Tunable Solvatochromic Response of Newly Synthesized Antioxidative Naphthalimide Derivatives: Intramolecular Charge Transfer Associated with Hydrogen Bonding Effect

Abstract

The solvatochromic behavior of two newly synthesized naphthalimide derivatives (I and II) which have potential antioxidative activities in anticarcinogenic drug development treatment, has been monitored in protic and aprotic solvents of different polarity applying steady-state and time-resolved fluorescence techniques. The compounds exhibit unique photophysical response in different solvent environments. The spectral trends do not appear to originate only from changes in the solvent polarity but also indicate that hydrogen bonding interactions and intramolecular charge transfer (ICT) influence the energy of electronic excitation of the compounds. Incorporation of an amino group at C(4) position of the naphthalimide ring in II makes it behave differently from I in terms of spectral characterization and fluorescence efficacy of the systems. The nonradiative relaxation process of the compounds is governed by medium polarity. The ground state geometry, lowest energy transition, and the UV-vis absorption energy of the compounds were studied using density functional theory (DFT) and time-dependent density functional theory (TDDFT) at the B3LYP/6-31G* level, which showed that the calculated outcomes were in good agreement with experimental data.

Integration of the 1,2,3‐Triazole “Click” Motif as a Potent Signalling Element in Metal Ion Responsive Fluorescent Probes

“…The fluorescence band of both compounds is also strongly shifted, to about 530 for 2 and 586 nm for 1 , which is in line with general findings on the fluorescence behavior of 4‐donor‐substituted NI dyes in water 105. 106 In the case of 2 , the fluorescence is still very weak, hampering any more reliable determination of the fluorescence data. Interaction of the protic solvent with the aniline’s nitrogen atom, which is expected to take place in this environment, is presumably not strong enough to lead to a significant increase in fluorescence quantum yield.…”

Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers

“…It was further proposed that intermolecular hydrogen-bonding of the carbonyl oxygen and/or the imide nitrogen with solvent molecules in protic solvents results in a drop of the quantum yield 26,29 accompanied by a pronounced red-shi of emission maxima. 21,23,31 Due to this strong environmental sensitivity, besides several reports regarding their use in chemosensors for detection of metal ions, 30,32,33 these uorophores were also exploited as a tool for monitoring protein-protein interactions, 27,34 or as a potential sensor for DNA. [35][36][37] Also, they have recently been used to signal the pH-induced conformational changes of a protein.…”

Photosensitized Oxidative Dimerization at Tyrosine by a Water‐Soluble 4‐Amino‐1,8‐naphthalimide

“…The singlet states of 1 and its monomeric counterpart exhibit strong ICT characteristics and are highly solvatochromic, consistent with studies concerning electronically excited states of 4-amino-1,8-napthalimides. [20][21][22][23][24][25][26] Interestingly, aqueous conditions are proposed to stabilize transient reactive intermediates while enhancing non-radiative decay pathways. This enhancement is markedly pronounced in studies using 1.…”