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Title: Direct observation of metal-to-ligand charge-transfer (MLCT) excited states of pentaammineruthenium(II) complexes

Abstract

Excited-state difference spectra and lifetimes are reported for Ru(tpy)/sub 2//sup 2 +/ (tpy = 2,2',2''-terpyridine) and a series of pentaammineruthenium(II) complexes. The initially formed excited states (generated by approx. 25-ps excitation with 532-nm light) are well modeled by a Ru/sup III/(L/sup .-/) electronic configuration (L is an aromatic, N-heterocyclic ligand) since an excellent correspondence is found between their absorption features and those of (L/sup .-)H/sup +/ radicals. The transients are, therefore, assigned as MLCT states. The Ru(tpy)/sub 2//sup 2 +/ excited-state lifetime is 250 ps. The Ru(NH/sub 3/)/sub 5/L/sup 2 +/ excited-state lifetimes vary from less than or equal to 20 (L = protonated pyrazine, protonated 4,4'-bipyridine, and 4-acetylpyridine) to approx. 200 (L = pyrazine, isonicotinamide, 4,4'-bipyridine) ps in water at approx. 22/sup 0/C. Ammine aquation products, Ru(NH/sub 3/)/sub 4/(H/sub 2/O)L/sup 2 +/, are also observed and are shown to result from multiphoton absorption of the ps-excitation pulses. The MLCT states of Ru(NH/sub 3/)/sub 5/L/sup 2 +/ (L = pz or 4,4'-bpy) undergo protonation by solvent water and deactivation to Ru(NH/sub 3/)/sub 5/LH/sup 3 +/; rate constants for proton loss from the protonated species (Ru(NH/sub 3/)/sub 5/LH/sup 3 +/ + H/sub 2/O ..-->.. Ru(NH/sub 3/)/sub 5/L/sup 2 +/ + H/submore » 3/O/sup +/) are (2-3) x 10/sup 7/ s/sup -1/ and 2 x 10/sup 5/ s/sup -1/ for L = pz and 4,4'-bpy, respectively. The Ru(NH/sub 3/)/sub 5/L/sup 2 +/ MLCT-excited-state lifetimes are discussed in terms of the lowest excited state tuning model of Ford and co-workers.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Lab., Upton, NY
OSTI Identifier:
6629357
DOE Contract Number:  
AC02-76CH00016
Resource Type:
Journal Article
Journal Name:
J. Am. Chem. Soc.; (United States)
Additional Journal Information:
Journal Volume: 109:8
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AMMINES; PHOTOLYSIS; PYRIDINES; RUTHENIUM COMPLEXES; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; CHEMICAL REACTION KINETICS; EXCITED STATES; EXPERIMENTAL DATA; LIFETIME; LIGANDS; PHOTOCHEMISTRY; PULSE TECHNIQUES; AZINES; CHEMICAL REACTIONS; CHEMISTRY; COMPLEXES; DATA; DECOMPOSITION; ENERGY LEVELS; HETEROCYCLIC COMPOUNDS; INFORMATION; KINETICS; NUMERICAL DATA; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; REACTION KINETICS; SPECTRA; SPECTROSCOPY; TRANSITION ELEMENT COMPLEXES; 400500* - Photochemistry

Citation Formats

Winkler, J R, Netzel, T L, Creutz, C, and Sutin, N. Direct observation of metal-to-ligand charge-transfer (MLCT) excited states of pentaammineruthenium(II) complexes. United States: N. p., 1987. Web. doi:10.1021/ja00242a023.
Winkler, J R, Netzel, T L, Creutz, C, & Sutin, N. Direct observation of metal-to-ligand charge-transfer (MLCT) excited states of pentaammineruthenium(II) complexes. United States. https://doi.org/10.1021/ja00242a023
Winkler, J R, Netzel, T L, Creutz, C, and Sutin, N. 1987. "Direct observation of metal-to-ligand charge-transfer (MLCT) excited states of pentaammineruthenium(II) complexes". United States. https://doi.org/10.1021/ja00242a023.
@article{osti_6629357,
title = {Direct observation of metal-to-ligand charge-transfer (MLCT) excited states of pentaammineruthenium(II) complexes},
author = {Winkler, J R and Netzel, T L and Creutz, C and Sutin, N},
abstractNote = {Excited-state difference spectra and lifetimes are reported for Ru(tpy)/sub 2//sup 2 +/ (tpy = 2,2',2''-terpyridine) and a series of pentaammineruthenium(II) complexes. The initially formed excited states (generated by approx. 25-ps excitation with 532-nm light) are well modeled by a Ru/sup III/(L/sup .-/) electronic configuration (L is an aromatic, N-heterocyclic ligand) since an excellent correspondence is found between their absorption features and those of (L/sup .-)H/sup +/ radicals. The transients are, therefore, assigned as MLCT states. The Ru(tpy)/sub 2//sup 2 +/ excited-state lifetime is 250 ps. The Ru(NH/sub 3/)/sub 5/L/sup 2 +/ excited-state lifetimes vary from less than or equal to 20 (L = protonated pyrazine, protonated 4,4'-bipyridine, and 4-acetylpyridine) to approx. 200 (L = pyrazine, isonicotinamide, 4,4'-bipyridine) ps in water at approx. 22/sup 0/C. Ammine aquation products, Ru(NH/sub 3/)/sub 4/(H/sub 2/O)L/sup 2 +/, are also observed and are shown to result from multiphoton absorption of the ps-excitation pulses. The MLCT states of Ru(NH/sub 3/)/sub 5/L/sup 2 +/ (L = pz or 4,4'-bpy) undergo protonation by solvent water and deactivation to Ru(NH/sub 3/)/sub 5/LH/sup 3 +/; rate constants for proton loss from the protonated species (Ru(NH/sub 3/)/sub 5/LH/sup 3 +/ + H/sub 2/O ..-->.. Ru(NH/sub 3/)/sub 5/L/sup 2 +/ + H/sub 3/O/sup +/) are (2-3) x 10/sup 7/ s/sup -1/ and 2 x 10/sup 5/ s/sup -1/ for L = pz and 4,4'-bpy, respectively. The Ru(NH/sub 3/)/sub 5/L/sup 2 +/ MLCT-excited-state lifetimes are discussed in terms of the lowest excited state tuning model of Ford and co-workers.},
doi = {10.1021/ja00242a023},
url = {https://www.osti.gov/biblio/6629357}, journal = {J. Am. Chem. Soc.; (United States)},
number = ,
volume = 109:8,
place = {United States},
year = {Wed Apr 15 00:00:00 EDT 1987},
month = {Wed Apr 15 00:00:00 EDT 1987}
}