Bis-Heteroleptic Ruthenium(II) Complex of Pendant Urea Functionalized Pyridyl Triazole and Phenathroline for Recognition, Sensing, and Extraction of Oxyanions.

A new bis-heteroleptic Ru complex based ditopic receptor, 1[PF], having an anion binding triazole -CH unit and appended 4-fluorophenyl urea arm has been developed. H NMR and isothermal titration calorimetry (ITC) experiments showed binding of 1[PF] toward oxyanions such as phosphates (e.g., HPO and HPO) and carboxylates (e.g., CHCO and CHCO) anions selectively. H NMR studies showed that highly basic phosphate anions such as HPO/HPO are bound by both -CH and -NH units of complex 1[PF]. However, comparatively less basic CHCO, CHCO anions interacted with the urea -NH protons only. Thermodynamic parameters obtained from ITC experiments suggested that binding of all the interacting anions with complex 1[PF] are highly enthalpy and entropy driven processes. Importantly, complex 1[PF] showed extraction of HPO, CHCO, and CHCO anions from aqueous solution via liquid-liquid extraction with efficiencies of 28%, 74%, and 80%, respectively. The influential role of the urea moiety in the course of extraction is demonstrated by comparison with a model complex, 2[PF]. Additionally, complex 1[PF] is capable of selective sensing of phosphate anions among all investigated anions.