TY - JOUR
T1 - Photophysical properties of ruthenium bipyridine (4-carboxylic acid-4′-methyl-2,2′-bipyridine) complexes and their acid-base chemistry
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.
UR - http://www.scopus.com/inward/record.url?scp=34547260085&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34547260085&partnerID=8YFLogxK
U2 - 10.1021/jp070847i
DO - 10.1021/jp070847i
M3 - Article
AN - SCOPUS:34547260085
SN - 1520-6106
VL - 111
SP - 6857
EP - 6860
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 24
ER -