Criteria for Liquid Crystal Formation in 5-alkoxy-, 5-alkylamino-, and 5-alkanoyl-tropolone Complexes of Transition Metals (CuII, ZnII, NiII, CoII, UO2VI, VOIV). the First Uranium Metallomesogen. Crystal Structure of Bis(5-hexadecyloxytropolonato)copper(II)


The mesophase properties of bis(5-alkoxytropolonato)copper(II) complexes are reported and interpreted in terms of d-layer spacings, which indicate considerable intertwining of the alkyl chains. The mesogenic properties depend on the nature of the 5-substituent: to be mesogenic, it must be alkoxy with n > 8, and may not be 5-alkanoyl or 5-alkylamino. The nature of the metal is also important: to be mesogenic, it may be CuII or UO2VI but not NiII, ZnII, CoII, or VOIV. The crystal structure of bis(5-hexadecyloxytropolonato)copper(II) shows how, even in the crystalline state, molecular packing is dominated by the interactions between alkyl chains, together with copper−oxygen interactions. In the CuII complexes, strong interactions occur between Cu atoms and O atoms of neighboring molecules. These are stronger than alkyl−alkyl interactions and therefore dominate alkyl−alkyl interactions between neighbors which otherwise govern the possibility and nature of mesogenic properties. The Cu···O interactions disrupt alkyl−alkyl chain interactions enough to produce a mesophase; such interactions do not obtain in the Td ZnII and CoII complexes, and indeed, these complexes are not mesogenic. Likewise, alkyl chain interactions by the oxygens of the UO2VI lead to a mesophase, and U constitutes the heaviest metal ever placed into a mesogenic molecule. In the case of VOIV, analogous synthetic steps from VOSO4 led to a new series of binuclear complexes [(VO)2(SO4)(5-alkoxytropoloato)2].


Mathematics and Statistics

Second Department



Engineering and Physical Sciences Research Council

Keywords and Phrases

bis(5-alkoxytropolonato)copper(II) complexes; d-layer spacings; mesophase properties

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Document Type

Article - Journal

Document Version


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© 2002 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jan 2002