Solution NIR CD and MCD in 4f-4f transitions of a series of chiral 3d-4f dinuclear complexes; X-ray structures of (LAMBDA-DELTA)-[(acac)_2Cr~(III)(u-ox)Ln~(III)(HBpz_3)_2] (Ln = Sm, Ho and Er)

摘要

A series of stereospecifically assembled configurational chiral h omplexes (LAMBDA-DELTA)-[(acac)_2Cr(ox)Ln HBpz_3)_2] (acac~- = acetylacetonate, ox~(2-) = oxalate, HBpz_3~- = hydrotris(pyrazol-1-yl)borate; Ln(III) = La, Nd, Sm, Ho, Er and Tm: (LAMBDA-DELTA)-Cr(ox)Ln, where (LAMBDA-DELTA) implies the absolute configuration around the Cr and Ln moieties, respectively) was synthesized and three of them (Sm, Ho and Er) were structurally characterized by X-ray analysis. The (LAMBDA-DELTA)-Cr(ox)Ln (Ln = Ho, Er, and Yb) complexes crystallize in the identical space group P2_12_12_1, whereas the (LAMBDA-DELTA)-Cr(ox)Sm complex crystallizes in the monoclinic space group P2_1. The absolute configurations of all of the Ln complexes were found to be identical with one another. Near infrared circular dichroism (NIR CD) spectra in the 4f-4f transitions of the (LAMBD-DELTA)-Cr(ox)Ln (Ln = Nd, Sm, Ho, Er, and Tm) complexes were studied for the first time in CH_2Cl_2 solution and were compared with those of the previously reported Yb(III) and Dy(III) ions in the (LAMBDA-DELTA)-Cr(ox)Ln. The dissymmetry factors g(= DELTAepsilon/epsilon) of the NIR CD for the 4f-4f transitions of these complexes were found to be of the order of 10~(-3) and 10~(-4), confirming the stereospecific formation and retention of the configurational chirality around the Ln(III) ions of the (LAMBD-DELTA)-Cr(ox)Ln complexes in solution. The solution NIR magnetic circular dichroism (MCD) spectra of the Cr(ox)Ln complexes (Ln = Nd, Sm, Dy, Ho, Er and Tm) were also studied in conjunction with the NIR CD spectra.