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

An organic charge transfer complex, 2-methylimidazolinium picrate was grown by slow evaporation solution growth method at room temperature. The optical properties of the complex were studied by using UV–visible absorption and optical transmittance studies. The thermal stability of the complex was studied by TG–DTA analyses and found that it is stable up to 110°C. The DSC study of the complex indicates the occurrence of a first order phase transition. The FTIR and polarized Raman spectra were used to confirm the presence of various functional groups. The single crystal X-ray analysis suggests that the complex crystallizes in monoclinic system with C2/c space group. The SHG property and antimicrobial activity of the grown complex were also studied. •Single crystal of 2-methylimidazolinium picrate was synthesized.•Thermal stability of the complex was studied.•The DSC study of the complex shows first order phase transition.•The complex exhibited good antibacterial and antifungal activities.•The complex has SHG efficiency twice than that of KDP. 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 381nm due to π–π* 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 1.85eV. The fluorescence spectrum of the complex shows a peak at 503nm, 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°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 1H and 13C NMR spectroscopic techniques. The second harmonic generation (SHG) efficiency of the complex was found to be twice th