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1.
The interaction energy of a molecule M with a point-like charge q can be partitioned into simpler contributions, two of which can be expressed in terms of the charge distribution M of the sole M. The first term, qV(r), represents the interaction of q with the undistorted charge
M
0
of M while the second q
2
P(r) gives the additional contributions due to the polarization of
M
0
under the influence of the charge q placed at the point r. In this paper we investigate the possibility of getting an inexpensive and sufficiently accurate analytical representation of P(r) over the whole space outside the van der Waals volume of M. 相似文献
2.
Soriaga RA Nguyen JM Albright TA Hoffman DM 《Journal of the American Chemical Society》2010,132(51):18014-18016
The addition of 4 equiv of LiN=C-t-Bu(2) to CrCl(3), MoCl(5), and WCl(6) in diethyl ether produced the complexes M(N=C-t-Bu(2))(4) (M = Cr, Mo, W). Single-crystal X-ray diffraction studies revealed that the molecules have flattened tetrahedral geometries with virtual D(2d) symmetry in the solid state. (1)H and (13)C NMR spectra indicated that the complexes are diamagnetic, and a qualitative MO analysis showed that the orthogonal π-donor and -acceptor orbitals of the ketimide ligand cooperatively split the d(xy) and d(z2) orbitals sufficiently to allow spin pairing in the d(xy) orbital. A more sophisticated quantum-mechanical analysis of Cr(N=C-t-Bu(2))(4) using density functional/molecular mechanics methods confirmed the qualitative analysis by showing that the singlet state is 27 kcal/mol more stable than the triplet state. 相似文献
3.
Rosanna Bonaccorsi Carlo Petrongolo Eolo Scrocco Jacopo Tomasi 《Theoretical chemistry accounts》1971,20(4):331-342
A model to facilitate the computation of the most stable conformer of associated M · H2O (M being a polar molecule) which depends upon the electrostatic interaction energy between the two associated molecules is proposed and tested. SCF electrostatic potentials for the M molecule and a suitable point charge distribution for H2O were employed in the model computations. Energies predicted by the model are found to be in good agreement with those resulting from an ab initio minimal STO basis SCF treatment of some conformations of the H2O dimer.
Work performed with the financial support of the Consiglio Nazionale delle Ricerche, through its Laboratorio di Chimica Quantistica ed Energetica Molecolare. 相似文献
Zusammenfassung Ein Modell zur Durchführung der Berechnung des stabilsten Konformeren eines Assoziationskomplexes M · H2O, wobei M ein polares Molekül ist, wird vorgeschlagen und untersucht. Es basiert auf der elektrostatischen Wechselwirkung zwischen beiden Partnern, und zwar wird für das Molekül M der elektrostatische Anteil seines SCF-Potentials und für H2O eine angemessene Punktladungsverteilung zugrunde gelegt. Die resultierenden Energien sind in guter Übereinstimmung mit denen, die sich bei einer ab initio Rechnung mit minimaler STO Basis ergeben.
Work performed with the financial support of the Consiglio Nazionale delle Ricerche, through its Laboratorio di Chimica Quantistica ed Energetica Molecolare. 相似文献
4.
Maria Gabriella Vigorita Rosaria Ottan Francesca Monforte Tindara Previtera Rosanna Maccari 《Journal of heterocyclic chemistry》2001,38(2):485-489
Diastereomers of antiinflammatory/analgesic and antihistaminic 3,3′[(1,2‐ethanediyl)bis(2‐aryl‐4‐thiazo‐lidinone)] derivatives possessing two stereogenic centers (indicated as BIS 2*C) have been widely investigated in recent years. The 5,5′‐dimethyl analogues (BIS 4*C), now reported, have been synthesized by reaction of (±) α‐mercaptopropionic acid and N,N'‐di(3‐fluorobenzyliden)ethylenediamine. Because the 2 and 2′carbons bear the same groups and similarly the 5 and 5′ carbons, and the latter groups are different from the former, four enantiomeric pairs and two meso forms exist in this situation. These diastereomers were identified by the concerted use of nmr spectroscopy and hplc on chiral stationary phase. 相似文献
5.
C R Clark C L McMillian J F Hoke K D Campagna W R Ravis 《Journal of chromatographic science》1987,25(6):247-251
An improved liquid chromatographic procedure is described for the quantitative determination of sulindac, sulindac sulfone, and sulindac sulfide from serum. The procedure makes use of acetonitrile extraction of the compounds of interest from acidified serum samples. Under these conditions extraction efficiencies in the 85 percent range are obtained for each of the compounds. The liquid chromatographic separation of the compounds of interest and the internal standard (indomethacin) is accomplished in an isocratic elution procedure using a nitrile (CN) stationary phase. The HPLC separation procedure is completed in less than 10 minutes, giving excellent resolution and peak shape. 相似文献
6.
