Spectroscopic, thermal, magnetic and structural characterization of K3VF6 prepared at room temperature

A straight forward room-temperature synthesis of V(III) containing complex fluoride K₃VF₆, using KF and vanadium(III) acetylacetonate is reported. The pale green colored powder was characterized by chemical analysis, powder X-ray diffraction; diffuse reflectance spectroscopy, infrared spectroscopy, Raman spectroscopy, differential scanning calorimetry, scanning electron microscopy, photoluminescence spectroscopy, magnetic susceptibility measurements and photoluminescence spectroscopy. The powder X-ray diffraction pattern was fitted in P2₁/n space group (monoclinic) with a = 12.106 (1) Å, b = 17.685 (0) Å, c = 11.802 (0) Å, β = 92.23° (1). Differential scanning calorimetry showed phase transitions, occurring at 158 °C and 190 °C. In the FT-IR spectrum, characteristic band for the VF₆³⁻ group was observed at 508 cm⁻¹. The bands observed in the 335-361 cm⁻¹ region and at 504 cm⁻¹ in the room temperature Raman spectrum of K₃VF₆ corresponded to the F_2g and A_1g modes, respectively. The ratio of the frequencies (F_2g/A_1g) observed in the diffuse reflectance spectrum was fitted on the Tanabe-Sugano diagram to determine the Racah parameter B value of 712 cm⁻¹. Magnetic ordering was not observed down to the lowest measured temperature of 5 K.     

Coordination frameworks containing the pyrimidin-4-olate ligand. Synthesis, thermal, magnetic, and ab initio XRPD structural characterization of nickel and zinc derivatives

Extended coordination frameworks containing the pyrimidin-4-olate ligand (4-pymo) and Zn(II) and Ni(II) metal ions have been obtained by solid state reactions and have been fully characterized by spectroscopic, thermal, and magnetic measurements and by ab initio XRPD. The reaction of ZnO and 4-Hpymo at 140 degrees C gives a solid microcrystalline phase, Zn(4-pymo)(2) (1). Its 3D framework contains Zn(II) centers linked by 4-pymo ligands acting in two different coordination modes, namely, the N,N'- and the N,O-exo-bidentate ones, which result in a pseudotetrahedral ZnN(3)O chromophore. Thermal treatment of the "molecular" Ni(4-pymo)(2)(H(2)O)(4) complex (2) above 140 degrees C gives an anhydrous amorphous material analyzing as Ni(4-pymo)(2) (3a). Further heating of this material above 388 degrees C results in the formation of the microcrystalline layered Ni(4-pymo)(2) species (3b), in which Ni(II) centers are bridged by N,O-exo-bidentate 4-pymo ligands (assisted by longer Ni.N contacts). The thermal dependence of the magnetic susceptibility has been studied for the paramagnetic species 2 and 3a. 2 shows a weak antiferromagnetic interaction [J = -0.313(5) cm(-)(1)] transmitted through the multiple H-bonding interactions between the exocyclic pyrimidine and water oxygen atoms coordinated to the metal centers. 3a behaves as a 2D Heisenberg antiferromagnet with J = -4.11(3) cm(-)(1).     

Structural,optical and magnetic characterization of ZnO nanorods synthesized using hydrothermal technique at low temperature

Pure ZnO nanorods were grown from aqueous solutions at low temperature (90 °C) by hydrothermal growth technique on sapphire (0001) substrate coated with ZnO thin film. X-ray diffraction results show that these nanorods crystallize in the wurtzite structure having space group P6₃mc and that they are oriented along the c-axis. Raman and photo-luminescence studies show the presence of oxygen vacancies in the ZnO nanorods. The ZnO nanorods show room temperature ferromagnetism.     

