Synthesis and Magnetic Properties of the Novel Dithiadiazolyl Radical, p-NCC6F4C6F4CNSSN

Abstract

Abstract:The dithiadiazolyl radical p-NCC 6 F 4 C 6 F 4 CNSSN• (4) retains its monomeric nature in the solid state with molecules linked together into chains via supramolecular CN···S interactions. Variable temperature magnetic studies on 4 show that it behaves as a near-ideal Curie paramagnet (|θ| less than 0.1 K), indicating negligible intermolecular exchange. The effective magnetic moment (1.78 µ B ) is temperature independent and in excellent agreement with the value expected for an S = ½ paramagnet with g = 2.01 (1.74µ B ). The lack of exchange coupling between radicals is attributed to the absence of significant orbital overlap between radical centres.

Spin Density Distribution and Interaction Mechanisms in Thiazyl-based Magnets

“…Conversely the p-O 2 NC 6 F 4 CNSSN• radical (3) shows ferromagnetic interactions and a ferromagnetic transition at 1.32K [22,40]. The fourth compound, the p-NCC 6 F 4 C 6 F 4 CNSSN• (4) exhibits a structure-directing CN•••S interaction as observed in 1a and 1b but exhibits near perfect Curie paramagnet (|q| < 1K) consistent with large distances between heterocyclic rings beyond 6Å [38]. The magnetic behaviour of the first four radicals will be explained in more detail later in this chapter.…”

“…To date, five perfluoroaryl-dithiadiazolyl radical crystals in which the dimerization tendency has been inhibited have been synthesized (see Fig. 3) [17,22,35,36,37,38]. These five structures exhibit very different magnetic behaviour.…”

Thiazyl radicals: old materials for new molecular devices

“…it behaves as a near perfect paramagnet. 89 A number of other dithiadiazolyl radicals have been prepared in which dimerisation has been inhibited. These are predominantly based upon derivatives comprising bulky substituents.…”

Experimental and theoretical charge density assessments for the 4-perfluoropyridyl- and 4-perflurophenyl-1,2,3,5-dithiadiazolyl radicals

“…To date, only a few examples of monomeric dithiadiazolyl radicals have been discovered in the solid state. [2][3][4][5][6] Much effort has been committed to understanding the nature of the dimerization interaction and to prevent unfavorable Peierls distortions (see D. A. Haynes 7 and references therein). In some cases bulky substituents are introduced to the system in order to cause steric hindrance and thus prevent the system from dimerizing.…”

“…It is clear from both experimental and computational studies that the dimerization energy is low, and the dimers readily dissociate into monomers in solution, as evidenced by the isotropic five-line EPR spectra obtained for these molecules. It is also apparent that dimerization in the solid state can be suppressed by the introduction of appropriate competing intermolecular interactions, resulting in monomers [2][3][4][5][6] or thermally accessible triplet states. 14 It is important to further understand the nature of this dimerization interaction, and experimental charge density analysis is a revealing tool in this regard.…”