Square-Planar Palladium Complexes with Trans Di- and Tribenzylphosphine Ligands Bearing O(CH2)4CH═CH2 Substituents; Two- and Three-Fold Intramolecular Ring-Closing Metatheses

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

The OsL_y moieties of the title complexes undergo rapid rotation within the diphosphine cages when L is restricted to Cl, Br, CO, H, and Me.

A pyrene-bridged macrocage showing no excimer fluorescence

A pyrene bridged macrocage shows fluorescence from a monomeric excited state without excimer due to cage effects.

Photochromic molecular gyroscope with solid state rotational states determined by an azobenzene bridge

We describe the synthesis, characterization, photochemical isomerization, and rotational dynamics of a crystalline molecular gyroscope containing an azobenzene bridge (trans-2) that spans from one end of the stator to other, with the intention of exploring its function as a molecular brake. While single crystal X-ray diffraction analysis of a photochemically inactive dichloromethane solvate was used to confirm the molecular and packing structures of trans-2, a nanocrystalline pseudopolymorph was shown to be photoactive, and it was analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy, and variable temperature solid state (2)H NMR before and after photoisomerization. It was shown that the nanocrystalline suspension irradiated with λ = 340 nm reaches a photostationary state with 34% of cis-isomer, as compared to that observed in solution where the corresponding value is 74%. Line shape analysis of solid state (2)H NMR spectra of a phenylene-d4 isotopologue, obtained as a function of temperature, indicated that rotation in crystals of the trans-2 isomer, with a mean activation energy of 4.6 ± 0.6 kcal/mol and a pre-exponential factor exp(29.4 ± 1.7), is ten times faster than that of samples containing the cis-2 isomer, which has a higher mean activation energy of 5.1 ± 0.6 kcal/mol and a lower pre-exponential factor of exp(27.9 ± 1.3).

Ring-closing metathesis for the synthesis of a molecular gyrotop

A molecular gyrotop was synthesized by ring-closing metathesis (RCM) under reflux, indicating that the cage is a thermodynamically controlled product.

A crystalline molecular gyrotop with germanium junctions between a phenylene rotor and alkyl spokes

A molecular gyrotop with germanium junctions was synthesized, and the dynamics of the phenylene and the optical properties were discussed.