HSAB principle applied to the time evolution of chemical reactions

Time evolution of various reactivity parameters such as electronegativity, hardness, and polarizability associated with a collision process between a proton and an X- atom/ion (X = He, Li(+), Be(2+), B(3+), C(4+)) in its ground ((1)S) and excited((1)P,(1)D,(1)F) electronic states as well as various complexions of a two-state ensemble is studied using time-dependent and excited-state density functional theory. This collision process may be considered to be a model mimicking the actual chemical reaction between an X-atom/ion and a proton to give rise to an XH(+) molecule. A favorable dynamical process is characterized by maximum hardness and minimum polarizability values according to the dynamical variants of the principles of maximum hardness and minimum polarizability. An electronic excitation or an increase in the excited-state contribution in a two-state ensemble makes the system softer and more polarizable, and the proton, being a hard acid, gradually prefers less to interact with X as has been discerned through the drop in maximum hardness value and the increase in the minimum polarizability value when the actual chemical process occurs. Among the noble gas elements, Xe is the most reactive. During the reaction: H(2) + H(+) --> H(3)(+) hardness maximizes and polarizability minimizes and H(2) is more reactive in its excited state. Regioselectivity of proton attack in the O-site of CO is clearly delineated wherein HOC(+) may eventually rearrange itself to go to the thermodynamically more stable HCO(+).     

Nomenclature of polymers (based on structure)

In the complete absence of a systematic polymer nomenclature, a scheme of nomenclature based on structure is proposed. The problem of naming a “mer” has been solved for an addition polymer by adding “ne” to the monomer name, the justification being on withdrawal of a π bond a monomer becomes a mer. To furnish completeness to the nomenclature, condensation polymers were included in the system. The present nomenclature system of polymers is very arbitrary. Some polymers are not chemically named, some named incorrectly, and there are some fantastic names. After pointing these out, the possible solutions were shown, encompassing a systematic discussion on nearly every type of polymer–linear, branched, or crosslinked–and copolymer (including block or graft), and plastic, fiber, or rubber, and stereospecific polymer. One or more names were proposed for different cases.     

Synthesis,structural and biochemical aspects of titanocene and zirconocene chelates of acetylferrocenyl thiosemicarbazones

The reactions of bis(cyclopentadienyl)titanium(IV)/zirconium(IV) dichloride with a new class of organometallic thiosemicarbazones (LH), derived by condensing acetylferrocene with substituted thiosemicarbazides, have been studied and two types of bimetallic products, viz. [Cp₂M(L)Cl] (M = Ti or Zr) and [CpZr(L)₃], have been isolated. On the basis of various physicochemical and spectral studies, five- and seven-coordinate structures have been assigned to these derivatives, respectively. Attempts have been made to establish a correlation between biological activity and the structures of the products.     

Oxofluorovanadates(V). IV. Dioxotetrafluorovanadates

Preparation and properties of the salts of the series MVO₂F₄, where M = NH, Na⁺, K⁺, 1/2 Ni²⁺, and 1/3 [Co(NH₃)₆]³⁺ are described. Molecular conductivity of Na₃VO₂F₄ at different dilutions indicates that Na₃VO₂F₄ dissociates into 3 Na⁺ and VOaF ions. Ion exchange study of (NH₄)₃VO₂F₄ solution through cation exchange resin (H⁺ form) suggests that the corresponding acid decomposes partly to vanadium pentoxide. Reaction between (NH₄)₃VO₂F₄ with BaCl₂ and AgNO₃ solutions shows the formation of BaVO₂F₃ and AgVO₃ respectively. Thermogravimetric study of (NH₄)₃VO₂F₄ shows the formation of impure vanadium pentoxide as the ultimate product on heating up to 450°C. X-ray powder diffraction data are given for (NH₄)₃VO₂F₄ and Na₃VO₂F₄.     

