Thiazyl radicals: old materials for new molecular devices

Abstract

This review describes recent advances in the development of thiazyl radicals, particularly dithiadiazolyl (RCNSSN) and dithiazolyl (RCSNSCR) as molecule-based materials. Particular emphasis is placed on their potential applications as molecular conductors, magnets and switchable materials and incorporates an overview of the structure-property relationships required in these molecular systems.

Effects of Halo-Substitution on 2′-Chloro-5′-halo-phenyl-1,2,3,5-dithiadiazolyl Radicals: A Crystallographic, Magnetic, and Electron Paramagnetic Resonance Case Study

“…3.20 -3.26 Å. This is slightly longer than what is normally observed for other DTDA derivatives, 64,65 but similar to the intra-dimer distances of radicals 1 -4 ( Table 2). The longer intra-dimer distances in these radicals result in To date, weakening of the dimerization in DTDA radicals has been achieved through the use of groups (F, CF 3 , Me) in the 2′/6′-positions to weaken π*-π* dimerization (GOTQEL, HAKYOI, HAWRAZ, ILUKIJ, YOMXUT).…”

“…1). 64,65 This interaction stabilizes the singlet ground state which is experimentally supported by χT values ~ 0 emu.K.mol -1 at low temperature. [26][27][28][29] Passmore was the first to indicate that the "closed-shell" dimerization of DTDA radicals inadequately described the electronic ground state of these materials and that they had some diradical character, 23 more recently studied computationally by Kertesz.…”

“…64 Dimerization typically proceeds via multi-centre two electron π*-π* interactions between the out-of-phase components of the two singly-occupied molecular orbitals (SOMOs) (Fig. 1).…”

The key role of vibrational entropy in the phase transitions of dithiazolyl-based bistable magnetic materials

“…Several p-stacked 1,3,2-dithiazolyl (DTA) radicals have been shown to feature spin-transition behaviour between a lowtemperature (LT) diamagnetic slipped stack of p-radical pairs and a high-temperature (HT) paramagnetic regular p-stack 16 . Some of these magnetic phase transitions are associated with a hysteretic behaviour 11,12,[16][17][18][19] (thus giving rise to a region of bistability), while other transitions occur without hysteresis 20,21 .…”

“…Some of these magnetic phase transitions are associated with a hysteretic behaviour 11,12,[16][17][18][19] (thus giving rise to a region of bistability), while other transitions occur without hysteresis 20,21 . In addition to these intriguing solid state phase transitions, many other members of the key family of thiazyl radicals show remarkable conductivity and magnetic properties 16,[22][23][24][25] .…”