排序方式: 共有23条查询结果,搜索用时 31 毫秒
1.
2.
On the basis of the investigation of the electronic absorption and fluorescence spectra of porphin introduced into inorganic and organo–inorganic silicate gel matrices, the participation of the surface hydroxyl groups in the formation of the dication form of porphin is shown. The influence of the gel matrix drying process on the reverse process of deprotonation of the porphin dication has been revealed. 相似文献
3.
E. V. Balantseva E. V. Antina M. B. Berezin A. I. Vyugin 《Journal of Thermal Analysis and Calorimetry》2008,92(3):671-675
The crystal solvates of complexes MP (P is the dianion of tetrakis(3,5-di-t-butylphenyl)porphin, M=Ni(II), Zn(II)) and (Ac)MnP with pyridine have been obtained by isothermal evaporation of corresponding solutions at 35°C.
The formation and the decomposition temperatures of crystal solvates and enthalpies of evaporation pyridine molecules from
those crystal solvates were received using thermogravimetric method. In addition to that, an influence of the type of metal
on the compositions, the energetic and thermal stabilities of the received complexes were analyzed. 相似文献
4.
5.
6.
Alexei A. Gridnev 《合成通讯》2013,43(9):1679-1689
Detailed kinetic investigation of Rothemund synthesis of porphyrins was conducted in different solvents. A one-pot synthesis of tetrakis(4-methoxyphenyl)porphin–Co(II) from pyrrole, anisic aldehyde, and cobalt acetate was developed that gave 35% isolated yield. Chlorobenzene was found to be the best solvent for the reaction. The synthesis can be done with either propionic or chloroacetic acid as catalyst with about the same yield. Cobalt prevents the synthesis of the porphyrin, so it has to be added in the reaction mixture only after the synthesis of the free porphyrin is finished. Optimum time is 2–2.5 h at a temperature of 130°C. Lower temperatures reduce the yield. Potentially, these dependencies can be applied to synthesis of other analogous porphyrins. 相似文献
7.
《Journal of computational chemistry》2018,39(13):763-772
Not only the molecular structure but also the presence or absence of aggregates determines many properties of organic materials. Theoretical investigation of such aggregates requires the prediction of a suitable set of diverse structures. Here, we present the open‐source program EnergyScan for the unbiased prediction of geometrically diverse sets of small aggregates. Its bottom‐up approach is complementary to existing ones by performing a detailed scan of an aggregate's potential energy surface, from which diverse local energy minima are selected. We crossvalidate this approach by predicting both literature‐known and heretofore unreported geometries of the urea dimer. We also predict a diverse set of dimers of the less intensely studied case of porphin, which we investigate further using quantum chemistry. For several dimers, we find strong deviations from a reference absorption spectrum, which we explain using computed transition densities. This proof of principle clearly shows that EnergyScan successfully predicts aggregates exhibiting large structural and spectral diversity. © 2018 Wiley Periodicals, Inc. 相似文献
8.
Shigeyoshi Yamamoto Hiroshi Tatewaki Osamu Kitao Geerd H.F. Diercksen 《Theoretical chemistry accounts》2001,106(4):287-296
The Rydberg character of the excited states of free-base porphin (FBP) has been investigated by the ab initio configuration
interaction singles (CIS) method and the state-averaged complete-active-space self-consistent-field method. Double-zeta basis
sets augmented with s, p, and d Rydberg functions and d polarization functions have been employed. Two types of molecular
orbitals sets, the restricted Hartree–Fock molecular orbitals obtained for the ground state (1A
g
) and for the cation state (2A
u
), have been used in the CIS calculations. All the calculations show that Rydberg-type excitations play important roles especially
in the N bands. In this article we propose applying the model of a perturbed Rydberg series to interpret the excited states
of FBP. By using this model, we have succeeded in analyzing the characteristics of the excited states as well as the experimental
oscillator strengths, which have considerable magnitude even in the higher excited states.
Received: 27 November 2000 / Accepted: 11 April 2001 / Published online: 27 June 2001 相似文献
9.
Using the DFT/B3LYP method with the base set 631G**, we carried out calculation of the frequencies of the normal vibrations of porphin and of its five isotopic types. Scaling of force constants for outofplane vibrations has been performed in independent natural coordinates. The symmetry coordinates are introduced and a force field for outof plane vibrations of a porphin molecule in independent coordinates of symmetry is obtained. A new correlation of the frequencies of vibrations in the type of the symmetry B
1u
for the isotopic type of the d
2 porphin molecule is suggested on the basis of discrete analysis of the distribution of a potential energy. 相似文献
10.
Calculating core‐level excitations and x‐ray absorption spectra of medium‐sized closed‐shell molecules with the algebraic‐diagrammatic construction scheme for the polarization propagator
下载免费PDF全文
![点击此处可从《Journal of computational chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Core‐level excitations are generated by absorption of high‐energy radiation such as X‐rays. To describe these energetically high‐lying excited states theoretically, we have implemented a variant of the algebraic‐diagrammatic construction scheme of second‐order ADC(2) by applying the core‐valence separation (CVS) approximation to the ADC(2) working equations. Besides excitation energies, the CVS‐ADC(2) method also provides access to properties of core‐excited states, thereby allowing for the calculation of X‐ray absorption spectra. To demonstrate the potential of our implementation of CVS‐ADC(2), we have chosen medium‐sized molecules as examples that have either biological importance or find application in organic electronics. The calculated results of CVS‐ADC(2) are compared with standard TD‐DFT/B3LYP values and experimental data. In particular, the extended variant, CVS‐ADC(2)‐x, provides the most accurate results, and the agreement between the calculated values and experiment is remarkable. © 2014 Wiley Periodicals, Inc. 相似文献