Preparation and structural,spectroscopic, thermal,and electrochemical characterizations of iron(III) compounds containing dipicolinate and 2-aminopyrimidine or acridine

Two new iron(III) compounds, (Hamp)[Fe(pydc)₂]?·?2H₂O (1) and (Hacr)[Fe(pydc)₂]?·?2H₂O (2) (pydc^2??=?pyridine-2,6-dicarboxylic acid, amp?=?2-aminopyrimidine, acr?=?acridine), have been hydrothermally synthesized. Both compounds were characterized by spectroscopic methods (IR, UV/Vis), and their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by thermogravimetric analysis/differential thermal analysis (TGA/DTA) methods. Compound 1 consists of Hamp⁺ cation and [Fe(pydc)₂]^? anion and 2 consists of Hacr⁺ cation and [Fe(pydc)₂]^? anion. Crystallographic characterization revealed an octahedron as a coordination polyhedron for the complex anion in 1 and 2 and the same O,N,O′-chelated coordination mode of pyridine-2,6-dicarboxylate. The crystal structures of 1 and 2 are stabilized by a complicated network of hydrogen bonds between the crystallization water molecules, counter ion, and carboxylates of pydc^2?. Thermogravimetric (TG) analyses of the two compounds were carried out to examine their thermal stabilities. Cyclic voltammetric response of bare glassy carbon electrode surface in 0.10?mol?L^?1 phosphate buffer containing 1 and 2 at different pH values indicated that they have the same voltammograms at all pH values and the electrochemical behavior of 1 and 2 has not been affected by different ion pairs. The formal potential of the solutions of 1 and 2 at the glassy carbon electrode surface was also pH-dependent with a slope of ?57.0?mV/pH unit at 25°C. This shows that the number of electrons and protons involved in the electrode process is equal.     

New metal complexes with diclofenac containing 2-pyridineethanol or 2-pyridinepropanol: synthesis,structural, spectroscopic,thermal properties,catechol oxidase and carbonic anhydrase activities

Four new neutral diclofenac-based complexes, [Co(dicl)2(2-pyet)2] 1, [Ni(dicl)2(2-pyet)2] 2, [Cu2(dicl)2(2-pyet)2] 3, and [Cu2(dicl)2(2-pypr)2] 4 have been synthesized and characterized by elemental analysis, FT-IR, thermal analysis. Complexes 1, 3, and 4 have also been characterized by X-ray single-crystal structural analysis. The compounds of Co(II) and Ni(II) have octahedral geometry with two diclofenac and two 2-pyridineethanol ligands in the coordination sphere. The compounds of Cu(II) have square-pyramidal geometry and Cu(II) ions are linked via oxygens to the bridging 2-pyridineethanol or 2-pyridinepropanol ligands. The Δν values acquired by FT-IR are in agreement with the single XRD data. Studies on the thermal properties are reported and the complexes are stable to 196, 216, 215, and 201 °C in air, respectively. Two dinuclear Cu(II) complexes have demonstrated catalytic activity on oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone showing saturation kinetics at high substrate concentrations. The diclofenac complexes are investigated as inhibitors of the human cytosolic isoforms hCA I and II. The complexes are good as hCA I inhibitors (Kis of 1.52–55.06 μM) but only moderately efficient as hCA II inhibitors (Kis of 0.23–5.61 μM).     

Syntheses and spectroscopic and structural characterization of molybdenum(VI) citrato monomeric raceme and dimer, K4[MoO3(cit)].2H2O and K4[(MoO2)2O(Hcit)2].4H2O

