The past decade has seen a diverse range of breakthrough inventions that are derived from gold complexes, including the application of aurophilic interactions in the preparation of stimuli-responsive materials. Examples of these gold-based materials include aurophilicity-induced metallogelators, mechanochromic, thermochromic, vapochromic, and solvatochromic luminescent compounds, as well as sensory materials for the detection of metal ions. Sophisticated properties of gold complexes with Au•••Au contacts have been explored at the edge of several disciplines including chemistry, crystallography, molecular engineering and advanced materials. As science paves its way to innovation, cross-disciplinary research moves from being a luxury to becoming a necessity. Development of the concept of aurophilicity and its use in designing novel materials is a true example of innovation on a multidisciplinary platform. As miniaturization continues to influence the next generation of technological advancement, using the properties of molecules as chemical tools to enable such developments becomes extremely important. In this Review, recent examples of gold complexes which exhibit a response to external stimuli have been collected and some of their potential applications discussed for selected cases.

No abstract

Treatment of [AuXL] (X = Br, L = AsPh(3); X = Cl, L = tht) with the lithium or trimethyltin derivatives of the carbanions [2-C6F4PPh2]- and [C6H3-n-F-2-PPh2]- (n = 5, 6) gives digold(I) complexes [Au2(mu-carbanion)2] (carbanion = 2-C6F4PPh2 2, C6H3-5-F-2-PPh2 3, C6H3-6-F-2-PPh2 4) which, like their 2-C6H4PPh2 counterpart, undergo oxidative addition with halogens X2 (X = Cl, Br, I) to give the corresponding, metal-metal bonded digold(II) complexes [Au2X2(mu-carbanion)2] (carbanion = 2-C6F4PPh2, X = Cl 5, Br 8, I 11; carbanion = C6H3-5-F-2-PPh2, X = Cl 6, Br 9, I 12; carbanion = C6H3-6-F-2-PPh2, X = Cl 7, Br 10, I 13). In the case of 2-C6F4PPh2 and C6H3-6-F-2-PPh2, the dihalodigold(II) complexes rearrange on heating to isomeric gold(I)-gold(III) complexes [XAu(I)(mu-P,C-carbanion)(kappa2-P,C-carbanion)Au(III)X] (carbanion = 2-C6F4PPh2, X = Cl 25, Br 26, I 27; carbanion = C6H3-6-F-2-PPh2, X = Cl 28, Br 29, I 30), in which one of the carbanions chelates to the gold(III) atom. This isomerisation is similar to, but occurs more slowly than, that in the corresponding C6H3-6-Me-2-PPh2 system. The Au2X2 complexes 6, 9 and 12, on the other hand, rearrange on heating via C-C coupling to give digold(I) complexes of the corresponding 2,2'-biphenyldiylbis(diphenylphosphine), [Au2X2(2,2'-Ph2P-5-F-C6H3C6H3-5-F-PPh2)] (X = Cl 32, Br 33, I 34), this behaviour resembling that of the 2-C6H4PPh2 and C6H3-5-Me-2-PPh2 systems. Since the C-C coupling probably occurs via undetected gold(I)-gold(III) intermediates, the presence of a 6-fluoro substituent is evidently sufficient to suppress the reductive eliminations, possibly because of an electronic effect that strengthens the gold(III)-aryl bond. Anation of 5 or 8 gives the bis(oxyanion)digold(II) complexes [Au2Y2(mu-2-C6F4PPh2)2] (Y = OAc 14, ONO2 15, OBz 16, O2CCF3 17 and OTf 20), which do not isomerise to the corresponding gold(I)-gold(III) complexes [YAu(mu-2-C6F4PPh2)(kappa2-2-C6F4PPh2)AuY] on heating, though the latter [Y = OAc 35, ONO2 36, OBz 37, O2CCF3 38] can be made by anation of 25-27. Reaction of the bis(benzoato)digold(II) complex 16 with dimethylzinc gives a dimethyl gold(I)-gold(III) complex, [Au(I)(mu-2-C6F4PPh2)2Au(III)(CH3)2] 19, in which both 2-C6F4PPh2 groups are bridging. In contrast, the corresponding reaction of 16 with C6F5Li gives a digold(II) complex [Au(II)2(C6F5)2(mu-2-C6F4PPh2)2] 18, which on heating isomerises to a gold(I)-gold(III) complex, [(C6F5)Au(I)(mu-2-C6F4PPh2)(kappa2-2-C6F4PPh2)Au(III)(C6F5)] 31, analogous to 25-27. The bis(triflato)digold(II) complex 20 is reduced by methanol or cyclohexanol in CH2Cl2 to a tetranuclear gold(I) complex [Au4(mu-2-C6F4PPh2)4] 21 in which the four carbanions bridge a square array of metal atoms, as shown by a single-crystal X-ray diffraction study. The corresponding tetramers [Au4(mu-C6H3-n-F-2-PPh2)4] (n = 5 22, 6 23) are formed as minor by-products in the preparation of dimers 3 and 4; the tetramers do not interconvert readily with, and are not in equilibrium with, the corresponding dimers 2-4. Addition of an excess ...

No abstract

The electrostatic interaction between the negatively charged phosphate groups of plasmid DNA and the cationic part of hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]), initiates spontaneous self-assembly to form the functional nanostructures made up of DNA and ionic liquid (IL). These functional nanostructures were demonstrated as promising synthetic nonviral vectors for the efficient bacterial pGFP gene transformation in cells. In particular, the functional nanostructures that were made up of 1 μL of IL ([Bmim][PF6]) and 1 μg of plasmid DNA can increase the transformation efficiency by 300-400% in microbial systems, without showing any toxicity for E. coli DH5α cells. (31)P nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron (XPS) spectroscopic analysis revealed that the electrostatic interaction between negatively charged phosphate oxygen and cationic Bmim(+) tends to initiate the self-assembly process. Thermogravimetric analysis of the DNA-IL functional nanostructures showed that these nanostructures consist of ∼16 wt % ionic liquid, which is considered to provide the stability to the plasmid DNA that eventually enhanced the transformation efficiency.