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Title: Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes

Abstract

The unsaturated bridging ligand 1,4-bis(2-(4{prime}-methyl-2,2{prime}-bipyrid-4-yl)ethenyl)benzene (dstyb) was prepared in a simple two-step sequence. The ruthenium complexes (((dmb){sub 2}Ru){sub n}(dstyb)){sup 2n+} (n = 1,2; dmb = 4,4-dimethyl-2,2{prime}-bipyridine) were prepared, and their redox and photophysical properties were examined. Both complexes have a single oxidation in cyclic voltammetry at 1.10 V vs SSCE, for the dinuclear complex n = 2. The first one-electron reductions are localized on the dstyb ligand and occur at {minus}1.32 and {minus}1.26 V for the mononuclear and dinuclear complexes, respectively. The emission maximum in room-temperature CH{sub 3}CN is 680 nm for ((dmb){sub 2}Ru(dstyb)){sup 2+} and 720 nm for (((dmb){sub 2}Ru){sub 2}(dstyb)){sup 4+}. For both complexes emission quantum yields are <0.05, and luminescence lifetimes are 622 ns for the monomer and 2.02 {mu} for the dimer at room temperature. The very low radiative decay rates ({psi}{sub em}/{tau}) observed result from low intersystem crossing efficiencies for population of the emitting {sup 3}MLCT state. Transient absorption spectra of the two complexes provide evidence for the presence of a {sup 3}({pi} {yields} {pi}*) state. In the mononuclear complex the lifetime of the T{sub 1}{yields}T{sub 2} absorbance of the {sup 3}({pi}{yields} {pi}*) state is 1.6 {mu}s, much longer than the emission lifetime. The {supmore » 3}MLCT emission and the {sup 3}({pi}{yields}{pi}*) absorption lifetimes of the dinuclear complex are within experimental error, indicating the states are equilibriated. Quenching of the transient absorbance with a series of triplet quenchers provides a measure of the triplet energy of the {sup 3}({pi}{yields}{pi}*) state of the complexes.« less

Authors:
; ;  [1]
  1. Tulane Univ., New Orleans, LA (USA)
Publication Date:
OSTI Identifier:
7123367
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society; (USA)
Additional Journal Information:
Journal Volume: 112:3; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; RUTHENIUM COMPLEXES; PHOTOCHEMICAL REACTIONS; REDOX REACTIONS; DATA ANALYSIS; ENERGY LEVELS; EXCITED STATES; EXPERIMENTAL DATA; MEASURING INSTRUMENTS; MEASURING METHODS; TRANSITION ELEMENT COMPLEXES; VOLTAMETRY; CHEMICAL REACTIONS; COMPLEXES; DATA; INFORMATION; NUMERICAL DATA; 360104* - Metals & Alloys- Physical Properties; 400500 - Photochemistry

Citation Formats

Shaw, J R, Webb, R T, and Schmehl, R H. Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes. United States: N. p., 1990. Web. doi:10.1021/ja00159a035.
Shaw, J R, Webb, R T, & Schmehl, R H. Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes. United States. doi:10.1021/ja00159a035.
Shaw, J R, Webb, R T, and Schmehl, R H. Wed . "Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes". United States. doi:10.1021/ja00159a035.
@article{osti_7123367,
title = {Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes},
author = {Shaw, J R and Webb, R T and Schmehl, R H},
abstractNote = {The unsaturated bridging ligand 1,4-bis(2-(4{prime}-methyl-2,2{prime}-bipyrid-4-yl)ethenyl)benzene (dstyb) was prepared in a simple two-step sequence. The ruthenium complexes (((dmb){sub 2}Ru){sub n}(dstyb)){sup 2n+} (n = 1,2; dmb = 4,4-dimethyl-2,2{prime}-bipyridine) were prepared, and their redox and photophysical properties were examined. Both complexes have a single oxidation in cyclic voltammetry at 1.10 V vs SSCE, for the dinuclear complex n = 2. The first one-electron reductions are localized on the dstyb ligand and occur at {minus}1.32 and {minus}1.26 V for the mononuclear and dinuclear complexes, respectively. The emission maximum in room-temperature CH{sub 3}CN is 680 nm for ((dmb){sub 2}Ru(dstyb)){sup 2+} and 720 nm for (((dmb){sub 2}Ru){sub 2}(dstyb)){sup 4+}. For both complexes emission quantum yields are <0.05, and luminescence lifetimes are 622 ns for the monomer and 2.02 {mu} for the dimer at room temperature. The very low radiative decay rates ({psi}{sub em}/{tau}) observed result from low intersystem crossing efficiencies for population of the emitting {sup 3}MLCT state. Transient absorption spectra of the two complexes provide evidence for the presence of a {sup 3}({pi} {yields} {pi}*) state. In the mononuclear complex the lifetime of the T{sub 1}{yields}T{sub 2} absorbance of the {sup 3}({pi}{yields} {pi}*) state is 1.6 {mu}s, much longer than the emission lifetime. The {sup 3}MLCT emission and the {sup 3}({pi}{yields}{pi}*) absorption lifetimes of the dinuclear complex are within experimental error, indicating the states are equilibriated. Quenching of the transient absorbance with a series of triplet quenchers provides a measure of the triplet energy of the {sup 3}({pi}{yields}{pi}*) state of the complexes.},
doi = {10.1021/ja00159a035},
journal = {Journal of the American Chemical Society; (USA)},
issn = {0002-7863},
number = ,
volume = 112:3,
place = {United States},
year = {1990},
month = {1}
}