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Review
. 2012;88(6):213-25.
doi: 10.2183/pjab.88.213.

Switchable molecular magnets

Osamu Sato  1
Affiliations
Review

Switchable molecular magnets

Osamu Sato. Proc Jpn Acad Ser B Phys Biol Sci. 2012.

Abstract

Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes.

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Figures

Figure 1.
Figure 1.
Structure of the unit cell of a Prussian blue analog (M and M′ denote metal ions). Random distribution of [M(CN)6]n− vacancies is omitted for clarity.
Figure 2.
Figure 2.
Field-cooled magnetization versus temperature curves before electrochemical reduction (solid symbols, right axis) and after electrochemical reduction (open symbols, left axis). The material property can be switched from ferrimagnetism and paramagnetism between 100 and 240 K. We should note that although SI unit is recommended to be used in scientific journals, cgs unit “G” is used in this Fig. 2 and Fig. 3. This is because cgs unit is usually used in the field of molecular magnetism.
Figure 3.
Figure 3.
(a) χMT versus T for Na0.07Co1.50Fe(CN)6·6.3H2O (Co/Fe = 1.50), Na0.37Co1.37Fe(CN)6·4.8H2O (Co/Fe = 1.37), and Na0.94Co1.15Fe(CN)6·3.0H2O (Co/Fe = 1.15) during cooling and warming at H = 5000 G. (b) Field-cooled magnetization curves for Na0.37Co1.37Fe(CN)6·4.8H2O (Co/Fe = 1.37) before (●) and after (○) light irradiation at H = 5 G.
Figure 4.
Figure 4.
(a) Top: Side view of [{FeIII(Tp)(CN)3}4{FeII(MeCN)(H2O)2}2]·10H2O·2MeCN. Bottom: Side view of [FeIII(Tp)(CN)3]4FeII(H2O)2FeII with 1-D double zigzag chain structure after heating. (b) M versus H plots at 2 K for [{FeIII(Tp)(CN)3}4{FeII(MeCN)(H2O)2}2]·10H2O·2MeCN (■) and [FeIII(Tp)(CN)3]4FeII(H2O)2FeII (●).
Figure 5.
Figure 5.
Temperature-dependent susceptibilities of [FeTp(CN)3]2Co(bpe) (line), and [FeTp(CN)3]2Co(bpe)·5H2O (□). (Inset) Side view of the double zigzag chain in [FeTp(CN)3]2Co(bpe)·5H2O along the c axis.
Figure 6.
Figure 6.
(a) Molecular structure of [{Mn(salen)}6{Fe(bpmb)(CN)2}6]·7H2O. (b) Hysteresis loop at different temperatures measured at a scan magnetic field speed of 0.14 T s−1.
Figure 7.
Figure 7.
(a) Side view of the 1-D double zigzag chain of the FeCo complex. (b) Temperature dependence of the imaginary part of ac susceptibility after irradiation in zero dc field at varying ac frequency and a 3 Oe ac field.
Figure 8.
Figure 8.
Photomagnetic behavior: χMT of [Fe(pap)2]PF6·MeOH as a function of temperature on cooling (▽), after irradiated at 5 K and warming up (▲).30)
Figure 9.
Figure 9.
μeff versus T plots before and after illumination. Inset: changes in the magnetization at 5 K. Variables hν and Δ represent illumination at 5 K and thermal treatment at 60 K, respectively.
Figure 10.
Figure 10.
(a) Splitting of d orbitals of high- and low-temperature phases. (b) Temperature dependence of χMT in cooling (○) and heating mode (●).
Figure 11.
Figure 11.
Temperature dependence of χMT–T plots and photoinduced changes after irradiation at 532 nm (inset).
Figure 12.
Figure 12.
Temperature dependence of χMT–T plots and photoinduced changes after irradiation at 532 nm (inset).
See this image and copyright information in PMC

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