Medium-size polarized basis sets for high-level-correlated calculations of molecular electric properties

Summary The basis set polarization method is used to derive the first-order polarized basis sets for Ge through Br for calculations of atomic and molecular electric properties. The performance of the [15.12.9/9.7.4] GTO/CGTO basis sets generated in this study is verified in calculations of atomic dipole polarizabilities and dipole moments and polarizabilities of the third-row atom hydrides. Whenever accurate reference data are available for comparison, the excellent performance of the derived first-order polarized basis sets is demonstrated. The role of the core polarization and relativistic contributions to atomic and molecular is also investigated. The detailed basis set data for Ge through Br are given in Appendix.     

Tetra-hydrides of the third-row transition elements: spin–orbit coupling effects on geometrical deformation in WH4 and OsH4

The dissociation energies of MH₄ (M =  La, Hf–Hg) were computed using full optimized reaction space (FORS) multi-configuration self-consistent field (MCSCF) and second-order multi-reference Møller–Plesset perturbation methods with the SBKJC basis sets augmented by a set of polarization functions (SBKJC(f,p)). It was shown that of the molecules examined, only four tetra-hydrides HfH₄, TaH₄, WH₄, and OsH₄ with T_d symmetry are lower in energy than the corresponding dissociation limits. For WH₄ and OsH₄, the potential energy surfaces from the D_4h to the T_d structure were explored from both theoretical calculations and symmetry arguments based on the pseudo-Jahn- Teller effect. As for WH₄, it is found that the ground state could be ³E_g, ³A_2g, or ³B_2g at the D_4h structure. The present calculations suggest that the ground state is ³E_g, and that this state is stabilized by the e_u deformation into a C_2v structure (³B₁) and then sequentially to the most stable T_d structure (³A₂). If the molecular system is promoted to the lowest ³B_2g state, the D_4h structure can directly deform into the most stable T_d structure along the b_2u vibrational mode. For OsH₄, the ground state (⁵B_1g) at the D_4h structure deforms into a D_2d structure and the resulting ⁵B₂ state strongly interacts with the lowest ³E and ¹A₁ states due to the spin-orbit couplings (SOCs). As a result, it was shown that the relativistic potential energy of the lowest spin-mixed state (ground state) monotonically decreases along the D_2d deformation path from the D_4h to the T_d structure.     

Gaussian basis set of double zeta quality for atoms K through Kr: application in DFT calculations of molecular properties

Contracted basis sets of double zeta (DZ) quality for the atoms from K to Kr are presented. They were determined from fully optimized basis sets of primitive Gaussian-type functions generated in atomic Hartree-Fock calculations. Sets of Gaussian polarization functions optimized at the Möller-Plesset second-order level were added to the DZ basis set. This extends earlier work on segmented contracted DZ basis set for atoms H-Ar. From this set, using the BP86 nonhybrid and B3LYP hybrid functionals, dissociation energy, geometric parameters, harmonic vibrational frequency, and electric dipole moment of a set of molecules were calculated and compared with results obtained with other basis sets and with experimental data reported in the literature. In addition, ⁵⁷Fe and ⁷⁷Se nuclear magnetic resonance chemical shifts in Fe(C₅H₅)₂, H₂Se, and CSe₂ were calculated using density functional theory and gauge-including atomic orbitals and, then, compared with theoretical and experimental values previously published in the literature. Except for chemical shift, one verifies that our results give the best agreement with experimental and benchmark values. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008     

Amperometric assay for collagenase

A sensitive and rapid amperometric assay for collagenase has been developed. The substrate for the assay is glucose oxidase covalently linked to insoluble collagen with dimethylsuberimidate. The collagenase cleaves the insoluble collagen-glucose oxidase conjugate into smaller, soluble fragments that have glucose oxidase activity. That activity is proportional to the collagenase activity hydrolyzing the insoluble conjugate. In the absence of collagenase, no glucose oxidase activity is found in the soluble phase. Glucose oxidase activity was assayed by measuring amperometrically the rate at which hydrogen peroxide is produced. The kinetics follow that proposed for a soluble enzyme acting on an insoluble substrate.     

Halogen exchange reactions of silicon tetrafluoride with phosphorus trichloride and phosphoryl chloride

Silicon tetrafluoride undergoes halogen exchange reactions with both phosphorus trichloride and phosphoryl chloride at temperatures of 500–600°C yielding mixed chlorofluorides of silicon and phosphorus. It is interesting to note that, at these high temperatures, PCl₃ undergoes complete exchange to form PF₃ while POCl₃ reacts only with partial substitution, the major products being phosphorus chloride difluoride and silicon trichloride fluoride.     

Crystal structure of copper(II) complex with N,N-bis(2-benzimidazolylmethyl)benzylamine

The copper(II) complex with N,N-bis(2-benzimidazolylmethyl)benzylamine has been synthesized and its crystal structure was determined by X-ray diffraction methods.     

Biuret complexes of divalent transition metals.

The complexes M bi₂ X₂ with M = Mn, Co, Ni and Cu, X = Cl, Br and I have been prepared. IR spectra and magnetic properties are given. The analysis of the ligand field parameters obtained from the electronic spectra for the cobalt and nickel compounds are in agreement with a trans octahedral structure.     

Substituted imidazole complexes of platinum(IV) halides

Platinum(IV) halides formed complexes of the type PtL₂X₄ [L=1-vinyl imidazole (1,-VIm), 1-methylimidazole (1-MeIm), 1,2-dimethylimidazole (1,2-Me₂Im), 1-vinyl-2-methylimidazole (1-V-2-MeIm), 2-methylimidazole (2-MeIm), 2-ethylimidazole (2-EtIm), 2-isopropylimidazole (2-i-PrIm), and 4-methylimidazole (4-MeIm); X=Cl, Br] in neutral aqueous solution. The 1-n-butylimidazole (1-n-BuIm) ligand yielded only (LH)₂PtX₆ compound in the same medium. The compounds were characterised by elemental analyses, IR, UV-VIS and ¹HNMR spectra.     

