STUDIES OF UNUSUAL PACKING AND OF POLYMORPHISM IN TWO CRYSTAL SYSTEMS

Author

Xiang Hao, University of Kentucky

Date Available

12-14-2011

Year of Publication

2005

Degree Name

Doctor of Philosophy (PhD)

Document Type

Dissertation

College

Arts and Sciences

Department

Chemistry

First Advisor

Dr. Carolyn P. Brock

Abstract

Crystal structures of anhydrous pinacol, the hexagonal pinacol, pinacol monohydrate, and pinacol hexahydrate were studied. In all the structures crystal packing is unusual and complicated. The origin of the complexity may be the difficulty in filling space densely and while also satisfying the H-bonding requirements when the molecule has few internal degrees of freedom.

Five 15-crown-5 complexes of M(NO₃)₂ (M = Cu, Zn, Mg, Co, Mn) were synthesized and characterized using X-ray diffraction and differential scanning calorimetry. The system is rich in polymorphs. Nine definite solid-state phases were identified. More phases probably exist in the solid state at temperatures slightly above the room temperature. Most phase transformations in this system take place in single crystals without the loss of crystallinity. The nine phases crystallize in five crystal structures. The crown ether ligands have very similar conformation in all the structures. The asymmetric units in all the structures are complicated and pseudosymmetric, which is the consequence of the presence of the packing problem. The origin of the packing problem that leads to the complicated phase behavior is the odd number of -CH₂-O-CH₂- units in the crown ether ligand.

Recommended Citation

Hao, Xiang, "STUDIES OF UNUSUAL PACKING AND OF POLYMORPHISM IN TWO CRYSTAL SYSTEMS" (2005). University of Kentucky Doctoral Dissertations. 285.
https://uknowledge.uky.edu/gradschool_diss/285