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-3'PAuC CC6H4-4-NHC(O)NHC6H4-4-R (R' = cyclohexyl, R = NO2 (2a), CF3 (2b), Cl (2c), H (2d), CH3 (2e), Bu-t (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)(3)PAuC 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 H-1 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) approximate to Bu-t (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-.