Crystal structures and magnetic properties of a nitronyl nitroxide and of its imino analog. Crystal packing and spin distribution dependence of ferromagnetic intermolecular interactions

Role of the demagnetizing field on the EPR of organic radical magnets

“…The structural and magnetic properties of this compound are published elsewhere. 13 The PymNN crystallizes in the tetragonal space group P4 2 bc. The magnetic properties may be represented by a one-dimensional ferromagnetic chain with an intrachain exchange of ϩ26.2 K and a weaker antiferromagnetic interchain coupling of Ϫ1.1 K. The studied sample has a needle shape elongated along the c axis ͑Fig.…”

Two-Dimensional Nitroxide-Based Molecular Magnetic Materials

“…The angles involving the nonbridging methyl groups, C3-Al1-C4, C7-Al2-C8, and C11-Al3-C12 (119.2(15), 116.8 (13), and 119.0(13)8, respectively), are considerably larger than the other C-Al-C angles. [19] The bridging Nd ± H distance can be estimated from the difference between NdÀC (2.77 ) [20] and ThÀC (2.83 ) [21] bond lengths in various Nd and Th cyclopentadienyl complexes, combined with the bridging Th ± H distance (2.29 ) in [{ThH 2 Cp* 2 } 2 ]. [21] This yields a value for Nd ± H bond distance of 2.23 .…”

“…[19] The bridging Nd ± H distance can be estimated from the difference between NdÀC (2.77 ) [20] and ThÀC (2.83 ) [21] bond lengths in various Nd and Th cyclopentadienyl complexes, combined with the bridging Th ± H distance (2.29 ) in [{ThH 2 Cp* 2 } 2 ]. [21] This yields a value for Nd ± H bond distance of 2.23 . Alternatively, if the difference between the ionic radii [22] of Nd III (1.16 , nine-coordinate) and Th IV (1.09 ) is used, an estimated Nd ± H distance of 2.36 is obtained.…”

“…[20] 3) Finally, direct through-space intramolecular interactions between the nitroxide ligands within the metal coordination spheres (O1A ± O1B 3.29(4) ) are difficult to quantify but can be rather large. [21,22] Therefore, no unambiguous correlation can be found between exchange interactions and structural parameters, but comparison of the high-and lowtemperature structures suggests that at lower temperature slight structural changes lessen the average coupling constant within the layers. Nevertheless, the low magnetic susceptibility at 400 K and the low magnetization at 5 K indicate that ferrimagnetic coupling occurs in both Curie ± Wiess regions of 1 and that such a coupling scheme holds for the other compounds in the series.…”

Zweidimensionale, molekulare magnetische Materialien auf Nitroxidbasis

“…[20] 3) Direkte intramolekulare Wechselwirkungen zwischen Nitroxidliganden durch den Raum und innerhalb der Koordinationssphären der Metallzentren sind schwer quantifizierbar, können aber recht stark sein. [21,22] Demzufolge läût sich keine eindeutige Zuordnung zwischen Austauschwechselwirkungen und Strukturparametern treffen, dem Vergleich der Hochund Niedertemperaturphase können aber Hinweise dafür entnommen werden, daû bei abnehmender Temperatur die durchschnittliche Kopplungskonstante innerhalb der Schichten wegen geringfügiger Strukturänderungen abnimmt. Dennoch weisen die niedrige magnetische Suszeptibilität bei 400 K sowie die geringe Magnetisierung bei 5 K darauf hin, daû ferrimagnetische Kopplungen in beiden Curie-Weiss-Bereichen von 1 auftreten, was auch für die anderen Verbindungen dieser Serie gilt.…”