The Effects of Solvent and pH on the Electronic Spectral Properties of Indolino Spirobenzoxazine

The UV-visible spectra of indolino spirobenzoxazine were recorded in polar protic solvents, methanol and ethanol and polar aprotic solvent, acetone. The results showed a hypsochromic shift in the wavelength of maximum absorption with increase in solvent polarity. pH variation from 3-11 showed significant effects on the absorption properties of the compound. The electronic spectral properties have been shown to correlate successfully with solvatochromic parameters using two variables linear solvation energy relationship (LSER) at 95% confidence level. The contribution of the solvatochromic parameters to the solute-solvent interaction has also been evaluated. Hydrogen bond donor acidity showed 63-67% contribution to the solute-solvent interaction whereas dipolarity/polarizability and hydrogen bond acceptor basicity contributed 37% and 33% respectively.