Vivekananda Mahavidyalaya, Haripal, Hooghly, West Bengal, India E-mail : ksharma7l@yahoo.co.in central Forensic Science Laboratory, 30, Gorachand Road, Kolkata-700 014, India E-mail : sujitclahiri@yahoo.com Fax : 91-33-22849442 Manuscript received 12 May 2011, accepted 20 May 2011 Lamotrigine, a well-known and extensively used antiseizure drug was found to form beautifully colored chargetransfer complexes with o-chloranil, chloranilic acid and dichlorodicyanobenzoquinone in acetonitrile. The

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... orption maxima of the complexes were 543 nm and 576 nm; 521 nm; 408 nm, 459 nm and 587 nm respectively (where Lamotriginc had no absorption but the acceptors had absorptions in these regions). The compositions of the complexes were determined to be 1 : 1 from the Job's method of continuous variations. FTIR spectra of the complexes and the corresponding acceptors were compared. The complexes showed considerable shifts in absorption peaks, change in intensities of the peaks and formation of new band probably due to H-bonding. The thermodynamic association constants of the complexes and other thermodynamic properties were determined spectrophotometrically taking D and A in stoichiometric ratios. The complex formations were found to be spontaneous and associated with negative changes of ΔG°, ΔH° and /ΔS° values. The energies hvCT of the charge-transfer complexes and vertical ionization potential IDv of Lamotriginc were compared with the theoretical values of hvCT obtained from HOMO and LUMO of the donors and acceptors calculated using Density Function Theory utilizing different basis sets. The agreement between the results can be regarded to be reasonable. Oscillator strengths and dipole strengths of the complexes were determined theoretically and experimentally and the limitations of the calculations were outlined. A physico-chemical approach has been put forward to explain the causes for the onset of sei [...]