Anions thiolates

The necessity of an anionic thiolate ligand was established by performing reactions with ferrocene thioethers 37 as ligands. Here, essentially racemic products were obtained. 

Density functional theory (DFT) and post-Hartree-Fock MP2 in conjunction with the B3LYP employing the 6-31G(d) basis set were used to predict structure and correlate assignments of the fundamental vibrational modes of 3/7-1,2-dithiole-3-one la and 3/7-1,2-dithiole-3-thione lb with experimental data <1998VSP77>. These sulfur-rich heterocycles, characterized by a long and weak S-S bond, are represented in accordance to the simple 7t-MO theory by resonance contributor 8, involving a cationic 67t-l,2-dithiolylium part and an anionic thiolate or olate part, and the exocyclic C=S bond is more delocalized than the C=0 bond. However, computational evidence suggests structures with localized bonds and relatively low aromatic delocalization, which is also supported by the low values of the dipole moments, that is, 3.54 D for la and 4.12 D for lb. 

Like alcoholate anions, thiolate, ° dithiocarbamate, ° °° and 0-ethyl dithiocarbonate anions °° add easily in boiling ethanol or acetonitrile at C-2 of 1,3-dithiolium salts (Eq. 39). 

In cysteine proteinases (CP), activity depends upon a cysteine thiol group. Papain, actinidin, and a few lysosomal cathepsins are the best known members of this family. They hydrolyze peptides and esters in a generally similar fashion to serine proteinases. Two residues are directly involved in the catalytic process, Cys and His, with apparent pKa values of 4.2 and 8.6, respectively. This is the reverse of their normal pKa order, with His being more acidic than Cys. A bell-shaped relation of activity vs. pH for papain is spread out, with maximal activity around pH=6.5 and about half of the activity is retained near 4.5 and 8.5, dropping fast below and above these values. Thus, the active species has a zwitterion state, with a cysteine anion (thiolate) and a histidine cation. CP were discussed in a few reviews (Baker and Drenth, 1987 Fersht, 1985 Polgar and Halasz, 1982)... 

The obtained DNA-functionalized AuNPs carry a negative surface charge provided by the anionic thiolated oligonucleotide. 

A closer inspection of the Fe-S bond distances in 3 reveals the Fe-S bond distances to the neutral thioether, 2.285(1) A, and anionic thiolates, 2.284(1) and 2.291(1) A, are equivalent within experimental error. As shown in Table I, the Fe-Sthiocthcr and Fe-Sthioiate bond distances in the low-spin complex 2 are also similar. This trend, however, does not apply to the high-spin complex 4. In 4,... 

Gold forms an intriguing array of clusters that have oxidations states of gold between 0 and +1. Two major classes can be distinguished one with phosphine ligands capping the outer surface [59], the other with anionic thiolates on the exterior. 

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