Structure-chiroptical property relationship of kinetically labile camphor-derivative beta-diketone Yb(III) complexes: do the adducts coexist as diastereomers or not?

The present work examines the relationship between the crystal structures and chiroptical properties of four chiral Yb(III) complexes with camphor-derivative beta-diketone ligands by means of solid-state circular dichroism (CD) spectroscopy. For the seven-coordinate complexes, [Yb(H(2)O)(d-hfc)(3)] (I) and [Yb(H(2)O)(l-hfc)(3)] (II) (d/l-hfc(-) = 3-heptafluorobutyryl-(+)/(-)-camphorate), the Lambda- and Delta-diastereomers coexist in their crystals and no apparent bisignate couplets are observed in their solid-state CD spectra. A theoretical study indicates that the ground-state energy difference between the two diastereomers I and II is only 0.913 kcal mol(-1), which explains why they could coexist in a crystal environment with the ratio of 1:1. While, eight-coordinate complexes Delta-[Yb(TPPO)(2)(d-hfc)(3)]center dot CHCl(3)center dot 3C(6)H(12) (III) and Lambda-[Yb(TPPO)(2)(l-hfc)(3)]center dot CHCl3 center dot 3C(6)H(12) (IV) (TPPO = triphenylphosphine oxide) are enantiopure in the solid-state, and typically negative and positive exciton splitting patterns around 330 nm are observed in their solid-state CD spectra. The solid-state CD spectra of these four complexes are in accordance with their X-ray single-crystal analyses. Besides, their solution CD spectra show that no particular isomer predominates in solution.NSFC[20973136, 20773098, 20673069]; NSF of Shanxi province[2007011021