Systematic investigation of the influence of electronic substituents on dinuclear gold(I) amidinates: synthesis, characterisation and photoluminescence studies.

Dinuclear gold(I) compounds are of great interest due to their aurophilic interactions that influence their photophysical properties. Herein, we showcase that gold-gold interactions can be influenced by tuning the electronic properties of the ligands. Therefore, various substituted (R) ,'-bis(2,6-dimethylphenyl)formamidinate ligands (RXylForm; Xyl = 2,6-dimethylphenyl and Form = formamidinate) were treated with Au(tht)Cl (tht = tetrahydrothiophene) to give salt metathesis the corresponding gold(I) compounds [RXylFormAu] (R = -OMe, -Me, -Ph, -H, -SMe, and -COMe). All complexes showed intense luminescence properties at low temperatures. Alignment with the Hammett parameter revealed the trends in the H and C NMR spectra. These results showed the influence of the donor-acceptor abilities of different substituents on the ligand system which were confirmed with calculated orbital energies. Photophysical investigations showed their lifetimes in the millisecond range indicating phosphorescence processes and revealed a redshift with the decreasing donor ability of the substituents in the solid state.