Light-Activated Metal-Coordinated Supramolecular Complexes with Charge-Directed Self-Assembly

Metal-coordinated. materials are attractive for many applications including catalysis, sensing, and controlled release. Adenine and its derivatives have been widely used to generate many coordination complexes, polymers, and nanoparticles. However, few of these materials display fluorescence. Herein, we report fluorescent gold complexes and nanoclusters formed with adenosine, deoxyadenosine, AMP, and ATP, where the former two produced micrometer-sized particles and the latter two produced molecular clusters. Only weak fluorescence was produced with adenine, while no emission was observed with uridine, cytidine, or guanosine. We found that adding citrate and light exposure are two key factors to generate fluorescence, and their mechanistic roles have been explored. In all the products, the ratio between gold and adenine was determined to be 1:1 using UV-vis spectroscopy. Mass spectrometry showed clusters containing 2, 4, and 6 gold atoms in the gas phase. The fluorescence peak is around 470 nm for the AMP and ATP complex and 480 nm for the (deoxy)adenosine complexes. This work has provided a systematic approach to obtain fluorescent metal coordinated polymers and materials with tunable sizes, which will find applications in analytical chemistry, drug delivery, and imaging. The fundamental physical chemistry of these materials has been systematically explored.