C CP MAS NMR, FTIR, X-ray diffraction and PM3 studies of some N-(ω-carboxyalkyl)morpholine hydrohalides

N-(ω-carboxyalkyl)morpholine hydrochlorides, OC₄H₈N(CH₂)_nCOOH·HCl, n=1–5, were obtained and analyzed by ¹³C cross polarization (CP) magic angle spinning (MAS) NMR, FTIR and PM3 calculations. The structure of N-(3-carboxypropyl)morpholine hydrochloride (n=3) has been solved by X-ray diffraction method at 100 K and refined to the R=0.031. The crystals are monoclinic, space group P2₁/c, a=14.307(3), b=9.879(2), c=7.166(1) Å, β=93.20(3)°, V=1011.3(3) ų, Z=4. In this compound the nitrogen atom is protonated and two molecules form a centrosymmetric dimer, connected by two N⁺–HCl⁻ (3.095(1) Å) and two O–HCl⁻ (3.003(1) Å) hydrogen bonds. ¹³C CP MAS NMR spectra, contrary to the solution, showed non-equivalence of the ring carbon atoms. The PM3 calculations predict a molecular dimer without proton transfer for an HCl complex, while for an HBr complex an ion pairs with proton transfer, and reproduces correctly the conformation of both dimers but overestimates H-bond distances. Shielding constants calculated from the PM3 geometry of ion pairs gave a linear correlation with the ¹³C chemical shifts in solids.     

Cationic cobaltammine as anion receptor: Synthesis, characterization, single crystal X-ray structure and packing analysis of hexaamminecobalt(III) chloride (R,R)-tartrate monohydrate

In an effort to utilize the [Co(NH₃)₆]³⁺ cation as a new anion receptor (binding agent) for dihydroxy dicarboxylate anion i.e., tartrate, orange single crystals of hexaamminecobalt(III) chloride (R,R)-tartrate monohydrate, [Co(NH₃)₆]Cl(C₄H₄O₆)·H₂O, were obtained by reacting hexaamminecobalt(III) chloride with potassium–sodium tartrate tetrahydrate in a 1:1 molar ratio in hot water. The single crystal X-ray structure determination of [Co(NH₃)₆]Cl(C₄H₄O₆)·H₂O revealed that a distinctive network of hydrogen bonding interactions (N–HO, N–HCl⁻, O–HO) stabilize the crystal lattice. This is the first complex salt of hexaamminecobalt(III) with dihydroxy dicarboxylate anion i.e., tartrate.     

Synthesis and crystal structure of two novel nickel (imidazole) complexes having hydrogen-bonded networks

Two nickel (imidazole) complexes, Ni(im)₆Cl₂·4H₂O (1) and Ni(im)₆(NO₃)₂ (2) (im=imidazole) have been synthesized and characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. 1 crystallizes in the triclinic space group P-1 with a=8.800(6) Å, b=9.081(6) Å, c=10.565(7) Å, =75.058(9)°, β=83.143(8)°, γ=61.722(8)°, V=718.3(8) Å³, Z=1 and R₁ (wR₂)=0.0469 (0.1497). 2 crystallizes in the trigonal space group R-3 with a=12.370(6) Å, b=12.370(6) Å, c=14.782(14) Å, =90.00°, β=90.00°, γ=120.00°, V=1959(2) Å³, Z=3 and R₁ (wR₂)=0.0358 (0.0955). 1 and 2 exhibit different supramolecular network due to their different counter anions and different hydrogen bonding connection. In compound 1, [Ni(im)₆]²⁺ cation and counter anions Cl⁻ alternatively array in an ABAB fashion via N–HCl hydrogen bonding. In compound 2, the plane of each NO₃²⁻ is almost parallel and each NO₃²⁻ connect three different [Ni(im)₆]²⁺ cations via N–HO hydrogen bonding.     

