High temperature Fe(iii) spin crossover behaviours in three unprecedented Fe^III–M^II–Fe^III(M = Fe, Cd) linear trinuclear complexes

Abstract

An azo-based ligand of azotetrazolyl-2,7-dihydroxynaphthalene (H3ATD) was used to synthesize three FeIII–MII–FeIII (M = Fe, Cd) linear trinuclear complexes with different high temperature spin crossover (SCO) behaviours for the terminal FeIII ions.

Anion Modified Spin Crossover in [Fe(qsal-4-F)]+ Complexes with a 4-Position Substituted Qsal Ligand

“…Compared with the Fe II SCO systems prone to oxidation, Fe III compounds have the advantage of generally being air-stable and thus may be expected to form more robust materials. , In the case of Fe III SCO complexes, the thermally induced SCO is associated with a switch between the S = 1/2 (LS) and S = 5/2 (HS) spin states. , Importantly, although the change of the spin value is the same (Δ S = 2) as that in the Fe II complexes, the changes of the spin entropy (9.13 J K –1 mol –1 ) and the metal–ligand bond lengths (0.10–0.13 Å) during the spin transition in the Fe III complexes are both significantly smaller than those in the Fe II complexes (13.38 J K –1 mol –1 and typically around 0.20 Å). These differences lead to significantly different behaviors of the Fe III SCO complexes, such as the rapid spin interconversion rates between the LS and HS states, difficulty to achieve Fe III SCO complexes with abrupt SCO transition, and rare observation of the LIESST effects. ,, To fulfill the desired ligand field for the SCO transition, a suitable coordination donor set is required, which is usually an N 6 donor set for the Fe II system and an N 4 O 2 donor set for the Fe III system. , Experimentally, the N 4 O 2 environment for the Fe III SCO system is usually realized by the coordination of two tridentate Schiff-base ligands, which are often easily prepared from salicylaldehyde and different amines. Among these Schiff-base ligands, the N -quinolylsalicylaldimine (Hqsal) ligand has been studied most widely, generating many interesting SCO materials of outstanding performances. , Many of these materials exhibit abrupt, hysteresis, and/or stepwise SCO behaviors.…”

Metal–cyanide hybrid materials exhibiting photochromic and photomagnetic responses based on viologen receptors

“…[19][20][21] These anionic metal complexes have also been utilized in creating bimetallic compounds, incorporating lanthanide (Ln) elements as the secondary metal component. [22][23][24] In previous studies, Guo's group 24 reported a photochromic and photomagnetic hexacyanoferrate with an 18-crown ether ligand that exhibited light-induced color change and magnetism at room temperature; however, a decrease in magnetization was observed post-irradiation. Subsequently, they developed a photoreactive semiconductor by cyanide-bridged Mn II -Fe III or Zn II -Fe III layers and viologen that responds to a broad spectrum of light (UV-SWIR).…”

Solvent effect on the structures of three manganese complexes based on azotetrazole-3-hydroxy-2-naphthoic acid: synthesis, structures, and magnetic and fluorescent properties

“…Taking this into consideration, tetrazole and its derivatives, which possess multiple coordination modes, can act as preeminent candidates. [49][50][51] In this study, we synthesized a tetrazole derivative ligand, namely azotetrazole-3-hydroxy-2-naphthoic acid (H 3 ATNA) (Scheme 1), and obtained three Mn complexes by changing the solvents: Mn 2 (HATNA) 2 (CH 3 OH) 4 (1),…”

“…Taking this into consideration, tetrazole and its derivatives, which possess multiple coordination modes, can act as preeminent candidates. 49–51 In this study, we synthesized a tetrazole derivative ligand, namely azotetrazole-3-hydroxy-2-naphthoic acid (H 3 ATNA) (Scheme 1), and obtained three Mn complexes by changing the solvents: Mn 2 (HATNA) 2 (CH 3 OH) 4 ( 1 ), {[Mn 3 (ATNA) 2 (DMF) 2 (H 2 O) 2 ]·0.5DMF·0.5H 2 O} n ( 2 , DMF = N , N -dimethylformamide), {[Mn 6 (ATNA) 4 (H 2 O) 10 ]·8DMSO·2.5H 2 O} n and ( 3 , DMSO = dimethyl sulphoxide). Complex 1 possessed a dinuclear structure with two Mn( ii ) ions that were doubly bridged through N–N linkers from the two tetrazole rings.…”