Syn and Anti Metal Complexes of 24π Antiaromatic Bis(Dicarbonylrhodium(I))Dithiaamethyrin.

From the reaction of sterically less hindered tetrapropyl[24]dithiaamethyrin(1.0.0.1.0.0) 5, with [Rh(CO)2 Cl]2 , a unique anti form of the bis(dicarbonylrhodium(I)) complex (6-anti), where two rhodium ions are on the opposite faces of the macrocyclic ligand, was isolated for the first time in 12% yield along with the corresponding syn isomer (6-syn, 61% yield). These structures were characterized in detail by single-crystal X-ray structure analysis. Compound 6-syn exhibited a bowl-shaped structure with the two rhodium atoms separated by a distance of ∼4.5 Å. In contrast, 6-anti contained a wave-shaped macrocycle with a distance of ∼5.3 Šbetween the two rhodium atoms. Furthermore, the 1 H nuclear magnetic resonance spectra and density functional theory calculation results revealed that 6-anti had a stronger paratropic ring current and a more planar structure than 6-syn. The isolation of both 6-anti and 6-syn enabled detailed discussion of the structure-property relationship.

Controlled clockwise-counterclockwise motion of the ring-shaped microtubules assembly.

The microtubule (MT)-kinesin system has been proposed as the building block of biomolecular motor based artificial biomachines. Considerable efforts have been devoted to integrate this system that produced a variety of ordered structures including the ring-shaped MT assembly which is being considered as a promising candidate for the further development of the biomachines. However, lack of proper knowledge that might help tune the direction of motion of ring-shaped microtubule assembly from counterclockwise to clockwise direction, and vice versa, significantly restricted their potential applications. We report our success in controlling the direction of rotational motion of ring-shaped MT assembly by altering the preparation conditions of microtubules. The change in the direction of rotation of MT rings could be interpreted in terms of the accompanied structural rearrangement of the MT lattice. For achieving handedness-regulated efficient biomachines having tunable asymmetric property, our study will be significantly directive.