Halogenation engineered metal cluster assemblies

ABSTRACT Translating the elegant precision of molecular design into materials with predictable macroscopic functions represents a central goal in supramolecular and materials chemistry. Atomically precise coinage metal clusters offer an ideal platform for achieving this objective. However, progress is frequently frustrated by the limited and poorly tunable nature of the forces that direct assembly, a challenge that is particularly formidable in achieving the atomically precise transfer and amplification of chirality from the molecular to the supramolecular level. Herein, we introduce a halogenation engineering strategy that selectively installs distinct halogen atoms (F, Cl, Br) at the termini of peripheral ligands on a tetranuclear gold cluster to produce rationally tunable, directional noncovalent interactions, including hydrogen bonding, halogen bonding, and halogen···halogen interactions. This strategy transcends the inherent constraints of conventional noncovalent interactions in metal-cluster systems and significantly enriches the supramolecular toolbox. Leveraging this molecular-level control, we demonstrate that subtle modulation of the external solvent environment selectively biases the competition and cooperativity among these directional interactions, thereby enabling single-precursor self-assembly into multiple, structurally distinct, atomically precise polymorphs such as discrete monomers, finite helices, and infinite chains. Control is particularly evident in the formation of compactly twisted helical super-structures, in which molecular chirality is not only preserved but also efficiently transferred and amplified, resulting in dominant supramolecular chiroptical properties. This is exemplified by the freshly prepared crystals of (Au4-Br)3 trimer, which exhibits intense circularly polarized luminescence with a near-unity quantum yield (94%) and a high luminescence dissymmetry factor (glum = 0.04). This work establishes clear design principles for directing the complex and precise self-assembly of clusters via peripheral atom substitution, offering a rational methodology for the bottom-up fabrication of advanced chiral nanomaterials.