Mononuclear Single-Molecule Magnets: Tailoring the Magnetic Anisotropy of First-Row Transition-Metal Complexes

Abstract

Magnetic anisotropy is the property that confers to the spin a preferred direction that could be not aligned with an external magnetic field. Molecules that exhibit a high degree of magnetic anisotropy can behave as individual nanomagnets in the absence of a magnetic field, due to their predisposition to maintain their inherent spin direction. Until now, it has proved very hard to predict magnetic anisotropy, and as a consequence, most synthetic work has been based on serendipitous processes in the search for large magnetic anisotropy systems. The present work shows how the property can be predicted based on the coordination numbers and electronic structures of paramagnetic centers. Using these indicators, two Co(II) complexes known from literature have been magnetically characterized and confirm the predicted single-molecule magnet behavior.

Field-Induced Single-Ion Magnet Behaviour in Two New Cobalt(II) Coordination Polymers with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

“…The best fit using Anisofit2.0 [28] gave D = 36.5 cm −1 , E = 0.01 cm −1 , and g = 2.351 for 1, and D = 56.8 cm −1 , E = 0.1 cm −1 , and g = 2.34 for 2, which agrees well with the fitting results by PHI. For mononuclear octahedral Co II SIMs, positive and negative D values were both observed experimentally and confirmed by theoretical calculations [29]. In addition, to gain a clear scope on reported non-isolated Co II SIMs, the magnetic properties of these systems, including magnetic anisotropy parameters and energy barriers, are compiled in Table S3.…”

Band-filling effect on magnetic anisotropy using a Green's function method

“…Since we are using a same half-width w of LDOS for m=±1 and m=±2 subbands, we haveK N i ≈ 1 4K F e because of the intra-|m| transitions coefficients m 2 , as shown in Eqns. (5,9). Fig.…”

“…If it is dominated by χ ↓↓ , then the system has a larger orbital moment along the easy axis and we have K= Using the expressions of coefficients in Eqns. (5,6), for a d-orbital system, Eq. (9) can be written as…”

Comparative Magnetic Studies in the Solid State and Solution of Two Isostructural 1D Coordination Polymers Containing CoII/NiII-Curcuminoid Moieties

“…Regarding SMMs, a fast-growing number of mononuclear 3d/4f compounds that display slow relaxation of the magnetization have recently been introduced [7][8][9]. In this regard, the use of external magnetic fields to cancel an often-present fast zero-field relaxation of the magnetization [10,11], as well as the observation www.mdpi.com/journal/magnetochemistry of frequency dependence in 3D mononuclear species with negative but also positive [12,13] zero-field splitting (D) values, have been key factors toward the development of the subject. Indeed, the SMM character of compounds with a positive D parameter has shaken up a well-established requirement for the occurrence of this unique behaviour.…”

“…Even though this aspect is still at a premature stage, it will make possible the anticipation of the results. Indeed, nowadays there are models that predict mononuclear 3d-SMMs in a rationalized way [10], and therefore, using such information with the right organic connectors, we may be able to tune SCM behaviour as well. Nevertheless, the proper progress of this subject requires a deep insight regarding extra factors that can affect the final properties [3][4][5][6]13,14].…”