Investigation of the aqueous coordination chemistry for citrate and molybdenum(VI) resulted in the isolation of molybdenum(VI) citrato monomeric raceme and dimer K4[MoO3(cit)].2H2O (1) and K4[(MoO2)2O(Hcit)2].4H2O (2) (H4cit = citric acid). Complex 1 can serve as the first structurally characterized monomeric citrato molybdate and may represent an early mobilized precursor in the biosynthesis of FeMo-co (FeMo-cofactor). The two complexes have been characterized by elemental analyses and IR and NMR spectroscopies. The IR and NMR spectra are consistent with a monomeric species or a monooxo-bridged dinuclear structure, as revealed by a single crystal X-ray diffraction study. Compound 1 is monoclinic space group P2(1)/c with a = 7.225(1) A, b = 9.151(2) A, c = 22.727(2) A, beta = 94.93(1) degrees, V = 1497.1(7) A3, and Z = 4. Full-matrix least-squares refinement resulted in residuals of R = 0.027 and Rw = 0.032. The molybdenum atom forms an octahedral coordination with three oxo groups and one tridentate citrate, in which the latter is coordinated through the alkoxy and vicinal carboxyl and much more weakly by one of the two terminal groups [2.411(3) A]. Compound 2 is triclinic space group P1 with a = 8.2728(8) A, b = 8.9514(8) A, c = 10.0605(9) A, alpha = 101.673(8) degrees, beta = 100.672(7) degrees, gamma = 112.938(7) degrees, V = 642.5(3) A3, and Z = 1. Full-matrix least-squares refinement resulted in residuals of R = 0.033 and Rw = 0.039. The complex anion contains a linear (O2Mo)O(MoO2) core with the bridging oxo group lying at the center of inversion symmetry (Mo-Ob-Mo, 180 degrees). Each citrate ligand is three-coordinated to one molybdenum atom through the deprotonated hydroxy, alpha-carboxyl, and one beta-carboxyl group, making each metal atom six-coordinate.     

Ferromagnetic exchange in the ground and (4)A(1) excited states of (Et(4)N)(3)Fe(2)F(9). A magnetic and optical spectroscopic study

The synthesis, crystal growth, magnetic susceptibility, and polarized optical absorption spectra in the visible and near UV of (Et(4)N)(3)Fe(2)F(9) are reported. From single-crystal magnetic susceptibility data and high-resolution absorption spectra in the region of the (6)A(1) --> (4)A(1) spin-flip transition, exchange splittings in the ground and excited states are derived. Ferromagnetic ground and excited state exchange parameters J(GS) = -1.55 cm(-1) and J(ES) = -0.53 cm(-1) are determined, respectively, and the relevant orbital contributions to the net exchange are derived from the spectra. The results are compared with those reported earlier for the structurally and electronically analogous [Mn(2)X(9)](5-) pairs in CsMgX(3):Mn(2+) (X = Cl(-), Br(-)), in which the splittings are antiferromagnetic. This major difference is found to be due to the increased metal charge of Fe(3+) compared to Mn(2+), leading to orbital contraction and thus to a strong decrease of the orbital overlaps and hence the antiferromagnetic interactions.     

Neutral solvent/crown ether interactions, 4. Crystallization and low temperature (−150°C) structural characterization of 18-crown-6 · 2(CH3CN)

The crystal structure of 18-crown-6 · 2(CH₃CN) has been determined via data collection at –150°C. The structure consists of two crown molecules each hydrogen bonded to two acetonitrile moieties in the asymmetric unit, each residing around a center of inversion. The crown ethers display their fullD _3d symmetry; methyl ... O contacts range from 3.189(8) to 3.598(8) Å. There are no close contacts indicative of any interaction between the crown/2(CH₃CN) units. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82056 (14 pages).For Part 3, see reference [1]     

[Mn(ATO)~2(H~2O)~4](PA)~2的制备、结构表征和热分 解机理研究

对新型配合物------苦味酸二(4-氨基-1,2,4-三唑-5-酮)四水合锰采用元素分析、FT-IR分析、粉末X射线衍射分析和单晶结构分析基础上,在线性升温条件下,用DSC,TG-DTG技术对该化合物的热分解过程进行了研究,得出了其热分解机理。     

Synthesis,structural and spectroscopic characterization of a new cadmium(II) complex containing imidazole (Im) as ligand, [Cd(Im)6](ClO4)2

Reaction between the 1,1′-carbonyldiimidazole ligand and mixtures of cadmium(II) acetate with sodium perchlorate provided the unusual crystalline material [Cd(Im)₆](ClO₄)_2, (Im?=?imidazole). This new Cd^II complex, has been characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR and ¹¹³Cd NMR spectroscopy. The coordination number in this complex is six, CdN₆ and coordination environment around the Cd(II) may be described as distorted octahedral with a D_2h point group. There are both edge-to-face π–π stacking and C–H(Im)?···?π interactions between aromatic “Im” rings belonging to adjacent chains in this network.     

