Substituent constant correlations as predictors of spectroscopic, electrochemical, and photophysical properties in ring-substituted 2,2 prime -bipyridine complexes of rhenium(I)

Journal Article · Wed Mar 18 00:00:00 EST 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00032a029· OSTI ID:7194094

Hino, J K; Ciana, L D ^[1]; Dressick, W J ^[2]; Sullivan, B P ^[3]

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1. IGEN, Inc., Rockville, MD (United States)
2. Naval Research Lab., Washington, DC (United States)
3. Univ. of Wyoming, Laramie (United States)

The synthesis and the spectroscopic, electrochemical and photophysical properties of the homologous series of photosensitizers, fac-(4,4{prime}-X{sub 2}-5,5{prime}-Y{sub 2}-2,2{prime}-bipyridine)Re(CO){sub 3}Etpy{sup +} (X = NEt{sub 2}, Me, OMe, H, Ph, Cl, CO{sub 2}Me, NO{sub 2} Y = H; X = Y = Me; Etpy = 4-ethylpyridine) are described. Both the quasi-reversible or irreversible oxidation of the Re(I) center and the reversible or quasi-reversible, one-electron reduction of the coordinated bipyridyl ligand are observed to vary with the electron donor/acceptor abilities of X, Y as measured by the sum of the Hammett substituent constants {sigma}{sub m} + {sigma}{sub p}. Hammett ({sigma}{sub T} = {sigma}{sub p} + {sigma}{sub m}) values for the X, Y groups are observed to correlate linearly with the metal-to-ligand charge-transfer (MLCT) absorption and emission energies and provide a convenient tool for the estimation of excited-state properties of the complexes. The complexes are moderately strong excited-state oxidants (E{sub 1/2}(+*/0) = 0.73-1.12 V vs SSCE) and exhibit emission maxima in the range 528 nm (X = NEt{sub 2}, Y = H) to 755 nm (X = NO{sub 2}, Y = H). MLCT excited-state decay is dominated by nonradiative decay from the {sup 3}MLCT state to the ground state and is governed by an energy gap law. It is shown that excited-state properties such as absorption energy, emission energy, rate of nonradiative decay (k{sub nr}), and the rate of radiative decay (k{sub r}) correlate with {sigma}{sub T}. The correlations can be derived from more fundamental considerations. The dependence of ln k{sub nr} on emission energy is similar to values obtained in earlier studies with bipyridyl Ru(II) or Os(II) complexes which do not contain coordinated CO and somewhat less than that observed in a previous study for fac-(bpy)Re(CO){sub 3}(L{prime}){sup +} complexes (L{prime} = monodentate, neutral ligands).

• OSTI ID: 7194094
• Journal Information: Inorganic Chemistry; (United States), Vol. 31:6; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
RHENIUM COMPLEXES
CHEMICAL PREPARATION
ELECTROCHEMISTRY
PHYSICAL PROPERTIES
ABSORPTION
BINDING ENERGY
BIPYRIDINES
CHARGE TRANSPORT
CHEMICAL REACTION KINETICS
ELECTRONS
EMISSION
EXCITED STATES
LIGANDS
PHOTOCHEMISTRY
RADIATIVE DECAY
SENSITIZERS
SOLAR ENERGY CONVERSION
VALENCE
AZINES
CHEMISTRY
COMPLEXES
CONVERSION
DECAY
ELEMENTARY PARTICLES
ENERGY
ENERGY CONVERSION
ENERGY LEVELS
FERMIONS
HETEROCYCLIC COMPOUNDS
KINETICS
LEPTONS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PARTICLE DECAY
PYRIDINES
REACTION KINETICS
REAGENTS
SORPTION
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)
400400 - Electrochemistry
400500 - Photochemistry