Uv-Visible Spectrophotometric Studies of Methylene Blue Dye With Selected Polar Solvents

K. P. Srivastava, and A. Kumar

Physical Chemistry Laboratory, Rajendra College, J.P. University, Chapra- 841 301 (India)

UV-visible spectrophotometric studies of methylene blue dye with selected polar solvents like- chloroform, water, acetone and amyl alcohol have shown the existence, in each case, a new intense long wavelength absorption band in the range of 640-700 nm of the visible range. Such band has been tentatively assigned as charge transfer band due to interaction between Zn+2 ion and Phenazothionium ion. The another band of the molecule observed within UV region within 291 nm in organic solvents and water shows solvent effect and probably due to H- bonding between solvent and solute. Further the oscillator strength and some spectral characteristics of solute-solvent interaction have also been determined and it has been found that observed red shift of such absorption band of the molecule in mentioned solvents in the order of chloroform-water-acetone and amyl alcohol is exactly in the order of their dipole moment values. The oscillator strengths which have been determined seem to be inversely related with their dipole moments.

Methylene blue; oscillator-strength; H-bonding; Red shift; Solute-solvent interaction