Kinetics and mechanism of the interaction of DL-methionine with cis-diaquaethylenediamine platinum(II) perchlorate in aqueous medium

The kinetics of the interaction of DL-methionine with [Pt(en)(H2O)2]2+ have been studied spectrophotometrically as a function of [Pt(en)(H2O)22+], [DL-methionine], PH and temperature. The reaction proceeds via a rapid outer sphere association followed by two slow consecutive steps having first order dependence on the aqua ion and methionine concentrations. Activation parameters have been evaluated using the Eyring equation. The low H1 (15.6 kJ mol–1) and large negative value of S1 (–230 J K–1 mol–1) as well as H2 (19.5 kJ mol–1) and S2 (–226 J K–1 mol–1) indicate an associative mode of activation for both the aqua ligand substitution processes in the two consecutive steps.     

Synthesis,spectroscopic and thermal studies on ruthenium(III), rhodium(III) and iridium(III) complexes with hydrazones derived from 2,6-diacetylpyridine and different aromatic hydrazides

Summary The reactions of MCl₃·3H₂O (M=Ru, Rh or Ir) with hydrazones have been studied by three different methods and complexes of the types [M(LH₂)(H₂O)₂]Cl₃, [M(L)Cl(H₂O)] and [M(LH₂)Cl₂]Cl·H₂O have been isolated. Tentative structural conclusions are drawn for these products based upon elemental analysis, electrical conductance, magnetic moment, and i.r. and¹H n.m.r. data. The thermal stability and mode of decomposition for the complexes have been studied by t.g.a., d.t.g. and d.s.c. techniques.     

Use of coupled-cluster based linear response theory and multireference hermitian MBPT to IP calculations of HF

We report in this paper the results of outer and inner valence IP calculations for the HF molecule using two different many-body methods for the direct evaluation of energy differences. The first is the nonperturbative coupled-cluster based linear response theory (LRT) and the second is the hermitian open-shell many-body perturbation theory (MBPT). A Huzinaga-Dunning (9s5p→ 5s3p/3s) basis has been used. LRT uses an “ionization operator” S as in the equation of motion method (EOM) to generate the ionized states from a coupled-cluster type of ground state. S is chosen to consist of single ionization and ionization-cum-shake-up operators, thus treating the Koopmans as well as the shake-up states on equal footing. LRT would thus be capable of computing both the outer and the inner valence regions with equal facility. This is borne out by the results. For the open-shell MBPT, the model space is chosen to be spanned by the singly ionized determinants. The convergence of the results for the inner valence region is slow, and the results obtained from the [2, 1] Pade' approximants are presented. Unlike the LRT, the inner valence region is not reproduced with full complexity in MBPT, indicating that it is essential to modify the theory by way of expanding the model space to contain the shake-up determinants also.     

Synthesis and physico-chemical and biological studies on ruthenium (III) complexes with Schiff bases derived from aminocarboxylic acids

Summary Ruthenium(III) complexes of types [Ru(L)₃], [Ru(L)Cl(H₂O)₂], [Ru(L)Cl₂]_n, [Ru(L)Cl(H₂O)]_n(LH =Schiff bases derived from anthranilic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; LH₂=Schiff bases derived from anthranilic acid and salicylaldehyde oro-hydroxyacetophenone; LH=Schiff bases derived fromp-aminobenzoic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; LH₂=Schiff bases derived fromp-aminobenzoic acid and salicylaldehyde oro-hydroxyacetophenone) have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moment and spectral (electronic, i.r. and¹H n.m.r.) data. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of crystal field theory and various parameters have been evaluated. On the basis of the electronic spectra, an octahedral geometry has been established for all these complexes except [Ru(L)Cl₂]_n. The complexes [Ru(L)Cl₂]_n are pentacoordinate and a trigonal-bipyramidal environment, D_3h, is suggested for the ruthenium(III) ion. The thermal behaviour of these complexes has also been studied by t.g., d.t.g and d.s.c techniques. Heats of reaction for the decomposition steps were calculated from the d.s.c. curves. The antifungal and antiviral activities of the complexes with Schiff bases derived from anthranilic acid were also investigated.