A Novel Fluorophore with Dual Fluorescence: Local Excited State and Photoinduced Electron‐Transfer‐Promoted Charge‐Transfer State

Abstract

Absorption and emission spectra of 9-N,N-dimethylaniline decahydroacridinedione (DMAADD) have been studied in different solvents. The fluorescence spectra of DMAADD are found to exhibit dual emission in aprotic solvents and single emission in protic solvents. The effect of solvent polarity and viscosity on the absorption and emission spectra has also been studied. The fluorescence excitation spectra of DMAADD monitored at both the emission bands are different. The presence of two different conformation of the same molecule in the ground state has lead to two close lying excited states, local excited (LE) and charge transfer (CT), and thereby results in the dual fluorescence of the dye. A CTstate involving the N,N-dimethylaniline group and the decahy droacridinedione chromophore as donor and acceptor, respectively, has been identified as the source of the long wavelength anomalous fluorescence. The experimental studies were supported by ab initio time dependent-density functional theory (TDDFT) calculations performed at the B3LYP/6-31G* level. The molecule possesses photoinduced electron transfer (PET) quenching in the LE state, which is confirmed by the fluorescence lifetime and fluorescent intensity enhancement in the presence of transition metal ions.

Photophysical properties of trans-3-(4-monomethylamino-phenyl)-acrylonitrile: Evidence of twisted intramolecular charge transfer (TICT) process

“…The fluorescence decay of CT band (415 nm) band in acetonitrile solvent is 0.375 ns. The charge transfer excited state decays faster than the LE state [38,39]. The fluorescence decay in polar solvent like water is of different nature.…”

Specific optical signalling of anions via intramolecular charge transfer pathway based on acridinedione fluorophore

“…Interestingly, these dyes have been shown to mimic the NADH analogs to a greater extent because of its tricyclic structure, which is capable of protecting the enamine moiety [34]. We are particularly interested in developing fluorescent chemosensors where the ion recognition takes place at the receptor site with concomitant changes in the photophysical properties of a ADD fluorophore by modulation of PET and ICT processes [35][36][37]. In this article, we report the simplest acridinedione-based fluorophore (ADD-1) that exhibits excellent specificity towards AcO À , H 2 PO 4 À and F À by different optical signal output via ICT pathway.…”

Spectroscopic and theoretical evidence for the photoinduced twisted intramolecular charge transfer state formation in N,N-dimethylaminonaphthyl-(acrylo)-nitrile

“…Even after decades of the discovery of dual fluorescence in 4-N,N-dimethylaminobenzonitrile (DMABN) by Lippert et al [1], new molecules are being designed for the possibility of photoinduced ICT reaction [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The need for new donor-acceptor charge transfer (CT) molecules crops up due to their vast applications in the field of pure and applied sciences such as pH and ion detectors, sensors for free volume in polymers, study of micro-heterogeneous environments, etc.…”