Fig. 6.
Capture of [Au25(SR)18CO]− intermediate. Electrospray ionization mass spectra of the CO-saturated [Au25(SR)18]− aqueous solution in a large m/z range of 1000–3000, b zoom-in m/z range of 2550–2625, and c isotope resolution. The dotted drop-lines in b are visual guides for [Au25(SR)18]− (blue lines) and [Au25(SR)18CO]− (magenta lines) associated with varied numbers of Na+. The blue and magenta lines in c are simulated isotope patterns of [Au25(SR)18+Na–3 H]3− and [Au25(SR)18CO–2 H]3−, respectively. The CO-saturated [Au25(SR)18]− solution is prepared by bubbling CO into an aqueous solution of purified [Au25(SR)18]− (0.2 mL, [Au] = 10 mM) for 2 min