Coordination Dependence of Magnetic Properties within a Family of Related [Fe^II₂] Complexes of a Triazine‐Based Ligand

Abstract

The coordination chemistry of the polydentate ligand 2,4,6-tris(dipyridin-2-ylamino)-1,3,5-triazine (dpyatriz) with Fe II has been explored, leading through variation of the counterion and the solvent system to the preparation of three different dinuclear complexes: 4 ) 4 (2) and [Fe 2 (dpyatriz) 2 Cl 2 ](CF 3 SO 3 ) 2 (3). The X-ray structure of these compounds has revealed that besides the difference in the noncoordinated anion, complex 1 differs from complex 2 only in the nature of the terminal ligands. Bulk magnetisation studies and Mössbauer spectroscopy have shown that such a subtle difference produces a change to the crystal field on the metal atoms, originating an important disparity of the magnetic behaviour. Thus, complex 1 experiences a partial spin crossover centred at approximately 265 K, whereas com-

A Molecule‐Based Nanoporous Material Showing Tuneable Spin‐Crossover Behavior near Room Temperature

“…A related exchange process in the solid state was previously observed for other dpyatriz-based systems, and led to important changes to the magnetic properties of the material, [18] comparable to a nonporous material recently reported by Coronado et al [20] Attempts to follow any possible structural changes accompanying the host-guest transition of Dpya-1 were hindered by the difficulties resulting from the rate of the process, which caused rapid loss of crystallinity. This shortcoming could be overcome by following the exchange through X-ray powder diffraction (XRPD) under a saturated atmosphere of propionitrile (also containing atmospheric water), as it took place during a gradual increase of the temperature (Fig.…”

“…[16,17] In addition, discrete dinuclear complexes of Fe II with dpyatriz have been obtained, and display (extremely rare) ferromagnetic exchange, or spin-crossover properties that can be easily modulated by changing the solvent, which acts as a terminal ligand. [18] The use of such dimeric units as building blocks in solvothermal reactions involving Fe II has now taken us one step further, providing access to a new metalorganic nanoporous material that exhibits room-temperature spin-crossover behavior. The structure of this material can be modified reversibly through exposure to various solvents; the transformation leading to significant changes to the spin-transition properties.…”

“…1), some of them exhibiting spin-crossover properties. [18] These complexes feature two free binding sites for metals, and can therefore be used as building blocks in the preparation of extended spin-transition structures.…”

Synthesis and Coordination Chemistry of 2-(Di-2-pyridylamino)pyrimidine; Structural Aspects of Spin Crossover in an FeII Complex

“…In the context of systems for spin crossover, the use of di-2-pyridylamine as a chelating motif has attracted considerable attention. [15][16][17][18][19][20][21][22] Kepert and Murray observed either a one-step or a two-step full spin crossover for dinuclear iron(II) complexes of 2,5-bis(di-2-pyridylamino)pyridine (1), with spin states HS-HS, HS-LS and LS-LS (HS: high spin, LS: low spin) for the two iron(II) centres at the three plateau temperatures in the two-step case. [15,16] The incorporation of pyrimidine as a core in such ligands in the form of 4,6-bis(di-2-pyridylamino)pyrimidine (2) and its application in a SCO system has been reported, [17,18] .…”

“…Triazine derivatives have also been much studied in respect of SCO chemistry; [23,24] some work on compounds containing two di-2-pyridylamine arms has been reported (3), [19] as has work on the tritopic version (4). [20][21][22] and 2-(di-2-pyridylamino)pyrimidine (L).…”