Cyclometalated rhodium(III) and iridium(III) complexes containing amino acids as N,O-chelates

The synthesis of bis-cyclometalated aminocarboxylato complexes [M(α-aminocarboxylato)(ptpy)2] (M = Rh, 3, 4, 5; M = Ir, 6, 7, 8), ptpy = 2-(p-tolyl)pyridinato; aminocarboxylato = glycinato, l-alaninato, l-prolinato) from [{M(μ-Cl)(ptpy)2}2] (M = Rh, 1; M = Ir, 2) is described. The molecular structure of [Ir(l-alaninato)(ptpy)2] (7) was confirmed by a single-crystal X-ray diffraction study. Compound 7 crystallized from methanol-iso-hexane in the space group P21. For 7 the two diastereoisomers ΔIr, SC and ΛIr, SC were found crystallizing twice per unit. Absorption and emission spectra were recorded. The rhodium compounds are weak yellow-green and the iridium species strong green emitters.

Graphical abstractSyntheses of the bis-cyclometalated amino-carboxylate complexes [M(α-aminocarboxylato)(ptpy)2] (M = Rh, 3, 4, 5, M = Ir, 6, 7, 8), ptpy = 2-(p-tolyl)pyridinato), (aminocarboxylato = glycinato, l-alaninato, l-prolinato) from [{M(μ-Cl)(ptpy)2}2] M = Rh (1), M = Ir (2) is described. Compound 7 crystallized from methanol/iso-hexane in the space group P21. Its molecular structure was confirmed by a single-crystal X-ray diffraction study. We found the two diastereoisomers ΔIr, SC and ΛIr, SC which crystallized twice per unit.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Amino acid anions split chloride bridges in [M(ptpy)2(μ-Cl)]2 dimers forming N,O chelates. ► With glycinate, ΔMΔM and ΛM enantiomers of the tris-chelate complexes are formed. ► With l-alaninate, the ΔMSC and ΛMSC′ diastereomers are formed in an approximate 1:1 ratio. ► With l-prolinate a 3:2 preference for one diastereomer is observed. ► The iridium l-alaninato complex crystallizes with both diastereomers in a 1:1 ratio.