Design and synthesis of heterobimetallic donor-acceptor chemodosimetric ensembles for the detection of sulfhydryl-containing amino acids and peptides

A competitive indicator displacement assay has been successfully developed for the ratiometric determination of sulfhydryl-containing amino acids and peptides using heterobimetallic donor-acceptor complexes as chemodosimetric ensembles. Chromotropic cis-[ML₂(CN)₂] (M = Fe ^II, Ru^II, Os^II; L = diimine) are used as signaling indicators and Pt^II(DMSO)Cl₂ acceptor moiety is used as the receptor for the sulfhydryl-containing analytes. A series of three heterobimetallic donor-acceptor complexes: cis-Fe^II(bpy) ₂[CN-Pt^II(DMSO)Cl₂]₂ (1), cir-Ru^II(bpy)₂[CN-Pt^II(DMSO)Cl ₂]₂ (2) and cis-Os^II(bpy)₂[CN- Pt^II(DMSO)Cl₂]₂ (3) are synthesized and characterized by X-ray crystallography. All the three ensembles are able to produce specific colorimetric/fluorimetric responses to sulfhydryl-containing amino acids (cysteine, homocysteine and methionine) as well as the sulfhydryl-containing small peptide glutathione. The mechanism of the competitive displacement assay is evaluated by examining the thermodynamics of formation of the donor-acceptor linkage and adducts between the acceptor metal and the sulfhydryl-containing analytes as well as by systematic variation of the donor and acceptor metals in the chemodosimetric ensembles. Copyright © 2005 Royal Society of Chemistry.