Spin-Crossover Behavior in Two New Supramolecular Isomers

Abstract

Two spin-crossover (SCO) supramolecular isomers formulated as [Fe(Mebpt){Au(CN)2}]n·xH2O (1, x = 0, and 2·H2O, x = n, MebptH = 3-(5-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole) have been successfully isolated and characterized by single-crystal X-ray crystallography, thermogravimetric analysis, differential scanning calorimetry, variable-temperature powder X-ray diffraction, and magnetic measurements. Structural analysis reveals that 1 is a two-dimensional coordination layer and 2·H2O is a one-dimensional coordination ladder structure, in which the Mebpt(-) ligands are coordinated in trans and cis bridging mode in 1 and 2·H2O, respectively. Dramatically, their SCO properties are further influenced by the octahedral coordination configuration of Fe(II). In 1, only the Fe(II) centers in trans configuration exhibit spin transition (Tc = 303 K), while in 2·H2O and the dehydrated 2, gradual two-step SCO (Tc1 = 235 K, Tc2 = 313 K) and one-step SCO behaviors (Tc = 315 K) occur, respectively.

Coligand and Solvent Effects on the Architectures and Spin-Crossover Properties of (4,4)-Connected Iron(II) Coordination Polymers

“…53,76 It should be also mentioned that supramolecular isomeric structures may influence the SCO behaviors. 8,77,78 However, because of the lack of supramolecular 2D isomers for complexes 6 and 7 and supramolecular 3D isomers for complexes 8 and 9 at present, the effect of isomeric structure on SCO behaviors in system of [Fe(bpb) 2 (NCX) 2 ] is not yet clear.…”

Extension of Azine-Triazole Synthesis to Azole-Triazoles Reduces Ligand Field, Leading to Spin Crossover in Tris-L Fe(II)

“…Generic 1,2,4-triazole showing ring numbering (top left), ditopic PMRT (4-R-substituted-3,5-bis­{[(2-pyridylmethyl)­amino]­methyl}-4 H -1,2,4-triazole) /PSRT (4-R-substituted-3,5-bis­{[(2-pyridylmethyl)­sulfanyl]­methyl}-4 H -1,2,4-triazole) (top middle) ,− and related thia-/oxazole ligands PMTD (2,5-bis­[(2-pyridylmethyl)­amino]­methyl-1,3,4-thiadiazole)/ PMOD (2,5-bis­{[(2-pyridylmethyl)­amino]­methyl}-1,3,4-oxadiazole) (top right). − ditopic R at ligands L 2/4pym‑meta/para (1, n -bis­(4-isobutyl-5-(pyrimidin-2/4-yl)-4 H -1,2,4-triazol-3-yl)­benzene (middle), and R dpt (4- R -substituted 3,5-di­(2-pyridyl)­triazole) (bottom left) as well as monotopic R at ligands (bottom), either azine -substituted L azine (bottom middle) ,,− or the new azole -substituted (bottom right, box) versions made and used in this study, L 4NMeIm and L 4SIm .…”

“…1,2,4-Triazole-based ligands have been targeted by many researchers, as 1,2,4-triazoles are readily functionalized at some or all of the C 3 , C 5 , and N 4 positions of the triazole ring (Figure ) and have generated many interesting complexes of a wide range of metal ions. ,,− Of interest herein is that many such 1,2,4-triazole based ligands, including the bis-terdentate PMRT/PSRT (Figure , top middle) ,− and the related thia-/oxa-diazoles PMTD/PMOD (Figure , top right), − as well as the bis- or monobidentate R dpt /R at ligand types (Figure , bottom), ,,− are reported in the literature to form SCO-active iron­(II) complexes.…”

Symmetry breakings in a metal organic framework with a confined guest

“…Combining both MOFs and SCO properties greatly enhance the richness in terms of instabilities both from the electronic and structural points of view, as reported recently. [16][17][18][19][20][21][22] The influence of a series of guest molecules, such as benzonitrile, nitrobenzene, benzaldehyde, acetonitrile/water, dimethylsulfoxide/water, on the SCO properties of this MOF-SCO was investigated more recently [16]. It was shown through the thermal dependence of χ M T (χ M = molar magnetic susceptibility, T = temperature) that the [F e(tvp) 2 (N CS) 2 ] n (tvp = trans(4,4-vinylenedipyridine)) system with no guest remains in the high spin state (HS, S=2) down to low temperature.…”