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pH-Responsive colorimetric, emission and redox switches based on Ru(ii)-terpyridine complexes
Poulami Pal1, Tanusree Ganguly, Soumi Das
1Inorganic Chemistry Section, Department of Chemistry, Jadavpur University, Kolkata 700032, India. sbaitalik@hotmail.com sujoy.baitalik@jadavpuruniversity.in.
Dalton Transactions (Cambridge, England : 2003)
|December 8, 2020
Summary
Ruthenium(II) luminophores exhibit pH-responsive optical and redox switching. Deprotonation alters emission, color, and oxidation potentials, enabling their use as tunable switches.
Area of Science:
- Coordination Chemistry
- Photophysics
- Electrochemistry
Background:
- Ruthenium(II) complexes with bis-tridentate ligands are known for their luminescent properties.
- pH-responsive materials are crucial for sensing and switching applications.
Purpose of the Study:
- To investigate the pH-responsive optical and redox switching behaviors of novel trans-bis-tridentate Ru(II) luminophores.
- To understand the effect of pH-induced deprotonation on photophysical and electrochemical properties.
Main Methods:
- Synthesis and characterization of [(H2pbbzim)Ru(tpy-pvp-X)]2+ complexes (X = H, Me, Cl, NO2, Ph).
- Spectroscopic (absorption, emission) and electrochemical (cyclic voltammetry) studies across a pH range.
- Determination of ground-state (pKa) and excited-state (pKa*) acidity constants.
Main Results:
- Proton dissociation of benzimidazole groups upon increasing pH.
- Significant quenching of emission, red-shift in absorption and emission spectra, and color change.
- Remarkable cathodic shift in oxidation potentials for deprotonated forms.
Conclusions:
- The studied Ru(II) complexes function as effective pH-responsive colorimetric, emission, and redox switches.
- The electronic nature of substituent X influences pKa values, showing a linear correlation with Hammett parameters.
- Proton-coupled electrochemical behavior provides insights into acid dissociation constants in different protonation states.
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