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The electronic energy relaxation of 1-nitronaphthalene (1NN) was studied in different solvents using broadband transient absorption spectroscopy with femtosecond time resolution. UV excitation of 1NN populates an unrelaxed S$1$($\pi \pi$) state, which decays by conformational relaxation (primarily twisting of the NO$2$ group) with a time constant of ~100 fs. The twisting of the NO$2$ group and formation of a structurally relaxed singlet state opens up a doorway for ultrafast intersystem crossing (ISC) to a high-energy receiver triplet state T(n$\pi$), which then undergoes internal conversion to form a vibrationally excited T$1$($\pi \pi$*) state. Quantum chemical calculations that include solvent effects support the experimental observations. Our results show that an essentially barrierless path connects the initial S$1$ state to the receiver T state, which enables the observation of vibrational energy transfer and its dependence on the surrounding solvent. According to this kinetic model, which was first proposed by Crespo-Hernandez et$$al. for 1-nitropyrene[1], the S$1$($\pi \pi$) electronic energy decays rapidly and irreversibly to dark triplet states, explaining why small nitro-polycyclic aromatic compounds are typically considered to be nonfluorescent.\ {\textbf {Reference}} [1] C.$$E. Crespo-Hernandez, G. Burdzinski, R. Arce, {\textit {J. Phys. Chem. A.}}, {\textbf{2008}}, 112,6313