IR, 1H NMR, mass, XRD and TGA/DTA investigations on the ciprofloxacin/iodine charge-transfer complex

The charge-transfer complex (CTC) of ciprofloxacin drug (CIP) as a donor with iodine (I2) as a sigma acceptor has been studied spectrophotometrically in CHCl3. At maximum absorption bands, the stoichiometry of CIP:iodine system was found to be 1:1 ratio according to molar ratio method. The essential spectroscopic data like formation constant (KCT), molar extinction coefficient (ɛCT), standard free energy (ΔG°), oscillator strength (f), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID) were estimated. The spectroscopic techniques such as IR, 1H NMR, mass and UV–vis spectra and elemental analyses (CHN) as well as TG-DTG and DTA investigations were used to characterize the chelating behavior of CIP/iodine charge-transfer complex. The iodine CT interaction was associated with a presence of intermolecular hydrogen bond. The X-ray investigation was carried out to investigate the iodine doping in the synthetic CT complex.

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► The X-ray powder diffraction of iodine complex has main characteristic scattering peaks at 13.19°, 24.19° and 26.49°.
► The shift in NMR spectrum concerning proton of –NH group to blue shift is attributed to the formation of the intermolecular hydrogen bond and the participation of –NH of piperazine ring in the CT complexation.
► The kinetic parameters as E, z, ΔS*, ΔH* and ΔG* were estimated.