Bidirectional Chemo‐Switching of Spin State in a Microporous Framework

Ohba, Masaaki; Yoneda, K.; Agustí, Gloria; Muñoz, M. Carmen; Gaspar, Ana B.; Real, José Antonio; Yamasaki, Mikio; Ando, Hideo; Nakao, Yoshiaki; Sakaki, Shigeyoshi; Kitagawa, Susumu

doi:10.1002/anie.200806039

Cited by 494 publications

(397 citation statements)

References 43 publications

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“…Another direction for future work is to include in our model external stimuli to modulate the ligand conformations and thus, indirectly, the host-guest interaction. For example, spin crossover transitions of a metal in a MOF (68) have been shown to modulate the rotational freedom of coordinating ligands (69), opening an avenue for switching the ligand state with an electric field, temperature, or light (70). For asymmetric ligands with polar groups, an electric field could modulate the rotational conformations (71,72).…”

Section: Discussionmentioning

confidence: 99%

Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Simon

Braun

Carraro

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes.metal-organic frameworks | flexible metal-organic frameworks | statistical mechanics | porous materials | gas storage M etal-organic frameworks (MOFs) are porous, crystalline materials with very large internal surface areas (1). The consequent adsorption properties of MOFs have demonstrated promise toward solving paramount energy problems (2) such as in gas storage (3) and gas separations (4). MOFs are also being explored for chemical sensing (5), drug delivery (6), and catalysis (7). In the synthesis of MOFs, metal nodes or clusters and organic linker molecules self-assemble (8). Owing to their modular and versatile chemistry, tens of thousands of MOFs have been synthesized (9).Some MOFs are dynamic/flexible and respond to gas molecules adsorbing into their pores by exhibiting structural changes while retaining their crystallinity (reviews in refs. 10-14). Reported modes of guest-induced structural changes in MOFs include breathing (15), swelling (16), and subnetwork displacement (17), as well as less dramatic changes, such as the rotation of a ligand (18) or deformation (19). In molecular recognition and enzyme catalysis in biology, a conformation change of the enzyme is often involved in substrate binding (20,21). Responsive, dynamic constituents thus may endow MOFs with enzymelike selectivities (11) for selective gas adsorption, chemical sensing, and catalysis.In the long run, a more intimate understanding of MOFs with moving parts may enable the construction of molecular machines (22). Because of their crystallinity and tunability, MOFs are an ideal scaffold on which to organize machine subunits and tune their response to stimuli. Notably, Zhu et al. (23) used a [2] rotaxane molecular switch as a building block in a MOF to construct a conceptual molecular machine.Several reported MOFs possess dynamic constituents, e.g., bridging ligands that can rotate, while maintaini...

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Section: Discussionmentioning

confidence: 99%

Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Simon

Braun

Carraro

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Thus, it has been shown that MOFs based on these molecular complexes exhibit magnetic switching at room temperature on physisorption of specific molecules within the porous framework 16,17 . The high sensitivity of these materials is also evidenced by the modification of the transition temperature on oxidative addition reactions following gas sorption at metal sites that are far from the magnetic centres 18,19 .…”

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confidence: 99%

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

et al. 2012

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Responsive materials for which physical or chemical properties can be tuned by applying an external stimulus are attracting considerable interest in view of their potential applications as chemical switches or molecular sensors. A potential source of such materials is metalorganic frameworks. These porous coordination polymers permit the physisorption of guest molecules that can provoke subtle changes in their porous structure, thus affecting their physical properties. Here we show that the chemisorption of gaseous HCl molecules by a nonporous one-dimensional coordination polymer instigates drastic modifications in the magnetic properties of the material. These changes result from profound structural changes, involving cleavage and formation of covalent bonds, but with no disruption of crystallinity.

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“…For material 2c with guest 3,5-lutidine species, another explanation about the outer high spin state sites may be possible such as π − π interactions between the ligands of 3,5-lutidine coordinated to iron(II) atoms and the guest molecules of 3,5-lutidine in 2D and 3D Hofmann-like coordination polymer compounds [10][11][12][13][14][15][16]. While 2c has the 2D host framework, guest 3,5-lutidine molecules probably have π − π interactions with ligand 3,5-lutidine species.…”

Section: Resultsmentioning

confidence: 99%

“…The related spin crossover coordination compounds have been developed [8][9][10][11][12][13][14][15][16][17][18]. Some of them contain 3D pillared Hofmann-type-organic frameworks [10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

New Hofmann-like spin crossover compound with 3,5-lutidine

Kitazawa

Takahashi

2013

Hyperfine Interact

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A new type III of 3,5-lutidine spin crossover coordination compound with formula Fe(3,5-lutidine) 2 Ni(CN) 4 ·2[(H 2 O)(3,5-lutidine)] 2c has been obtained. The ratio of the high spin state (HS) iron (II) changing to the low spin state (LS) iron (II) in 2c is higher than that of type I and type II 3,5-lutidine coordination polymer 2a and 2b previously reported.57 Fe Mössbauer spectra of 2c show two different doublets which correspond to HS1 (inner doublet lines) and HS2 (outer doublet lines). The intensity of the HS1 doublet decreases on cooling to 80 K while the intensity of another component, the LS singlet, increases. The 90 % of the HS1 doublet change to the LS singlet is probably due to suitable environments of octahedral iron (II) ions coordinated by four nitrogen atoms of cyano groups and two nitrogen atoms of 3,5-lutidine ligands. We also prepared the Hofmann-like 3,5-dichloropyridine coordination compound Fe(3,5-dichloropyridine) 2 Ni(CN) 4 ·2[(3,5-dichloropyridine)(H 2 O)] 2d to compare it with 2c.57 Fe Mössbauer spectra of 2d show that 2d is not a spin crossover coordination compound.

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Bidirectional Chemo‐Switching of Spin State in a Microporous Framework

Cited by 494 publications

References 43 publications

Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

New Hofmann-like spin crossover compound with 3,5-lutidine

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