Scaling in pseudopotential theory

Simple Gaussian nonlocal pseudopotentials are determined for K shells. Extrapolation formulas are derived for the parameters as functions of the reduced atomic number. Small hydrids are used for the basis function analysis. Comparison is made with the set of molecules in the book by Snyder and Basch, and detailed results are presented for the molecules BH₃, CH₄, NH₃, H₂O, HF, N₂, CO, BF, CH₃F, C₂H₂, HCN, CHONH₂, and CHOOH. Results on energy levels, total energy, total valence energy and dipolmoment and in a few cases some geometry predictions are made.     

Geometry optimization in ab initio SCF calculations. VII. Proton affinities and ion structures calculated with floating orbital geometry optimization (FOGO)

The FOGO method is used to calculate absolute proton affinities of the molecules H₂, HF, NH₃, H₂O, CH₃OH, C₂H₅OH, H₂O₂, CH₂O, CO, and CH₂CO. Comparison with experimental values demonstrates that the geometrical and energetical data resulting from this type of ab initio calculation are of chemical accuracy. Predictive data for higher energy isomers, such as hydroxymethylene and ethynol are given as possible aid for the identification of these species.     

On the use of localized orbitals and restricted alternant orbitals in chemical systems

An analysis of the transformation of localized orbitals into restricted alternant orbitals is proposed. This approach has the advantage of expressing the wave-function in an orbital product while some electron correlation is introduced permitting the study of dissociation reactions. All applications of the orbital technique may be made as easily as with RHF, but with the additional possibility of studying chemical radicals. Some illustrations of this fact are shown for the molecules HF, H₂O, NH₃, CH₄, C₂H₆ and for the dissociation reactions of CH₄ and C₂H₆ generating CH₃ radicals.     

Solvatomorphism in (E)‐2‐(2,6‐dichloro‐4‐hydroxybenzylidene)hydrazinecarboximidamide

The structures of orthorhombic (E)‐4‐(2‐{[amino(iminio)methyl]amino}vinyl)‐3,5‐dichlorophenolate dihydrate, C₈H₈Cl₂N₄O·2H₂O, (I), triclinic (E)‐4‐(2‐{[amino(iminio)methyl]amino}vinyl)‐3,5‐dichlorophenolate methanol disolvate, C₈H₈Cl₂N₄O·2CH₄O, (II), and orthorhombic (E)‐amino[(2,6‐dichloro‐4‐hydroxystyryl)amino]methaniminium acetate, C₈H₉Cl₂N₄O⁺·C₂H₃O₂⁻, (III), all crystallize with one formula unit in the asymmetric unit, with the molecule in an E configuration and the phenol H atom transferred to the guanidine N atom. Although the molecules of the title compounds form extended chains via hydrogen bonding in all three forms, owing to the presence of different solvent molecules, those chains are connected differently in the individual forms. In (II), the molecules are all coplanar, while in (I) and (III), adjacent molecules are tilted relative to one another to varying degrees. Also, because of the variation in hydrogen‐bond‐formation ability of the solvents, the hydrogen‐bonding arrangements vary in the three forms.     

Extended Koopmans' theorem: Approximate ionization energies from MCSCF wave functions

The extended Koopmans' theorem has been implemented using multiconfigurational self-consistent field wave functions calculated with the GAMESS, HONDO, and SIRIUS programs. The results of illustrative calculations are presented for the molecules HF, H₂O, NH₃, CH₄, N₂, CO, HNC, HCN, C₂H₂, H₂CO, and B₂H₆. The lowest extended Koopmans' theorem ionization potentials agree well within the experimental values and the ionization potentials representing excited states of the ions show some improvements over the Koopmans' theorem values in most cases. The extended Koopmans' theorem is easily implemented and the time required to calculate the ionization energies is insignificant compared to the time required to calculate the wave function of the un-ionized molecule. © 1992 by John Wiley & Sons, Inc.     

Interstitial and lattice substituted models of an expanded ice-I hlattice

An ice-I _hlattice (O?O=0.286 nm) with small molecules placed interstitially and with some placed at lattice positions was investigated by the CNDO/2-MO technique. The interstitial molecules included H₂, N₂, O₂, HF, CO₂, H₂O, NH₃, CH₄ and CH₂O, whereas those involved in lattice substitution included HF, NH₃ and H₂O. From the calculations it is found that all interstitial and lattice substituted systems are stabler than the sum of the components, the enhanced stability depending on the system. Generally, lattice substituted systems are stabler than the corresponding interstitial models. Charges residing on the atomic positions reflect the amount of interaction with the matrix as well as indicating how the change in charge would facilitate other interactions with the solvent.     