Hydrogen bonds in the crystal packings of mesalazine and mesalazine hydrochloride

The crystal structures of pharmaceutical product mesalazine (marketed also under different proprietary names as Salofalk, Asacol, Asacolitin, and Claversal) and its hydrochloride are reported. In the crystal mesalazine is in zwitterion form as 5-ammoniosalicylate (1) whereas mesalazine hydrochloride crystallizes in an ionized form as 5-ammoniosalicylium chloride (2). Compound 1 (C₇H₇O₃N) crystallizes in the monoclinic space group P2₁/n with a = 3.769(1) Å, b = 7.353(2) Å, c = 23.475(5) Å, β = 94.38(2)°, V = 648.7(8) ų, Z = 4, D_c = 1.568 g cm⁻³ and μ(MoK) = 1.2 cm⁻¹. Compound 2 (C₇H₈O₃NCl) crystallizes in the triclinic space group P with a = 4.4839(2) Å, b = 5.7936(2) Å, c = 15.6819(5) Å, = 81.329(3)°, β = 88.026(3)°, γ = 79.317(4)°, V = 395.74(3) ų, Z = 2, D_c = 1.591 g cm⁻³ and μ(CuK) = 40.8 cm⁻¹. The crystal structures were solved by direct methods and refined to R = 0.041 for 1 and 0.028 for 2, using 607 and 1374 observed reflections, respectively. The configuration of both molecules, with the ortho hydroxyl to a carboxyl group, favours the intramolecular hydrogen bonds. Very complex systems of intermolecular hydrogen bonds were observed in both crystal packings. They are discussed in terms of graph-set notation. The mesalazine crystal structure is characterized by two-dimensional network of hydrogen bonds in the ab plane. The crystal structure pattern of mesalazine hydrochloride is a three-dimensional network significantly supported by N⁺---HCl⁻ interactions.     

2D Cu(I) and 3D mixed-valence Cu(I)/Cu(II) coordination polymers: Synthesis and structural characterization of [CuCl(pyz-H)2]·2H2O and [Cu2Cl2(pyz)(H2O)]·H2O (pyz-H = pyrazinic acid)

Two new coordination polymers of copper(I) chloride and pyrazinic acid (pyz-H), namely [CuCl(pyz-H)₂]·2H₂O (1) and [Cu₂Cl₂(pyz)(H₂O)]·H₂O (2) have been prepared and characterized by spectroscopic, magnetic and crystallographic methods. The overall physical measurements suggest that 1 is diamagnetic and contains monodentate N-pyrazinic acid, whereas 2 is paramagnetic and contains tridentate N,N′,O- chelating bridging pyrazinato anion. In the structure of 1 as elucidated by X-ray single crystal analysis, the asymmetric units [CuCl(pyz)₂] are linked together forming a zigzag chain with tetrahedral copper(I) environment. The two lattice water molecules form hydrogen bonds with the uncoordinated N atom and carboxylate group O atom of pyz-H molecules. The Cu–N bond lengths are 2.009(6) Å and Cu–Cl distances are 2.337(2) Å. Complex 2 has a three-dimensional structure with the chains [Cu(I)Cu(II)(C₅H₃N₂O₂)Cl₂(H₂O)] interconnected by [Cu(I)Cl₂N] tetrahedral unit and [Cu(II)NO₂Cl₂] polyhedra. The Cu(I)–Cl and Cu(I)–N distances are 2.327(2)–2.581(2) Å and 1.988(6) Å, respectively, whereas the Cu(II)–Cl and Cu(II)–N bond lengths are 2.258(2), 2.581(2) Å, and 2.017(6) Å, respectively. Hydrogen bonds of the type O–HO are formed between lattice and coordinated water, and carboxylate oxygens of pyrazinato ligand giving rise to a three-dimensional network. The Cl⁻ anions act as bridging ligands in both complexes. The magnetic data of complex 2 have been measured from 2 to 300 K and discussed.     

