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

ABSTRACT We report the covalent functionalization of exfoliated MoS ₂ and WS ₂ 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 MoS ₂ ‐based 2a‐c and WS ₂ ‐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 MoS ₂ or WS ₂ 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 ¹ BODIPY ^* to TMD are within the time‐resolution of our instrumental setup, the rate of electron transfer, k _ET , from ¹ TMD ^* to BODIPY resulting in TMD ^{• +} ‐BODIPY ^•− is in the range of 1–2 × 10 ⁹ s ⁻¹ , revealing efficient charge separation in these hybrids.