New Persistent Heteroaromatic Radicals as Building Blocks for Paramagnetic Liquid Crystals

Jozef Zienkiewicz ,  Anna Fryszkowska ,  Katarzyna Zienkiewicz ,  Piotr Kaszynski 

Vanderbilt University, 7330 Stevenson Center, VU Station B, 351822, Nashville, TN 37235, United States

Abstract

In pursuit of paramagnetic liquid crystals for the study of molecular magnetism in organized media, we focused on the -N-S- fragment as the spin source. The thioaminyl fragment was incorporated into aromatic hydrocarbons leading to de novo designed π-delocalized heteroaromatic radicals that satisfy electronic and geometrical requirements for this new class of materials [1, 2]. In this context, we have recently investigated a series of thiadiazinyl radicals 1 [3]. We studied the efficiency of radical generation and their stability as a function of the adjacent ring structure. The high stability of the halogenated radicals 1d and 1e permitted their isolation and complete structural, spectroscopic, and electrochemical characterization. Experimental data was rationalized with the results of DFT calculations. The particularly promising parent radical 1d was further substituted with groups that promote liquid crystallinity to give radicals 2-4. Out of the three radicals, only 4 was successfully generated, and showed liquid crystalline properties.

[1] a) M. K. Patel, J. Huang, P. Kaszynski, Mol. Cryst. Liq. Cryst. 1995, 272, 87. b) P. Kaszynski, in Magnetic Properties of Organic Materials; P. M. Lahti, Ed.; Marcel Dekker: New York, 1999; p 305.
[2] P. Kaszynski, Molecules 2004, 9, 716-724.
[3] J. Zienkiewicz, P. Kaszynski, V. G. Young Jr., J. Org. Chem. 2004, 69, 2551-2561 and 7525-7536.

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Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 1, by Piotr Kaszynski
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-04-29 20:11
Revised:   2009-06-07 00:44
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