Nonisothermal membrane phenomena across perfluorosulfonic acid-type membranes,Flemion S: part I. Thermoosmosis and transported entropy of water

Solvent transports across the perfluorosulfonic acid-type membrane Flemion S were measured for aqueous electrolyte solutions under a temperature difference and under an osmotic pressure difference. H⁺, Li⁺, Na⁺, K⁺, NH ₄ ⁺ , CH₃NH ₃ ⁺ , (CH₃)₂NH ₂ ⁺ , (CH₃)₃NH⁺, (CH₃)₄N⁺, (C₂H₅)₄N⁺, (n-C₃H₇)₄N⁺ and (n-C₄H₉)₄N⁺ were used as counterions. Water flux across the membrane in HCl solution is higher than that in the other electrolyte solutions because hydrogen ions can exchange with the hydrogen of the neighbor water molecules and contribute to the water transport across the membrane as a proton jump in conductivity. The direction of thermoosmosis across the membrane in HCl, NaCl, (CH₃)₄NCl and (C₂H₅)₄NCl solutions was from the cold side to the hot side and that in LiCl, KCl, NH₄Cl, CH₃NH₃Cl, (CH₃)₂NH₂Cl and (n-C₄H₉)₄NBr solutions was from the hot side to the cold side, although thermoosmosis across anion-exchange membranes always occurs toward the hot side.     

Quantum-Chemical Study of the Electronic and Steric Structure of Vinyltetrazoles: II. 2-Vinyltetrazoles

The total Mulliken charges on the C and N atoms, populations of the S-trans-(N¹) conformers, and rotation barriers in the molecules of 2-vinyl-5-R-tetrazoles (R = H, CH₃, CH = CH₂, C₆H₅, CH₂Cl, CF₃) were calculated ab initio (HF/6-31G**, MP2/6-31G**). The results were compared with the ¹H and ¹³C NMR data for these compounds.     

Density localization of atomic and molecular orbitals

Density localized molecular Orbitals are computed for the molecules LiH, LiF, BF, BN, CO, C₂H₂, CH₄, NH₃, H₂O, and HF. The density localization method is based on the minimization of the sum of the interorbital density overlap integrals. The results of this method are compared to the results of the energy localization method of Edmiston and Ruedenberg and the localization procedures of Boys and of Magnasco and Perico. The agreement among the results obtained by these four methods is in general good. With a few exceptions the localized molecular orbitals agree with the classical chemical concepts.

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Zusammenfassung Dichtelokalisierte Molekülorbitale sind berechnet worden für die Moleküle LiH, LiF, BF, BN, CO, C₂H₂, CH₄, NH₃, H₂O und HF. Die Dichtelokalisierungsmethode beruht auf der Minimisierung der Summe der Dichteüberlappungsintegrale zwischen verschiedenen Orbitalen. Die Ergebnisse dieses Verfahrens werden verglichen mit den Resultaten der Energielokalisierungsmethode von Edmiston und Ruedenberg und den Verfahren von Boys und von Magnasco und Perico. Die übereinstimmung zwischen den verschiedenen Methoden ist im allgemeinen gut. Mit einigen Ausnahmen werden die klassischen chemischen Vorstellungen von Elektronenpaaren reproduziert.

     

The multiconfigurational spin tensor electron propagator method (MCSTEP): Comparison with extended Koopmans' theorem results

Summary We applied the multiconfigurational spin tensor electron propagator method (MCSTEP) for determining the lowest few (in energy) vertical ionization potentials (IPs) of HF, H₂O, NH₃, CH₄, N₂, CO, HNC, HCN, C₂H₂, H₂CO, and B₂H₆. We chose these molecules so that we could compare MCSTEP IPs with recently reported extended Koopmans' theorem (EKT) IPs on the same molecules. Using standard Dunning core-valence basis sets with relatively small complete active spaces, MCSTEP results are in very good to excellent agreement with experiment. These MCSTEP IPs are obtained using matrices no larger than 400 × 400. EKT matrices are even smaller; however, to obtain similar but generally slightly worse agreement with experiment, fairly large active spaces are required with EKT.     

