A spin-crossover framework endowed with pore-adjustable behavior by slow structural dynamics

Abstract

Host-guest interactions play critical roles in achieving switchable structures and functionalities in porous materials, but design and control remain challenging. Here, we report a two-dimensional porous magnetic compound, [FeII(prentrz)2PdII(CN)4] (prentrz = (1E,2E)−3-phenyl-N-(4H-1,2,4-triazol-4-yl)prop-2-en-1-imine), which exhibits an atypical pore transformation that directly entangles with a spin state transition in response to water adsorption. In this material, the adsorption-induced, non-uniform pedal motion of the axial prentrz ligands and the crumpling/unfolding of the layer structure actuate a reversible narrow quasi-discrete pore (nqp) to large channel-type pore (lcp) change that leads to a pore rearrangement associated with simultaneous pore opening and closing. The unusual pore transformation results in programmable adsorption in which the lcp structure type must be achieved first by the long-time exposure of the nqp structure type in a steam-saturated atmosphere to accomplish the gate-opening adsorption. The structural transformation is accompanied by a variation in the spin-crossover (SCO) property of FeII, i.e., two-step SCO with a large plateau for the lcp phase and two-step SCO with no plateau for the nqp phase. The unusual adsorption-induced pore rearrangement and the related SCO property offer a way to design and control the pore structure and physical properties of dynamic frameworks.

Metal‐Organic Frameworks for Greenhouse Gas Applications

“…The exploitation of a series of mesoporous coordination polymers as new framework prototypes to rapidly expand pore size is a research hotspot for the storage and separation of GHG gases. [262,263] A series of three mesoporous MOFs equipped with enlargement of pore size as well as the profound influence of pore size on adsorption heat conversion are demonstrated by Zhang et al In this work, a honeycomb-like structure based upon ditopic inorganic chains and tritopic ligands with ultra-large pore size is depicted in Figure 28a. [264] Three kinds of tritopic [264] Reproduced with permission.…”

An iron(II) complex shows bistable spin-state switching characteristic with T1/2 centred at room temperature

“…Finally, the grand old phenomenon of SCO continues to evolve keeping abreast with the contemporary developments in molecular magnetism and related topics. 5,[28][29][30][31][32][33][34][35][36][37][38][39] We are happy that the topic has chosen us to express interesting facets, as discussed in this script.…”

Broad-range spin-crossover modulation in guest-responsive 2D Hofmann-type coordination polymers

“…[18][19][20][21][22] An archetype platform to design new SCO compounds is the family of two-dimensional (2D) Hofmann-type coordi-nation polymers (HCPs) formulated as {Fe(L) 2 [M(CN) n ] m } (where L is a pyridine, pyrimidine, pyrazole, imidazole or triazole type axial ligand and M = Pt II , Pd II , Ni II (n = 4; m = 0) or Ag I , Au I (n = 2, m = 2)). [23][24][25][26][27][28] This family of HCPs offers the structural flexibility required to achieve a synergistic interaction of SCO with additional functions by direct replacement of the aromatic ligands in the apical positions of the Fe II sites. A recent example highlighting this strategy involves the functionalization of the axial pyridine with an anthracene fluorescent agent affording the compounds {Fe(AnPy) 2 [M(CN) 2 ] 2 } (AnPy = 9-anthracenepyridine, M = Au, Ag) which display luminescence coupled to SCO.…”