Investigation on the mechanism of ESIPT of 2-hydroxy-1-naphthaldehyde-(4- pyridinecarboxylic)-hydrazone and detection of [Al.sup.3+] ion

The sensing mechanism of 2-hydroxy-1-naphthaldehyde-(4-pyridinecarboxylic)- hydrazone for [Al.sup.3+] is investigated based on the excited-state intramolecular proton transfer (ESIPT) and photo- induced electron transfer (PET) processes. Absorption and fluorescence spectra are calculated, which are consistent with experimental results. By analyzing the major bond parameters, infrared vibrational spectra as well as frontier molecular orbitals, it can be concluded that the hydrogen bond is enhanced in the first singlet excited state ([S.sub.1]), which can also be visualized by the reduced density gradient function. Potential energy curves are also scanned, which can elucidate that the ESIPT process is more likely to occur in the [S.sub.1] state. Changes in molecular configuration and intensity of fluorescence emission confirmed that the ESIPT and PET processes are forbidden in the presence of [Al.sup.3+]. Key words: ESIPT, hydrogen bond, [Al.sup.3+] sensing, reduced density gradient, potential energy curve. Nous examinons le mecanisme de detection de [Al.sup.3+], du compose 2-hydroxy- naphthaldehyde-(4- pyridicarboxyclique)hydrazone, sur la base du transfert intramoleculaire de proton de l'etat excite (TIPEE) et des processus de transfert electronique induit par photon (TEP). Nos calculs des spectres d'absorption et de fluorescence s'averent coherents avec les valeurs experimentales. En analysant les parametres de liaisons majeures, les spectres vibrationnels infrarouges, ainsi que les orbitales moleculaires frontieres, nous pouvons conclure que la liaison hydrogene est renforcee dans le premier etat excite singlet ([S.sub.1]), ce qui peut aussi etre visualise par la fonction du gradient de densite reduite. Nous balayons egalement les courbes d'energie potentielle, ce qui peut eclaircir le fait que le processus TIPEE a plus de probabilite de se produire dans l'etat [S.sub.1]. Les changements dans la configuration moleculaire et l'intensite de remission de fluorescence confirment que les mecanismes TIPEE et TEP sont interdits en presence de [Al.sup.3+]. [Traduit par la Redaction] Mots-cles: TIPE, liaison hydrogene, courbe d'energie potentielle, detection de [Al.sup.3+], gradient de densite reduite.
1. Introduction Intra- and intermolecular hydrogen bonds are crucial in the study of photochemistry, photophysics, and photobiology [1-4]. Hydrogen bond dynamics have been the subject of a lot of studies [...]