Tautomeric properties, conformations and structure of N-(2-hydroxy-5-chlorophenyl) salicylaldimine

The crystal structure of N-(2-hydroxy-5-chlorophenyl) salicylaldimine (C₁₃H₁₀NO₂Cl) was determined by X-ray analysis. It crystallizes orthorhombic space group P2₁2₁2₁ with a=12.967(2) Å, b=14.438(3) Å, c=6.231(3) Å, V=1166.5(6) Å³, Z=4, D_c=1.41 g cm⁻³ and μ(MoK)=0.315 mm⁻¹. The title compound is thermochromic and the molecule is nearly planar. Both tautomeric forms (keto and enol forms in 68(3) and 32(3)%, respectively) are present in the solid state. The molecules contain strong intramolecular hydrogen bonds, N1–H1O1/O2 (2.515(1) and 2.581(2) Å) for the keto form and O1–H01N1 for the enol one. There is also strong intermolecular O2–HO1 hydrogen bonding (2.599(2) Å) between neighbouring molecules. Minimum energy conformations AM1 were calculated as a function of the three torsion angles, θ₁(N1–C7–C6–C5), θ₂(C8–N1–C7–C6) and θ₃(C9–C8–N1–C7), varied every 10°. Although the molecule is nearly planar, the AM1 optimized geometry of the title compound is not planar. The non-planar conformation of the title compound corresponding to the optimized X-ray structure is the most stable conformation in all calculations.     

Second sphere interaction in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate

Trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate was synthesised and detailed packing analysis was undertaken to delineate the topological complimentarity of [trans-Co(en)₂Cl₂]⁺ and BF₄⁻ ions by second sphere coordination. The complex was completely characterised by elemental analyses, solubility product measurement and spectroscopic studies (IR, UV–Vis, multinuclear NMR). In the crystal lattice, discrete ions [trans-Co(en)₂Cl₂]⁺ and BF₄⁻ are arranged in A–B–A–B pattern (in both a and c directions of the lattice) forming columns of anions and cations. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. N–HF⁻ and N–HCl involving second sphere coordination. It appears that the topological features of [trans-Co(en)₂Cl₂]⁺ are conducive for generating second sphere interactions. This strategy may be used as a viable method for the capture of other fluoroanions.     

Synthesis, structural characterization and ab initio calculation of dipyridyltetraazathiapentalene: a highly conjugative polycyclic molecule with hypervalent N–S–N bond

A highly conjugative polyheterocyclic compound, tetraazathiapentalene fused with pyridine rings, was synthesized by reacting 2-aminopyridine with carbon disulfide. The single crystal X-ray determination reveals that the molecule crystallizes in monoclinic space group C2/c, with the following unit cell dimensions: a=11.062(2), b=9.030(1), c=20.898(5) Å, β=102.98(1)°, V=2034.00(3) Å³, Z=8, and that a hypervalent N–S–N bond exists in the molecule. Ab initio calculations predict its IR and ¹H NMR spectra that are coincident with the experimental ones and reveal the bonding nature of the hypervalent N–S–N bond and the electronic structure of the molecule.     

The quasi-symmetric OHN and ODN bridges in the adducts of 3,5-dimethylpyridine with 3,5-dinitrobenzoic acid

The crystal structure of the adduct of 3,5-dimethylpyridine and 3,5-dinitrobenzoic acid (DMP-DNB) has been determined at room temperature and 80 K for both undeuterated and deuterated compounds. The monoclinic crystals are isomorphous, space group P2₁/c and Z = 4. Very strong OHN hydrogen bonds are almost linear with fully disordered (1:1) bridge hydrogen atoms between oxygen and nitrogen atoms. This is well reflected in the difference in electron density maps the contours of which depend both on cooling and deuteration. The intramolecular hydrogen bond lengths are 2.550(2) Å for the (OHN) and 2.563(2) Å for (ODN) at room temperature and 2.529(2) Å for (OHN) and 2.531(2) Å for (ODN) at 80 K. Therefore, there is a small but meaningful isotope effect upon the O…N hydrogen bridge length at room temperature and no Ubbelohde isotope effect is observed at 80 K. The infra-red spectra show very broad stretching protonic bands in the 200–1600 cm⁻¹ range. The isotopic ratio v(H)/v(D) at room temperature is about 1.1.     

