Pressure-Induced Hysteretic and Abrupt Spin Transition in Amine Functionalized Isoquinoline-Based Two-Dimensional Fe<sup>II</sup> Hofmann Frameworks
Dibya Jyoti Mondal, Neelabhro Mukherjee, Sanjit Konar
Abstract
Two two-dimensional (2D) Hofmann-type coordination frameworks are synthesized by employing the square planar tetracyanometallate building blocks and an amine-functionalized isoquinoline ligand with the general formula of [Fe(L) 2 {M(CN) 4 }] (L = 5-amino isoquinoline) (M = Pt ( 1Pt ) and Pd ( 1Pd )) to explore the spin-state switching behavior. The inclusion of the amine functional group in the isoquinoline ligand plays a major role in exhibiting a complete spin crossover (SCO) behavior under ambient atmospheric pressure. The effective host–host supramolecular interaction such as strong π···π stacking and N–H···C interactions between interlayer 2D sheets of {Fe II [Pt (CN) 4 ]} n is responsible for the abrupt hysteretic spin transition behavior. Interestingly, the applied external pressure enhances the stabilization of the low spin states revealing a one-step abrupt and hysteretic spin transition near room temperature.