Mixed-valence {FeII2FeIII4} hexanuclear complexes with thermally induced Fe(iii) spin-crossover behavior

Abstract

Cyano-bridged mixed-valence {Fe6} hexanuclear complexes {[Tp4-MeFeII(CN)3]2[FeIII(Tpa)]2[FeIII(OR)(Tpa)]2}·6ClO4·S {Tp4-Me = tri(4-methyl-pyrazol-1-yl)borate, Tpa = Tris(2-pyridylmethyl)amine; R = -CH3 S = 8MeOH 1, R = -C2H5 S = 6EtOH 2 } have been obtained...

Cyanido-Bridged Heterobimetallic Molecular Squares: Low-Dimensional Models of Prussian Blue Analogues and Beyond

“…Consequently, the d - d / d ′ squares became a very fruitful research area devoted to the magnetic behavior of the tetranuclear PBAs. Among the cyanido building-blocks, the dicyano-[Fe II/III (AA) 2 (CN) 2 ] n+ (AA = didentate ligand; n = 0 and 1) − and tricyano- fac -[M­(CN) 3 {RB­(R′(pz) 3 }] (R = H, methyl, 2-methyl propyl, pyrazol; R′ = H, methyl) derivatives − proved to be suitable to synthesize molecular squares in their reactions with 3 d metal ions whose coordination sphere is partially blocked with didentate AA ligands, such as bipy, 4,4′-dimethyl 2,2′-bipyridine (4,4′-Me 2 bipy), and 1,10-phenantroline (phen) or a tridentate one coordinated to the M III cation in a fac stereochemistry.…”

“…The cyanido-based fac -[Fe III (CN) 3 {RB­(R 1–3 (pz) 3 }] − complexes, bearing three coordination sites blocked by the pyrazolylborate type ligand and three terminal cyanide groups in a fac arrangement, were extensively used to assemble molecular squares (R = H, 2-methylpropyl, pyrazol; R 1,2,3 = H, methyl; Scheme ). Therefore, the resulting d - d / d ′ square-like tetranuclear compounds became a rich area of investigation of reversible thermal-/light-/X-ray induced magnetism, ,− spin crossover, − as well as slow relaxation of the magnetization and SMM properties. − …”

“…Also, the mixed-valence {[{HBR 4 (pz) 3 }­Fe II (CN) 3 ] 2 [Fe III (tpa)] 2 [Fe III (OR′)­(tpa)] 2 }­(ClO 4 ) 6 ·Sol hexanuclear complexes decorated with Fe III -bearing arms were obtained from a similar Fe III tricyanide linker, the six-coordinate [{HBR 4 (pz) 3 }­Fe III (CN) 3 ] − metalloligand, in its reaction with the [Fe II (tpa)] 2+ complex cation (R′ = −CH 3 and −C 2 H 5 with Sol = 8MeOH and 6EtOH molecules, respectively). This represents a rare example in which the SCO is due to the Fe III ions at the corners of the square-like core of the hexanuclear compounds (Figure b) …”

“…Views of the cyanido-bridged mixed-valence (a) square-shaped tetranuclear unit {[{HBR 3,5 (pz) 3 }­Fe III (CN) 3 ] 2 [Fe II (TPPO)­(NCX)] 2 } and (b) hexanuclear entity {[{HBR 4 (pz) 3 }­Fe II (CN) 3 ] 2 [Fe III (tpa)] 2 [Fe III (OR′)­(tpa)] 2 } 6+ with an inner square motif …”

First crystal structure of an Fe(iii) anionic complex based on a pyruvic acid thiosemicarbazone ligand with Li+: synthesis, features of magnetic behavior and theoretical analysis

“…[1][2][3] Spin-crossover compounds represent an important direction of research in the development of new high-tech materials because they can exhibit a spin response to changes in external conditions (temperature, pressure, light irradiation, etc.). [4][5][6] Among the SCO compounds based on Fe(III) with d 5 electron configuration, complexes with an octahedral coordination sphere are the most common and demonstrate the SCO transition from the low-spin state (LS, S = 1/2) to the high-spin state (HS, S = 5/2). 7 A rich chemical diversity of Schiff bases allows one to tune the degree of iron(III) ion σ-/π-bonding with the ligand environment in order to change the splitting energy † Electronic supplementary information (ESI) available: Photo of the ligand and powder of 1 and 2 (Fig.…”