A series of p-alkylthio-substituted phenyl-1,2,3,5-dithiadiazolyl radicals,p-R-PhDTDA(R=SMe(2),SEt(3),S^(n)Pr(4),S^(i)Pr(5),S^(t)Bu(6)),and the prototypical(R=H(1))phenyl derivative exhibit a thermally driven solid-li...A series of p-alkylthio-substituted phenyl-1,2,3,5-dithiadiazolyl radicals,p-R-PhDTDA(R=SMe(2),SEt(3),S^(n)Pr(4),S^(i)Pr(5),S^(t)Bu(6)),and the prototypical(R=H(1))phenyl derivative exhibit a thermally driven solid-liquid transition accompanied by a spin-state change from diamagnetic(S=0)π-dimers to a pair of paramagnetic(S=1/2)radicals.X-ray crystallography reveals that most derivatives form phase-pure ciscofacial dimers,except 3 which crystallizes as three distinct polymorphs:3αdisplays a sandwich-type herringbone structure stabilized by intermolecular S…S chalcogen bonding(isostructural with 2)while 3βand 3γfeature slippedπ-stacked herringbone arrangements(ABAB and AA’BB’,respectively).In these latter forms,the alkyl groups act as steric buffers between adjacent stacks,a structural motif retained in derivatives 4-6.Differential scanning calorimetry(DSC),hot-stage microscopy,and vibrating sample magnetometry(VSM)collectively demonstrate a hysteretic phase transition in 1-6 with magnetic bistability arising from supercooling of the paramagnetic liquid phase.These results establish a new design paradigm for stimuli-responsive materials in which molecular packing,thermal behavior,and spin states are intrinsically linked through phase transitions.展开更多
基金supported by the Academy of Finland(projects 358156,336456,333565)the University of Jyväskylä,and the authors are grateful for technical and human support provided by SGIker(UPV/EHU/ERDF,EU),especially the fruitful discussions with Dr I.Orue.
文摘A series of p-alkylthio-substituted phenyl-1,2,3,5-dithiadiazolyl radicals,p-R-PhDTDA(R=SMe(2),SEt(3),S^(n)Pr(4),S^(i)Pr(5),S^(t)Bu(6)),and the prototypical(R=H(1))phenyl derivative exhibit a thermally driven solid-liquid transition accompanied by a spin-state change from diamagnetic(S=0)π-dimers to a pair of paramagnetic(S=1/2)radicals.X-ray crystallography reveals that most derivatives form phase-pure ciscofacial dimers,except 3 which crystallizes as three distinct polymorphs:3αdisplays a sandwich-type herringbone structure stabilized by intermolecular S…S chalcogen bonding(isostructural with 2)while 3βand 3γfeature slippedπ-stacked herringbone arrangements(ABAB and AA’BB’,respectively).In these latter forms,the alkyl groups act as steric buffers between adjacent stacks,a structural motif retained in derivatives 4-6.Differential scanning calorimetry(DSC),hot-stage microscopy,and vibrating sample magnetometry(VSM)collectively demonstrate a hysteretic phase transition in 1-6 with magnetic bistability arising from supercooling of the paramagnetic liquid phase.These results establish a new design paradigm for stimuli-responsive materials in which molecular packing,thermal behavior,and spin states are intrinsically linked through phase transitions.
