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.
