Modification of Cooperativity and Critical Temperatures on a Hofmann-Like Template Structure by Modular Substituent

Abstract

Abstract:In a series of Hofmann-like spin crossover complexes, two new compounds, {Fe(3-F-4-Methyl-py) 2 [Au(CN) 2 ] 2 } (1) and {Fe(3-Methyl-py) 2 [Au(CN) 2 ] 2 } (2) (py = pyridine) are described. The series maintains a uniform 2-dimentional (2-D) layer structure of {Fe[Au(CN) 2 ] 2 }. The layers are combined with another layer by strong aurophilic interactions, which results in a bilayer structure. Both coordination compounds 1 and 2 at 293 K crystallize in the centrosymmetric space groups P2 1 /c. The asymmetric unit contains two pyridine derivative ligands, one type of Fe 2+ , and two types of crystallographically distinct [Au(CN) 2 ] − units. Compound 1 undergoes a complete two-step spin transition. On the other hand, 2 maintains the characteristic of the high-spin state. The present compounds and other closely related bilayer compounds are compared and discussed in terms of the cooperativity and critical temperature. The bilayer structure is able to be further linked by substituent-substituent contact resulting in 3-dimentional (3-D) network cooperativity.

Systematic Design of Crystal Structure for Hofmann-Like Spin Crossover Fe(L)2[Ag(CN)2]2 Complexes

“…Despite the lattice expansion, these compounds completely maintain their bilayer structure. In a previous paper, we investigated the Fe-Au analogous series [16], which shows the same cell expansion tendency. In the present, we demonstrated the wider range of substituent sizes available to systematically construct the bilayer structure.…”

“…Suppressing the structural diversity is required to systematically design the crystal structure and clarify the structure-property relationships. Since 2000, many 2D layers ({Fe II (L) 2 [M I (CN) 2 ] 2 } n [5][6][7][8][9][10][11][12][13][14][15][16], where M I = Ag or Au, L = monodentate pyridine derivatives) have been developed. These compounds exhibit a crystallographically similar structure.…”

Structural Insights into the Two-Step Spin-Crossover Compound Fe(3,4-dimethyl-pyridine)2[Ag(CN)2]2

“…In turn, the use of the bicyclic ligand 1,6-naphthyridine, has allowed a wide thermal hysteresis centred near room temperature to be obtained [19]. In other closely related systems, also derived from [M I (CN) 2 ] -(M I = Ag, Au) building blocks, like Fe(3-F-4-methyl-py) 2 [Au(CN) 2 ] 2 [20] or Fe(4-(3-pentyl)py) 2 [Au(CN) 2 ] 2 [21], two-step transitions are also observed. Finally, opening the focus to the Fe(II) Hofmann-like coordination polymers constituted of [M II (CN) 4 ] 2-(MII = Ni, Pd, Pt) building blocks, multistep spin transitions are also found [22,23].…”

New Iron(II) Spin Crossover Complexes with Unique Supramolecular Networks Assembled by Hydrogen Bonding and Intermetallic Bonding

“…Therefore, control of structural diversity represents fundamental research in crystal engineering. Since we reported the first Hofmann like two-dimensional (2-D) SCO coordination polymer {Fe(py) 2 [Ni(CN) 4 ]} n (py = pyridine) [7], many 2-D layers of {Fe II (L) 2 [M I (CN) 2 ] 2 } n [8][9][10][11][12][13][14][15][16] (M I = Ag, or Au, L = monodentate pyridine derivatives) have been developed. These compounds show an almost similar bilayer structure because of their strongly determinate self-assembly process in which they link octahedral metal centers through the N atoms of the bidentate [Au(CN) 2 ] − unit with strong aurophilic interaction between layers.…”