Molecular‐Rotor‐Driven Advanced Porous Materials

Abstract

Advanced porous materials (APMs)—such as metal‐organic frameworks (MOFs) and porous organic polymers (POPs)—have emerged as an exciting research frontier of chemistry and materials science. Given their tunable pore size and extensive diversity, APMs have found widespread applications. In addition, adding dynamic functional groups to porous solids furthers the development of stimuli‐responsive materials. By incorporating moving elements—molecular rotors—into the porous frameworks, molecular‐rotor‐driven advanced porous materials (MR‐APMs) can respond reversibly to chemical and physical stimuli, thus imparting dynamic functionalities that have not been found in conventional porous materials. This Minireview discusses exemplary MR‐APMs in terms of their design, synthesis, rotor dynamics, and potential applications.

Multidynamic Crystalline Molecular Rotors Comprising an N‐Heterocyclic Carbene Binuclear Au(I) Complex Bearing Multiple Rotators

“…To explore the molecular dynamics of the central pyrazine and included THF molecules, we carried out variable‐temperature solid‐state 2 H NMR spin‐echo measurements of 1 ‐ d 4 ‐2(THF) and 1 – 2 (THF‐ d 8 ), respectively, and explored the site‐exchange dynamics using broad‐line shape simulations. This method is a well‐established technique for deuterium‐enriched moieties with varying exchange rates and rotational trajectories [1–8,28] …”

“…The design of molecular rotation in crystalline media has attracted much interest not only in the field of molecular machines but also in solid‐state functional materials, because the rotation‐induced molecular geometry alteration can provide an avenue for switching the physical properties of solid compounds [1–8] . To construct the crystalline materials, known as crystalline molecular rotors, gyroscope‐like molecular rotors, [2–4,9–11] dumbbell‐shaped molecules, [2–3,12–17] and porous solid‐state materials such as metal–organic frameworks (MOFs) [5–8,18–23] have been utilized. The general blueprint of this design is based on the combination of a rotator moiety with a bulky and rigid domain as a stator that is used to construct the ordered frame as well as the local space that can undergoes molecular rotation.…”

“…The general blueprint of this design is based on the combination of a rotator moiety with a bulky and rigid domain as a stator that is used to construct the ordered frame as well as the local space that can undergoes molecular rotation. Many examples have utilized a single‐component rotator that generally shows a simple rotational dynamics [1–8] . To broaden the application of crystalline molecular rotors, realizing larger complexity of molecular motions in the solid‐state is important because the multiple molecular dynamics in crystals have a high potential to integrate various functions such as photophysical or dielectric properties (Figure 1a).…”

Confinement‐Driven Photophysics in Hydrazone‐Based Hierarchical Materials

“…In contrast, derivatives in which the phenyl groups rotate out of plane tend to switch in the solid state more efficiently because of amorphous, “loose packing,” which affords the space required for photoisomerization to occur [25, 46] . Thus, we hypothesize that void pre‐organization could promote hydrazone isomerization and advance efficient switching in the solid state [55, 56] . Well‐defined porous materials such as metal‐organic and covalent‐organic frameworks (MOFs and COFs) [57–77] offer such space for isomerization to occur, and therefore, can be used to promote photochromic performance of hydrazone derivatives.…”

Electrostatically-gated molecular rotors

“…The development and study of synthetic molecular devices and molecular machines are an exciting new area of research. [1][2][3][4][5] An important challenge in the field is developing effective methods of controlling molecular-scale motion using macroscale inputs and stimuli. For example, stimuli used to control the rates of rotation of molecular rotors have included: light, [6][7][8][9][10][11] metal ions, [12][13][14] hydrogen bonds, [15][16][17] redox, [18][19][20] anions, 21 guests, 16,22,23 and protons.…”