Spectral characteristics of sulphadiazine, sulphisomidine: effect of solvents, pH and β-cyclodextrin

Abstract

The absorption and fluorescence spectra of sulphadiazine (SDA), sulphisomidine (SFM) and sulphanilamide (SAM) have been analysed in different solvents, pH and β-cyclodextin. The inclusion complexes of the above sulphonamides with β-CD were investigated by UV–Vis, fluorometry, DFT, FT–IR and ¹H-NMR. The solvent study shows that the absorption and emission maxima of the SDA and SFM are more red-shifted than SAM molecule. In non-aqueous solvents, a single fluorescence band (340 nm) is observed, whereas in water and β-CD solutions, dual emission (at 340 and 430 nm) is noticed for SDA and SFM molecules. The dual emission is due to twisted intramolecular charge transfer band (TICT). Studies on β-CD solutions reveal that (1) sulphonamides form 1 : 1 inclusion complex with β-CD; and (2) the red-shift and the presence of TICT in the β-CD medium confirm that the heterocyclic ring is encapsulated in the hydrophobic part and aniline ring is present in the hydrophilic part of the β-CD cavity.

Keywords:

• sulphonamides
• β-cyclodextrin
• TICT
• inclusion complex

Acknowledgements

This study is supported by the Department of Science and Technology, New Delhi (Fast Track Proposal-Young Scientist Scheme no. SR/FTP/CS-14/2005) and University Grants Commission, New Delhi (project no. F-31-98/2005 (SR). One of the authors, A. Antony Muthu Prabhu, is thankful to CSIR, New Delhi for awarding a Senior Research Fellowship (SRF).