A 1H-imidazo[4,5-f][1,10]phenanthroline based ligand and its binuclear Cu(I) complexes: Syntheses, structures and luminescence sensing for Cr2O72− and MnO4−

Dichromate (Cr₂O₇²⁻) and permanganate (MnO₄⁻) ions have been important targets for sensing and detection in the field of luminescent complexes and their corresponding ligands due to their significant impact on the ecological environment and human health. However, many Cu(I) complexes with good room-temperature phosphorescence are rarely used as luminescent sensors for ions in water due to the insolubility and the disproportionation of the Cu(I) ion. Herein, 2,6-di-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl-4-tertbutylphenol (diptpH₃) and its two luminescent binuclear Cu(I) complexes, [Cu(diptpH₃)(POP)]ClO₄ (1) and [Cu(diptpH₃)(xantphos)]ClO₄ (2), were designed and synthesized (POP = bis[(2-diphenylphosphino)phenyl] ether, and xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene). All compounds in DMSO/H₂O (1: 9, v: v) show high stability to water, which was confirmed by the results of electrospray ionization mass spectrometry (ESI-MS). Cr₂O₇²⁻ and MnO₄⁻ ions showed high luminescence quenching coefficients (Cr₂O₇²⁻: 3.042 × 10⁴ − 2.946 × 10⁵ M⁻¹; MnO₄⁻: 1.476 × 10⁴ − 2.254 × 10⁵ M⁻¹) for all the three compounds. DiptpH₃, complexes 1 and 2 exhibited good luminescent sensing properties toward Cr₂O₇²⁻ and MnO₄⁻ ions with short response times, good selectivity and low detection limits (Cr₂O₇²⁻: 1.845 × 10⁻⁷ − 2.359 × 10⁻⁶ mol⋅L⁻¹; MnO₄⁻: 1.850 × 10⁻⁷ − 6.221 × 10⁻⁶ mol⋅L⁻¹) in DMSO/H₂O. The plausible sensing mechanisms were fully discussed.