Holmium(III) Single-Ion Magnet for Cryomagnetic Refrigeration Based on an MRI Contrast Agent Derivative

Abstract

The coexistence of field-induced blockage of the magnetization and significant magnetocaloric effects in the low-temperature region occurs in a mononuclear holmium(III) diethylenetriamine- N , N , N ′, N ″, N ″-pentaacetate complex, whose gadolinium(III) analogue is a commercial MRI contrast agent. Both properties make it a suitable candidate for cryogenic magnetic refrigeration, thus enlarging the variety of applications of this simple class of multifunctional molecular nanomagnets.

Magnetocaloric efficiency tuning through solvent-triggered 3D to 2D interconversion in holmium(iii)-based dynamic MOFs

“…3), being even farther than that found for the Ho(III)/Na(I)based 3D MOF of formula {[Na 2 Ho III (DTPA)(H 2 O)]Á8H 2 O} n (DTPA = diethylenetriamine-N,N,N 0 ,N 00 ,N 00 -pentaacetate) [T m = 3.2-9.5 K for DH = 2-8 T]. 2 The overall enhancement of the optimal working temperature in the order 3 o 1 o 2 is just the opposite to that mentioned above for the ÀDS M values. This feature is also related to the MCE efficiency and, eventually, to the practical applications of Ho III sesquioxalates as cryomagnetic coolers operating near the strategically relevant H 2 liquefaction.…”

“…9 Our research focuses on the well-known family of neutral two-and three-dimensional (nD, n = 2 and 3) lanthanide(III) sesquioxalate hydrates (Scheme S1, ESI †). 10,11 Herein we report the synthesis, general physico-chemical and structural characterization, thermal stability and water sorption behavior, as well as magnetic and magnetothermal properties of the holmium(III) sesquioxalates hydrates of general formula {[Ho 2 (ox) 3 (H 2 O) 6 ]ÁxH 2 O} n [x = 4 (1) and 12 (2)]. Interestingly, a structural interconversion is found within this solvatomorphic pair of neutral oxalato-bridged holmium(III)-based 2D (1) and 3D (2) MOFs upon dehydration/rehydration, which is accompanied by a dramatic magnetocaloric solvatoswitching behavior.…”

“…The metal coordination polyhedra for 1 and 2 are intermediate between tricapped trigonal prism (TCTPR) and monocapped square antiprism (CSAPR) of approximate D 3h and C 4v molecular symmetries (Tables S2 and S3, ESI †). 12 The continuous shape measures (CShM) 13 slightly (1) or markedly (2) favor the TCTPR over the CSAPR geometry with a spherical-type distortion of the regular (Johnson-type) polyhedron (Tables S2-S4 and Fig. S3, ESI †).…”

“…Lanthanide-based metal–organic frameworks (Ln MOFs) have attracted considerable attention in the last two decades because of their potential technological applications in cryogenic magnetic refrigeration (CMR). 1 Nowadays, the attention in this field is moving toward magnetically anisotropic holmium( iii )-based MOFs, 2 because they exhibit magnetocaloric effects (MCE) at higher temperatures than their largely investigated magnetically isotropic gadolinium( iii ) counterparts. 3,4 In this respect, metallic holmium itself and the related intermetallic alloys HoB 2 , HoAl 2 and Ho(Co,Ni,Fe) 2 are proposed as efficient cryomagnetic coolers operating between the strategically relevant hydrogen and nitrogen liquefaction temperatures, 5–8 in place of traditional oxides, such as gadolinium( iii )–gallium( iii ) garnet (GGG) and its dysprosium( iii )-substituted derivatives of general formula (Dy x Gd 1− x ) 3 Ga 5 O 12 [ x = 0 (GGG), 0.5 (DGGG), and 1 (DGG)], working between the helium and hydrogen liquefaction temperatures.…”

One-Dimensional Gadolinium (III) Complexes Based on Alpha- and Beta-Amino Acids Exhibiting Field-Induced Slow Relaxation of Magnetization

“…Heterometallic 3d-4f mixed systems, radical bridged compounds, mono-and polynuclear lanthanide (III) complexes containing highly anisotropic 4f ions, mainly Dy (III) and to a lesser extent Tb (III), Ho (III) and Er (III), were investigated during the last two decades in the field of molecular magnetism [9][10][11][12][13][14][15][16][17]. More recently, mononuclear SMMs, also known as single-ion magnets (SIMs), based on dysprosium metallocenes were reported displaying energy barriers of magnetization reversal exceeding the 1500 cm -1 value and blocking temperatures as high as that of the liquid nitrogen (>77 K), which exemplify the current progress in this research area [18,19].…”