Alexander Tuan-Huy Duong Bryan J. Simmons Mohammad Parvez Alam Jesus Campagna Neil K. Garg Varghese John 《Tetrahedron letters》2019,60(3):322-326
This study describes our development of a microfluidic reaction scheme for the synthesis of fused indoline ring systems found in several bioactive compounds. We have utilized a continuous-flow microfluidic reactor for the reaction of hydrazines with latent aldehydes through the interrupted Fischer indolization reaction to form fused indoline and azaindoline products. We have identified optimal conditions and evaluated the scope of this microfluidic reaction using various hydrazine and latent aldehyde surrogates. This green chemistry approach can be of general utility to rapidly produce indoline scaffolds and intermediates in a continuous manner. 相似文献
7.
Leveque J Moucheron C Kirsch-De Mesmaeker A Loiseau F Serroni S Puntoriero F Campagna S Nierengarten H Van Dorsselaer A 《Chemical communications (Cambridge, England)》2004,(7):878-879
The first ligand-cored dendrimer based on branching Ru(II) centers and containing mixed polypyridine bridging ligands has been prepared; redox experiments suggest that the redox-active core is not reduced at the expected potential, probably as a consequence of shielding induced by the rigid dendritic array. 相似文献
8.
Fortage J Puntoriero F Tuyèras F Dupeyre G Arrigo A Ciofini I Lainé PP Campagna S 《Inorganic chemistry》2012,51(9):5342-5352
A series of linearly arranged donor-spacer-acceptor (D-S-A) systems 1-3, has been prepared and characterized. These dyads combine an Os(II)bis(terpyridine) unit as the photoactivable electron donor (D), a biphenylene (2) or phenylene-xylylene (3) fragment as the spacer (S), and a N-aryl-2,6-diphenylpyridinium electrophore (with aryl = 4-pyridyl or 4-pyridylium in 1 or 2/3, respectively) as the acceptor (A). Their absorption spectra, redox behavior, and luminescence properties (both at 77 K in rigid matrix and at 298 K in fluid solution) have been studied. The electronic structure and spectroscopic properties of a representative compound of the series (i.e., 2) have also been investigated at the theoretical level, performing Density Functional Theory (DFT)-based calculations. Time-dependent transient absorption spectra of 1-3 have also been recorded at room temperature. The results indicate that efficient photoinduced oxidative electron transfer takes place in the D-S-A systems at room temperature in fluid solution, for which rate constants (in the range 4 × 10(8)-2 × 10(10) s(-1)) depend on the driving force of the process and the spacer nature. In all the D-S-A systems, charge recombination is faster than photoinduced charge separation, in spite of the relatively large energy of the D(+)-S-A(-) charge-separated states (between 1.47 and 1.78 eV for the various species), which would suggest that the charge recombination occurs in the Marcus inverted region. Considerations based on superexchange mechanism suggest that the reason for the fast charge recombination is the presence of a virtual D-S(+)-A(-) state at low energy--because of the involvement of the easily oxidizable biphenylene spacer--which is beneficial for charge recombination via superexchange but unsuitable for photoinduced charge separation. To further support the above statement, we prepared a fourth D-S-A species, 4, analogous to 2 but with a (hardly oxidizable) single phenylene fragment serving as the spacer. For such a species, charge recombination (about 3 × 10(10) s(-1)) is slower than photoinduced charge separation (about 1 × 10(11) s(-1)), thereby confirming our suggestions. 相似文献
9.
B. Biyani A. J. Campagna D. Daruwalla C. M. Srivastava P. Ehrlich 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):327-339
The molecular weight distribution (MWD) of crystallizable polyphenylacetylene prepared near room temperature in the presence of ferric acetylacetonate and triethylaluminum was determined through use of fractions characterized by vapor pressure osmometry and gel permeation chromatography (GPC). The number- and weight-average molecular weights (M n and M w) are both less than the molecular weight corresponding to the maximum of the weight distribution function, which lacks a high molecular weight tail. M wandM n is less than is consistent with models allowing for chain termination characteristic of vinyl polymers. GPC elution volumes are much less than those characteristic of polystyrene of similar molecular weight, and the Mark-Houwink exponent is high (2.4 for M v 4800 to 6800). These data indicate more rodlike behavior than for polystyrene of equivalent molecular weight. The MWD and other data suggest intramolecular chain termination, possibly associated with the molecule's tendency to form paramagnetic defect states. 相似文献
10.