Formation and characterization of the hexanuclear platinum cluster [Pt6(mu-PBu(t)2)4(CO)6](CF3SO3)2 through structural, electrochemical, and computational analyses

The reaction between equimolar amounts of Pt(3)(mu-PBu(t)()(2))(3)(H)(CO)(2), Pt(3)()H, and CF(3)SO(3)H under CO atmosphere affords the triangular species [Pt(3)(mu-PBu(t)()(2))(3)(CO)(3)]X, [Pt(3)()(CO)(3)()(+)()]X (X = CF(3)SO(3)(-)), characterized by X-ray crystallography, or in an excess of acid, [Pt(6)(mu-PBu(t)()(2))(4)(CO)(6)]X(2), [Pt(6)()(2+)()]X(2)(). Structural determination shows the latter to be a rare hexanuclear cluster with a Pt(4) tetrahedral core formed by joining the unbridged sides of two orthogonal Pt(3) triangles. The dication Pt(6)()(2+)() features also extensive redox properties as it undergoes two reversible one-electron reductions to the congeners [Pt(6)(mu-PBu(t)()(2))(4)(CO)(6)](+) (Pt(6)()(+)(), E(1/2) = -0.27 V) and Pt(6)(mu-PBu(t)()(2))(4)(CO)(6) (Pt(6)(), E(1/2) = -0.54 V) and a further quasi-reversible two-electron reduction to the unstable dianion Pt(6)()(2)()(-)() (E(1/2) = -1.72 V). The stable radical (Pt(6)()(+)()) and diamagnetic (Pt(6)()) species are also formed via chemical methods by using 1 or 2 equiv of Cp(2)Co, respectively; further reduction of Pt(6)()(2+)() causes fast decomposition. The chloride derivatives [Pt(6)(mu-PBu(t)()(2))(4)(CO)(5)Cl]X, (Pt(6)()Cl(+)())X, and Pt(6)(mu-PBu(t)()(2))(4)(CO)(4)Cl(2), Pt(6)()Cl(2)(), observed as side-products in some electrochemical experiments, were prepared independently. The reaction leading to Pt(3)()(CO)(3)()(+)() has been analyzed with DFT methods, and identification of key intermediates allows outlining the reaction mechanism. Moreover, calculations for the whole series Pt(6)()(2+)() --> Pt(6)()(2)()(-)()( )()afford the otherwise unknown structures of the reduced derivatives. While the primary geometry is maintained by increasing electron population, the system undergoes progressive and concerted out-of-plane rotation of the four phosphido bridges (from D(2)(d)() to D(2) symmetry). The bonding at the central Pt(4) tetrahedron of the hexanuclear clusters (an example of 4c-2e(-) inorganic tetrahedral aromaticity in Pt(6)()(2+)()) is explained in simple MO terms.     

Synthesis and characterization of Ru2(DMBA)4X2 (X = CN, N3, N(CN)2, I): controlling structural, redox, and magnetic properties with axial ligands

Metathesis reactions between Ru(2)(DMBA)(4)Cl(2) (DMBA = N,N'-dimethylbenzamidinate) and MX (M = Na and K) yielded bis-adduct derivatives Ru(2)(DMBA)(4)X(2) (X = CN (1), N(3) (2), N(CN)(2) (3)). Metathesis reactions between Ru(2)(DMBA)(4)(NO(3))(2) and KI resulted in Ru(2)(DMBA)(4)I(2) (4). Compound 1 is diamagnetic, while compounds 2-4 are paramagnetic (S = 1). Both compounds 1 and 2 undergo two reversible one-electron processes, an oxidation and a reduction, while compound 3 features a quasireversible reduction. Single-crystal X-ray diffraction studies revealed that the Ru-Ru bond lengths are 2.4508(9), 2.3166(7), 2.304[1], and 2.328(1) A for compounds 1-4, respectively. Structural and electrochemical data clearly indicate that the axial ligands impart a significant influence on the electronic structures of diruthenium species.     

