Tuning Photophysical Properties by p-Functional Groups in Zn(II) and Cd(II) Complexes with Piperonylic Acid

Francisco Sánchez-Férez, Joaquim Ma Rius-Bartra, José A. Ayllón, Teresa Calvet, Mercè Font-Bardia, Josefina Pons*

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

Aggregation between discrete molecules is an essential factor to prevent aggregationcaused quenching (ACQ). Indeed, functional groups capable of generating strong hydrogen bonds are likely to assemble and cause ACQ and photoinduced electron transfer processes. Thus, it is possible to compare absorption and emission properties by incorporating two ligands with a different bias toward intra-and intermolecular interactions that can induce a specific structural arrangement. In parallel, the π electron-donor or electron-withdrawing character of the functional groups could modify the Highest Ocuppied Molecular Orbital (HOMO)–Lowest Unocuppied Molecular Orbital (LUMO) energy gap. Reactions of M(OAc)2·2H2O (M = Zn(II) and Cd(II); OAc = acetate) with 1,3benzodioxole-5-carboxylic acid (Piperonylic acid, HPip) and 4-acetylpyridine (4-Acpy) or isonicotinamide (Isn) resulted in the formation of four complexes. The elucidation of their crystal structure showed the formation of one paddle-wheel [Zn(μ-Pip)2(4-Acpy)]2 (1); a mixture of one dimer and two monomers [Zn(µ-Pip)(Pip)(Isn)2]2·2[Zn(Pip)2(HPip)(Isn)]·2MeOH (2); and two dimers [Cd(μPip)(Pip)(4-Acpy)2]2 (3) and [Cd(μ-Pip)(Pip)(Isn)2]2·MeOH (4). They exhibit bridged (1, µ2-η11), bridged, chelated and monodentated (2, µ2-η11, µ1-η11 and µ1-η1), or simultaneously bridged and chelated (3 and 4, µ2-η21) coordination modes. Zn(II) centers accommodate coordination numbers 5 and 6, whereas Cd(II) presents coordination number 7. We have related their photophysical properties and fluorescence quantum yields with their geometric variations and interactions supported by TD-DFT calculations.

Original languageEnglish
Article number1365
JournalMolecules
Volume27
Issue number4
DOIs
Publication statusPublished - 17 Feb 2022

Keywords

  • 4-acetylpyridine
  • Isonicotinamide
  • Photoluminescence
  • Piperonylic acid
  • Zn(II) and Cd(II)

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