How to Switch Spin‐Crossover Metal Complexes at Constant Room Temperature

Abstract

Spin-crossover metal complexes represent a highly promising class of molecular switches, the diverse physicochemical properties of which can be reversibly changed by different physical and chemical stimuli. One of the most interesting and examined features of these materials is the change of magnetic properties by changing the temperature or by irradiation with light at low temperatures. However, most prospective applications of such complexes require functioning at room temperature. This Concept article provides an overview about how the switching of spin-crossover metal complexes can be achieved at constant room temperature. The principles of switching by different physical and chemical methods in solution and in the solid state are presented in an easy-to-read form for nonspecialists. These are further supported and clarified by examples from the literature. The overview might also be interesting for experts that target spin-crossover systems functioning at ambient conditions.

Rational Design of Electronically Labile Dinuclear Fe and Co complexes with 1,10‐Phenanthroline‐5,6‐Diimine: A DFT study

“…Due to lability of their electronic shells transition metal coordination compounds with switchable magnetic properties represent key substructures of molecular electronics and spintronics devices . They have a good application prospect as single‐ion and single‐molecule magnets, molecular switches, sensors, and logical elements of quantum computers . Among the magnetically active systems, a special place is belonged to the transition metal complexes with redox‐active (noninnocent ) ligands, in which proximity of energy levels of the metal valence d ‐electrons and frontier molecular orbitals of the ligand creates opportunities for low‐energy barrier intramolecular electronic transfers (IETs).…”

Switching Magnetic Properties by a Mechanical Motion

“…Spin-crossover complexes [16][17][18][19][20] are particularly interesting for such purpose, as they can exist in two stable spin states and have been largely studied. Even if spin-crossover behavior is theoretically expected to occur in octahedral complexes with 3d 4 to 3d 7 electronic configurations, most spin-crossover complexes are based on Fe(III), Fe(II), and Co(II), with only few reported examples of compounds of Mn(II), Mn(III), Cr(II), and Co(III).…”

“…Several stimuli have been used to trigger magnetic properties changes [3] in three main areas: (i) changing the spin state of a transition metal in spin crossover (SCO) systems [4][5][6][7][8][9][10][11]; (ii) switching the exchange interaction between different spin carriers [12,13]; and (iii) switching single-molecule magnet (SMM) properties [14,15]. Spin-crossover complexes [16][17][18][19][20] are particularly interesting for such purpose, as they can exist in two stable spin states and have been largely studied. Even if spin-crossover behavior is theoretically expected to occur in octahedral complexes with 3d 4 to 3d 7 electronic configurations, most spin-crossover complexes are based on Fe(III), Fe(II), and Co(II), with only few reported examples of compounds of Mn(II), Mn(III), Cr(II), and Co(III).…”

Photo‐ and Electronically Switchable Spin‐Crossover Iron(II) Metal–Organic Frameworks Based on a Tetrathiafulvalene Ligand

“…[32] Framework 2 shows a( 4,6)connected binodal sqc11-type 3D structure,a nd ac rystal-tocrystal structure transformation by I 2 doping has been observed for the first time in this type of material. [32] Framework 2 shows a( 4,6)connected binodal sqc11-type 3D structure,a nd ac rystal-tocrystal structure transformation by I 2 doping has been observed for the first time in this type of material.…”