Spectral, thermal, structural, optical and antimicrobial activity studies on 2-methylimidazolinium picrate - An organic charge transfer complex

An organic charge transfer (CT) complex, 2-methylimidazolinium picrate was grown by slow evaporation solution growth method at ambient temperature. While the stoichiometric ratio of the complex was confirmed by CHN analysis, its crystallinity was evident from the powder X-ray diffraction pattern. The absorption study of the complex shows a peak at 381 nm due to pi-pi* transition. The transmittance window and cut-off wavelength were ascertained by optical transmittance spectroscopic technique. The band gap energy of the complex was found to be 1.85 eV. The fluorescence spectrum of the complex shows a peak at 503 nm, which reveals that it exhibits green fluorescence emission. The thermogravimetry and differential thermal (TG-DTA) analyses indicated that the complex was thermally stable up to 110 degrees C. The TG-DTA study also confirmed the stoichiometric ratio and decomposition pattern of the complex. The low temperature differential scanning calorimetry (DSC) study shows thermal hysterses in the cooling and heating curves indicating the occurrence of first order phase transition in the complex. The various characteristic absorption bands and other chemical bonds were assigned through FTIR and polarized Raman spectroscopic studies. The different kinds of protons and carbons in the complex were confirmed by H-1 and C-13 NMR spectroscopic techniques. The second harmonic generation (SHG) efficiency of the complex was found to be twice than that of KDP. Single crystal X-ray structural study indicates that the complex crystallizes in monoclinic crystal system with C2/c space group. The antibacterial and antifungal activities of the complex indicate that it exhibits good antibacterial and antifungal activities. (C) 2013 Elsevier B.V. All rights reserved.