Spectral and luminescent properties of bromcresol purple

The influence of the solvent on the spectral-luminescent properties of bromcresol purple (BCP) has been studied. The spectral characteristics of the BCP are determined: half-width Δν1/2, Stokes shift Δν cm , molar absorption coefficient ε, intrinsic excited state lifetime τ, oscillator strength f . Using the Lippert equation, the dependence of the Stokes shift of the BCP on the orientational polarizability of the solvent was constructed. An analysis of the experimental data showed that the position of the maximum of the BCP absorption band in the region of 350-480 nm correlates with the acceptor number of the solvent: with a decrease in the acceptor number, the maximum of the band shifts to a shorter wavelength region (water > ethanol > toluene > acetone). The lowest absorption capacity of BCP was registered in toluene. Using the Lippert-Matagi equation, the change in the dipole moment in polar protic solvents upon excitation (16.2 D) was determined, which is higher than in aprotic solvents (10.4 D) due to the formation of H-bonds.