A new method for partition of interaction energy. Relation between stabilization energy and orbital mixing

A new method for partition of interaction energy is proposed. The scheme given here easily connects the calculated stabilization energy with the orbital mixing in analyzing orbital interactions of molecules. The method can reveal the relation between the change of electron distribution and stabilization energy. As an example, orbital interaction energies are estimated for diazocompounds, diazomethane and diazirine.     

Vibronic interactions and possible electron pairing in positively charged cyanodienes

The conditions under which the attractive electron-electron interactions are realized in the monocations of sigma-conjugated cyanodienes such as C(6)N(4)H(4), C(8)N(6)H(4), and C(10)N(8)H(4) and of pi-conjugated acenes are discussed. The total electron-phonon coupling constants for the monocations l(HOMO) of cyanodienes are much larger than those for the monocations of acenes. The strong sigma orbital interactions between two neighboring atoms in the highest occupied molecular orbitals (HOMO) of sigma-conjugated cyanodienes are the main reason for the calculated results. Furthermore, we discuss how the conditions under which the monocation crystals become good conductor are related to the molecular size. Both the l(HOMO) values and the reorganization energies between the neutral molecules and the monocations decrease with an increase in molecular size in cyanodienes. The calculated results for the sigma-conjugated cyanodienes are compared with those for the pi-conjugated acenes in order to investigate how the CH-N substitutions in cyanodienes are closely related to the l(HOMO) values and the reorganization energies. Both the l(HOMO) and the reorganization energies in the positively charged sigma-conjugated cyanodienes are much larger than those in the positively charged pi-conjugated acenes. This means that in order to become good conductors, the positively charged sigma-conjugated cyanodienes need larger overlap integral between two adjacent molecules than the positively charged pi-conjugated acenes. On the other hand, since the l(HOMO) values for cyanodienes are much larger than those for acenes, the condition of attractive electron-electron interactions is more easily to be realized in the monocations of cyanodienes than in the monocations of acenes. It is suggested that the positively charged sigma-conjugated cyanodienes cannot easily become good conductors, but the conditions under which the electron-electron interactions become attractive are realized more easily in the positively charged sigma-conjugated cyanodienes than in the positively charged pi-conjugated acenes.     

Vibronic dressed electronic states and nonadiabatic effects in polyacetylene

Conditions for low and high T_c superconductors following from the nonadiabatic electron-vibrational theory at ab initio level have been obtained. According to the presented results, the supercurrent is realized by the motion of the ground-state electronic-charge distribution of the fully occupied band. The motion of the electronic-charge distribution is conditioned by the newly arisen, nondissipative degrees of freedom of nuclear, Jahn–Teller-like, microflows. The Meissner effect is also interpreted.     

Electronic structures of vinylazide,vinylnitrene and 2H-azirine. Mechanism of the reaction from vinylazide to 2H-azirine

The mechanism of the conversion of vinylazides into 2H-azirines is examined by use of ab initio MO calculations. It is ascertained that vinylnitrenes have very weak bonds between the vinylazides and nitrogen molecule parts. It seems to decompose readily into the two fragments. This is one of the most characteristic features of vinylazides. The reaction is shown to proceed with N₂ at the tail of the vinylnitrene part. This mechanism accounts well for experimental results of the reaction.     

13C high-resolution NMR study of undoped polyacetylene

¹³C NMR spectra of undoped polyacetylene,(CH)_x, have been measured. The existence of 3.4 mol% methylene moieties as defects in the (CH)_x chains has been observed in trans-(CH)_x. Measurements of partially cis-to-trans isomerized (CH)_x suggest the existence of isolated cis regions.     

