Search

The derivatives of isatin have already been known to display a variety of biological activities. Therefore, the studies on their activity and its relation to structure have recently become a popular subject for investigation. The examined compounds were synthesized by the reaction of isatin and substituted primary amines and characterized by spectroscopic methods. The investigation of the antimicrobial and antioxidative activity of the synthesized compounds was performed by broth microdilution method. As for the characterization of the investigated isatin based Schiff bases, the linear solvation energy relationships (LSER) were used to analyze the solvent influence on the UV absorption maxima shifts (max), using the well known Kamlet–Taft model and taking geometrical isomers into consideration when possible. Linear free energy relationships (LFER) were used to analyze substituent effect on pKa, as well as NMR chemical shifts and max values. The antimicrobial activity and characterization were related using both experimental and theoretical methods. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013]

The ratios of E/Z isomers of sixteen synthesized 1,3-dihydro-3-(substituted phenylimino)-2H-indol-2-one were studied using experimental and theoretical methodology. Linear solvation energy relationships (LSER) rationalized solvent influence of the solvent-solute interactions on the UV-Vis absorption maxima shifts (v(max)) of both geometrical isomers using the Kamlet-Taft equation. Linear free energy relationships (LEER) in the form of single substituent parameter equation (SSP) was used to analyze substituent effect on pK(a), NMR chemical shifts and v(max) values. Electron charge density was obtained by the use of Quantum Theory of Atoms in Molecules, i.e. Bader's analysis. The substituent and solvent effect on intramolecular charge transfer (ICT) were interpreted with the aid of time-dependent density functional (TD-DFT) method. Additionally, the results of TD-DFT calculations quantified the efficiency of ICT from the calculated charge-transfer distance (D-CT) and amount of transferred charge (Q(CT)). The antimicrobial activity was evaluated using broth microdilution method. 3D QSAR modeling was used to demonstrate the influence of substituents effect as well as molecule geometry on antimicrobial activity. (C) 2018 Elsevier B.V. All rights reserved. This is peer-reviewed version of the following article: Brkić, D. R.; Božić, A. R.; Marinković, A. D.; Milčić, M. K.; Prlainović, N. Ž.; Assaleh, F. H.; Cvijetić, I. N.; Nikolić, J. B.; Drmanić, S. Ž. Detailed Solvent, Structural, Quantum Chemical Study and Antimicrobial Activity of Isatin Schiff Base. Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy 2018, 196, 16–30. [https://doi.org/10.1016/j.saa.2018.01.080] Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3197]

The derivatives of isatin have already been reported to show a variety of biological activities. However, there has been no report on solvatochromic effect of isatin derivatives so far, and that could be of interest to study and relate to their electronic structure, as a part of the characterisation of these compounds. Linear solvation energy relationships (LSER) were used to analyze solvent influence on the UV absorption maxima shifts of investigated isatin derivatives, i.e. isatin based Schiff bases, by using Kamlet-Taft model. Linear free energy relationships (LFER) were applied to the substituent-induced NMR chemical shifts (SCS) using SSP (single substituent parameter). The obtained correlations together with theoretical calculations gave insight into the influence of the molecular conformation on the transmission of substituent effects, as well as on solute/solvent interactions. The molecular electrostatic potential (MEP) surface map was plotted over the optimized geometry of the molecules in order to visualize electron density distribution and explain origin of solvent/solute interactions. [Projekat Ministarstva nauke Republike Srbije, br. 172013]

Linear free energy relationships (LFER) were applied to the IR, H-1- and C-13-NMR spectral data of N-(substituted phenyl)-2-cyanoacetamides. A variety of substituents were employed for phenyl substitution and fairly good correlations were obtained using the simple Hammett and the Hammett-Taft dual substituent parameter equations. The correlation results of the substituent induced C-13-NMR chemical shifts (SCS) of the Cl, C=O and N-H atom indicated different sensitivity with respect to electronic substituent effects. A better correlation of the SCSc=O with a combination of electrophllic and nucleophilic substituent constants indicated a significant contribution of extended resonance interaction (pi-delocalization) within the pi(1)-unit. The conformations of the investigated compounds were studied using the OFT B3LYP/6-311G** method and, together with the results of C-13-NMR and IR spectroscopic studies, a better insight into the influence of such a structure on the transmission of electronic substituent effects was obtained. Principi linearnih korelacija slobodnih energija (LFER) su primenjeni na IR, 1H- i 13C-NMR spektralne podatke N-(supstituisanih fenil)-2-cijanoacetamida. Pri sintezi N-(supstituisanih fenil)-2-cijanoacetamida izvršen je zadovoljavajući izbor supstituenata u pogledu elektronskih svojstava kako bi se adekvatno sagledao uticaj elektronskih efekata supstituenata na pomeranja u IR, 1H- i 13C-NMR spektralnim podacima. Primenom proste Hametove jednačine dobijene su zadovoljavajuće korelacije. Na osnovu korelacionih rezultata uočen je primaran uticaj elektronskih efekata na SCS (supstituentom indukovana hemijska pomeranja) vrednosti N-H vodonika, C1 i C=O ugljenika ispitivanih jedinjenja. Korelacioni rezultati za C=O ugljenik se značajno popravljaju ako se koristi kombinacija Ϭ+ i Ϭ- konstanti supstituenata, takozvane elektrofilne i nukleofilne konstante supstituenata, što ukazuje na postojanje značajne proširene rezonancione interakcije supstituenata i elektronske gustine karbonilne grupe. Vrednosti konstanti proporcionalnosti pF i pR za sve atome, ukazuju na približno isti doprinos efekta polja i rezonancionog efekta supstituenata. Efekat polja je nešto izraženji na N-H vodoniku, i za sve atome pokazuje značajne razlike u odnosu na njihov položaj u molekulskoj strukturi ispitivanih jedinjenja. Uticaj efekata supstituenata na IR vibracije istezanja N-H (simetrične i antisimetrične), C=O i CN veze je prevashodno elektronske prirode što se može zaključiti na osnovu dobrih korelacija dobijenih primenom Hametove jednačine i Ϭ parametara supstituenata. Osim toga izvršena je optimizacija geometrije ispitivanih jedinjenja primenom DFT B3LYP/ 6-311G**metode, pri čemu je nađeno da je trans-izomer nešto stabilnji, izuzev u slučaju jedinjenja 3. Supstituisana fenil-grupa i amidna grupa, kod trans-izomera, su približno koplanarne, dok se kod cis- izomera uočava značajna devijacija koja je značajno određena elektronskim efektima prisutnog supstituenta. Takođe je ispitivan položaj cis/trans ravnoteže u ugjen-tetrahloridu, i na osnovu rezultata FT/R analize, kada je prisutan H, CH3, OCH3, Br, i COOH supstituent, nađeno je da je cis izomer u velikom višku, a za ostala jedinjenja utvrđeno je postojanje ravnoteže cis- i trans-izomera.