Electronic Properties of 4-Substituted Naphthalimides

Abstract

This paper describes a study of excited-state properties of naphthalimide (NI) and four 4-substituted derivatives: 4-chloronaphthalimide (Cl-NI), 4-methylthionaphthalimide (MeS-NI), 4-nitronaphthalimide (O(2)N-NI), and 4-(N,N-dimethylaminonaphthalimide (Me(2)N-NI). Steady-state absorption and fluorescence spectra were collected in solvents of varying polarity to determine the excited-state character of NI derivatives. Furthermore, the excited-state dynamics were studied using femtosecond transient absorption spectroscopy. The experimental findings were compared to calculated data obtained using time-dependent density functional (TD-DFT) methods. We found that light absorption by all NI derivatives leads to the production of the second excited state (S(2)), which was found to have a n,pi* character. Within approximately 40 ps, the S(2) state undergoes internal conversion to produce the S(1) state. The S(1) state is relatively long-lived (approximately 4 ns) and has charge-transfer character in NI derivatives with electron-withdrawing and electron-donating groups (MeS-NI, O(2)N-NI, and Me(2)N-NI). In the case of NI and Cl-NI, the S(1) state has a pi,pi* character and undergoes intersystem crossing to produce the T(1) state within 400 ps.

Photoinduced Electron Transfer Involving a Naphthalimide Chromophore in Switchable and Flexible [2]Rotaxanes

“…For all the compounds (except DB24C8‐PTZ ), a band centered at ca. 350 nm, with ϵ ≈14 000 mol −1 L cm −1 typical of the NI chromophore is observed . In all the rotaxanes, the absorption band of the DB24C8 macrocycle ( λ max =275 nm) is also detected.…”

“…The decay shows a second component, almost constant in the time range of the experiment, due to the formed triplet. The observed transient spectra are in reasonable agreement with those reported for singlet and triplet excited states of NI chromophores . Very similar features are observed for NI‐amH + , where the spectral evolution is consistent with intersystem crossing (Figure S54 a).…”

An ultrafast time‐resolved infrared and UV–vis spectroscopic and computational study of the photochemistry of acyl azides

“…To overcome this problem, one can compute the electronic density distribution in both the ground state and the Frank–Condon excited state followed by subtraction of the ground state electronic density from the Frank–Condon excited state electronic density, thereby giving an electron density difference plot. In the recent past, we have utilized this strategy to analyze the photochemical behavior of many different chemical systems . For these plots, a red or green contour indicates depletion or accumulation of electronic density in the excited state relative to the ground state, respectively.…”

Ultrafast Spectroscopy and Computational Study of the Photochemistry of Diphenylphosphoryl Azide: Direct Spectroscopic Observation of a Singlet Phosphorylnitrene

“…We have recently applied this methodology for different photochemical problems such as predicting the photochemistry of aryl azides, 21,22 naphthylimides, 24 and inorganic complexes, 25 investigating the photochemical mechanism of nitro-substituted polycyclic aromatic hydrocarbons, 26 and predicting the character of the excited states of N-confused porphyrins. 27 This strategy has also been used earlier with other ab initio methods.…”