Photophysical properties of ruthenium bipyridine (4-carboxylic acid-4′-methyl-2,2′-bipyridine) complexes and their acid-base chemistry

Chien Hua Su; Hsuan Ying Chen; Kelvin Yun Da Tsai; I. Jy Chang

doi:10.1021/jp070847i

Photophysical properties of ruthenium bipyridine (4-carboxylic acid-4′-methyl-2,2′-bipyridine) complexes and their acid-base chemistry

Chien Hua Su
, Hsuan Ying Chen
, Kelvin Yun Da Tsai
, I. Jy Chang^*

^*Corresponding author for this work

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

Photophysical properties such as absorption and emission spectra, lifetimes, and redox potentials of eight ruthenium complexes, Ru(LL) ₂(MebpyCOOH)²⁺, where LL represents bpy, phen, Me ₂bpy, Me₄bpy, (MeO)₂bpy, (EtO)₂bpy, Cl₂bpy, and NO₂phen, have been measured. The acid dissociation constants of ground and excited states have been determined. The ground-state pK_a values were obtained from the pH dependence of the complex absorbance changes. The excited-state pK_a* values were extracted from the emission titration curve and corrected for the excited-state lifetime of both protonated and deprotonated species. The largest ΔpK _a, pK_a* - pK_a, found for Ru(Me ₂bpy)₂(MebpyCOOH)²⁺ and Ru(Me ₄bpy)₂(MebpyCOOH)²⁺ of 1.7 indicate that MebpyCOOH gains most of the MLCT excited-state electron. The big negative ΔpK_a found for Ru(Cl₂bpy)₂-(MebpyCOOH) ²⁺, -4.2, clearly indicates the metal-to-ligand charge transfer to the Cl₂bpy ligands.

Original language	English
Pages (from-to)	6857-6860
Number of pages	4
Journal	Journal of Physical Chemistry B
Volume	111
Issue number	24
DOIs	https://doi.org/10.1021/jp070847i
Publication status	Published - 2007 Jun 21

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Surfaces, Coatings and Films
Materials Chemistry

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@article{b37aa897c1fd41cab716df807ea36f72,

title = "Photophysical properties of ruthenium bipyridine (4-carboxylic acid-4′-methyl-2,2′-bipyridine) complexes and their acid-base chemistry",

abstract = "Photophysical properties such as absorption and emission spectra, lifetimes, and redox potentials of eight ruthenium complexes, Ru(LL) 2(MebpyCOOH)2+, where LL represents bpy, phen, Me 2bpy, Me4bpy, (MeO)2bpy, (EtO)2bpy, Cl2bpy, and NO2phen, have been measured. The acid dissociation constants of ground and excited states have been determined. The ground-state pKa values were obtained from the pH dependence of the complex absorbance changes. The excited-state pKa* values were extracted from the emission titration curve and corrected for the excited-state lifetime of both protonated and deprotonated species. The largest ΔpK a, pKa* - pKa, found for Ru(Me 2bpy)2(MebpyCOOH)2+ and Ru(Me 4bpy)2(MebpyCOOH)2+ of 1.7 indicate that MebpyCOOH gains most of the MLCT excited-state electron. The big negative ΔpKa found for Ru(Cl2bpy)2-(MebpyCOOH) 2+, -4.2, clearly indicates the metal-to-ligand charge transfer to the Cl2bpy ligands.",

author = "Su, \{Chien Hua\} and Chen, \{Hsuan Ying\} and Tsai, \{Kelvin Yun Da\} and Chang, \{I. Jy\}",

year = "2007",

month = jun,

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doi = "10.1021/jp070847i",

language = "English",

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journal = "Journal of Physical Chemistry B",

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AU - Su, Chien Hua

AU - Chen, Hsuan Ying

AU - Tsai, Kelvin Yun Da

AU - Chang, I. Jy

PY - 2007/6/21

Y1 - 2007/6/21

N2 - Photophysical properties such as absorption and emission spectra, lifetimes, and redox potentials of eight ruthenium complexes, Ru(LL) 2(MebpyCOOH)2+, where LL represents bpy, phen, Me 2bpy, Me4bpy, (MeO)2bpy, (EtO)2bpy, Cl2bpy, and NO2phen, have been measured. The acid dissociation constants of ground and excited states have been determined. The ground-state pKa values were obtained from the pH dependence of the complex absorbance changes. The excited-state pKa* values were extracted from the emission titration curve and corrected for the excited-state lifetime of both protonated and deprotonated species. The largest ΔpK a, pKa* - pKa, found for Ru(Me 2bpy)2(MebpyCOOH)2+ and Ru(Me 4bpy)2(MebpyCOOH)2+ of 1.7 indicate that MebpyCOOH gains most of the MLCT excited-state electron. The big negative ΔpKa found for Ru(Cl2bpy)2-(MebpyCOOH) 2+, -4.2, clearly indicates the metal-to-ligand charge transfer to the Cl2bpy ligands.

AB - Photophysical properties such as absorption and emission spectra, lifetimes, and redox potentials of eight ruthenium complexes, Ru(LL) 2(MebpyCOOH)2+, where LL represents bpy, phen, Me 2bpy, Me4bpy, (MeO)2bpy, (EtO)2bpy, Cl2bpy, and NO2phen, have been measured. The acid dissociation constants of ground and excited states have been determined. The ground-state pKa values were obtained from the pH dependence of the complex absorbance changes. The excited-state pKa* values were extracted from the emission titration curve and corrected for the excited-state lifetime of both protonated and deprotonated species. The largest ΔpK a, pKa* - pKa, found for Ru(Me 2bpy)2(MebpyCOOH)2+ and Ru(Me 4bpy)2(MebpyCOOH)2+ of 1.7 indicate that MebpyCOOH gains most of the MLCT excited-state electron. The big negative ΔpKa found for Ru(Cl2bpy)2-(MebpyCOOH) 2+, -4.2, clearly indicates the metal-to-ligand charge transfer to the Cl2bpy ligands.

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Photophysical properties of ruthenium bipyridine (4-carboxylic acid-4′-methyl-2,2′-bipyridine) complexes and their acid-base chemistry

Abstract

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