Elucidation of optical rotation by X-ray structure analysis of metal complexes

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 07640760
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Inorganic chemistry
• Research Institution: School of Science, Kitasato Univrtsity
• Principal Investigator: SAKABE Yuzuru Kitasato University, School of Science, Assistant, 理学部, 助手 (10050593)
• Co-Investigator(Kenkyū-buntansha): TAKAYANAGI Hiroaki Kitasato University, School of Pharmaceutical Science, 薬学部, 教授 (00050477)
• Project Period (FY): 1995 – 1997
• Keywords: Metal complex / Chirality / Single-crystal X-ray diffraction / Circular dichroism / Optical rotation

Research Abstract

(+)_<589>-[Cr(CN)_2(S-pn)(R-pn)]Cl has been prepared as the first metal complex expected to contain a chiral central metal and a pair of enantiomers of bidentate propylenediamines (pn=1,2 diaminopropane=propylenediamine). This compound is specific in their usefulness for elucidating unknown problems related to the correlation among multiple chiralities in its molecule, that is, for solving factors which determine the optical properties such as the optical rotation and circular dichroism of this metal complex. Single crystal X-ray characterization of this compound is essential to the discussions for the above problems. Now, difficulties in confirming the absence of geometric isomers and forming single-crystals have been overcome and such characterization has been carried out. This complex crystallizes in the monoclinic space group P2_1 with a=6.603(4)*, b=18.23(2)*, c=6.606(9)*, beta=114.62(3)^ﾟ, V=722(1)*^3, Z=2, R=0.045, and R_W=0.062 ; the absolute configuration is LAMBDA. The CH-CH_2 bond axis of the S-pn chelate ring is nearly parallel to the dummy three-fold axis of the compound ion, whereas that of the R-pn ring is roughly perpendicular to the same axis (oblique strueture), which enhances its repulsion with the S-pn chelate ring. The CH_3 groups of both chelate rings occupy positions that separate them as much as possible and minimize their repulsion. The following conclusion has been clarified. A fairly accurate additive property is induced among the chiralities generated by the metal and ligands in this metal complex. The chiral contribution of chromium to the molar rotations and the CD spevtra does not depend upon its chelation with pn or en (ethylenediamine). And the contribution of each chirality to the molar rotation of LAMBDA-cis-[Cr(CN)_2(S-pn)(R-pn)]Cl is evaluated.