Photomagnetism in Clusters and Extended Molecule-Based Magnets

Abstract

Photomagnetism in molecular systems is a new development in molecular magnetism. It traces back to 1982 and 1984 when a transient effect and then the light-induced excited-spin-state-trapping effect was discovered in spin-crossover complexes. The present contribution gives a definition of the phenomenon, a process that changes the magnetism of a (molecular) system after absorption of a photon. It is limited to the discussion of photomagnetism based on metal-metal electron transfer in clusters and extended molecule-based magnets. The paper is organized around the main pairs of spin bearers, which allowed us to evidence and to study the phenomenon: Cu-Mo, Co-Fe, and Co-W. For each metallic pair, we report and discuss the conditions of appearance of the effect and its characteristics, both in extended structures and in molecular units: structure, spectroscopy, magnetism, thermodynamics and kinetics, and applications. We conclude with some brief prospects. The field is in rapid expansion. We are convinced that the interaction of photons with magnetized matter, to provide original magnetic properties, will meet more and more interest in the future.

Switching Magnetic Properties by a Mechanical Motion

“…Apart from temperature and light, chemical [25], electrical [26], or pressure [27] stimuli have also been used to induce a spin crossover. 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.…”

The First Homoleptic Complex of Seven-Coordinated Osmium: Synthesis and Crystallographical Evidence of Pentagonal Bipyramidal Polyhedron of Heptacyanoosmate(IV)

“…Inspired by a successful ligand exchange preparation of (n-Bu 4 N) 3 [Re IV (CN) 7 ] performed by M.V. Bennett and J.R. Long [36], we have adapted this procedure for the synthesis of osmium cyanides starting from (n-Bu 4 N) 2 Os IV Cl 6 .…”

“…Almost 300 years later this compound, the mixed iron cyanide Fe III 4 [Fe II (CN) 6 ] 3 ·xH 2 O, named Prussian Blue became a focus of one of the most developed and extensively studied fields of coordination chemistry [4,5]. Cyanide-based compounds were found to act as photoswitchable magnetic solids [6][7][8][9][10], antidotes for radioactive poisoning [11], molecular sieves [12], hydrogen storage materials [13,14], high-temperature molecular magnets [15][16][17] and low-dimensional nanomagnets [18][19][20][21][22].…”

“…Moreover, the homoleptic coordination compounds of Os with purely inorganic ligands comprise mainly hexaligated complexes, unlike its nearest neighbor of the 5d row, Re, which demonstrates coordination numbers from six to eight [33][34][35][36]. The recent isolation of heptacyanotungstate(IV) as a salt (n-Bu 4 N) 3 [W IV (CN) 7 ] (n-Bu 4 N = tetra-n-butylammonium) [37] has widened the family of rare heptacyanometallate anions. tetra-n-butylammonium) [37] has widened the family of rare heptacyanometallate anions.…”

“…tetra-n-butylammonium) [37] has widened the family of rare heptacyanometallate anions. Here, we present the pioneering results in osmium coordination chemistry involving the synthesis and exhaustive structural study of the (n-Bu4N)3[Os IV (CN) 7], (1)-the only homoleptic complex with heptacoordinated osmium (Figure 1), which also represents the first example of fully characterized cyanoosmate(IV).…”