Inorganic Chemistry, Vol.59, No.8, 5394-5404, 2020
Steric and Electrostatic Control of the pH-Regulated Interconversion of Au-16(SR)(12) and Au-18(SR)(14) (SR: Deprotonated Captopril)
An understanding of the response of nanomaterials to specific environmental parameters is an essential prerequisite for their practical use, especially in living systems. Herein, we disclose the preparation of a watersoluble nanocluster Au-16(SR)(12) (SR denotes deprotonated captopril) and its characterization by a combination of theoretical (e.g., density functional theory calculations) and experimental (UV-vis, electrospray ionization mass spectrometry, etc.) methods. Interestingly, Au-16(SR)(12) was found to convert to Au-18(SR)(14) under acidic conditions, while the reverse conversion from Au-18(SR)(14) to Au-16(SR)(12) occurred upon the addition of base. A mechanistic investigation determined this pH regulation to originate from the distinct steric and electrostatic properties of these two clusters. This study is the first to report the susceptibility of Au-18(SR)(14) and Au-16(SR)(12) to pH, and the distinct pH stability unambiguously reveals the importance of size-tracking of nanomaterials in living systems for future clinical applications.