Invariant Photoinduced Energy‐Transfer Followed by Electron‐Transfer Events in Boron Dipyrromethene Derivatives Covalently Anchored to MoS ₂ and WS ₂

We report the covalent functionalization of exfoliated MoS₂ and WS₂ via a 1,2-dithiolane-based reaction using boron dipyrromethene (BODIPY) derivatives 1a-c featuring either methyl, phenothiazine (PTZ), or triphenylamine (TPA) units at the α-carbons of BODIPY, shifting the light-harvesting capability of the MoS₂-based 2a-c and WS₂-based 3a-c hybrids from the visible to the near-infrared region. All new hybrids are comprehensively characterized via spectroscopic, thermal, and microscopy imaging techniques. Markedly, femtosecond transient absorption spectroscopy assays revealed a multi-step sequence of events under light illumination, beginning with energy transfer from the BODIPY derivatives to the TMDs, followed by electron-transfer from the excited TMDs to BODIPYs, forming a thermodynamically stable charge-separated state TMD^• ⁺-BODIPY^•-. Interestingly, while the presence of electron-donating substituents of PTZ and TPA in BODIPY derivatives 1b-c partially inhibits these processes, all hybrids 2a-c and 3a-c exhibit similar photoinduced electronic behavior, signifying that the electronic interface of MoS₂ or WS₂ and BODIPYs remains largely unaffected by the specific region of the electromagnetic spectrum from which light is harvested, the nature of TMDs, or their electron-donating/accepting character. While the rates of energy transfer, k_ENT, from ¹BODIPY^* to TMD are within the time-resolution of our instrumental setup, the rate of electron transfer, k_ET, from ¹TMD^* to BODIPY resulting in TMD^• ⁺-BODIPY^•- is in the range of 1-2 × 10⁹ s^-1, revealing efficient charge separation in these hybrids.