Structural and spectral studies on N-(4-chloro)benzoyl-N′-(4-tolyl)thiourea

The crystal and molecular structure of the N-(4-chloro)benzoyl-N′-(4-tolyl)thiourea (C₁₅H₁₃N₂OSCl, M_r=304.79) is determined by X-ray diffraction. The crystal structure is monoclinic, space group: P2₁/n, a=16.097(6), b=4.5989(2), c=19.388(7) Å and β=89.299(6)° V=1434.7(9)ų, Z=4. FTIR and NMR spectra have been characterized. The interactions of intramolecular and intermolecular hydrogen bonds have been discussed. Density functional theory (DFT) (B3LYP) methods have been used to determine the structure and energies of stable conformers. Minimum energy conformations are calculated as a function of the torsion angle θ (C13–N1–C14–N2) varied every 30°. The optimized geometry corresponding to crystal structure is the most stable conformation. This has partly been attributed to intramolecular hydrogen bonds. With the basis sets of the 6-311G* quality, the DFT calculated bond parameters and harmonic vibrations are predicted in a very good agreement with experimental data.     

Peri-interaction: crystal structure of 1,8-bis-(methylene-4,4′-bipyridinium)-naphthalene

C₃₂H₂₆N₄Br₂, M = 626.4, triclic ₁---C¹; (No. 2) with a = 13.530(5) Å, b = 10.781(5) Å, c = 10.444(5) Å, β = 97.62(3), V = 1493(1) ų, Z = 2, μ = 27.1 cm⁻¹, F = (000) = (600), D_c = 1.84 g cm⁻³. Several molecular conformations are possible for the title compound. Although free rotation of the bipyridyl moieties around the C---C bonds is possible, the bulky 4,4′-bipyridyls impose steric hindrance and restrict the free rotation. Examination of the Drieding model of the molecule eliminated those arrangements where considerable overlapping of the bipyridyls occurred. NMR results were not useful in choosing the most likely candidate for the structure from the remaining possibilities. Three-dimensional diffraction data was collected at 20+1 C on a computer-controlled four circle Nicolet audiodiffractometer using graphite crystal monochromated Mo-radiation. The most probable conformation where the hydrogen—hydrogen and bipyridyl—bipyridyl interactions are minimum is shown in Fig. 1.     

Observation and rovibrational analysis of the ν2 band of HCN–HCl

The high-resolution infrared absorption spectrum of an equilibrium mixture of HCN and HCl in a static gas long-path absorption cell is recorded in the 2500–2900 cm⁻¹ spectral region at 205 K. The spectrum shows rovibrational structure which has the typical appearance of a parallel band of a linear molecule and is assigned to the intramolecular H–Cl stretching vibration band ν₂ of the linear HCN–H³⁵Cl heterodimer. The rovibrational analysis of the band yield a band origin ν₀ of 2779.0968(12) cm⁻¹ together with a value for the upper-state rotational constant B′ of 0.067722(2) cm⁻¹. The observed red shift of 107 cm⁻¹ for the ν₂ band of HCN–H³⁵Cl relative to the H–Cl stretching vibration band of monomer H³⁵Cl is in excellent agreement with results from the MP2/6−311++G** level of theory. The value of the upper-state rotational constant shows that the intermolecular hydrogen bond shortens by 0.022 Å upon intramolecular vibrational excitation of the ν₂ mode.     

Crystal structure of Schiff base derivative of 2,2′-dihydroxybiphenyl-3-carbaldehyde with n-butylamine

Crystals of the Schiff base derivative of 2,2′-dihydroxybiphenyl-3-carbaldehyde with n-butylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. Their space group is with a=8.377(2), b=12.214(2), c=14.774(3) Å, =76.62(3)°, β=81.34(3)°, γ=86.62(3)° and Z=4. The unit cell contains two symmetry-independent zwitterions. The hydrogen atom of the protonated N atom of the Schiff base is linked to the oxygen atom of the carbonyl group at position 2, which in turn is linked to the hydroxyl group by a short hydrogen bond [molecule A: NO=2.614(3), OO=2.520(3) Å; molecule B: NO=2.594(4), OO=2.526(3) Å]. The OHO⁻H⁺N bifurcated intramolecular hydrogen bonds are crystallographically asymmetric. The results of the FT-IR, ¹H, ¹³C, ¹⁵N NMR and CPMAS study of the crystals are in agreement with the X-ray data. Instead of a continuous absorption, only a broad band is found indicating relatively low proton polarizability in the two types of the cooperative relatively short intramolecular hydrogen bonds. The ¹⁵N NMR chemical shift indicates the protonation of the Schiff base.     

