Low-dose electron diffraction has been instrumental in determining the crystal structures of two compounds with metal-radical coordination frameworks{[Mn2^(Ⅱ)(NITIm)^(3)]CF^(3)SO_(3)·CH^(3)OH}n(1)and{[Mn_(2)^(Ⅱ...Low-dose electron diffraction has been instrumental in determining the crystal structures of two compounds with metal-radical coordination frameworks{[Mn2^(Ⅱ)(NITIm)^(3)]CF^(3)SO_(3)·CH^(3)OH}n(1)and{[Mn_(2)^(Ⅱ)(NITImMe_(2))_(3)]ClO_(4)}_(n)(2)that could never be grown to a crystal size large enough for single-crystal X-ray diffraction characterization.The compounds crystallize as nanocrystals upon addition of triflate(1)and perchlorate(2)anions and coordination of manganese(Ⅱ)with bis-chelate nitronyl nitroxide radicals NITImH(1)and NITImHMe_(2)(2)which are respectively 2-(2-imidazolyl)-and 2-(4,5-dimethylimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl.The two compounds have layered crystal structures in which cationic 2D metal-radical coordination polymers{[Mn2^(Ⅱ)(NITIm)_(3)]^(+)}_(n)(1)and{[Mn2^(Ⅱ)(NITImMe_(2))_(3)]^(+)}_(n)(2)are separated by layers of triflate(1)or perchlorate(2)anions.Magnetic measurements evidence a ferrimagnetic behavior within the 2D metal-radical sheets due to alternating antiferromagnetically coupled spins(S_(Mn)^(2+)=5/2 and S_(radical)=1/2).Both compounds exhibit a long-range 3D ordering of weak-ferromagnetic type due to spin canting with Curie temperatures T_(c)=45 K(1)and 40 K(2).This is associated with a field-induced metamagnetic transition from antiferromagnetic to ferromagnetic coupling of 2D metal-radical sheets.Studies of the crystal structures allows to rationalize how the molecular structure of nitronyl nitroxide radicals and of the counter-anions along with crystal packing affect the magnetic behavior related to interlayer distance and framework flexibility.These results are striking evidence that electron crystallography is a unique tool to solve structures of metal-organic compounds crystallizing as nanocrystals even with nitronyl nitroxide radical components too sensitive to typical electron doses.Overcoming the crystal size barrier,it allows the validation of chemical synthesis and the establishment of magneto-structural relationships fostering new advances in the design of molecule-based magnets.展开更多
基金supported by CNRS collaborative research program(PRC 2017-2019 No.1536)the Russian Science Foundation(grant No.21-73-20079)+6 种基金Magdesign Project(ANR-22-CE29-0018-03)Platforms of the Grenoble Instruct-ERIC center(ISBG,UAR 3518 CNRS-CEA-UGA-EMBL)within the Grenoble Partnership for Structural Biology(PSB)supported by FRISBI(ANR-10-INBS-0005-02)GRAL,financed within the University Grenoble Alpes graduate school(Ecoles Universitaires de Recherche)CBH-EUR-GS(ANR-17-EURE-0003)The IBS-ISBG electron microscope facility is supported by the Région Auvergne-Rhône-Alpes,Fondation pour la Recherche Médicale(FRM),Fonds FEDER and the GIS-Infrastructures en Biologie Santéet Agronomie(IBiSA)supported by Grant-in-Aid for Scientific Research(No.25220803 and 22H02053)CResCent(Chirality Research Center)in Hiroshima University(the MEXT program for promoting the enhancement of research universities,Japan)Core-to-Core Program,A.Advanced Research Networks.
文摘Low-dose electron diffraction has been instrumental in determining the crystal structures of two compounds with metal-radical coordination frameworks{[Mn2^(Ⅱ)(NITIm)^(3)]CF^(3)SO_(3)·CH^(3)OH}n(1)and{[Mn_(2)^(Ⅱ)(NITImMe_(2))_(3)]ClO_(4)}_(n)(2)that could never be grown to a crystal size large enough for single-crystal X-ray diffraction characterization.The compounds crystallize as nanocrystals upon addition of triflate(1)and perchlorate(2)anions and coordination of manganese(Ⅱ)with bis-chelate nitronyl nitroxide radicals NITImH(1)and NITImHMe_(2)(2)which are respectively 2-(2-imidazolyl)-and 2-(4,5-dimethylimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl.The two compounds have layered crystal structures in which cationic 2D metal-radical coordination polymers{[Mn2^(Ⅱ)(NITIm)_(3)]^(+)}_(n)(1)and{[Mn2^(Ⅱ)(NITImMe_(2))_(3)]^(+)}_(n)(2)are separated by layers of triflate(1)or perchlorate(2)anions.Magnetic measurements evidence a ferrimagnetic behavior within the 2D metal-radical sheets due to alternating antiferromagnetically coupled spins(S_(Mn)^(2+)=5/2 and S_(radical)=1/2).Both compounds exhibit a long-range 3D ordering of weak-ferromagnetic type due to spin canting with Curie temperatures T_(c)=45 K(1)and 40 K(2).This is associated with a field-induced metamagnetic transition from antiferromagnetic to ferromagnetic coupling of 2D metal-radical sheets.Studies of the crystal structures allows to rationalize how the molecular structure of nitronyl nitroxide radicals and of the counter-anions along with crystal packing affect the magnetic behavior related to interlayer distance and framework flexibility.These results are striking evidence that electron crystallography is a unique tool to solve structures of metal-organic compounds crystallizing as nanocrystals even with nitronyl nitroxide radical components too sensitive to typical electron doses.Overcoming the crystal size barrier,it allows the validation of chemical synthesis and the establishment of magneto-structural relationships fostering new advances in the design of molecule-based magnets.
