In the Bocarsly group, we affectionately refer to [(NC)6FeII-CN-PtIV(NH3)4-NC-FeII(CN)6]4-
as "trimer." This complex undergoes a two-electron intervalent
chargetransfer process. When a single photon is absorbed, an electron
is transferred from one of the FeII centers to the PtIV center, yielding a short-lived FeII-PtIII-FeIII intermediate. An electron is then transferred from the remaining FeII center to the PtIII center, resulting in the dissociation of the complex into 2[FeIII(CN)63-] and Pt(NH3)42+. Thus, the absorption of a single photon gives rise to the transfer of two electrons.
Previous studies of trimer and related systems:
1) Crystal structure determination of the Pt(NH3)42+ salt of trimer.
2) Investigation of ground and excited state energetics of trimer
andseveral closely-related complexes using classical Marcus-Hush
electron transfer theory and a resonance Raman intensity analysis.
3) Polymerization of trimer onto transparent conductive surfaces and
the photolithographic properties of these sytems. Selectivity of
electron transfer processes within oligomeric and polymeric chains
insolution and on surfaces.
4) Surface-attachment of trimer to TiO2 nanoparticles and investigation of the photoinduced electron transfer processes in these sytems.
5) Photolithography in a trimer-based "cyanogel" sol-gel system.
6) Transient absorption spectroscopy to probe the lifetime of the proposed FeII-PtIII-FeIII intermediate using both 400 and 530 as probe wavelengths. Here's a schematic of the one-color pump-probe experiment. This is a photo of the setup. Both are courtesy of Dr. Dave Watson.
7) Pt-ligand replacements to enable the generation of cis-platinin upon
photodissociation, and Fe-ligand replacements to affect the solubility.
Current Research involving trimer:
1) Continuation of pump-probe spectroscopy of trimer and related intervalent charge transfer complexes.
2) Excited state absorption measurements on trimer and related
compounds using femtosecond white light generation with calcium
fluoride. Here's a photo of white light generation. We're sending 800 nm light of 100 fs pulses through a quartz cuvette filled with water.
Here are some of the important papers that have come out of this project:
151."Femtosecond
Pump-ProbeSpectroscopy of Trinuclear Transition Metal Mixed-Valence
Complexes," David F. Watson, Howe Siang Tan, Elmar Schreiber, Carolyn
J. Mordas, and Andrew B. Bocarsly, J. Phys. Chem. A, 2004, 108,
3261-3267.
142."Excited-State
Electronic Coupling and Photoinduced Multiple Electron Transfer in Two
Related Ligand-Bridged Hexanuclear Mixed-Valence Compounds," Brian W.
Pfennig, Carolyn J. Mordas, Alex McCloskey, Jenny V. Lockard, Patty
M.Salmon, Jamie L. Cohen, David F. Watson, and Andrew B. Bocarsly,
Inorg. Chem., 2002, 41, 4389.
133."Photochemical Image
Generation in a Cyanogel System Synthesized from
Tetrachloropalladate(II) and the Trimetallic Mixed-Valence Complex,
[(NC)5FeII-CN-PtIV(NH3)4-NC-FeII(CN)5]4-: Consideration
of Photochemical and Dark Mechanistic Pathways of Prussian Blue
Formation," David F. Watson, Jennifer L. Willson, and Andrew B.
Bocarsly, Inorganic Chemistry, 2002, 41, 2408.