Tautomeric properties, conformations and structure of N-(2-hydroxyphenyl)-4-amino-3-penten-2-on

N-(2-hydroxyphenyl)-4-amino-3-penten-2-on (C₁₁H₁₃NO₂) has been studied by X-ray analysis. It crystallizes the orthorhombic space group P2₁2₁2₁ with a=8.834(1), b=10.508(2), c=11.212(2) Å, V=1040.8(3) Å³, Z=4, D_c=1.22 g cm⁻³ and μ(MoK)=0.084 mm⁻¹. The structure was solved by direct methods and refined to R=0.038 for 1373 reflections (I>2σ(I)). The title compound is photochromic and the molecule is not planar. Intramolecular hydrogen bonds occur between the pairs of atoms N(1) and O(1) [2.631(2) Å], and N(1) and O(2) [2.641(2) Å], the H atom essentially being bonded to the N atom. There is also a strong intermolecular O–HO hydrogen bonding [2.647(2) Å] between neighbouring molecules. Tautomeric properties and conformations of the title compound were investigated by semi-empirical quantum mechanical AM1 calculations and the results are compared with the X-ray results.     

Complexation of trivalent lanthanide cations by inositol in solid state. The crystal structure and Raman spectra study of NdCl3·inositol·9H2O

The crystal structure of NdCl₃·C₆H₁₂O₆·9H₂O has been determined. It crystallizes in the monoclinic system, p2(1)/n space group with cell dimensions: a=15.824(3) Å, b=8.633(2) Å, c=16.219(3) Å, β=107.24°, V=2116.1(7) ų and Z=4. Each Nd ion is coordinated to nine oxygen atoms, two from inositol and seven from water molecules, with an Nd–O distance of 2.449–2.683 Å, the other two water molecules are hydrogen bonded. No direct contacts exist between Nd and Cl. There is an extensive network of hydrogen bonds in hydroxyl groups, water molecules and chloride ions in the crystal structure of the lanthanide complex. The Raman spectra of Pr–, Nd– and Sm–inositol are similar, which show that the three metal ions have the same coordination mode. The Raman spectra are consistent with their structures.     

Structural characterisation of [Pt(NH3)4]2[W(CN)8][NO3]·2H2O donor–acceptor complex

The bimetallic [Pt(NH₃)₄]₂[W(CN)₈][NO₃]·2H₂O is characterised by single-crystal X-ray diffraction [S.G.P2₁/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D_4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D_4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)^* separations of 4.77(2), 4.55(2)^* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO₃⁻ between parallel [Pt(1)(NH₃)₄]²⁺ planes and the second consists of [W(CN)₈]³⁻ interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH₃)₄]²⁺. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH₃ ligands, water molecules and oxygen atoms of NO₃⁻ counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.     

[NHN] and [OHO] hydrogen bonding in the adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 1,8-dihydroxy-2,4-dinitronaphthalene (DHDNN)

X-Ray diffraction, IR and ¹H NMR studies were performed on the 1:1 adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 1,8-dihydroxy-2,4-dinitronaphthalene (DHDNN). The adduct crystallizes in the triclinic system, space group , a = 9.911(2) Å, b = 11.212(2) Å, c = 11.194(2) Å, = 68.95(2)°, β = 79.72(2)°, γ = 73.78(2)°, Z = 2. Both [NHN]⁺ and [OHO]⁻ hydrogen bonds formed in the ion pairs are asymmetrical with lengths equal to 2.574(2) Å and 2.466(4) Å respectively. The [NHN]⁺ bridge shows a typical behaviour in the IR spectrum, i.e. a low-frequency absorption between 300 and 700 cm⁻¹. The coupling of [OHO]⁻ hydrogen bonds with the naphthalene π-electron system is so strong that no absorption related to the proton stretching vibrations can be detected in the high- and low-frequency regions. The ¹H NMR chemical shifts for the [NHN]⁺ and [OHO]⁻ bridge protons of 18.63 and 15.81 ppm respectively confirm the strong hydrogen bonds.     

