(2)° and Z = 2). The POM was electrochemically active and its behavior was studied by cyclic voltammetry at different scan rates. Bond valence sum (BVS) calculation was used to determine the oxidation state of Co. The magnetic susceptibility study indicated antiferromagnetic interactions between Co(II) ions and at lower temperature ferromagnetic behavior dominant in the structure.

Magnetic Properties of End-to-End Azide-Bridged Tetranuclear Mixed-Valence Cobalt(III)/Cobalt(II) Complexes with Reduced Schiff Base Blocking Ligands and DFT Study.

Two tetranuclear mixed-valence cobalt(III/II) complexes having the general formula [(μ1,3-N3){CoII(Ln)(μ-O2CC6H4NO2)CoIII(N3)}2]PF6 (where H2L1 and H2L2 are two reduced Schiff base ligands) have been synthesized and characterized. The structures of both complexes show cobalt(II) and cobalt(III) centers with a distorted octahedral geometry with cobalt(III) and cobalt(II) centers located at the inner N2O2 and outer O4 cavities of the reduced Schiff base ligands, respectively. The oxidation states of both cobalt centers have been confirmed by bond valence sum (BVS) calculations. The magnetic properties show that both compounds behave as cobalt(II) dimers connected through an end-to-end azido bridging ligand and show moderate antiferromagnetic Co(II)–Co(II) couplings of −11.0 and −14.4 cm–1 for 1 and 2, respectively, as also corroborated by DFT calculations, Jtheo = −13.07 cm–1 for 1 and −12.49 cm–1 for 2. The calculated spin densities of both complexes at the cobalt(II) centers are −2.75 and +2.75, respectively, clearly supporting that they are the magnetic centers.

Synthesis, crystal structure, optical absorption study, and electronic structure of Cs3FeCl5

The single crystals of Cs3FeCl5 were synthesized at 973 K using the sealed tube solid-state molten flux method using CsCl as a reactive flux. The polycrystalline sample of Cs3FeCl5 was obtained by the stoichiometric reaction of CsCl and FeCl2 powders at 823 K by the sealed tube solid-state method. The crystal structure of Cs3FeCl5 was determined by single-crystal X-ray diffraction study at 298 (2) K. This ternary halide crystallizes in the body-centered tetragonal crystal system in I4/mcm space group with cell constants of a = b = 9.279 (1) Å and c = 14.824 (3) Å with four formula units per cell. The asymmetric unit of Cs3FeCl5 contains five crystallographically independent atomic sites: Cs1 (site symmetry: m.2 m), Cs2 (422), Fe1 (4¯2 m), Cl1 (..m), and Cl2 (4/m..). Each Fe atom in Cs3FeCl5 structure is bonded to four Cl1 atoms in a slightly distorted tetrahedral fashion to form isolated FeCl42− units. These FeCl42− units are separated by the Cs+ cations and infinite [CsCl] linear chains. Charge balance in this closed-shell compound can be achieved by 3 × Cs+, 1 × Fe2+, and 5 × Cl−. Bond valence sum (BVS) calculation also supports this assignment of formal oxidation states of elements in Cs3FeCl5 structure. The electronic structure calculation for Cs3FeCl5 performed within a density functional theoretical framework predicts a band gap of 3.5 eV, which is in good agreement with the experimental band gap of 3.71 (2) eV, that was estimated from the UV–vis absorption edge study of polycrystalline Cs3FeCl5.

