A TD-DFT/DFT study on the ESIPT and photophysical properties of symmetrical 2-hydroxybenzilidene1,3-diamines derivatives

The geometries and relative stabilities of 15 tautomeric forms and the corresponding isomers of the studied molecules have been identified and their relative stabilities are investigated. The potential energy profiles and intrinsic reaction coordinates (IRC) calculations along the proton transfer coordinates both in the ground and in the excited state are monitored as well. The impact of the donating (OMe) and withdrawing (NO2) groups on the single and double proton transfers are investigated both in the gas phase and solution.
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A TD-DFT/DFT study on the ESIPT and photophysical properties of symmetrical 2-hydroxybenzilidene1,3-diamines derivativesCite this paper: Vietnam J. Chem., 2023, 61(5), 612-620 Research articleDOI: 10.1002/vjch.202300108 A TD-DFT/DFT study on the ESIPT and photophysical properties of symmetrical 2-hydroxybenzilidene1,3-diamines derivatives Shaaban A. Elroby1*, Osman I. Osman1, Abdesslem Jedidi1, Walid I. Hassan1, Saadullah G. Aziz1, Rifaat Hilal2 1 Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi Arabia 2 Chemistry Department, Faculty of Science, University of Cairo, Egypt Submitted March 7, 2023; Revised May 15, 2023; Accepted June 5, 2023Abstract Density functional theory (DFT) and Time dependent density functional theory (TD-DFT) methods are used tosimulate the photoexcitation and emission of the symmetrical 2-hydroxybenzilidene1,3-diamine (HBDA) Schiff baseand some of its derivatives in the gas phase and solution. Our aim here is to explore the details of Excited-StateIntramolecular Proton Transfer (ESIPT) which underlies the activity of HBDA molecules as fluorescent probes. Thestructures of HBDA in S0 and the S1 states are optimized utilizing the DFT and TD-DFT methods, respectively.Geometric configurations, electronic spectra, frontier molecular orbitals, and potential energy surfaces have all beencomputed and analyzed for the purpose of interpreting the mechanism of ESIPT. The geometries and relative stabilitiesof 15 tautomeric forms and the corresponding isomers of the studied molecules have been identified and their relativestabilities are investigated. The potential energy profiles and intrinsic reaction coordinates (IRC) calculations along theproton transfer coordinates both in the ground and in the excited state are monitored as well. The impact of the donating(OMe) and withdrawing (NO2) groups on the single and double proton transfers are investigated both in the gas phaseand solution. Keywords. Hydrogen bond, molecular switches, proton transfer, excited state intramolecular proton transfer(ESIPT), Schiff bases, DFT, TD-DFT.1. INTRODUCTION one another have been well established as hydrogen donor and acceptor sites, respectively, for buildingCarbonyl compounds and primary amines are ESIPT-based compounds that serve as metal ions-condensed to produce Schiff bases, commonly specific probes.[24,25]referred to as imines. They are of great chemical and Through keto-enol tautomerisms, the capacity ofbiological significance because of their simple hydrogen donor and acceptor sites increases in theirsynthetic flexibility, ease of synthesis, and unique excited state and causes the ESIPT phenomena.imine (CN) group characteristic, which makes During the proton transfer in the excited state, whichimines good chelating agents.[1] Additionally, it has results in dual emission with a significant Stokesbeen noted that Schiff bases are frequently utilized shift, the keto-form is stable relative to its enol-as precursors to numerous compounds with form.[26] A proton is engaged in intramolecularbiological and economic significance.[2–6] hydrogen bonding exchanges between two Commonly referred to as molecular switches,[7] electronegative centers during the ultrafastsalicylidene aniline Schiff bases (SAS) are dynamic photoinduced transition known as ESIPT. In lightingsystems that exhibit thermochromism, applications, the photochemical properties ofphotochromism, solvatochromism, and nonlinear compounds having two PT sites provide a new routeoptical (NLO) switching features[8-21] both in for full-color tunability. Widespread interest issolution and as solids. When stimulated by changes generated for two PT site compounds when thein temperature or light, SASs can experience keto- excited state intramolecular double proton transferenol tautomerism.[22–23] This is true for both of their (ESIDPT) reaction occurs. Salicylaldehyde is aintramolecular H-bond-characterized cis and trans classic compound having a derivative called HBDAisomers. The probes with the characteristic OH Schiff base (figure 1).(phenolic) and N (imine) functional groups next to Salicylaldehyde Schiff base is a typical molecule612 Wiley Online Library © 2023 Vietnam Academy of Science and Technol ...