Mononuclear Gold(I) Acetylide Complexes with Urea Group: Synthesis, Characterization, Photophysics, and Anion Sensing Properties

A series of mononuclear gold(I) acetylide complexes with urea moiety, R′3PAuC≡CC6H4-4-NHC(O)NHC6H4-4-R (R′ = cyclohexyl, R = NO2 (2a), CF3 (2b), Cl (2c), H (2d), CH3 (2e), tBu (2f), OCH3 (2g); R′ = phenyl, R = NO2 (3a), OCH3 (3b); R′ = 4-methoxyphenyl, R = H (4a), OCH3 (4b)), have been synthesized and characterized. The crystal structures of Ph3PAuC≡CC6H4-4-NHC(O)NHC6H4-4-NO2 (3a) and (4-CH3OC6H4)3PAuC≡CC6H4-4-NHC(O)NHC6H5 (4a) have been determined by X-ray diffraction. Complexes 2a–2g, 3b, and 4a–4b show intense luminescence both in the solid state and in degassed THF solution at 298 K. Anion binding properties of complexes 2a–2g, 3a–3b, and 4a–4b have been studied by UV–vis and 1H NMR titration experiments. In general, the log K values of 2a–2g with the same anion in THF depend on the substituent R on the acetylide ligand of 2a–2g: R = NO2 (2a) > CF3 (2b) ≥ Cl (2c) > H (2d) > CH3 (2e) ≈ tBu (2f) ≥ OCH3 (2g). Complex 2a with NO2 group shows the dramatic color change toward F– in DMSO, which provides an access of naked eye detection of F–.