A Trigonal Prismatic Mononuclear Cobalt(II) Complex Showing Single-Molecule Magnet Behavior

Abstract

Single-molecule magnets (SMMs) with one transition-metal ion often rely on unusual geometry as a source of magnetically anisotropic ground state. Here we report a cobalt(II) cage complex with a trigonal prism geometry showing single ion magnet behavior with very high Orbach relaxation barrier of 152 cm(-1). This, to our knowledge, is the largest reported relaxation barrier for a cobalt-based mononuclear SMM. The trigonal prismatic coordination provided by the macrocyclic ligand gives intrinsically more stable molecular species than previously reported SMMs, thus making this type of cage complexes more amendable to possible functionalization that will boost their magnetic anisotropy even further.

Trigonal antiprismatic Co(ii) single molecule magnets with large uniaxial anisotropies: importance of Raman and tunneling mechanisms

“…The D values are among the largest negative ones reported for mononuclear transition metal complexes 3–5 and comparable to those for the Co( ii ) ion in a trigonal prismatic geometry. 29,31,32 …”

“…2 Another interesting case is the work of Novikov and co-workers who reported a trigonal prismatic Co( ii ) cage complex with relaxation of the spin being observed at zero dc field and D values of –82, –109 and –110 cm –1 determined by a fit of magnetic susceptibility, NMR spectroscopy and from CASSCF/NEVPT2 calculations respectively. 32 An ongoing interest in this coordination geometry is apparent from recent literature. 32,54 …”

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

“…The double well model holds up in the case of monometallic cobalt(II) SMMs with negative D values [9,[11][12][13][14][15][16][17][18][19], but the observation of similar behaviour in monometallic cobalt(II) complexes with positive D values [20][21][22] suggests that the picture is more complex. Indeed, slow relaxation in positive-D compounds is a phenomenon that is not yet fully understood-although attempts have been made to explain it [23,24].…”

Molecular single-ion magnets based on lanthanides and actinides: Design considerations and new advances in the context of quantum technologies

“…Single-ion magnets (SIMs) are simply a subclass of SMMs wherein the electronic spin term originates from a single magnetic centre [7,8]. In SIMs, the ion bearing the spin is most commonly a transition metal [9][10][11][12][13], lanthanoid [14][15][16][17][18][19][20][21][22], or actinoid [23][24][25][26][27][28][29][30]. The term SIM is somewhat of a misnomer: all SIMs are molecular in nature since the ligand field is a vital prerequisite for their slow relaxation.…”