Bio-mimetic of catecholase and phosphatase activity by a tetra-iron(III) cluster

An oxido- and acetato-bridged tetranuclear iron(III) cluster, [Fe4III(µ-O)2(µ-OAc)6(phen)2(H2O)2](NO3)2·(H2O)3 (1), [OAc = acetate; phen = 1,10-phenanthroline] has been prepared in the crystalline phase. X-ray structural analysis of the compound reveals that all the Fe(III) centres in 1 adopt an octahedral coordination geometry and the tetra-iron(III) core exists in an unusual asymmetric conformation. Bond valence sum (BVS) calculations recommend the existence of all iron ions in the +3 oxidation state in the crystalline phase. The tetra-iron(III) cluster elegantly catalyzes the oxidation of 3,5-di-tert-butylcatechol (DTBC), viz. catecholase-like activity, with a good turnover number, kcat = 9.28 × 102 h−1 in acetonitrile medium. Spectrophotometric titration shows the existence of two distinct isosbestic points, which unanimously proves the rarely observed enzyme-substrate binding phenomenon in solution. Electrochemical analysis recommends the production of Fe(II)–semiquinone species in the course of the catalytic oxidation of DTBC. Furthermore, the same iron(III) cluster displays phosphoester cleavage activity towards the disodium salt of p-nitrophenylphosphate (PNPP) in aqueous-methanol medium with rate of 7.20 × 10−4 m−1. ESI-MS measurements of the tetra-iron(III) complex in the presence of PNPP indicate the formation of an organophosphorus intermediate in solution and solvent aqua molecules probably make a nucleophilic attack on the phosphorus centre, favouring the generation of the organophosphorus intermediate.

Studies of the fergusonite to scheelite phase transition in LnNbO4 orthoniobates

Synchrotron X-ray powder diffraction methods have been used to obtain accurate structures of the lanthanoid orthoniobates, LnNbO4 at room temperature. The observed decrease in the unit cell volume in going from Ln = La to Lu correlates with a decrease in the volume of the LnO8 polyhedra due to the changing size of the Ln3+ cation. In all cases the Nb is in a highly distorted six-coordinate geometry with two long, ~2.5 Å, and four short ~1.9 Å Nb–O distances. The importance of the long Nb–O bonds is evident from Bond Valence Sum Calculations. Variable temperature structural studies of three examples, Ln = La, Sm and Gd, showed each transformed to a high temperature tetragonal scheelite type structure in space group I41/a. In the high temperature structure the Nb are tetrahedrally coordinated and it appears that monoclinic – tetragonal transition is best described as a reconstructive transition in which the long Nb–O(1) bond is broken upon heating.

Crystal structure, large distortion of the Zn tetrahedron, and statistical displacement of water molecules in skorpionite

The crystal structures of skorpionite from the Skorpion zinc deposit in Namibia [Ca3Zn2(PO4)2CO3(OH)2·H2O; monoclinic; a = 19.0715(8), b = 9.3321(3), c = 6.5338(3) Å, β = 92.6773(12)°; space group C2/c] and [a = 19.0570(14), b = 9.3346(5), c = 6.5322(4) Å, β = 92.752(2)°; space group Cc] are analyzed using single–crystal X–ray diffraction and refined to yield R values of 0.0253 and 0.0272 for 1576 and 2446 unique reflections with Fo > 4σ(Fo), respectively. Hydrogen atoms in the structure determined by the difference Fourier method. Although two space groups, C2/c and Cc, are possible, the Cc space group without center of symmetry is more likely the structure of skorpionite, which shows that skorpionite is a ferroelectric mineral. The disordered structure is induced in skorpionite by twinning and/or domain structures because of the relaxation of the natural polarization caused by the arrangement of polarized water molecules. The space group Cc model without the center of symmetry eliminates the need for statistical distribution. Bond valence sum calculations and hydrogen bond networks can be explained in detail by the model. In the complicated structure caused by the chemical composition, the local structure with a non–ideal coordination environment is observed near the Zn sites. Hydrogen atoms are continuously arranged with regular arrangements of water molecules in the tunnel structure.

Synthesis, structural characterization and C[sbnd]H activation property of a tetra-iron(III) cluster

A non-heme tetra-iron cluster, [Fe4III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3−)(OH−) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary CH bond oxidation products. Oxidation of secondary CH bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.

