Diastereoselective synthesis of coordination compounds: a chiral tripodal ligand based on bipyridine units and its ruthenium(ii) and iron(ii) complexes

Abstract

The enantiomerically pure chiral tris-chelating ligand (+)-(7S,10R)-L (L) comprising three 4,5-pinenobipyridine subunits connected through a mesityl spacer has been synthesized. Complexes of L with Ru^II and Fe^II have been prepared and characterised. NMR spectroscopy indicates that only one diastereoisomer is formed, and the CD spectra show that the complexes have the Λ configuration on the metal centre. The X-ray crystal structure of the iron complex shows that in the octahedral complex, the ligand L coils around the metal and confirms the absolute configuration. The Ru^II and Fe^II compounds were also characterised by mass spectrometry, electronic absorption, and, in the case of Ru(II), fluorescence spectroscopy. The photostability of the ruthenium compound was checked by photochemical experiments.