A new water-soluble heteronuclear PdII–AuI pincer complex as two-photon luminescent probe for biological Co2+ detection

Abstract

The heterodinuclear NCN pincer complex K[(L)Pd^II(DPS)Au^ICl], 1, (HL = 5-methoxy-1,3-bis(1-methyl-1H-benzo[d]imidazol-2-yl)benzene, DPSH₂ = 4,4′-dicyanamidodiphenyl sulfone) with two-photon induced luminescent properties was synthesized and investigated for biological Co²⁺ detection. Importantly, 1 can selectively recognize Co²⁺ in aqueous media in the presence of other abundant cellular cations (such as Na⁺, K⁺, Mg²⁺, and Ca²⁺), trace metal ions in organisms (such as Zn²⁺, Ag⁺, Fe³⁺, Fe²⁺, Ni²⁺, Mn²⁺, and Cu²⁺), prevalent toxic metal ions in the environment (such as Cd²⁺, Hg²⁺, and Cr³⁺), and amino acids, with high sensitivity. The fluorescence response of 1-Co²⁺ with respect to pH change was studied and the resulting demonstrated fluorescence enhancement was observed in the pH range of 4–10. The water-soluble probe 1 was successfully applied in the visualizing of the site of Co²⁺ accumulation as well as estimating of trace amounts of Co²⁺ ions in live HeLa cells by two-photon microscopy.