Hydrogenmaleato bridged supramolecular double chains via π–π stacking interactions: syntheses, crystal structures and magnetic properties of ∞[Cu(phen)X(HL)2/2] with X=Cl (1), NO3 (2) and H2L=maleic acid

Two novel hydrogen maleato (HL) bridged Cu(II) complexes _∞¹[Cu(phen)Cl(HL)_2/2] 1 and _∞¹[Cu(phen)(NO₃)(HL)_2/2] 2 were obtained from reactions of 1,10-phenanthroline, maleic acid with CuCl₂·2H₂O and Cu(NO₃)₂·3H₂O, respectively, in CH₃OH/H₂O (1:1 v/v) at pH=2.0 and the crystal structures were determined by single crystal X-ray diffraction methods. Both complexes crystallize isostructurally in the monoclinic space group P2₁/n with cell dimensions: 1 a=8.639(2) Å, b=15.614(3) Å, c=11.326(2) Å, β=94.67(3)°, Z=4, D_calc=1.720 g/cm³ and 2 a=8.544(1) Å, b=15.517(2) Å, c=12.160(1) Å, β=90.84(8)°, Z=4, D_calc=1.734 g/cm³. In both complexes, the square pyramidally coordinated Cu atoms are bridged by hydrogen maleato ligands into 1D chains with the coordinating phen ligands parallel on one side. Interdigitation of the chelating phen ligands of two neighbouring chains via π–π stacking interactions forms supramolecular double chains, which are then arranged in the crystal structures according to pseudo 1D close packing patterns. Both complexes exhibit similar paramagnetic behavior obeying Curie–Weiss laws χ_m(T−θ)=0.414 cm³ mol⁻¹ K with the Weiss constants θ=−1.45, −1.0 K for 1 and 2, respectively.     

Structure and conformational properties of carbonylbisimidosulfuryl fluoride, O=C(N=S(O)F2)2

The molecular structure and conformational properties of O=C(N=S(O)F₂)₂ (carbonylbisimidosulfuryl fluoride) were determined by gas electron diffraction (GED) and quantumchemical calculations (HF/3-21G* and B3LYP/6-31G*). The analysis of the GED intensities resulted in a mixture of 76(12)% syn–syn and 24(12)% syn–anti conformer (ΔH⁰=H⁰(syn–anti)−H⁰(syn–syn)=1.11(32) kcal mol⁻¹) which is in agreement with the interpretation of the IR spectra (68(5)% syn–syn and 32(5)% syn–anti, ΔH⁰=0.87(11) kcal mol⁻¹). syn and anti describe the orientation of the S=N bonds relative to the C=O bond. In both conformers the S=O bonds of the two N=S(O)F₂ groups are trans to the C–N bonds. According to the theoretical calculations, structures with cis orientation of an S=O bond with respect to a C–N bond do not correspond to minima on the energy hyperface. The HF/3-21G* approximation predicts preference of the syn–anti structure (ΔE=−0.11 kcal mol⁻¹) and the B3LYP/6-31G* method results in an energy difference (ΔE=1.85 kcal mol⁻¹) which is slightly larger than the experimental values. The following geometric parameters for the O=C(N=S)₂ skeleton were derived (r_a values with 3σ uncertainties): C=O 1.193 (9) Å, C–N 1.365 (9) Å, S=N 1.466 (5) Å, O=C–N 125.1 (6)° and C–N=S 125.3 (10)°. The geometric parameters are reproduced satisfactorily by the HF/3-21G* approximation, except for the C–N=S angle which is too large by ca. 6°. The B3LYP method predicts all bonds to be too long by 0.02–0.05 Å and the C–N=S angle to be too small by ca. 4°.     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.