Preparation and Properties of Organic Radical Compounds with Mesogenic Cores

Abstract

Several organic spin systems based on 4-(N-alkyl)amino-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidinyl-1-oxy) radicals were prepared in which cholesterol or biphenyl mesogenic cores with long alkyl or alkoxy substituents were incorporated in order to investigate the possible occurrence of liquid crystalline properties. Of these radicals a lamellar structure was found in a biphenyl derivative with the 4-(N-methyl)amino-TEMPO-substituent 13; this compound showed mesogenic properties. The local antiferromagnetic spin interactions based on a singlet-triplet model observed during the heating process in the radical were found to turn to a Curie−Weiss behavior after the thermal transition during the cooling process. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)