Bioorganometallics: First examples of cyclometalated iridium(III) complexes containing di- and tripeptide ester ligands

The synthesis of bis-cyclometalated [Ir(ptpy)2(gly-gly-OEt)] (2, ptpy = 2-(p-tolyl)pyridinato; gly-gly-OEt = glycylglycine ethyl ester) and [Ir(ptpy)2(gly-gly-gly-OEt)] (3, gly-gly-gly-OEt = glycylglycylglycine ethyl ester) from the reaction of [{Ir(μ-Cl)(ptpy)2}2] (1) with the corresponding peptide ester hydrochlorides in the presence of NaOMe is described. The molecular structure of 2 was confirmed by a single-crystal X-ray diffraction study. The compound crystallized from dichloromethane/iso-hexane in the space group P21/a. In the crystal packing the molecules of 2 exhibit N–H⋯O hydrogen bonds to the neighbor molecules to form dimeric units. The absorption and emission spectra of 2 and 3 were recorded and exhibit these compounds as strong green-emitting complexes.

Graphical abstractThe synthesis of the bis-cyclometalated peptide ester complexes [Ir(ptpy)2(gly-gly-OEt)] (2, ptpy = 2-(p-tolyl)pyridinato, gly-gly-OEt = glycylglycine ethyl ester) and [Ir(ptpy)2(gly-gly-gly-OEt)] (3, gly-gly-gly-OEt = glycylglycylglycine ethyl ester) from the reaction of [{Ir(μ-Cl)(ptpy)2}2] 1 with the peptide ester hydrochlorides is described. The molecular structure of 2 was confirmed by a single-crystal X-ray diffraction study.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► First Synthesis of N,N chelated peptide ester complexes of Ir(III) with cyclometalated tolylpyridinato ligands. ► X-ray diffraction study of 2 shows formation of hydrogen bonded dimers in the crystal. ► Complexes show green phosphorescence.