Induction of Columnar Discotic Behavior in Verdazyl Radicals with Alkylsulfanyl Substituents

Abstract

Substitution of the 1,3,5-triphenyl-6-oxoverdazyl radical with n-alkylsulfanyl groups lead to derivatives 1[n], which exhibit a columnar rectangular phase (Col_r ) below 60 °C. Compounds 1[n] have a broad absorption band in the visible region with maxima at 540 and 610 nm and redox potentials E^0/+1 _1/2 = +0.99 V and E^0/−1 _1/2 = −0.45 V vs. SCE. Time-of-flight (TOF) investigation of 1[8] revealed hole mobility of μ_h = 1.52 × 10⁻³ cm² V⁻¹ s⁻¹ in the columnar phase with an activation energy E_a = 0.06 ± 0.01 eV. Magnetization studies of 1[8] demonstrated nearly ideal paramagnetic behavior in both solid and fluid phases above 200 K and weak antiferromagnetic interactions at low temperatures. Verdazyl derivatives 1[n] were prepared in a sequence of reactions starting from 1-bromo-3,4,5-trifluorobenzene by alkylsulfanylation, followed by hydrazinylation, and finally 6-oxoverdazyl ring assembly using the Milcent method.

GRAPHICAL ABSTRACT

Acknowledgments

This work was supported by Vanderbilt University Discovery Grant and NSF grant (CHE-1214104). We thank Prof. Andrzej Twardowski for funding SQUID measurements and Ms. Ola Kruczkowska for her technical assistance.