Substituent effects on the photophysical properties of amino-aurone-derivatives

ABSTRACT

Aurones are potential candidates to be employed as fluorescent probes or as pharmacophores for biological applications. This work describes a density functional theory (DFT) and time-dependent -DFT study at the PBE0/6-31 + G(d) level of theory to analyse the structural, electronic and photophysical properties of a series of new proposed 4′-amine-aurone derivatives in its E and Z isomeric conformations. The maximum absorption wavelength of the proposed aurones appears in the range 390 − 514 nm, while the most allowed emission pathways were computed in the range 493–530 nm. The bathochromic shift of these compounds with respect to the non-substituted aurone is modulated by the acceptor strength of the added 4-substituents, in addition to the ability of the substituents to localise the frontier molecular orbitals over the acceptor benzofuranone moiety without losing the tricyclic planarity, which favours the push–pull nature of these molecules. The influence of the 4-substituent is also evidenced in the Stokes shifts for the whole series; as the electron-withdrawing character of the 4-substituents enhances, higher is the polarisation of the structure resulting in higher Stokes shifts. As a result, -CF₃ and -NO₂ substituents were responsible of larger Stokes shifts, then compounds containing these substituents are proposed as potential fluorescence probes for useful applications in biological systems.

GRAPHICAL ABSTRACT

KEYWORDS:

• Aurones
• DFT calculations
• chromophores
• organic dyes
• fluorescence probes

Acknowledgements

This paper honours Professor Dieter Cremer (RIP). His outstanding scientific achievements will always be an inspiration for us.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Karina Muñoz-Becerra http://orcid.org/0000-0001-9882-6342

Nery Villegas-Escobar http://orcid.org/0000-0002-6370-617X

César Zúñiga-Loyola http://orcid.org/0000-0002-0894-3383

Diego Cortés-Arriagada http://orcid.org/0000-0002-6709-1723

Alejandro Toro-Labbé http://orcid.org/0000-0001-9906-2153