Integrating Diphenyl Diselenide and Its MeHg+ Detoxificant Mechanism on a Conceptual DFT Framework

: Methylmercury (MeHg + ) is an important environmental contaminant and its toxicity is associated with its interaction with selenium (e.g., selenol groups of selenoproteins or HSe − , which is the pivotal metabolite for Se incorporation into selenoproteins). We hypothesized that (PhSe) 2 mediated MeHg + detoxification could be indirectly altered by its open or closed conformation. The two conformations of (PhSe) 2 were located on the potential energy surface (PES) computed at ZORA-OPBE-D3(BJ)/ZORA-def2-TZVP level of theory. HPLC analysis indicated that (PhSe) 2 did not react with MeHg + , but its reduced intermediate formed a stable complex with MeHg + . The nudged elastic band (NEB) method revealed conformational changes from closed to open state with an H − (2 electrons) transfer from NaBH 4 , forming a reactant complex-like transition state (TS). The UV-Vis spectrophotometer used in combination with the time-dependent density functional theory (TD-DFT) indicated that the signal of (PhSe) 2 at 239 nm was possibly the open conformer’s signal with oscillator strength 0.1 and a π → π * electron transfer character. The experimental band gap energy of (PhSe) 2 at 5.20 eV matched to the excitation energy of the open conformation. The local softness (S − ) on the selenium atoms almost doubles, as state changes from closed to open. The theoretical results have indicated that the open conformation of (PhSe) 2 is likely the one that reacts with NaBH 4 to form the PhSeH, which can react with MeHg + .