Supramolecular Tuning of Spin Crossover Properties in Isostructural Cocrystal Solvates

Abstract

In order to improve strategies for the design of spin-crossover materials, it is necessary to develop and understand structure–property relationships, and this is best achieved by obtaining isostructural materials. In this work we synthesized a series of four isostructural cocrystal solvates using the [Fe(3-bpp)2][A]2 complex and the 2,2-dipyridyl disulfide coformer in methanol and ethanol (A = BF4 – or PF6 –). The spin-crossover properties of the materials were determined by variable temperature single-crystal X-ray diffraction. They show the same SCO behavior but with shifted spin-crossover temperatures, which has been related to the hydrogen bond basicity, pK BHX of the anions, and solvents present. This relationship between hydrogen bond basicity and the spin-crossover transition temperature offers a design strategy for the supramolecular tuning of spin-crossover properties in specific isostructural materials.

Spin in Organic Cocrystals

“…The carrier mobility of the Fe‐based cocrystal on PVDF was calculated to be 50×10 −5 cm 2 V −1 s −1 . Although this value is low mobility, it is higher than the expected value for organic electronics [41c] …”

“…The Fe‐based cocrystal was found to exhibit enhanced conductivity and drift carrier lifetimes. To our knowledge, the magnetic bi‐stability can be triggered to achieve reversible transitions between LS and HS states, which can be utilized for flexible nonvolatile memory devices [41c] . Therefore, preserving the spin state changes and stable conductances becomes another main challenge.…”

Iron(ii) complexes of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine and related ligands with annelated distal heterocyclic donors

“…Both complexes form solvated single crystals and, while 2[BF 4 ] 2 was obtained as a solvent-free material after drying in vacuo , samples of 1[BF 4 ] 2 always contained residual solvent or lattice water by microanalysis. Since the spin state properties of some solvated iron complexes depend significantly on the lattice solvent, 75–81 multiple solvates of 1[BF 4 ] 2 and 2[BF 4 ] 2 were isolated for characterisation.…”

Probing the effect of substituents and solvent on [Mn(R-sal-N-1,5,8,12)]BPh4: a systematic investigation of SCO properties

“…Subject to these factors, SCO may become synergistic, and the octahedral configuration of the corresponding complexes will be distorted. 13,26,[30][31][32][33][34][35][36] The SCO might be associated with crystallographic phase transition, and in turn, the detailed SCO study has clarified phase-transition modes like stepwise and hysteretic.…”