Self-assembly processes of 2D Au(I)-S(CH₂)₂COOH lamellae

Solving the assembled structure of Au(I)-thiolate linear coordination polymers has been a challenging task as they generally lack good crystallinity. This has prevented the elucidation of their assembly processes at the molecular level. In this paper, selected area electron diffraction (SAED) patterns of two-dimensional (2D) Au(I)-S(CH₂)₂COOH (Au(I)-MPA) lamellae are obtained by applying cryogenic transmission electron microscopy. The SAED patterns allow to propose a packing mode of Au(I)-MPA chains in the 2D structure by comparison with the crystal structure of Ag(I)-MPA solved from powder X-ray diffraction. Then, multi-step self-assembly processes to 2D lamellae via the aggregation and crystallization of an intermediate of 1D pre-assemblies are disclosed, which explains the difficulty in synthesize their large single crystals. Based on these results, 2D Au(I)-MPA lamellae with tunable sizes and degrees of crystallinity are synthesized by kinetic control of solvent composition and temperature.