Temperature influence on 4-aminophthalimide emission in 1-chloroalkanes plus water mixtures.

Thermochromic emission shifts of 4-aminophthalimide (4-AP) dissolved in three 1-chloroalkanes, namely, 1-chloropropane, 1-chlorobutane, and 1-chlorohexane, together with fluorescence decays measured at different wavelengths, all solvents containing different small amounts of water (10(-4)-10(-2) M), are reported in a broad temperature range covering the bulk water melting point. Our studies have shown that 4-AP is an effective indicator of water presence even at concentrations given by solvent suppliers for so-called "dry" solvents. Additionally, indications of water ice-clusters formation in 1-chloroalkanes, starting at different temperatures depending on water concentration, have been found. Finally, 4-AP in 1-chloroalkane + water mixture is shown to present at different temperatures three basic types of sources of time-resolved emission spectra (TRES) time/spectral evolution: emission of two kinetically coupled species, solvent relaxation, and simultaneous emission of two independent species.