Fig. 5: Detailed structural transformation upon water adsorption.
From: A spin-crossover framework endowed with pore-adjustable behavior by slow structural dynamics
a Conformations of flexible prentrz ligands in the lcp (1·9/2H2O) and nqp (1·4/3H2O) phases. b Local pedal rotations of prentrz molecules and the directional shifts of axial Fe−N coordination bonds. The ligands III, IV, and V perform in-plane pedal rotations around their N−N single bonds, and ligands II, III, IV, and V undergo distinct directional shifts with angles of 12.9°, 22.1°, 37.8°, and 18.0°, respectively. The pedal rotations and the reorientations of Fe−N bonds have opposite influences on the principal directions of axial ligands. Consequently, ligands II and IV show the most significant shifts in their molecular orientations (as dashed lines indicated). c The directional shift of ligand II upon adsorption expands channel A1’ and closes channel A2’, while the directional shift of ligand IV opens channel B1’ and closes channel A3’. Accordingly, the four water molecules accommodated in pore A2’ and A3’ of nqp phase must be evacuated to facilitate the nqp–to–lcp lattice transformation. d The coordination layer demonstrated a remarkable crumpling/unfolding motion to assist the reorientation of the Fe−N coordination bonds. The structures of lcp (1·9/2H2O) and nqp (1·4/3H2O) phases are drawn in blue and red, respectively.
