Tetracoordinated copper(I) complexes featuring aggregationinduced emission characteristics for sensitive detection of mercury ions

Abstract

Eight tetracoordinated copper(I) complexes Cu1–Cu8, were synthesized using 1,10-phenanthroline derivatives as diimine ligands and 4,5-bis(diphenylphosphino)-9,9-dimethyloxanthene (XantPhos) and bis[(2-diphenylphosphino)phenyl]ether (DPEPhos) as diphosphine ligands. Complexes Cu1–Cu8 exhibited green to red emission with peaks ranging from 520 nm to 647 nm in solid powder, all of which showed photoluminescence quantum yields (PLQYs) of 0.06–0.26. Complexes Cu1 and Cu6 containing thiophene groups exhibited weak photoluminescence in pure acetonitrile, but their photoluminescence is significantly enhanced when the water content in the acetonitrile solution was increased, exhibiting aggregation-induced emission (AIE) properties, which enables them to be applied in the detection of Hg²⁺ in solution. Upon addition Hg²⁺ to CH₃CN/H₂O mixture solution of complexes Cu1 and Cu6, both complexes displayed significant photoluminescence quenching, showing high selectivity with detection limit on the order of 10^–7 M. The sensing mechanism was elucidated by spectroscopy, mass spectrometry and theoretical calculations.