Unique Reactivity of Heterodinuclear Pentacarbonyl(fulvalene)molybdenumruthenium with Alkynes: Fluxionality, Rearrangements, Structures, and First Reversible Conversion of a “Side-on”- to a Semi-Bridging Alkenylidene Ligand
✍ Scribed by Prof. Dr. Roland Boese; Dr. Mark A. Huffman; Prof. Dr. K. Peter C. Vollhardt
- Book ID
- 101553314
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 390 KB
- Volume
- 30
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
polarization transfer from TP-Q, whereas after longer times spectra in pure emission develop owing to the differing recombination rates from the triplet sublevels (cf. Figs. 2 and3). A more exact analysis of the amplitude ratios of the high-field and low-field x',y' signals of 1 and 2 reveals a stronger mixing of the singlet and T-state in 2, which, in turn. indicates a larger I JI in comparison to 1. This is likewise expected because of the smaller porphyrin4uinone distance in 2 compared to 1.
The kinetics of primary ET reactions in covalently linked P-Q's have been investigated up to now almost exclusively by time-revolved optical spectroscopy."] Only in multistep complex donor-acceptor cascades have states with far-separated charges been found to be sufficiently long-lived for detection by time-resolved EPR spectroscopy.['61 The strong decrease of ET in polar solvents of high viscosity (ethanol, 150 K), however, also enables the observation of primary ET reactions in covalently linked, simple P-Q's from the excited triplet state of the porphyrin to the triplet state of the chargeseparated radical pair T(P''-Q'-) by time-resolved EPR spectroscopy in the time range of 0.1 ps to several 10 V S . ' ~] Augmenting optical spectroscopy, EPR allows an unequivocal identification of both triplet species on the basis of the measured electron dipole-dipole interaction. The observed spin polarization in the transient radical pairs of these model compounds contains information about these interactions, which also determine the ET and spin dynamics of the transient radical pairs in photosynthetic organisms.'l6I