Synthesis, Characterization And Electrical Conductivity Studies Of Naphthoyl-Thiourea Derivatives As Potential Organic Light Emitting Diode

Abstract

Thiourea motif has attracted considerably great interest in numerous applications. Molecular framework featuring thiourea derivatives as molecular wire consists of conjugated systems which promises wide range of electronic properties and suitable to be applied in molecular electronics application. Regarding to this matter, this study was carried out to determine the electrical conductivity and performance as OLED of this linear conjugated organic compounds with general formula A-ArC(O)NHC(S)NHAr-D. All synthesized compounds (1-5) were spectroscopically and analytically characterized via CHNS Elemental Microanalysis, Fourier Transform Infrared (FTIR), UltravioletVisible Spectroscopy (UV-Vis), Ultraviolet-Fluorescence Spectroscopy (UV-F), 1 H and 13 C Nuclear Magnetic Resonance (NMR), Single Crystal X-Ray Crystallography Analysis, X-Ray Diffraction Spectroscopy (XRD), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Cyclic Voltammetry (CV) Analysis. The compounds were fabricated on ITO substrate by using electrochemical deposition method (ECD) before the electrical conductivity and performances as OLED were tested by using Four Point Probe and Two Point Probe. The Gaussian 09 Software was used to calculate the energy band gap and the electrical conductivity of the synthesized compounds to compare with experimental evaluation. The infrared spectra for 1-5 showed five and six significant absorptions within the expected range. From UV-Vis spectra, they show the presence of -* and n-* electronic transitions which referred to C=O and C=S chromophores whereas from UV-F spectra, the emission spectra were observed for 1-5. The 1 H NMR spectra exhibit all expected resonances especially for δH 13 (NH). Whilst, C NMR spectra also show expected resonances of δC (C=O) and δC (C=S) to indicate that these compounds indeed thiourea derivatives. In addition, the energy bandgaps (Eg) of all synthesized compound were measured and confirmed by theoretical calculation. The energy bandgaps (Eg) of these compounds were at around 4.49-4.72 eV and it is in a good agreement with the theoretical calculation. From the electrical conductivity study, these compounds fall in the range of semiconductor materials which is 1.61x10 -4 -4 -1 -1.72x10 Scm under dark condition.