Synthesis, characterization, and substitution chemistry of [Bu4N]2[W6Cl8(OSO2CF3)6]. A versatile precursor for axially substituted clusters containing the (W6Cl8)4+ core

The new cluster [Bu4N]2[W6Cl8(OSO2CF3)6] (1) has been prepared and structurally characterized. This material is an effective precursor for the generation of cluster ions with the general formula [W6C18L6]n (L = Cl-, Br-, I-, NCS-, NCO-, NCSe-, and O=PPh3; n = 2- or 4+). The last three clusters are new. The products have been characterized by IR spectroscopy, NMR spectroscopy, and FAB mass spectrometry. In addition to 1, the products [Bu4N]2[W6C18(NCS)6] (5) and [Bu4N]2[W6C18(NCO)6] (7) were structurally characterized. Crystal data for 1: space group, P2(1/c) (No. 14); a = 11.116(5) A; b = 27.952(1) A; c = 24.516(1) A; beta = 95.182(9) degrees; V = 7586.3(5) A3; Z = 4. Crystal data for 5: space group, P2(1/n) (No. 14); a = 11.3323(9) A; b = 12.3404(9) A; c = 44.583(3) A; beta = 97.089(1) degrees ; V = 6187.1(7) A3; Z = 4. Crystal data for 7: space group, P1 (No. 2); a = 11.8009(8) A; b = 11.9332(8) A; c = 11.9522(8) A; alpha = 77.904(1) degrees; beta = 95.182(9) degrees; gamma = 62.574(1) degrees V = 1450.5(2) A3; Z = 1.     

Tuning intermolecular magnetic exchange interactions in the solids C(x)F(2)(x)(CNSSS)(2)(AsF(6))(2): structural, EPR, and magnetic characterization of dimeric (x = 2, 4) diradicals

A series of diradical containing salts CxF2x(CNSSS)2(**2+0(AsF6-)2 {x = 2, 1[AsF6]2; x = 3, 3[AsF6]2; x = 4, 2[AsF6]2} have been prepared. 1[AsF6]2 and 2[AsF6]2 were fully characterized by X-ray, variable-temperature magnetic susceptibility, and solid-state EPR measurements, further allowing us to extend the number of examples of the family of rare 7pi RCNSSS(*+) radical cations. 1[AsF6]2: a = 6.5314(7) A, b = 7.5658(9) A, c = 9.6048(11) A, alpha = 100.962(2) degrees , beta = 96.885(2) degrees , gamma = 107.436(2) degrees , triclinic, space group P, Z = 1, T = 173 K. 2[AsF6]2: a = 10.6398(16) A, b = 7.9680(11) A, c = 12.7468(19) A, beta = 99.758(2) degrees , monoclinic, space group P21/c, Z = 2, T = 173 K. In the solid-state, CxF2x(CNSSS)2(**2+) (x = 2, 4) formed one-dimensional polymeric chains of dications containing discrete centrosymmetric radical pairs in which radicals were linked by four centered two-electron pi*-pi* bonds [12+, d(S...S) = 3.455(1) A; 22+, d(S...S) = 3.306(2) A]. The exchange interactions in these bonds were determined to be -500 +/- 30 and -900 +/- 90 cm-1, by variable temperature magnetic susceptibility measurements, respectively, providing rare experimental data on the singlet-triplet gaps in the field of thiazyl radicals. For 2[AsF6]2, the thermally excited triplet state was unambiguously characterized by EPR techniques [/D/ = 0.0254(8) cm(-1), /E/ = 0.0013(8) cm(-1)]. These experimental data implied a weakly associated nature of the radical moieties contained in the solids 1[AsF6]2 and 2[AsF6]2. Computational analysis of the dimerization process is presented, and we show that the 2c 4 electron pi*-pi* bonds in 1[AsF6]2 and 2[AsF6]2 have ca. 50% and 40% diradical character, respectively. In contrast, 3[AsF6]2.SO2, containing diradical C3F6(CNSSS)2(**2+) with an odd number of CF2 spacers, showed magnetic behavior that was consistent with the presence of monomeric radical centers in the solid state.     

