Substituent Effect on the Photophysics and ESIPT Mechanism ofN,N′-Bis(salicylidene)-p-phenylenediamine: A DFT/TD-DFT Analysis

Abstract

Excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) processes are widely exploited in the designing of organic materials for multifarious applications. This work explores the aftereffects of combining both ESIPT and ICT events in a single molecule, namely, N,N′-bis(salicylidene)-p-phenylenediamine (BSP) exploiting DFT and TD-DFT formalisms. The PBE0 functional employed in the present study is found to yield results with better accuracy for excited-state calculations. The results reveal that introduction of electron donor (−NH 2 ) and electron acceptor (−NO 2 ) substituents on BSP produces a strikingly red-shifted emission with respect to the corresponding emission from the unsubstituted analogue in polar solvents. This red-shifted emission originated due to the coupled effect of ESIPT and planar-ICT (PICT) processes from the coplanar geometry adopted by the substituted molecule (s-BSP). Based on the computed potential energy curves, the ground-state intramolecular proton transfer (GSIPT) was found to take place more favorably in s-BSP than in BSP under all solvent conditions. In the case of ESIPT, the barrier and relative energies of the phototautomers of s-BSP were slightly higher than BSP, which shows that simultaneous substitution of −NH 2 and −NO 2 groups causes slight perturbation to the ESIPT process. Overall, the computed results show that simultaneous substitution of suitable electron donor and acceptor substituents provides profitable changes in the photophysical properties of ESIPT molecules like BSP. These molecular-level insights will pave way for designing better materials for diverse applications.

Novel isatin–triazole based thiosemicarbazones as potential anticancer agents: synthesis, DFT and molecular docking studies

“…22 In this context, the Density Functional Theory (DFT) calculations, specifically the 6-311G (d,p) basis set at the B3LYP level were carried out. 57–59…”

“…22 In this context, the Density Functional Theory (DFT) calculations, specically the 6-311G (d,p) basis set at the B3LYP level were carried out. [57][58][59] The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are two popular quantum chemical parameters. 60 The energies of these molecular orbitals, also known as frontier molecular orbitals (FMOs), are important parameters for predicting the reactivity of a chemical species.…”

Interrogating the nature of aggregates formed in a model azine based ESIPT coupled AIE active probe: stark differences in photodynamics in the solid state and aggregates in water

“…The low Stokes shift of the said band (5864.2 cm À1 ) along with the high Stokes shift of the low energy band hinted at the probability of ESIPT being operative in BNHMP as o-hydroxy Schiff bases are reported to undergo ESIPT reaction in solutions. 16,[40][41][42][43] Following previous reports, the low energy band was assigned to the ESIPT emission arising from the keto-tautomer of BNHMP in the excited state, whereas the high energy band was assigned to the enol-emission or S 1 -S 0 transition of BNHMP. The reasonable overlap between the excitation spectra of BNHMP and the absorption spectra in all solvents indicates a common origin of the emission bands in the ground state.…”

Effects of Twisted Intramolecular Charge Transfer Behavior on Excited-State Intramolecular Proton Transfer Reactions of Methyl Benzoate Derivatives in Water Solution

“…In this work, we used the implicit solvation model based on density combined with a self-consistent reaction field method to simulate the solvent environment and optimized the configurations of solute molecules. All the calculation details involved in this paper adopted the DFT and TD-DFT theoretical method combined with Becke’s three-parameter hybrid exchange functional with the Lee-Yang-Parr gradient-correct correlation (B3LYP) functional and 6-311G* basis set, , which have been successfully used in other organic systems. , In order to describe the weak interaction of the research system more accurately, we also added dispersion correction (D3) to correct the energy of the system on the basis of DFT theory, namely, the DFT-D3 method. To judge the stability of our optimized structures (reactants and products), the vibrational frequency analyses at the same theoretical level should not contain any virtual frequency.…”