Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Polish Journal of Chemistry

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: substituents

Sortuj według:

Ogranicz wyniki do:

Role of Substituents in Excited State Intramolecular Proton Transfer (ESIPT) Processes

Sepioł J.

Polish Journal of Chemistry

2009

Vol. 83, nr 10

1671-1692

The increasing interest in molecular systems exhibiting ESIPT reaction has triggered – due to their broad field of potential applications – an extensive search for properly substituted compounds with well-tailored properties. This review is based on selected papers dealing with some commonly known ESIPT systems modified by specific substituents. The results of several studies concerning the rate of ultrafast ESIPT reactions in supersonic molecular beams are presented. Articles reporting on phototautomeric fluorescence in solutions illustrated a big role of substituents, which influence the emission quantum yield. Theoretical works pointed to the increasing role of advanced calculations in predicting and understanding the structural, electronic, and spectroscopic properties of diverse ESIPT-capable compounds.

Correlations of Charges of Substituent Active Region in C-substituted Tetrazoles with Their Gas-phase Acidity, Hammett Constants, and Charge Distribution in Tetrazolic Rings

Sadlej-Sosnowska N., Murłowska K.

Polish Journal of Chemistry

2008

Vol. 82, nr 4

935-945

Electron distribution was investigated in molecules of 5C-substituted tetrazoles by means of Natural Population Analysis. The analysis of the impact of substituents on the excess of p electrons in the ring and on the uniformity of their distribution produced similar results as were recently reported for derivatives of p-benzoic acid. The significant correlation coefficients of the two properties with the Hammett constants have been found. The more uniform the p electron distribution, measured by means of standard deviation of p electrons amounts localized on individual atoms in the ring, the more acidic is the molecule. On the other hand, an increase of the p electron number in the ring brings about an opposite effect. No correlation was found between the substituent charges and the Hammett constants. However, a new variable, namely charge of the substituent active region, composed of charge of a substituent added to charge of the ring Cipso atom, was highly correlated with the Hammett constants, as well as with charge of acidic hydrogen of the >N-H group. The results prove that the set of charges of the substituent active region may be perceived as a theoretical equivalent of the experimental set of Hammett constants and that it is closely related to properties of this group of compounds.