Molecular Connectivity Controls Electronic Coupling and Charge-Transfer Dynamics at Anthracene-MoS2 Interfaces

Controlling interfacial charge-transfer (CT) interactions is a central challenge in two-dimensional (2D) organic-inorganic hybrid materials. Here, we show that molecular connectivity strongly governs excited-state evolution at a 2D heterointerface using anthracene (An) donors covalently attached to few-layer MoS2 nanosheets through an N-benzylsuccinimide linker at either the 2- or 9-position, generating two constitutional isomers, MoS2-2-An and MoS2-9-An. Ultrafast transient absorption spectroscopy reveals markedly different photodynamics that depend strongly on the donor attachment position. Photoexcitation of MoS2-2-An produces a long-lived interfacial CT excited state, whereas MoS2-9-An undergoes rapid formation of a full charge-separated state. The contrasting behavior is consistent with connectivity-controlled differences in donor orientation at the interface, which modulate orbital overlap and electronic coupling and may influence structural reorganization. Theoretical calculations further support that the more coplanar geometry of 2-An, exhibiting a calculated tilt angle (θ) of 29.5° relative to the MoS2 basal plane, enhances electronic coupling and stabilizes an intermediately coupled CT state, whereas the more upright 9-An orientation (θ = 42.1°) weakens orbital mixing and favors direct charge separation. These findings demonstrate that constitutional connectivity can serve as a molecular-level design parameter for tuning interfacial electronic coupling and directing excited-state evolution in 2D hybrid heterostructures relevant to optoelectronics, photocatalysis, and solar-energy conversion.