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<p>The current article demonstrates the theoretical possibility of occurrence of intramolecular proton transfer (IPT) reactions in four functional compounds, ortho-vanillin and Schiff bases, namely, salicylaldazine, 2-((E)-(ethylimino) methyl)-6 methoxy phenol (2EM6MP) and Bis 2-((E)-(ethylimino) methyl)-6 methoxy phenol (B2EM6MP) scanning their potential energy curves in different electronic states. Quantum chemical calculations on the ground (S<sub>0</sub>) and excited (S<sub>1</sub>, T<sub>1</sub> and S<sub>2</sub>) states reveal that none of the compounds undergo IPT process in the ground (S<sub>0</sub>) state, whereas excited state intramolecular proton transfer (ESIPT) is possible for all of them. Potential energy curves (PECs) and frontier molecular orbital (FMO) diagrams have been generated to depict the propositions in the different electronic states. These show single-proton transfer (SPT) to be viable in all molecular systems in S<sub>1</sub>, S<sub>2</sub> and T<sub>1</sub> states. In addition, feasibility of the double-proton transfer (DPT) reaction in B2EM6MP and salicylaldazine is also examined given their structural propensity to DPT. Calculations indicate that ESDPT is viable for B2EM6MP in S<sub>1</sub>, S<sub>2</sub> and T<sub>1</sub> states but does not seem to occur for these electronic states theoretically in salicylaldazine. The differential proposition is rationalized since for ESDPT reaction the two proton transfer sites are in isolation through saturated carbon centers for B2EM6MP while they are directly connected in salicylaldazine.</p> Graphical Abstract <p>Ortho-vanillin and some structurally related imine-functionalized derivatives, such as salicylaldazine, 2-((E)-(ethylimino)methyl)-6 methoxy phenol (2EM6MP) and Bis 2-((E)-(ethylimino)methyl)-6 methoxy phenol (B2EM6MP), are theoretically established to be fluorescent possessing excited state intramolecular proton transfer (ESIPT) property. The DFT study reveals the occurrence of SPT in the S<sub>1</sub> state of all four compounds, whereas DPT is feasible only in the S<sub>1</sub> state of B2EM6MP.</p> <p></p>

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Computational insights to look for the feasibility of intramolecular proton transfer reaction in some imine-functionalized derivatives: a comparative Ab-initio analysis

  • 期刊论文

  • 发表日期：

    2025年2月6日

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  • Debosreeta Bose

摘要

The current article demonstrates the theoretical possibility of occurrence of intramolecular proton transfer (IPT) reactions in four functional compounds, ortho-vanillin and Schiff bases, namely, salicylaldazine, 2-((E)-(ethylimino) methyl)-6 methoxy phenol (2EM6MP) and Bis 2-((E)-(ethylimino) methyl)-6 methoxy phenol (B2EM6MP) scanning their potential energy curves in different electronic states. Quantum chemical calculations on the ground (S0) and excited (S1, T1 and S2) states reveal that none of the compounds undergo IPT process in the ground (S0) state, whereas excited state intramolecular proton transfer (ESIPT) is possible for all of them. Potential energy curves (PECs) and frontier molecular orbital (FMO) diagrams have been generated to depict the propositions in the different electronic states. These show single-proton transfer (SPT) to be viable in all molecular systems in S1, S2 and T1 states. In addition, feasibility of the double-proton transfer (DPT) reaction in B2EM6MP and salicylaldazine is also examined given their structural propensity to DPT. Calculations indicate that ESDPT is viable for B2EM6MP in S1, S2 and T1 states but does not seem to occur for these electronic states theoretically in salicylaldazine. The differential proposition is rationalized since for ESDPT reaction the two proton transfer sites are in isolation through saturated carbon centers for B2EM6MP while they are directly connected in salicylaldazine.

Graphical Abstract

Ortho-vanillin and some structurally related imine-functionalized derivatives, such as salicylaldazine, 2-((E)-(ethylimino)methyl)-6 methoxy phenol (2EM6MP) and Bis 2-((E)-(ethylimino)methyl)-6 methoxy phenol (B2EM6MP), are theoretically established to be fluorescent possessing excited state intramolecular proton transfer (ESIPT) property. The DFT study reveals the occurrence of SPT in the S1 state of all four compounds, whereas DPT is feasible only in the S1 state of B2EM6MP.