Crystal Growth & Design
The 4ʹ-alkoxy-tetrafluorophenyl dithiadiazolyls, ROC6F4CNSSN [R = Me (1), Et (2), nPr (3), nBu(4)] all adopt cis-oid dimers in the solid state. The methoxy derivative 1 adopts a π-stacked AA’AA’ motif whereas propoxy (3) and butoxy (4) derivatives exhibit an AA’BB’ stacking. The ethoxy derivative (2) is polymorphic. The α-phase (2α) adopts an AA’BB’ motif comparable with 3 and 4, whereas 2β and 2γ are reminiscent of 1 but combine a mixture of both monomers and dimers in the solid state. The structure of 2β exhibits Z’ = 6 with two dimers and two monomers in the asymmetric unit but undergoes a thermally-induced phase transition upon cooling below -25 oC to form 2γ (Z’ = 14) with six dimers and two monomers in the asymmetric unit. The transition is associated with both rotation and translation of the dithiadiazol-yl ring. Detailed DSC and variable temperature PXRD studies coupled with SQUID magnetometry have been used to show that 2αconverts irreversibly to 2β upon heating and that 2β and 2γ interconvert through a reversible phase transition with a small thermal hysteresis in its magnetic response.
Beldjoudi, Yassine; Sun, Rui; Arauzo, Ana; Campo, Javier; Less, Robert J.; and Rawson, Jeremy M.. (2017). Structural variations in the dithiadiazolyl radicals p-ROC6F4CNSSN (R = Me, Et, nPr, nBu): A case study of reversible and irreversible phase transitions in p-EtOC6F4CNSSN. Crystal Growth & Design.
Available for download on Wednesday, November 28, 2018