Planar intramolecular charge transfer effects on meloxicam and piroxicam drugs with α- and β-cyclodextrins : Spectral and molecular modeling studies

Department of Chemistry, Annamalai University, Annamalainagar-608 002, Tamilnadu, India E-mail : drrajendiran@rediffmail.com Manuscript received online 24 February 2016, accepted 25 June 2016 Inclusion complexation of meloxicam and piroxicam with α-CD and β-CD were studied by UV-Visible, fluorescence, time resolved fluorescence and molecular modeling techniques. Dual emission noticed in the CD solutions recommended that the energy of the intramolecular charge transfer (ICT) state is lower than that of the locally excited state. The shorter wavelength band was originated from the locally excited state and the longer wavelength band was due to the planar intramolecular charge transfer (PICT) state emission. The ratio of the PICT emission to the normal emission marginally increased with β-CD concentration, while it was slightly increased upon addition of α-CD. The above behavior indicating the formation of different 1 : 1 drug : CD inclusion complexes. The size of the benzamido ring suggested that the orientation of the drug in the β-CD complex is different from that in the α-CD complex. PM3 calculations were also carried out to assign the encapsulation of the drug molecules