Polynuclear oxomolybdates(VI): Products of inadvertent oxidation of molybdenum(V) species

Unplanned oxidation of molybdenum(V) in the presence of carboxylic acid afforded three fully-oxidized polynuclear oxomolybdates. In very similar reaction mixtures, the initial oxidation state of the metal ion was retained and species with the frequently-encountered dinuclear {MoV(O)(μ2-O)2MoV(O)}2+ core formed. The chosen carboxylic acid contained either two COOH groups or another functional group, i.e., OH moiety. The carboxylic acid was introduced with the idea that with both of its functional groups engaged in coordination discrete clusters composed of the {MoV(O)(μ2-O)2MoV(O)}2+ units and the organic linkers would form. Reaction systems with dimethylmalonic acid (dmmH2) yielded two products, (Bu4N)2[Mo3O8(dmm)2] (1) with a trinuclear anion and [{MoV2O4Py2(dmmMe)}2(OCH3)2] (2) (Py = pyridine, dmmMe− = monomethyl dimethylmalonate ester) as the non-oxidized counterpart. The dmm2− ion engaged in coordination to Mo(VI) centers both carboxylate groups, whereas the dmmMe− ion coordinated to Mo(V) centers via its carboxylate moiety in a bidentate bridging mode. Reactions with mandelic (H2man) acid resulted in {(C6H5)4P}2[Mo4O10(OCH3)4Cl2] (3) with a tetranuclear core and in (PyH)3[MoV2O4Cl4(Hman)] (4). Only the non-oxidized compound 4 contains coordinated mandelate ion, whereas the role of the acid in the synthesis of 3 became that of a templating agent. (PyH)4[Mo8O26Py2] (5) with an octanuclear anion is a fully-oxidized compound obtained from the reaction mixture with succinic acid. The compounds were characterized by X-ray structure analysis, bond valence sum (BVS) calculations, IR vibrational and 1H NMR spectroscopy. The TG and DSC experiments were performed on fully-oxidized compounds. Powder X-ray diffraction has confirmed molybdenum(VI) oxide as the end product of the thermal decomposition of (Bu4N)2[Mo3O8(dmm)2] (1) and (PyH)4[Mo8O26Py2] (5) in the air atmosphere.

Mixing SbIIIand GeIVoccupancy in the polyoxovanadate {V14E8} archetype

AbstractThe first mixed germanato-antimonato derivative of the {V14E8O42} (E=semi-metal) cluster archetype has been synthesized under hydrothermal conditions and isolated as {Ni(phen)3}2[α-VIV14SbIII5GeIV3O42(OH)3(H2O)]· ≈16H2O (phen=1,10-phenanthroline). In the cluster anion, seven of the eight hetero-metal positions are occupied by disordered Ge/Sb atoms, while one position is fully occupied by Sb atoms. The [V14Sb5Ge3O42(OH)3(H2O)]6−anions are arranged in pairs with remarkably short inter-cluster Sb···O contacts. Bond valence sum calculation strongly suggests that the Sb···O contact must be taken into account as a weak bond. The magnetic properties are dominated by strong intra-cluster antiferromagnetic exchange interactions, and the cluster anion is magnetically quasi-isolated from the spins of the Ni2+complex cations.

Unprecedented Deep-Red Ce3+ Luminescence of the Nitridolithosilicates Li38.7RE3.3Ca5.7[Li2Si30N59]O2F (RE = La, Ce, Y)

Ce3+ doped solids find broad application, e.g. in phosphor converted light emitting diodes, utilizing the usually broad blue to yellow-orange emission of the respective phosphors. The red to infrared spectral range was not yet accessible with the activator Ce3+, even in nitride host materials. Here, we report on the nitridolithosilicates Li38.7RE3.3Ca5.7[Li2Si30N59]O2F (RE = La, Ce, Y) with unique, red-shifted Ce3+ luminescence. The materials were synthesized by solid-state metathesis reactions in tantalum ampules. The isotypic crystal structures exhibit a highly condensed three-dimensional network made up of SiN4 and LiN4 tetrahedra. Crystal structures were refined from single-crystal and powder X-ray diffraction data. The results are supported by energy-dispersive X-ray spectroscopy as well as charge distribution, lattice energy, and bond valence sum calculations. Optical band gaps of ≈4 eV were determined from diffuse reflectance UV/vis data using Tauc plots. The nitridolithosilicates are highly excita...

