Electronic coupling in cyano-bridged ruthenium polypyridine complexes and role of electronic effects on cyanide stretching frequencies

Journal Article · Wed Dec 09 00:00:00 EST 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00051a018· OSTI ID:6904319

Bignozzi, C A; Argazzi, R; Scandola, F ^[1]; Schoonover, J R ^[2]; Gordon, K C; Dyer, R B ^[3]

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1. Universita di Ferrara (Italy)
2. Univ. of North Carolina, Chapel Hill (United States)
3. Los Alamos National Lab., NM (United States)

The spectroscopic and electrochemical properties of a series of polynuclear complexes containing cyano-bridged ruthenium polypyridine units are consistent with a valence-localized model. In all the Ru(II) forms, the lowest metal-to-ligand charge-transfer (MLCT) states are localized on N-bonded moieties. The photophysical properties at 298 and 77 K indicate that efficient intercomponent energy-transfer processes from C-bonded to N-bonded chromophoric units take place. The mixed-valence forms of these complexes show low-energy absorption bands which are assigned to metal-to-metal charge-transfer transitions involving C-bonded Ru(II) and N-bonded Ru(III) centers. The resonance Raman spectrum of [NC-Ru[sup II](bpy)[sub 2]-CN-Ru[sup III](bpy)[sub 2]-CN][sup 2+] under near-resonance conditions with the Ru(II) [yields] Ru(III) charge-transfer band shows enhancement of the bridging cyanide stretching as expected for this type of electronic transition. In the infrared spectra the number of cyanide stretching bands supports the valence-localized model. For the representative [NC-Ru[sup II](bpy)[sub 2]-CN-Ru[sup III](bpy)[sub 2]-CN][sup 2+] complex, three CN stretches (one bridging, two terminal) are observed. Time-resolved infrared measurements for the MLCT excited state of [NC-Ru[sup II](bpy)[sub 2]-CN-Ru[sup II](bpy)[sub 2]-CN][sup +] are reported. The excited-state IR spectrum shows features similar to those of the chemically prepared mixed-valence dimer, [NC-Ru[sup II](bpy)[sub 2]-CN-Ru[sup III](bpy)[sub 2]-CN][sup 2+], strongly suggesting that valence delocalization is not significant in the excited state. The electronic factors affecting the frequency of the bridging cyanide are analyzed by examining the behavior of the mixed-valence ions [M-NC-M[prime](bpy)[sub 2]-CN-M][sup 6+/4+] and [NC-M[prime](bpy)[sub 2]-CN-M][sup 3+/2+] (M = [Ru(NH[sub 3])[sub 5]][sup 2+/3+]; M[prime] = Ru[sup II], Os[sup II], Re[sup I]).

• OSTI ID: 6904319
• Journal Information: Inorganic Chemistry; (United States), Vol. 31:25; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
RUTHENIUM COMPLEXES
CHEMICAL PREPARATION
SPECTROSCOPY
ABSORPTION SPECTRA
EMISSION SPECTRA
ENERGY TRANSFER
EXCITED STATES
INFRARED SPECTRA
LIGANDS
PHOTOLUMINESCENCE
PYRIDINES
RAMAN SPECTROSCOPY
REDOX POTENTIAL
TEMPERATURE EFFECTS
AZINES
COMPLEXES
ENERGY LEVELS
HETEROCYCLIC COMPOUNDS
LASER SPECTROSCOPY
LUMINESCENCE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SPECTRA
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties