Gold i Alkynyls

The photophysical properties of this class of compounds have since then been extensively investigated by the groups of Che [183-186], Yam [19, 20], Mingos [187], Puddephatt [87, 188-190] and others [101] with emissive states ranging from IL to MLCT and admixtures of these manifolds. Inter- and intramolecular 

Au Au interactions also play a pivotal role in the photophysical characteristics of Au(i) alkynyl complexes. A red shift in the solid-state emission energies relative to that in solution is commonly observed for complexes with such interactions [87, 183, 188, 189]. In addition, the nonlinear optical (NLO) properties of a number of di- and trinuclear Au(i) alkynyl complexes with di- and tri-ethynylbenzene cores have been investigated by Humphrey and coworkers [191-194], These complexes may serve as potential NLO materials with reasonable first and second hyperpolarizabilities. Introduction of nitro group into these systems was suggested to enhance the optical nonlinearity. 

With the recent developments and growing interest in metal-based chemosen-sors [196-198], some work toward the utilization of the luminescent Au(i) system in chemosensing has been described [199]. A series of gold(i) calix[4]crown-5 alkynyl complexes has been reported by Yam et al. [200, 201]. These calix[4]crown-5 alkynyl complexes were found to bind K+ ions preferentially over Na+ ions with UV-vis absorption spectral changes. It is noteworthy that the crown size of these alkynyl complexes could be fine-tuned by a subtle change in the steric demands on the triarylphosphine ligands, providing a firm basis for the further development of these classes of selective metalloreceptors for various metal ions. 

These tetranuclear complexes are strong emitters in the orange region at room temperature with luminescence quantum yields of up to 0.22. Red-shifts in emis- 

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Gold(i) alkynyls and their complexes have been an important class of organogold compounds from the very beginning of organogold chemistry.2 By contrast, the class of gold(m) alkynyls is poorly developed and only a small number of representative compounds is known. Alkynylgold compounds have recently been reviewed, focusing on various aspects of their chemistry.40-43... 

Donor-free gold(i) alkynyls play an important role as precursors in the synthesis of related complexes. The compounds are generally prepared from the alkyne, a gold(i) compound with ligands L, which are readily displaced, and a base (Equations (10) and (11)). 

The luminescence behavior of a binuclear gold(I) alkynyl complex with a bridging dppf ligand, [(dppf)Au2 C=CC(Me)=CH2)2], was also reported... 

Figure 1.11 Selected examples of linear gold(I) alkynyl chromophores...

There has also been a report of dinuclear gold(I) alkynyl complexes, [RC=C(AuPPh3)2][BF4] (R = Ph, i-Pr), which are prepared in the same way139-141. 

FIGURE 5.7 Luminescent tetranuclear gold(I) alkynyl complexes with a novel planar Tj, Tj -coordination mode. 

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