The fluorescence decay times and quantum efficiencies of 1,4,5,8-naphthalisoimides

Presented herein are the luminescence properties of several 1,4,5,8- polinahthalisoimides. The luminescence decay curves after deconvolution exhibit three decay times: τ1, τ2, and τ3.The luminescence lifetimes change along with the growth of excitation energy, as well as the contribution of each luminescence decay mechanism (A1, A2, and A3). The manner of change is distinct for one sample, namely, the pure E-isomer, in comparison to the others. The radiative deexcitation coupled with radiationless vibrational energy transfer to other luminescence centers, mainly other isomer units, is discussed as a possible deexcitation mechanism of fluorescence. The Kasha-Vavilov empirical rule is not fulfilled for the studied samples, as the luminescence quantum efficiency (ΦF) distinctly depends on the excitation wavelength (λexc). The quantum yield of one sample (about 63% of Z-isomer) is quite high, at 1%.