Reactions involving hydrogen transfer from triosmium clusters to an activated nitrile

The reactions of H₂Os₃(CO)₁₀, Ia and H₂Os₃(CO)₉PMe₂Ph, Ib with CF₃CN have been investigated. Both la and Ib react with CF₃CN to give the products HOs₃[μ-η₂-(CF₃)CNH](CO)₉Land HOs₃[μ-η¹-NC(H)CF3](CO)₉L, IIa, IIIa, L = CO; IIb and IIIb, L = PMe₂Ph. IIb and IIIb have been characterized crystallographically. In each, one nitrile molecule was added to the cluster and one hydride ligand was transferred to the nitrile ligand, but in IIb the hydride was transferred to the nitrogen atom to form a CF₃CNH ligand which bridges an edge of the cluster while in IIIb the hydride was transferred to the carbon atom to form a CF₃(H)CN ligand which also bridges an edge of the cluster. On the basis of spectroscopic measurements IIa and IIIa are believed to have analogous structures. An isotope scrambling experiment established that the formation of Ilia occurs by an intramolecular process. IIa was decarbonylated to yield the compound HOs₃[μ₃-η₂-(CF₃)CNH](CO)₉, which is believed to contain a triply-bridging iminyl ligand. Ilia reacts with PMe₂Ph to give two mono-substitution products, one of which is IIIb.     

Cationic carbonyl complexes of manganese (I) with nitriles and dinitriles

The reaction of Mn(CO)₅OClO₃ with nitriles,L, and dinitriles,L-L, in a wide variety of conditions affords cationic pentacarbonyls, [Mn(CO)₅(L)] ClO₄ and [Mn (CO)₅(L-L)] ClO₄ and fac-tricarbonyls, [Mn (CO)₃ (L)₃] ClO₄ and [(CO) ₃Mn (μ L-L) ₃Mn (CO)₃] (ClO₄)₂     

Halide and complex halogeno anions as salts of oxinate chelates of titanium(IV)

(η⁵-Cyclopentadienyl)(η⁵-pyrrolyl)titanium(IV) dichloride, (η⁵-indenyl)-(η⁵-pyrrolyl)titanium(IV) dichloride and (η⁵-cyclopentadienyl)(η⁵-indenyl)-titanium(IV) dichloride, when treated with 8-hydroxyquinoline (oxine) in aqueous medium form ionic derivatives of the type, [(η⁵-R)(η⁵-R′)TiL]⁺ Cl^- (R = C₅H₅, C₉H₇, R′ = C₄H₄N; R = C₅H₅, R′ = C₉H₇; L is the conjugate base of (oxine). A number of halide and complex halogeno anions present in aqueous solution were isolated as salts of these ionic complexes giving derivatives of the type, [(η⁵-R)(η⁵-R′)TiL]⁺ X^- (X = Br^-, I^-, ZnCl₃(H₂O)^-, CdCl₄^2-, HgCl₃^-). Conductivity measurements in nitrobenzene solution indicate that these complexes are electrolytes. Both the IR and ¹H NMR spectral studies demonstrate that the ligand L is chelating. Consequently there is tetrahedral coordination about the titanium(IV) ion.     

Analysis of a theoretical model for anisotropic enzyme membranes application to enzyme electrodes

A theoretical model of diffusion and reaction in an anisotropic enzyme membrane is presented with particular emphasis on the application of such membranes in enzyme electrodes. The dynamic response of systems in which the kinetics are linear, which comprises the practical operating regime for enzyme electrodes in analysis, is investigated via an analytic solution of the governing differential equations. The response is presented as a function of a single dimensionless group, Μ, that is the membrane modulus.     

Preparations of some tributyltin phosphates

Different complex tributyltin organophosphates have been prepared; in some cases the organotin cation is directly linked to the phosphate group, in other cases it is linked to a carboxylate or to a thioate function in a RO-P substituent. The direct phosphorylation of a tributyltin hydroxy salt is only possible for a marked covalent salt. Intramolecular rearrangements were observed.     

Spatial effects and the structure of organoantimony aldehydes and ketones

A number of organoantimony aldehydes and ketones have been synthesised. An increase in the spatial hindrance at either the α-carbon or the antimony increases the O-isomer relative content.     

Template reactions with polynuclear complexes. The reaction of octachlorodimolybdate(II) with 2-aminobenzaldehyde

The binuclear molybdenum(II) anion [Mo₂Cl₈]^4? acts as a template for the self-condensation of 2-aminobenzaldehyde. The dimolybdenum unit is retained in the molybdenum(IV) product, [Mo₂(A)₂(H₂O)⁴⁺.4Cl^?, where A is a macrocyclic tetradentate ligand containing two Schiff base nitrogen donors. The product forms as two isomers, whose ¹H nmr spectra are discussed.     

Complexes of copper and silver with tetracyanobiimidazole

We have recently reported the synthesis and properties of a remarkable new ligand 4,4′,5,5′-tetracyano-2,2′-biimidazole (H₂Tcbiim).¹ This acidic ligand readily binds metal ions in its dianionic form and appears to act as a strong pi acceptor. Its use as a quadridentáte bridging ligand allows study of metal-metal interactions through a planar conjugated system and extends earlier work by us² and by Hendrickson and coworkers³ on 2,2′-biimidazole. In this communication we report on the reactions of H₂Tcbiim with Ag(I), Cu(I) and Cu(II) salts.