Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push-pull electronic systems: Experimental and quantum chemical study

Ivana N Stojiljković; Milica P Rančić; Aleksandar D Marinković; Ilija N Cvijetić; Miloš K Milčić

doi:10.1016/j.saa.2021.119576

Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push-pull electronic systems: Experimental and quantum chemical study

Spectrochim Acta A Mol Biomol Spectrosc. 2021 May 15:253:119576. doi: 10.1016/j.saa.2021.119576. Epub 2021 Feb 13.

Authors

Ivana N Stojiljković¹, Milica P Rančić¹, Aleksandar D Marinković², Ilija N Cvijetić³, Miloš K Milčić⁴

Affiliations

¹ Faculty of Forestry, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia.
² Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia.
³ Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia.
⁴ Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia. Electronic address: mmilcic@chem.bg.ac.rs.

PMID: 33631625
DOI: 10.1016/j.saa.2021.119576

Abstract

Electronic interactions in donor-π-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push-pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and ¹³C NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push-pull character of barbituric acid derivatives was performed by the ¹³CNMR chemical shift differences, Mayer π bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push-pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor.

Keywords: Barbituric acid derivatives; Hole-electron distribution analysis; ICT process; LFER analysis; Push–pull systems.