Synthesis, Characterization, and Luminescence Studies of Gold(I) Complexes with PNP- and PNB-Based Ligand Systems

The synthesis, X-ray crystal structures, and spectroscopic studies of a series of PPh₂N­(2,6-iPr₂C₆H₃)­PPh₂ (PNP) and PPh₂N­(2,6-iPr₂C₆H₃)­BCy₂ (PNB; Cy = cyclohexyl) based gold­(I) complexes are presented herein. The gold­(I) chloride complexes 2 and 6 were treated with AgSbF₆ to yield the corresponding dimeric dinuclear Au^I cation (3) and dimeric mononuclear Au^I cation (7) with PNP and PNB systems, respectively. The molecular structure of 3 revealed the presence of a strong intramolecular aurophilic interaction with a Au···Au bond distance of 2.7944(19) Å, one of the shortest aurophilic interactions known in the literature. However, complex 7 displays no aurophilic interaction. The reaction of 3 with diphenyl disulfide was performed, which led to a multinuclear tetragold­(I) complex (4), keeping the aurophilic interaction intact. The effect of an aurophilic interaction is also illustrated through the study of the luminescent properties of these gold­(I) complexes. Complexes 3 and 4 exhibit luminescence in solution as well as in the solid state, whereas the other gold­(I) complexes remain nonluminescent.