Stereospecific assembly of chiral Lambda-Cr(III)-Delta-Ln(III)-oxalato-bridged dinuclear 3d-4f complexes (Ln = Yb or Dy) and near infrared circular dichroism in the 4f -> 4f transitions

Stereospecific formation of the chiral heterodinuclear 3d-4f complexes (Lam bda-Delta)-[(acac)(2)Cr(ox)Ln(HBpz(3))(2)] (acac(-)=acetylacetonate, ox(2-) =oxalato, HBpz(3)(-)=hydrotris(pyrazol-1-yl)borato; Ln=Yb: 1, Dy: 2 where ( Lambda-Delta) implies the absolute configuration around the octahedral Cr a nd square antiprismatic Ln moiety, respectively) was demonstrated by compar ing the near infrared circular dichroism (NIR CD) in the 4f --> 4f transiti ons and/or the single crystal X-ray analysis with those of a diastereomeric mixture of the mononuclear Lambda-, and Delta-[Yb(HBpz(3))(2)(S-pba)] 3 (S -pba=S-(+)-2-phenylbutyrate) complex. The NIR CD spectra for the 4f --> 4f transitions of the 3d-4f (Lambda-Delta)-Cr(ox)Ln complexes 1 and 2 with con figurational chirality around the Ln ion with no asymmetric carbon were obs erved for the first time in CH2Cl2.This observation is supported by the sel ection rule for the optical activity of the 4f --> 4f transitions. The firs t solution NIR magnetic circular dichroism (MCD) of the racemic Cr(ox)Yb an d Cr(ox)Dy complexes is also reported.