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On the spectroscopic analyses of thioindigo dye.

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy (2013-06-08)
M Ibrahim, M M El-Nahass, M A Kamel, A A El-Barbary, B D Wagner, M A M El-Mansy
ABSTRACT

A combined experimental and theoretical study on molecular structure and vibrational frequencies of thioindigo was reported. The FT-IR spectrum of thioindigo is recorded in the solid phase. The equilibrium geometries, harmonic vibrational frequencies, thermo-chemical parameters, total dipole moment and HOMO-LUMO energies are calculated by density functional theory DFT/B3LYP utilizing 6-311G(d,p) basis set. Results showed that cis-isomer is highly recommended to be a promising structure for many applications in optoelectronic devices due to its high calculated dipole moment value (3.44 Debye) which indicates its high reactivity to interact with the surrounding molecules as compared to the trans-isomer which has no dipole moment. Both isomers have a similar HOMO-LUMO energy gap, of 3.02 eV (cis-isomer) and 2.78 eV (trans-isomer).

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Indigo carmine, certified by the Biological Stain Commission, Dye content 85 %
Sigma-Aldrich
Indigo carmine, for microscopy (Bact., Hist.), indicator (pH 11.5-14.0)
Supelco
Indigo carmine, analytical standard
Sigma-Aldrich
Indigo, synthetic, Dye content 95 %