| Summary: | Two analogous 2-D Hofmann-type frameworks, which incorporate the novel ligand <i>N</i>-(pyridin-4-yl)benzamide (benpy) [Fe<sup>II</sup>(benpy)<sub>2</sub>M(CN)<sub>4</sub>]·2H<sub>2</sub>O (M = Pd (<b>Pd(benpy)</b>) and Pt (<b>Pt(benpy)</b>)) are reported. The benpy ligand was explored to facilitate spin-crossover (SCO) cooperativity via amide group hydrogen bonding. Structural analyses of the 2-D Hofmann frameworks revealed benpy-guest hydrogen bonding and benpy-benpy aromatic contacts. Both analogues exhibited single-step hysteretic spin-crossover (SCO) transitions, with the metal-cyanide linker (M = Pd or Pt) impacting the SCO spin-state transition temperature and hysteresis loop width (<b>Pd(benpy)</b>: <i>T</i><sub>½</sub>↓↑: 201, 218 K, ∆<i>T</i>: 17 K and <b>Pt(benpy)</b>: <i>T</i><sub>½</sub>↓↑: 206, 226 K, ∆<i>T</i>: 20 K). The parallel structural and SCO changes over the high-spin to low-spin transition were investigated using variable-temperature, single-crystal, and powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. These studies indicated that the ligand–guest interactions facilitated by the amide group acted to support the cooperative spin-state transitions displayed by these two Hofmann-type frameworks, providing further insight into cooperativity and structure–property relationships.
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