Gold® thiolates

Hakkinen, H., Walter, M. and Gronbeck, H. (2006) Divide and Protect Capping Gold Nanoclusters with Molecular Gold-Thiolate Rings. The Journal of Physical Chemistry B, 110, 9927-9931. 

The earliest use of gold complexes in medicine primarily involved gold thiolates, which being yellow or even gold-colored in solution, led to their designation as chrysotherapy (chrysos is Greek for gold). 

These bis(thiolato)gold(I) complexes are useful models for providing insights into the chemistry of the end products of the reactions between 1 1 gold thiolates and any excess (including other) thiol, including some reactions with proteins in vivo. 

Covalent attachment of enzymes to surfaces is often intuitively perceived as being more reliable than direct adsorption, but multisite physical interactions can in fact yield a comparably strong and stable union, as demonstrated by several biological examples. The biotin/streptavidin interaction requires a force of about 0.3 nN to be severed [Lee et al., 2007], and protein/protein interactions typically require 0.1 nN to break, but values over 1 nN have also been reported [Weisel et al., 2003]. These forces are comparable to those required to mpture weaker chemical bonds such as the gold-thiolate bond (1 nN for an alkanethiol, and even only 0.3 nN for a 1,3-aUcanedithiol [Langry et al., 2005]) and the poly(His)-Ni(NTA) bond (0.24 nN, [Levy and Maaloum, 2005]). 

Thiols like pyridine-2-thiol yield (carbene)gold thiolates, and onium salts give cationic (carbene)gold ylide complexes, isolated and characterized as the perchlorates.170 The reaction of dithiocatechol with (cyclohexylisocya-nide)gold chloride affords a carbene complex [(CyNC)AuC(NHCy)2]+Cl-, which co-crystallizes with a neutral tetranuclear complex [(CyNCAu)2Au2(S2C6H4)2].224... 

Figure 7.3 Gold-thiolate bonds encourage the adsorption of the bisthiol 5 on the surface of gold in the form of a monolayer (a). The subsequent and spontaneous formation of disulfide linkages promotes the deposition of additional molecules of 5 to produce multilayers (b).

There is still intense interest in developing better gold thiolate drugs and new modifications of the complexes are being sought (equation 35) 274... 

Several reviews on gold therapy have appeared recently, with an emphasis on metabolism by Shaw,19 on ligand exchange reactions by Sadler and coworkers,20 on EXAFS and XANES studies by Elder et al.,21 and on studies of gold thiolate complexes in vivo and in vitro by Brown and Smith.22... 

Fig. 7 Red shift in emission energy of binuclear gold thiolate complexes via metal-ion encapsulation...

Gold is known not having a stable oxide at its surface,20 which makes it a good candidate substrate to study self-assembled monolayers. The deposition of an alkanethiol SAM on a gold surface is done by immersion of a clean gold substrate into the solution, and a spontaneous chemisorption at the interface produces gold thiolate species (See Figure 3.1) 11,12... 

Gold thiolates formed from sulfurized terpene resins are used for decorating glass and china they decompose to gold films on heating. 

II. COPPER(I) THIOLATE COMPLEXES A. Copper, Silver, and Gold Thiolates in Perspective... 

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