Unusual spectral shifts of imipramine and carbamazepine drugs.

The absorption and fluorescence spectra of imipramine and carbamazepine have been recorded in solvents of different polarity and β-cyclodextrin (β-CD). The inclusion complexes for both drugs are investigated by UV-visible, fluorimetry and DFT. Solvents study shows isotropic polarizability structure is present in imipramine while the amide group inhibits the above structure in carbamazepine. The band width half a maximum of carbamazepine decreased in polar solvents suggest that different species present in non-polar solvents and among that one of this species is affected in protic solvents. Both drugs form two different 1:2 inclusion complexes with β-CD. The structured longer wavelength emission in β-CD solution suggests viscosity plays major roles in the inclusion complex. This study also confirms van der Waals forces and hydrophobic interactions are the driving forces in imipramine and hydrogen bonding interactions play major roles in carbamazepine.