Studies on Oxidants' Generation in a Foaming Column with a Needle to Dielectric Covered Plate Electrode

The generation of oxidative products in the newly investigated foaming system was improved by a discharge between a high voltage multineedle electrode and a dielectric covered plate electrode. A uniformity of the discharge was observed. The presence of alumina dielectric seems to be responsible of the homogenous spatial distribution of the discharge. The absolute power and energy of the discharge was determined. Besides, in larger gap space the foam quality was improved.This way of oxidant's generation, which might be prospective for the treatment of exhaust gas and wastewater, has not been investigated by the other researchers' groups as yet. During the laboratory test 875 ppm of gaseous ozone, 0.5 mg/l of dissolved ozone and 62 mg/l of hydrogen peroxide was obtained at 14 kV of applied voltage and 5 l/min of oxygen gas flow in the present configuration used for the discharge generation. The average yield of gaseous ozone production ranged 55 gO₃/kWh.     

Reaction paths of tautomerization between hydroxypyridines and pyridones

Tautomerization paths of 2(and 4)-hydroxypyridine (called here HP) to 2(and 4)-pyridone (called here PY) with water molecules were investigated by the use of density functional theory calculations. Potential energies were compared for a number of water molecules. The 2-HP molecule was found to be isomerized most readily and concertedly to the 2-PY one via proton relays with two water molecules. The reaction pattern is invariant even when outer water molecules are added. The 4-HP(H(2)O)(n) --> 4-PY(H(2)O)(n) reaction model did not give small activation energies. However, a reaction of (4-HP)(2)(H(2)O)(2) --> (4-PY)(2)(H(2)O)(2) was found to occur readily through a transient ion-pair intermediate. The conversion processes of (2-PY)(2) to the tautomerization reacting system were discussed. The hydrogen-bond directionality regulates the tautomerization paths.     

A heuristic potential function for intramolecular and intrasupermolecular chemical reactions

A heuristic fitting procedure to obtain an analytical potential function for describing a reactive potential energy surface in the neighborhood of the intrinsic reaction coordinate (IRC ) has been developed. For discussion, the pairwise potential function form, ∑a_nr^?n, is assumed in order to fit ab initio quantum mechanical calculations of intramolecular (or intrasupermolecular) interaction energies and its use is found advantageous because all the calculation can be carried out by the linear least squares method. Normal modes perpendicular to IRC are utilized to prepare an initial data base for the potential fitting in the neighborhood of IRC . Some trial molecular dynamics (MD ) simulations are performed in order to check the fitted potential function and, unless they lead to reasonable energies within the tolerance assumed, their results are utilized to construct an improved data base (the dynamic sampling). The present systematic optimization procedure has been applied to the proton transfer reaction of the formamidine–water (FW ) system. The normal mode analysis in both the transition state (TS ) and the stable state (SS ) regions suggests that the present fitted potential function can reproduce satisfactorily the Born–Oppenheimer (BO ) adiabatic surface obtained by ab initio molecular orbital (MO ) calculations. We conclude that our procedure works well for the chemical reaction molecular dynamics (CRMD ) simulation.     

A computational study of interactions between acetic acid and water molecules

Density functional theory calculations were performed for the title reactions to elucidate the difference between the strong cyclic hydrogen bond of (Me-COOH)(2) and the electrolytic dissociation, MeCOOH <==> Me-COO(-) + H(+), as a weak acid. The association of water clusters with acetic acid dimers strengthens the cyclic hydrogen bond. A nucleophilic attack of the carboxylic carbon by a water cluster leads to a first zwitterionic intermediate, MeCOO(-) + H(3)O(+) + (HO)(3)C-Me. The intermediate is unstable and is isomerized to a neutral interacting system, MeCOOH...(HO)(3)C-Me + H(2)O. The ethanetriol, (HO)(3)-CMe is transformed to an acetic acid monomer. The monomer may be dissociated to give a second zwitterionic intermediate with reasonable proton-relay patterns and energy changes. In proton relay reaction channels, H in MeCOOH is not an acidic proton but is always a hydroxy proton.     

Theoretical study on the stability and the structure

The structure of H⁺_n(n = 3, 5, 7, 9, 11) is determined from ab initio MO calculations. The result for H⁺_n(n = 5, 7, 9) obtained by energy optimization in the 4-31G and 4-31G + p bais sets is reasonably explained in terms of a charge-transfer interaction from H₂ to H⁺_n?2 site. The orientation of H₂ toward the H⁺₉ cluster (D_3H) is found to be critically influenced by the basis set adopted.