Luminescent gold phosphine complexes

Luminescence has been noted [88] in numerous gold phosphine complexes. 

Zhang, H.-X. and Che, C.-M. (2001) Aurophilic Attraction and Luminescence of Binuclear Gold(I) Complexes with Bridging Phosphine Ligands ah initio Study. Chemistry - A European Journal, 7, 4887-4893. 

Assefa, Z Forward, J.M., Grant T.A., Staples, R.J., Hanson, B.E., Mohamed, A.A. and Fackler, J.P. Jr (2003) Three-coordinate, luminescent, water-soluble gold(l) phosphine complexes structural characterization and photoluminescence properties in aqueous solution. Inorganica Chimica Acta, 352, 31 5. 

The (alkenyl-ethynyl)gold(i) complexes shown in Scheme 13 were prepared with mono- and ditertiary phosphine ligands and used as substrates for the coordination of coinage metal cations. The products are strongly luminescent.60... 

Yam and co-workers reported the first luminescent study of 4-coordinate gold(I) phosphine complexes, [Au(PAP)2]X (PAP = l,8-bis(diphenylphos-phino)naphthalene, 4-methyl-l,8-bis(diphenylphosphino)naphthalene X = Cl, PF6) in 2000 [28]. The complexes were shown to exhibit orange-red photoluminescence both in the solid state and in dichloromethane, and the emission origin was attributed to the triplet state derived from a [a -> 77- (naphthyl)] IL transition. The PF6 salt of the complexes were also employed as an emissive layer in the fabrication of OLEDs. 

The idea of metal-metal bond establishment in the excited state of this complex has also stimulated the interest on the photophysical and photochemical investigations of related d -d complexes. In 1970, Dori and co-workers first reported the luminescence properties of phosphine complexes of d metal centers such as copper(I), silver(I), gold(I), nickel(0), palladium(0), and platinum(0) [12]. Later in 1985, Caspar reported the luminescence properties of polynuclear nickel(O), palladium(O), and platinum(O) complexes of phosphine, phosphite, and arsine [13]. Similar to the related d -d systems, the emissive states of [Pd2(dppm)3] and [Pd Cdpam),] have been suggested to be metal-centered (d-p) in nature modified by metal-metal interaction. 

Thus, the addition of tertiary phosphine to the solution, or cooling the solution to entropically favor the 3-coordinate gold(I) complex AuL3, results in increased emission. The luminescence is a phosphorescence that is assigned to the triplet-to-singlet pz (rf/-/, dxy) transition, and the emission does not appear to be primarily the result of intermolecular Au...Au interactions. ... 

Data reported for compound 17a revealed that excitation at = 332 nm afforded emissions in the solid state at = 482 nm at room temperature and = 465 nm at 77 K, while an acetone solution produced = 429 following excitation at = 379 nm. As the data for compound 17b showed little difference in photophysical behavior, the authors concluded that this emission could not result from a phosphine-located excitation. At this time no other rationale was offered for the lack of luminescence from the parent closo species 16 other than a significant change in electronic structure. Nevertheless, the ligating ability of the phosphine arms in the nido compounds 17 was exploited to produce luminescent gold complexes, which is discussed in the next section. 

Laguna and co-workers (283,1813,1814) also examined the optical properties of a number of trinuclear gold(l) phosphine complexes. At low temperature, most are luminescent and a red shift, related to the number of dithiocarbamate ligands present, is proposed to arise firom gold(l)-gold(I) interactions that perturb the orbital energies involved in the LMCT transition (283). 

Apart from gold(I) phosphine systems, gold(I) chalcogenido and thiolato complexes represent another fast growing area of research in luminescent gold complexes. One of the reasons for such... 

Aurophilic attraction and luminescence of binuclear gold(I) complexes with bridging phosphine ligands ab initio study, H. X. Zhang, C. M. Che, Chem. Eur. J. 2001, 7, 4887. 

---