Reversible low temperature phase change and twinning in lithium acetyl acetonate

Abstract

Lithium acetyl acetonate undergoes a perfectly reversible phase change from orthorhombic to non-merohedrally twinned monoclinic between 195 and 200 K. The phase transfer is associated with a sudden slight deviation of the orthorhombic γ-angle from 90°, with the initial coordinate changes following the phase transfer being very subtle. The connectivity within the lithium acetyl acetonate chains and the basic structural motif remain unchanged and the main difference between the orthorhombic and monoclinic structures is associated with a departure of the Li atoms – along with the Li(acac) chains as a whole – from a perfectly linear fashion in the room temperature structure to a slightly curved chain in the low temperature phase. Detailed descriptions of experimental procedures for the handling of non-merohedrally twinned datasets are given and discussed.

Keywords:

• acteyl acetonates
• non-merohedral twinning
• pseudo-merohedral twinning
• phase transfer
• variable temperature XRD measurements

Acknowledgements

The authors would like to thank Michael Ruf and Susan Byram of Bruker AXS for providing a copy of twinabs version 2007/3 prior to its official release. The diffractometer was funded by NSF grant 0087210, by Ohio Board of Regents grant CAP-491, and by YSU.