On the use of local basis sets for localized molecular orbitals

Two procedures are discussed for the direct variational optimization of localized molecular orbitals which are expanded in local subsets of the molecular basis set. It is shown that a Newton-Raphson approach is more efficient than an iterative diagonalization scheme. The effect of the basis-set truncation on the quality ofab-initio SCF results is investigated for Be, Li₂, HF, H₂O, NH₃, CH₄ and C₂H₆.     

ORGANISCHE PHOSPHORVERBINDUNGEN 85.1 HERSTELLUNG,EIGENSCHAFTEN UND BIOLOGISCHE WIRKUNG VON N-AMINOGLYPHOSATE UND AZAGLYPHOSATE

Abstract

The synthesis and the chemical, physical and spectral properties of N-aminoglyphosate ethylester (hydrazino-N′-carbethoxymethyl-N′-methylphosphonic acid) 4a, H₂OPCH₂N(NH₂)CH₂CO₂C₂H₅, of hydrazino-N′-carbethoxymethyl-N′-methyl-P-methylphosphinic acid 4b, CH₃(HO₂)PCH₂N(NH₂)-CH₂CO₂C₂H₅, and of azaglyphosate ethylester (hydrazino-N-carbethoxymethyl-N-methyl-phosphonic acid 9, H₂O₃PCH₂NHNHCH₂CO₂C₂H₅, are described. 4a, 9 and 10 exhibit plant growth regulating properties.     

Past,present and future of the clathrate inclusion compounds built of cyanometallate hosts

One-, two- and three-dimensional CN-bridged metal complex structures made up of building blocks such as linear [Ag(CN)₂]^–, square planar [Ni(CN)₄]^2– or tetrahedral [Cd(CN)₄]^2–, and of the complementary ligands such as ammonia, water, unidentate amine, bidentate a,w- diaminoalkane, etc., are reviewed with an emphasis on their behaviour as hosts to afford clathrate inclusion compounds with guest molecules and as self-assemblies to form supramolecular structures with or without guests. The historical background is explained for Prussian blue and Hofmann's benzene clathrate based on their single crystal structure determinations. The strategies the author and coworkers have been applying to develop varieties of clathrate inclusion compounds from the Hofmann-type are demonstrated with the features observed for the developed structures determined by single crystal X-ray diffraction methods.Abbreviations for Ligands and Guests mma NMeH₂ - dma NMe₂H - tma NMe₃ - mea NH₂(CH₂)₂OH - en NH₂(CH₂)₂NH₂ - pn NH₂CHMeCH₂NH₂ - tn NH₂(CH₂)₃NH₂ - dabtn NH₂(CH₂)₄NH₂ - daptn NH₂(CH₂)₅NH₂ - dahxn NH₂(CH₂)₆NH₂ - dahpn NH₂(CH₂)₇NH₂ - daotn NH₂(CH₂)₈NH₂ - danon NH₂(CH₂)₉NH₂ - dadcn NH₂(CH₂)₁₀NH₂ - mtn NMeH(CH₂)₃NH₂ - dmtn NMe₂(CH₂)₃NH₂ - detn NEt₂(CH₂)₃NH₂ - temtn NMe₂(CH₂)₃NMe₂ - dien NH₂(CH₂)₂NH(CH₂)₂NH₂ - pXdam p-C₆H₄(NH₂CH₂)₂ - rnXdam m-C₆H₄(NH₂CH₂)₂ - py C₅H₅N pyridine - ampy NH₂C₅H₄N aminopyridine - Clpy CIC₅H₄N chloropyridine - Mepy MeC₅H₄N methylpyridine - dmpy Me₂C₅H₃N dimethylpyridine - bpy NC₅H₄C₅H₄N bipyridine - quin C₇H₉N quinoline - iquin iso-C₇H₉N isoquinoline - qxln C₈H₆N₂ quinoxaline - Pe C₅H₁₁-pentyl imH: C₃N₂H₄ imidazole - pyrz N(CHCH)₂N pyrazine - Mequin MeC₇H₈N methylquinoline - bppn C₁₃H₁₄N₂ 1,3-bis(4-pyridyl)propane - bpb C₁₄H₈N₂ 1,4-bis(4-pyridyl)butadiyne - N-Meim C₃N₂H₃Me N-methylimidazole - 2-MeimH C₃N₂H₃Me 2-methylimidazole - dmf HOCNMe₂ dimethylformamide - hmta C₆H₁₂N₄ hexamethylenetetramine - o-phen C₁₂H₈N₂ 1,10-phenanthroline - den HN(CH₂CH₂)₂NH piperazine - morph HN(CH₂CH₂)₂O morpholine - ten N(CH₂CH₂)₃N 1,4-diazabicyclo[2.2.2]octane - ameden NH₂(CH₂)₂N(CH₂CH₂)₂NH N-(2-aminoethyl)piperazine Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Theoretical study of the influence of para- and meta-substituents on X-pyridineHF hydrogen bonding

