Synthesis of Crystalline Molecular Gyrotops and Phenylene Rotation inside the Cage

Abstract

Phenylene-bridged macrocage molecules were synthesized as molecular gyrotops because the rotor can rotate even in a crystal. The chain-length-dependent properties of the molecular gyrotops were investigated in order to explore the potential to create new molecular materials. The formation of the cage in the synthesis of each molecular gyrotop depended on the length of the alkyl chains of the precursor. The rotation modes and energy barriers for phenylene rotation inside the crystals of the molecular gyrotops were changed by varying the chain length of the cage.

Ultra‐Fast Molecular Rotors within Porous Organic Cages

“…Moreover, while the [D 12 ]TCC2‐ R rate is comparable to other organic frameworks,27, 28, 29, 36 the very fast reorientation rate value obtained for the [D 12 ]TCC3‐ R is larger than in any exclusively organic systems reported previously below ≈200 K (Table S3) 18, 19, 24, 29, 32, 37, 38, 39. In particular, below this temperature, the dynamics of [D 12 ]TCC3‐ R are faster than the ones observed very recently for the para ‐phenylene reorientation in bis(sulfophenylethynyl)‐benzene frameworks based on an overall similar architecture of a phenylene molecular rotor sandwiched between two acetylene moieties (Figure 1 (b)), which previously showed the largest reorientation rate for porous organic materials to date 32…”

“…The larger E a value obtained for [D 12 ]TCC2‐ R versus [D 12 ]TCC3‐ R is again consistent with stronger steric interactions in the terphenylene cage structure. The k 0 values obtained are on the low side of the ≈10 12  Hz22 value often associated with para ‐phenylene rotation, although these values vary significantly with the systems studied and k 0 in the 10 8 –10 41  Hz range are known 19, 23, 24, 27, 28, 29, 32, 36, 37, 40, 41. The associated change in entropy (Δ S ) is negative and is tentatively assigned to correlated rotational motion (Table S2) 41, 42…”

“…With decreasing temperature a gradual change in the 2 H NMR line shape is observed for these materials, however, the motion induced T 2 anisotropy is dependent on the particular cage. Line shape simulations of the 2 H NMR spectra support a motion consisting of a rapid two‐site 180° flip reorientation of the para ‐phenylene ring along its para axis, and this provides the rate of molecular reorientation ( k ) at each temperature on the kHz timescale 19, 34, 35…”

“…The intrinsic pore within these molecules permits guest sorption into the tubular cavities 4, 16. The static imine cyclohexane linkers and rotating phenylene groups allow these POCs to be classified as molecular rotors 17, 18, 19. It is likely that the window dynamics in these molecules control guest loading into the molecular pore, and we therefore set out to understand the response of these cages to external stimuli, such as guest inclusion.…”

Gyroscope like molecules consisting of trigonal or square planar osmium rotators within three-spoked dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties

“…2 Although the term "gyroscope" has been applied rather loosely to molecules, 3 only a few investigators have been actively trying to engineer working devices. [4][5][6] A common denominator among these efforts has been the construction of cage like housings, often termed "stators", which shield the rotating moieties or "rotators" from their surroundings. As shown in Scheme 1, we have discovered that three fold intramolecular and interligand ring closing alkene metatheses of trans bis( phosphine) complexes of the type I can be effected in surprisingly high yields.…”