@article {ISI:000270186500047,
	title = {Influence of oxygenation on the reactivity of ruthenium-thiolato bonds in arene anticancer complexes: insights from XAS and DFT.},
	journal = {J. Am. Chem. Soc.},
	volume = {131},
	number = {37},
	year = {2009},
	month = {sep},
	pages = {13355{\textendash}61},
	publisher = {American Chemical Society},
	abstract = {Thiolate ligand oxygenation is believed to activate cytotoxic half-sandwich [(eta(6)-arene)Ru(en)(SR)](+) complexes toward DNA binding. We have made detailed comparisons of the nature of the Ru-S bond in the parent thiolato complexes and mono- (sulfenato) and bis- (sulfinato) oxygenated species including the influence of substituents on the sulfur and arene. Sulfur K-edge XAS indicates that S(3p) donation into the Ru(4d) manifold depends strongly on the oxidation state of the sulfur atom, whereas Ru K-edge data suggest little change at the metal center. DFT results are in agreement with the experimental data and allow a more detailed analysis of the electronic contributions to the Ru-S bond. Overall, the total ligand charge donation to the metal center remains essentially unchanged upon ligand oxygenation, but the origin of the donation differs markedly. In sulfenato complexes, the terminal oxo group makes a large contribution to charge donation and even small electronic changes in the thiolato complexes are amplified upon ligand oxygenation, an observation which carries direct implications for the biological activity of this family of complexes. Details of Ru-S bonding in the mono-oxygenated complexes suggest that these should be most susceptible to ligand exchange, yet only if protonation of the terminal oxo group can occur. The potential consequences of these results for biological activation are discussed.},
	keywords = {Antineoplastic Agents, Antineoplastic Agents: chemical synthesis, Antineoplastic Agents: chemistry, Antineoplastic Agents: metabolism, AROMATIC, Aromatic: chemistry, DFT, DNA, DNA: metabolism, Drug Design, ELECTRONS, HYDROCARBONS, LIGANDS, metal-based drugs, models, MOLECULAR, Molecular Conformation, ORGANOMETALLIC COMPOUNDS, Organometallic Compounds: chemical synthesis, Organometallic Compounds: chemistry, Organometallic Compounds: metabolism, OXYGEN, Oxygen: chemistry, quantum theory, ruthenium, Ruthenium: chemistry, Spectrum Analysis, Sulfhydryl Compounds, Sulfhydryl Compounds: chemistry, X-Rays, XAS},
	issn = {1520-5126},
	doi = {10.1021/ja903405z},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/19719101 http://dx.doi.org/10.1021/ja903405z},
	author = {Sriskandakumar, Thamayanthy and Petzold, Holm and Bruijnincx, Pieter C A and Habtemariam, Abraha and Sadler, Peter J and Kennepohl, Pierre}
}
@article {ISI:000244896900002,
	title = {Sulfur K-edge XAS as a probe of sulfur-centered radical intermediates.},
	journal = {J. Am. Chem. Soc.},
	volume = {129},
	number = {11},
	year = {2007},
	month = {mar},
	pages = {3034{\textendash}5},
	abstract = {Sulfur K-edge XAS is used in the identification and characterization of sulfur based radicals obtained from UV irradiated glutathione. Ground state and time-dependent DFT calculations are used to identify thiyl (RS center dot) and perthiyl (RSS center dot) radical species.},
	keywords = {DFT, Free Radicals, Free Radicals: analysis, Free Radicals: chemistry, GLUTATHIONE, Glutathione: chemistry, Oxidation-Reduction, PHOTOCHEMISTRY, SPECTROMETRY, SPECTROPHOTOMETRY, Sulfhydryl Compounds, Sulfhydryl Compounds: chemistry, SULFUR, sulfur redox, Sulfur: chemistry, ULTRAVIOLET, X-Ray Emission, X-Ray Emission: methods, XAS},
	issn = {0002-7863},
	doi = {10.1021/ja0676760},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/17319664},
	author = {Martin-Diaconescu, Vlad and Kennepohl, Pierre}
}
@article {ISI:000227764700020,
	title = {Spectroscopy of non-heme iron thiolate complexes: insight into the electronic structure of the low-spin active site of nitrile hydratase.},
	journal = {Inorg. Chem.},
	volume = {44},
	number = {6},
	year = {2005},
	month = {mar},
	pages = {1826{\textendash}36},
	abstract = {Detailed spectroscopic and computational studies of the low-spin iron complexes [Fe(III)(S2(Me2)N3 (Pr,Pr))(N3)] (1) and [Fe(III)(S2(Me2)N3 (Pr,Pr))]1+ (2) were performed to investigate the unique electronic features of these species and their relation to the low-spin ferric active sites of nitrile hydratases. Low-temperature UV/vis/NIR and MCD spectra of 1 and 2 reflect electronic structures that are dominated by antibonding interactions of the Fe 3d manifold and the equatorial thiolate S 3p orbitals. The six-coordinate complex 1 exhibits a low-energy S(pi) {\textendash}> Fe 3d(xy) (approximately 13,000 cm(-1)) charge-transfer transition that results predominantly from the low energy of the singly occupied Fe 3d(xy) orbital, due to pure pi interactions between this acceptor orbital and both thiolate donor ligands in the equatorial plane. The 3d(pi) {\textendash}> 3d(sigma) ligand-field transitions in this species occur at higher energies (>15,000 cm(-1)), reflecting its near-octahedral symmetry. The Fe 3d(xz,yz) {\textendash}> Fe 3d(xy) (d(pi) {\textendash}> d(pi)) transition occurs in the near-IR and probes the Fe(III)-S pi-donor bond; this transition reveals vibronic structure that reflects the strength of this bond (nu(e) approximately 340 cm(-1)). In contrast, the ligand-field transitions of the five-coordinate complex 2 are generally at low energy, and the S(pi) {\textendash}> Fe charge-transfer transitions occur at much higher energies relative to those in 1. This reflects changes in thiolate bonding in the equatorial plane involving the Fe 3d(xy) and Fe 3d(x2-y2) orbitals. The spectroscopic data lead to a simple bonding model that focuses on the sigma and pi interactions between the ferric ion and the equatorial thiolate ligands, which depend on the S-Fe-S bond angle in each of the complexes. These electronic descriptions provide insight into the unusual S = 1/2 ground spin state of these complexes: the orientation of the thiolate ligands in these complexes restricts their pi-donor interactions to the equatorial plane and enforces a low-spin state. These anisotropic orbital considerations provide some intriguing insights into the possible electronic interactions at the active site of nitrile hydratases and form the foundation for further studies into these low-spin ferric enzymes.},
	keywords = {BINDING SITES, Computational Biology, ELECTROCHEMISTRY, Ferric Compounds, Ferric Compounds: chemical synthesis, Ferric Compounds: chemistry, Hydro-Lyases, Hydro-Lyases: chemistry, iron, Iron: chemistry, models, MOLECULAR, Molecular Conformation, molecular structure, PhD, SPECTROPHOTOMETRY, Sulfhydryl Compounds, Sulfhydryl Compounds: chemistry},
	issn = {0020-1669},
	doi = {10.1021/ic0487068},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/15762709},
	author = {Kennepohl, Pierre and Neese, Frank and Schweitzer, Dirk and Jackson, Henry L and Kovacs, Julie A and Solomon, Edward I}
}
