A strategically synthesized arseno-discriminatory tetra-phenoxido hetero-trinuclear complex envisioned for the recognition of iAs and oAs from Oryza sp. and aquatic crustaceans

Abstract

A heterotrimetallic [Mn^II(Cu^II)₂(C₁₈H₁₈N₂O₂)₂] complex VBCMERI has been unveiled herein to monitor its synergistic propensity towards aqueous phase As³⁺ (iAs and oAs) detection. VBCMERI was structurally probed by numerous analytical tools like ESI-MS, FT-IR, and SCXRD. The aqueous phase selective chromogenic alteration of the sensory probe from greenish-yellow to colorless was observed owing to interaction with As³⁺ (cationic form, iAs). This phenomenon can be ascribed to the displacement of the Mn²⁺ center with As³⁺, which has further been experimentally validated through cyclic voltammetric titration studies, FT-IR, and ESI-MS, and theoretically corroborated with density functional theory calculations. Interestingly, aqueous phase selective turn-on fluorogenic enhancement of the sensory probe was observed upon interaction with AsO₂⁻ (anionic form, iAs) owing to the displacement of the arsenite anion with the pivalic acid group. The distinct chromogenic alteration from greenish-yellow to colorless and the fluorogenic enhancement of VBCMERI upon interaction with the respective As³⁺ (iAs) and AsO₂⁻ (iAs) were successfully implemented for monitoring arsenic contamination in groundwater samples and diverse types of Oryza sp. grains from the assorted arsenic-affected zones. The competitive accumulation of arsenobetaine (oAs) in the exoskeleton and muscles of aquatic crustaceans (herein, Penaeus sp.) can be distinctly differentiated based on the turn-on fluorogenic response. Based on the sensing response and competitive accumulation tendency of different forms of arsenic in different environments, arseno-adducts with VBCMERI have been theoretically modeled for corroboration with experimental findings. The VBCMERI-AsO₂⁻ adduct was also highly efficient in regenerating the VBCMERI sensor selectively in the presence of contaminants like Pb²⁺. This reversible behavior was further exploited to mimic a molecular-level 3-input–2-output logic gate ensemble.