The effects of O⁻, N (CH₃)₂, NH (CH₃), NH₂, C₂H₅, CH₃, OH, F, Cl, OF, Br, NO₂ and substituents in para- and meta-positions on X-pyridineHF hydrogen bond has been studied by HF, B3LYP and MP2 methods using 6-311++G(d,p) basis set. The relationship between hydrogen bond formation energy ΔE and electron donating (or withdrawing) of substituents has been investigated. In this respect, population analysis has been performed by atoms in molecules (AIM) and natural bond orbital (NBO) theories. The results of AIM and NBO analyses are in good agreement with calculated energy values. The relationship between Hammett coefficient and complexation energy has been established and the ρ constant has been calculated for hydrogen bonding. There is a relationship between σ and ΔE with a correlation coefficient equal to 0.94.     

Synergism in cationic gemini – additive systems

A series of dicationic gemini surfactants with the general formula C₁₆H₃₃(CH₃)₂N⁺?(CH₂)_s?N⁺(CH₃)₂C₁₆H₃₃, 2Br^? (where s?=?4–6), designated as 16-s-16, were synthesised. Their interaction with organic additives: n-alcohols (C₃H₇OH, C₇H₁₅OH, C₈H₁₇OH) and the corresponding amines (C₃H₇NH₂, C₇H₁₅NH₂, C₈H₁₇NH₂) in the absence and presence of KNO₃ at 30°C was studied viscometrically to observe their effect on assembly formation and micellar transition. The simultaneous presence of KNO₃ and organics induced rich aggregates morphologies in the gemini micellar systems by giving high viscosity values. On comparing the behaviour of the gemini surfactant series for a given alkyl chain length of the organic additive, the spacer is found to markedly influence the behaviour; shorter the spacer, earlier the sphere-to-rod transition. In the case of the conventional surfactant, CTAB, the concentration of KNO₃ used with the geminis was insufficient to induce any transition.     

Cyclopalladation of mono-, di- and tribenzylamine by palladium(II) acetate: Influence of bulkiness around the nitrogen atom of benzylamine upon internal metallation

Cyclopalladation of mono-, di- and tribenzylamine has been investigated by reacting the corresponding amines with an equimolar amount of palladium(II) acetate (reaction i), or by heating the corresponding bis-amine complexes [Pd(O₂CMe)₂{(PhCH₂)_nNH_3−n}₂] (n=1, 2) (reaction ii). By the reaction i, all the three amines undergo cyclopalladation. However, in the case of the reaction ii, only the dibenzylamine complex [Pd(O₂CMe)₂{(PhCH₂)₂NH}₂] has been converted into a cyclopalladated complex. The reactivity of the three benzylamines towards cyclopalladation has been discussed in terms of the co-ordinating ability influenced by the bulkiness around the nitrogen atom. Temperature-dependent ¹H-NMR spectra are observed for mononuclear cyclopalladated complexes [Pd(O₂CMe){C₆H₄CH₂N(CH₂Ph)₂–C¹, N}L] (L=PPh₃, AsPh₃) and are attributed to the dissociation of the nitrogen atom in the cyclopalladated chelate ring. A heteroleptic bis-cyclopalladated complex [Pd[C₆H₄CH₂N(CH₂Ph)₂–C¹, N](C₆H₄CH₂NMe₂–C¹, N)] has also been prepared. X-ray crystallographic studies on [{Pd(O₂CMe)[C₆H₄CH₂N(CH₂Ph)₂–C¹, N]}₂] and [Pd[C₆H₄CH₂N(CH₂Ph)₂–C¹, N](C₆H₄CH₂NMe₂–C¹, N)] have been reported.     

