Large Room Temperature Magnetization Enhancement in a Copper-Based Photoactive Metal–Organic Framework

Abstract

The tris­(pyridin-4-yl)­amine ligand was found to exhibit a radical-actuated coloration phenomenon, and a novel copper-based color-changeable metal–organic framework (MOF) was synthesized via this photoactive ligand. After light irradiation, the photogenerated stable radicals in this framework induced increasing amplitude of magnetization (32%) at room temperature, being the largest enhancement among radical-based photochromic systems.

Photoinduced Significant Magnetization Enhancement in a Viologen-Based Photochromic Compound

“…Interestingly, the χ M T value after irradiation in the entire temperature range increased, and at 300 K it improved to 17.76 cm 3 ·mol –1 ·K and was 31.1% higher than that of the as-synthesized sample, displaying a clear photomagnetization effect after photochromism. This high moment should originate from the photogenerated radicals and the appreciable ferromagnetic coupling between paramagnetic centers even at RT, similar to other radical-based photomagnetic complexes. , And such amplification is the second largest enhancement among the reported radical-based photomagnetic complexes …”

“…This high moment should originate from the photogenerated radicals and the appreciable ferromagnetic coupling between paramagnetic centers even at RT, similar to other radical-based photomagnetic complexes. 26,28 And such amplification is the second largest enhancement among the reported radical-based photomagnetic complexes. 26 Field-dependent magnetization at 2, 3, 5, and 10 K for 1 was performed before and after photo irradiation.…”

“…26,28 And such amplification is the second largest enhancement among the reported radical-based photomagnetic complexes. 26 Field-dependent magnetization at 2, 3, 5, and 10 K for 1 was performed before and after photo irradiation. As seen in Figure 4, before irradiation, the field dependence of the magnetization value is 5.4 Nβ at 2 K, which is lower than the saturation value of 10 Nβ for one Dy 3+ ion.…”

“…The use of an electron transfer photochromic viologen ligand stems from its minor structural change and the formation of free radical species during the coloration process. A minor structural change is less impacted by the steric space and thus more suitable for solid-state magnetic media. , More importantly, a photoinduced radical can magnetically couple with paramagnetic metal centers and further provoke amazing magnetic behavior such as photoinduced magnetic thermal hysteresis, magnetic phase transition, single-molecule magnetism on/off, , and magnetization change. − Large enhancement of magnetization at room temperature is highly desirable for real application of photomagnets because it can improve the materials’ storage density. However, until now only three electron transfer photochromic compounds show a large increase above 20% at RT; ,, it is still a challenge to achieve a photoinduced remarkable increase in the magnetization around RT.…”

“…materials' storage density. However, until now only three electron transfer photochromic compounds show a large increase above 20% at RT; 18,24,26 it is still a challenge to achieve a photoinduced remarkable increase in the magnetization around RT.…”