Preparation and characterization of sulfated zirconia (SO4/ZrO2)/Nafion composite membranes for PEMFC operation at high temperature/low humidity

Fine particle superacidic sulfated zirconia (SO₄²⁻/ZrO₂, S-ZrO₂) was synthesized by ameliorated method, and composite membranes with different S-ZrO₂ contents were prepared by a recasting procedure from a suspension of S-ZrO₂ powder and Nafion solution. The physico-chemical properties of the membranes were studied by ion exchange capacity (IEC) and liquid water uptake measurements, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, thermogravimetry–mass spectrometry (TG–MS) and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the IEC of composite membrane increased with the content of S-ZrO₂, S-ZrO₂ was compatible with the Nafion matrix, the incorporation of the S-ZrO₂ could increase the crystallinity and also improve the initial degradation temperature of the composite membrane. The performance of single cell was the best when the S-ZrO₂ content was 15 wt.%, and achieved 1.35 W/cm² at 80 °C and 0.99 W/cm² at 120 °C based on H₂/O₂ and at a pressure of 2 atm, the performance of the single cell with optimized S-ZrO₂ was far more than that of the Nafion at the same condition (e.g. 1.28 W/cm² at 80 °C, 0.75 W/cm² at 120 °C). The 15 wt.% S-ZrO₂/Nafion composite membrane showed lower fuel cell internal resistance than Nafion membranes at high temperature and low relative humidity (RH).     

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

Synthesis, spectroscopic characterization and thermal behavior of metal complexes formed with N'-(1-(4-hydroxyphenyl) ethylidene)-2-oxo-2-(phenylamino) acetohydrazide (H3OPAH)

Complexes of Co(II), Ni(II), Cu(II), Mn(II), Cd(II), Zn(II), Hg(II) and U(IV)O(2)(2+) with N'-(1-(4-hydroxyphenyl) ethylidene)-2-oxo-2-(phenylamino) acetohydrazide (H(3)OPAH) are reported and have been characterized by various spectroscopic techniques like IR, UV-visible, (1)H NMR and ESR as well as magnetic and thermal (TG and DTA) measurements. It is found that the ligand behaves as a neutral bidentate, monoanionic tridentate or tetradentate and dianionic tetradentate. An octahedral geometry for [Mn(H(3)OPAH)(2)Cl(2)], [Co(2)(H(2)OPAH)(2)Cl(2)(H(2)O)(4)] and [(UO(2))(2)(HOPAH)(OAc)(2)(H(2)O)(2)] complexes, a square planar geometry for [Cu(2)(H(2)OPAH)Cl(3)(H(2)O)]H(2)O complex, a tetrahedral structure for [Cd(H(3)OPAH)Cl(2)], [Zn(H(3)OPAH)(OAc)(2)] and [Hg(H(3)OPAH)Cl(2)]H(2)O complexes. The binuclear [Ni(2)(HOPAH)Cl(2)(H(2)O)(2)]H(2)O complex contains a mixed geometry of both tetrahedral and square planar structures. The protonation constants of ligand and stepwise stability constants of its complexes at 298, 308 and 318 K as well as the thermodynamic parameters are being calculated. The bond lengths, bond angles, HOMO, LUMO and dipole moments have been calculated to confirm the geometry of the ligand and the investigated complexes. Also, thermal properties and decomposition kinetics of all compounds are investigated. The interpretation, mathematical analysis and evaluation of kinetic parameters (E(a), A, ΔH, ΔS and ΔG) of all thermal decomposition stages have been evaluated using Coats-Redfern and Horowitz-Metzger methods.     