Average dipole polarizabilities from the unsold approximation and ab initio data

An approximate static dipole polarizability equation is developed on the basis of the Unsold approximation, and is cast in closed shell LCAO MO SCF formalism. A brief study is made of the use of Koopmans' theorem as a means of obtaining an average ionization energy, necessary in the polarizability equation presented. Average polarizabilities for the systems He, Ne, H₂, HF, H₂O, NH₂, CH₄, HCN, N₂, C₂H₂, C₂H₄, C₂H₆, C₆H₆, and C₆H₅F are calculated from the dipole polarizability expression developed using a small 4-31G basis set level. Results show good agreement with experimental data.     

Generation and High‐Resolution Photoelectron Spectroscopy of Small Organic Radicals in Cold Supersonic Expansions

A general method of generating radicals in cold supersonic expansions in the gas phase is presented. The method relies on excimer laser photolysis of suitable precursor molecules in a thin quartz capillary mounted at the orifice of a pulsed gas nozzle and can easily be combined with vacuum‐UV photoionization mass spectrometry and high‐resolution photoelectron spectroscopy to study the reactivity and the rovibronic energy level structure of neutral radicals and their ions, as well as to determine highly accurate adiabatic ionization energies. The characteristics of the radical source are described in detail, and its performance is illustrated by mass spectrometric and high‐resolution photoelectron spectroscopic investigations of NH₂, CH₂, CH₃, C₂H, C₂H₃, and C₂H₅. The radical source is not only suitable to produce cold samples (rotational temperature of ca. 30 K) of radicals of moderate reactivity, such as NH₂, CH₃, or C₂H₅, but it is also useful to prepare highly reactive radicals (e.g., C₂H) for spectroscopic investigations.     

New Heterocyclic Organophosphorus–Sulfur–Nitrogen Compounds,Syntheses and Structures

The new compound C₁₀H₆P(S)[NSi(CH₃)₃]₂P(S) ( 3 ) which contains a P₂N₂ heterocycle has been prepared in low yield by partial thermal decomposition of 1-{[N,N′-bis(trimethylsilyl)acetamidinium]sulfido}-3-(trimethylsilylamino)-1 H,3 H,1 λ⁵,3 λ⁵-naphtho[1,8 a,8-cd][1,2,6]thiadiphosphinine-1,3-dithione [CH₃C{NHSi(CH₃)₃}₂]⁺[C₁₀H₆P(S)(NHSiMe₃)SP(S)₂]^– ( 2 ). Reaction of 2 with potassium hydroxide in acetonitrile gives the completely desilylated product [CH₃C(NH₂)₂]⁺[C₁₀H₆P(S)(NH₂)SP(S)₂]^– ( 4 ). The structures of the new compounds 3 and 4 were elucidated by FTIR and NMR spectroscopy methods and by X-ray structure analyses.     

Theoretical influence of third molecule on reaction channels of weakly bound complex CO2… HF systems

In this investigation, reaction channels of weakly bound complexes CO₂…HF, CO₂…HF…NH₃, CO₂…HF…H₂O and CO₂…HF…CH₃OH systems were established at the B3LYP/6‐311++G(3df,2pd) level, using the Gaussian 98 program. The conformers of syn‐fluoroformic acid or syn‐fluoroformic acid plus a third molecule (NH₃, H₂O, or CH₃OH) were found to be more stable than the conformers of the related anti‐fluoroformic acid or anti‐fluoroformic acid plus a third molecule (NH₃, H₂O, or CH₃OH). However, the weakly bound complexes were found to be more stable than either the related syn‐ and anti‐type fluoroformic acid or the acid plus third molecule (NH₃, H₂O, or CH₃OH) conformers. They decomposed into CO₂ + HF, CO₂ + NH₄F, CO₂ + H₃OF or CO₂ + (CH₃)OH₂F combined molecular systems. The weakly bound complexes have four reaction channels, each of which includes weakly bound complexes and related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti‐fluoroformic acid type structure (T₁₃) is significantly larger than that of internal rotation (T₂₃) between the syn‐ and anti‐FCO₂H (or FCO₂H…NH₃, FCO₂H…H₂O, or FCO₂H…CH₃OH) structures. However, adding the third molecule NH₃, H₂O, or CH₃OH can significantly reduce the activation energy of T₁₃. The catalytic strengths of the third molecules are predicted to follow the order H₂O < NH₃ < CH₃OH. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006