Quaternary rare-earth selenides Ba2REGaSe5 and Ba2REInSe5

Twelve quaternary rare-earth selenides Ba2REGaSe5 and Ba2REInSe5 were prepared in the form of single crystals from reactions of BaSe, RE, M2Se3 (M = Ga, In), and Se at 1373 K. The compounds Ba2REGaSe5 fall into two separate series adopting an orthorhombic (RE = La, Ce; space group Pnma, Z = 4, a = 12.49–12.50 Å, b = 9.60–9.63 Å, c = 8.74 Å) or a triclinic structure (RE = Tb, Ho, Tm, Yb, Lu; space group P1¯, Z = 2, a = 7.28–7.31 Å, b = 8.61–8.72 Å, c = 9.37–9.43 Å, α = 103.4–103.5°, β = 103.0–103.1°, γ = 107.3–107.5°). The compounds Ba2REInSe5 adopt an orthorhombic structure (RE = Pr, Tb, Ho, Tm, Lu; space group Cmc21, Z = 4, a = 4.23–4.33 Å, b = 18.75–18.96 Å, c = 13.29–13.31 Å). All structures contain anionic M-centred tetrahedra, isolated Se2– anions, Ba2+ cations in eight-fold coordination, and RE3+ cations in either six- or seven-fold coordination. A structure map developed based on radius ratios involving the RE3+, M3+, and Ch2– ions is effective in segregating four structures (in space groups Cmc21, P1¯, Pnma, and I4/mcm) found for Ba2REMCh5 (M = Ga, In; Ch = S, Se, Te). Bond valence sum calculations reveal that the upper limit for the largest RE components that can be substituted within a given structural series is set by the need to avoid overbonding of the RE atoms. An optical band gap of 1.34(2) eV was measured for the compound Ba2LaGaSe5, slightly less than a value of 1.76 eV obtained from electronic band structure calculations, which suggest an indirect transition.

Superconductivity in La1−xCex OBiSSe: Carrier doping by mixed valence of Ce ions

We report the effects of Ce substitution on the structural, electronic, and magnetic properties of the layered bismuth-chalcogenide La1−xCexOBiSSe , which are newly obtained in this study. Metallic conductivity was observed for because of electron carriers induced by mixed valence of Ce ions, as revealed by the bond valence sum calculation and magnetization measurements. Zero resistivity and clear diamagnetic susceptibility were obtained for , indicating the emergence of bulk superconductivity in these compounds. Dome-shaped superconductivity phase diagram with the highest transition temperature of 3.1 K, which is slightly lower than that of F-doped LaOBiSSe , was established. The present study clearly shows that the mixed valence of Ce ions can be utilized as an alternative approach for electron-doping in layered bismuth-chalcogenides to induce superconductivity.

Synthesis and single crystal structures of V(OH)ndc·H2O, V(OH)ndc, and VOndc

The vanadium analog of MIL-69, V(OH)ndc·H2O (ndc = 2,6-naphthalenedicarboxylate) was prepared solvothermally and the structure determined by single crystal X-ray diffraction (Space Group P21/c (#14), a = 6.7936(2) Å, b = 14.6816(4) Å, c = 23.9156(6) Å, β = 91.734(2)°, V = 2394.3(1) Å3). Anhydrous V(OH)ndc was obtained from V(OH)ndc·H2O by heating under nitrogen flow at 378 K in situ the crystal used to determine the structure of the as synthesized hydrated compound. The water molecules are removed on heating in a crystal to crystal transformation. Minor changes in the structure occur with no change in the V3+ oxidation state though the space group symmetry changes from P21/c to C2/c. (Space Group C2/c (#15), a = 24.684(4) Å, b = 7.079(2) Å, c = 6.853(1) Å, β = 104.35(1)°, V = 1160.2(4) Å3). The structure of VOndc (Space Group C2/c (#15), a = 24.628 (2) Å, b = 7.1434(5)Å, c = 6.7428(4) Å, β = 104.637(3)°, V = 1147.8 Å3) obtained by heating V(OH)ndc·H2O in air at 573 K, in contrast shows a change in oxidation state from V3+ to V4+ evidenced by bond valence sum calculations and by the appearance of a characteristic distorted VO6 octahedron and an O⋯V(IV) = O chain.