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Dual Substituent Parameter Modeling of Theoretical, NMR and IR Spectral Data of 5-Substituted Indole-2,3-diones

Author(s): Ghazwan F. Fadhil | Hanan A. Radhy | Alexander Perjéssy | Mária Šamalíková | Erkki Kolehmainen | Walter M.F. Fabian | Katri Laihia | Zora Šusteková

Journal: Molecules
ISSN 1420-3049

Volume: 7;
Issue: 11;
Start page: 833;
Date: 2002;
Original page

Keywords: 5-Substituted indole-2 | 3-diones | AM1 and PM3 theoretical data | IR and NMR data DSP correlations | π-polarization | reverse substituent effect

Correlations of AM1 and PM3 theoretical data, 13C-NMR substituent chemical shifts (13C-SCS) and IR carbonyl group wave numbers [ν(C3═O)] were studied using dual substituent parameter (DSP) models for 5-substituted indole-2,3-diones. For the C7 atom a reverse substituent effect attributed to extended π-polarization was observed. On the other hand, the DSP approaches for the C3 atom showed normal substituent effects with some contribution of reverse effect supported strongly by 13C-SCS correlations. In the ν(C3═O) and p(C3═O) DSP correlations the field effect contribution predominates over the resonance effect, which justifies the using of earlier suggested vibrational coupling (V-C) model for 5- and 6-substituted indole-2,3-diones.