Superiority of imidazolium over triazole moiety in bis-heteroleptic ruthenium(II) complex toward selective sensing of phosphates

A new bis-heteroleptic Ru(II) complex, Ru-1 (C 42 H 42 F 24 RuN 10 P 4 ) with pendant imidazolium bypyridine unit has been synthesized and characterized by different spectroscopic and spectrometric methods. Imidazolium ion-based complex, Ru-1 has shown superiority in phosphate sensing in CH 3 CN as compared to its triazole-based complex Ru-2 in terms of enhanced binding constant values, longer excited state lifetimes, and lower detection limit values. • New bis-heteroleptic Ru(II) complex Ru-1 with a pendent imidazolium-bipyridine unit was designed and synthesized. • Non-covalent C H•••anion HB interactions significantly influenced the binding of H 2 PO 4 − and HP 2 O 7 3− . • PL studies revealed Ru-1 's efficiency over Ru-2 in terms of binding constant, LOD, and excited state lifetime. A new phosphorescent ruthenium-based receptor, designated as Ru-1, functionalized with imidazolium as an anion-binding moiety was synthesized and characterized for selective recognition and sensing of H 2 PO 4 − and HP 2 O 7 3− . The binding affinity of Ru-1 towards numerous anions was assessed using UV–visible and phosphorescent spectroscopic techniques in CH 3 CN solvents. Notably, phosphate and pyrophosphate exhibited superior binding constants compared to other anions, with measured binding constants (K a ) of 7.95 × 10 4 and 4.78 × 10 4 M −1 respectively. Moreover, discernible blue shifts of 25 nm and 28 nm respectively, corresponding to H 2 PO 4 − and HP 2 O 7 3− and significant enhancements in photoluminescence intensities by ∼5-fold and ∼4-fold, respectively were observed with H 2 PO 4 − and HP 2 O 7 3− . Despite the existence of excess other anions, Ru-1 demonstrated selectivity towards these ions, facilitating sensitive detection with a limit of detection (LOD) of 0.045 µM for H 2 PO 4 − and 0.017 µM for HP 2 O 7 3− . In the presence of H 2 PO 4 − , the lifetime of Ru-1 was amplified noticeably from 0.2329 μs to 0.7914 μs, whereas exposure to HP 2 O 7 3− resulted in an observed increase of 0.7465 μs. Furthermore, comparative photophysical studies revealed that the imidazolium moiety-based Ru-1 receptor outperformed the triazole-based Ru-2 receptor in terms of excited state lifetime, binding constant, and detection limit of the anions.