Gold(i) complexes are an expanding area of investigation due to the possibility of giving rise to supramolecular aggregates with particular morphologies that can be modulated together with their luminescent properties. A detailed study has been carried out for gold(i) complexes that self-assemble in aqueous media (in pure water or in mixtures of water and organic solvents in different proportions). The majority of the examples reported until now were found in mixtures of water and DMSO, acetone, DMF or acetonitrile. The addition of cations to a solution of gold(i) complexes has been observed to show a direct impact on the resulting process of aggregation. The use of perhalogenated ligands together with isocyanide moieties should be highlighted to promote the resulting self-organization. Nevertheless, other ligands like alkynyls or carbenes also promote self-assembly. A careful analysis of the data shows that aurophilic interactions have a key role in the formation of the resulting aggregates and in the enhancement of luminescence (aggregation induced emission, AIE).

Six gold(I) complexes (R 3 P-Au-Coum) containing three different alkynylcoumarin chromophores (Coum) with different electron-donating and electron-withdrawing characteristics and two different water-soluble phosphanes (PR 3 = PTA (a) and DAPTA (b)) have been synthesized (1a,b, unsubstituted coumarin; 2a,b, 4-methyl substituted coumarin; 3a,b, 3-chloro and 4-methyl substituted coumarin). A comprehensive study of the photophysical properties of the R 3 P-Au-Coum, together with their propynyloxycoumarin precursors 1−3, was performed in solution at room and low temperatures. Spectral and photophysical characteristics of the R 3 P-Au-Coum essentially depend on the electronic characteristics of the propynyloxycoumarin ligand. The presence of the Au(I) atom was found to be responsible for an increase of the intersystem crossing, with triplet state quantum yield values, ϕ T , ranging from ∼0.05 to 0.35 and high coumarin phosphorescence quantum yield values for derivatives 1 and 2; fluorescence dominates the deactivation in derivatives 3. Efficient singlet oxygen photosensitization was observed for the new compounds 3a,b. From TDDFT calculations, the relevant HOMO and LUMO of the compounds, i.e., those involved in the transitions, are dominated by the frontier orbitals associated with the coumarin core. The Au(I)-phosphane structure introduces a new transition assigned to an intraligand transition involving the phosphane ligand, and π(CC) system, to the p orbitals of phosphorus and gold atoms.

Aggregation-induced emission (AIE) has gained a remarkable amount of interest in the past 20 years, but the majority of the studies are based on organic structures. Herein, three dinuclear gold(I) complexes, with the general formula [PPh 2 XPPh 2 -Au 2 -Coum 2 ], where the Au(I) atom is linked to three different diphosphanes [PPh 2 XPPh 2 ; DPPM for X = CH 2 (1.1), DPPP for X = (CH 2 ) 3 (1.2), and DPPA for X = CC (1.3)] and the propynyloxycoumarin precursor (1, 4-methyl-substituted coumarin), have been synthesized. The compounds present AIE characteristics, AIEgens, with high luminescence quantum yields in the solid state when they are compared to dilute solutions. Photophysical studies (steady-state and time-resolved fluorescence) were obtained, with AIE being observed with the three gold(I) complexes in acetonitrile/water mixtures. This was further corroborated with dynamic light scattering measurements. Time-dependent density functional theory (TDDFT) electronic calculations show that the compounds have different syn and anti conformations (relative to the coumarin core) with 1.1 syn and 1.2 and 1.3 both anti. From time-resolved fluorescence experiments, the augment in the contribution of the longer decay component is found to be associated with the emission of the aggregate (AIE effect) and its nature (involving a dimer) rationalized from TDDFT electronic calculations.

The synthesis of two gold(I) complexes containing a pyridyl ligand with a polyethylenglycol pendant arm at one position and a chromophore (aniline, for compound 3 or coumarine, for compound 4)...