DFT study of the geometry and energy order of the low singlet and triplet states of [d4-eta5-CpMo(CO)2X] 16-electron complexes (X = halogen, CN, H, and CH3)

DFT methods have been used to investigate the dependence of the geometry and energy order of the low energy states of [d(4)-eta(5)-CpMo(CO)(2)X] 16-electron complexes on X (X = halogen, CN, H and CH(3)). The calculations use a double-zeta plus polarization valence basis set on all atoms and utilize relativistic ECPs on Mo and the heavier halogens. In every case two singlet and two triplet electronic states have been considered and minimized at the B3LYP level. For X = Cl, additional calculations were carried out at the BPW91, CCSD(T), and CASSCF levels. In the C(s) point group, the singlet states are from the (1a')(2)(1a')(2) and (1a')(2)(2a')(2) configurations of the valence d(4) electrons of the metal, and are denoted (1)A'-a and (1)A'-b, respectively. The triplet species are for the lowest (3)A' and (3)A' states from the (1a')(2)(2a')(1)(1a')(1) and (1a')(2)(1a')(1)(2a')(1) d(4) configurations. For all substituents, the geometry of both the singlet and triplet states is found to distort substantially from the uniform 3-leg piano-stool structural motif, a behavior that can be related to Jahn-Teller effects. When X is a halogen or a methyl, (1)A'-b is predicted to be lower than (1)A'-a, while the reverse order of these two singlet states is calculated for X = H and CN. For all substituents (3)A' is substantially higher than (3)A'. In turn, the energy of (3)A' is calculated to be comparable to the lower singlet state of each complex. Attempts are made to rationalize some of these results using qualitative MO theory.     

Determination of the rate constants for the NH2(X2B1) + NH2(X2B1) and NH2(X2B1) + H Recombination reactions with collision partners CH4, C2H6, CO2, CF4, and SF6 at low pressures and 296 K. Part 2

The recombination rate constants for the reactions NH2(X2B1) + NH2(X2B1) + M → N2H4 + M and NH2(X2B1) + H + M → NH3 + M, where M was CH4, C2H6, CO2, CF4, or SF6, were measured in the same experiment over presseure ranges of 1-20 and 7-20 Torr, respectively, at 296 ± 2 K. The NH2 radical was produced by the 193 nm laser photolysis of NH3. Both NH2 and NH3 were monitored simultaneously following the photolysis laser pulse. High-resolution time-resolved absorption spectroscopy was used to monitor the temporal dependence of both species: NH2 on the (1)2(21) ← (1)3(31) rotational transition of the (0,7,0)A2A1 ← (0,0,0)X2B1 electronic transition near 675 nm and NH3 in the IR on either of the inversion doublets of the qQ3(3) rotational transition of the ν1 fundamental near 2999 nm. The NH2 self-recombination clearly exhibited falloff behavior for the third-body collision partners used in this work. The pressure dependences of the NH2 self-recombination rate constants were fit using Troe’s parametrization scheme, k(inf), k(0), and F(cent), with k(inf) = 7.9 × 10(-11) cm3 molecule(-1) s(-1), the theoretical value calculated by Klippenstein et al. (J. Phys. Chem. A113, 113, 10241). The individual Troe parameters were CH4, k(0)(CH4) = 9.4 × 10(-29) and F(cent)(CH4) = 0.61; C2H6, k(0)(C2H6) = 1.5 × 10(-28) and F(cent)(C2H6) = 0.80; CO2, k(0)(CO2) = 8.6 × 10(-29) and F(cent)(CO2) = 0.66; CF4, k(0)(CF4) = 1.1 × 10(-28) and F(cent)(CF4) = 0.55; and SF6, k(0)(SF6) = 1.9 × 10(-28) and F(cent)(SF6) = 0.52, where the units of k0 are cm6 molecule(-2) s(-1). The NH2 + H + M reaction rate constant was assumed to be in the three-body pressure regime, and the association rate constants were CH4, (6.0 ± 1.8) × 10(-30); C2H6, (1.1 ± 0.41) × 10(-29); CO2, (6.5 ± 1.8) × 10(-30); CF4, (8.3 ± 1.7) × 10(-30); and SF6, (1.4 ± 0.30) × 10(-29), with units cm6 molecule(-1) s,(-1) and the systematic and experimental errors are given at the 2σ confidence level.