Toward a light-driven motorized nanocar: synthesis and initial imaging of single molecules

Controlling many differential-drive robots with uniform control inputs

This paper derives both open-loop and closed-loop control policies that steer a finite set of differential-drive robots to desired positions in a two-dimensional workspace, when all robots receive the same control inputs but each robot turns at a slightly different rate. In the absence of perturbation, the open-loop policy achieves zero error in finite time. In the presence of perturbation, the closed-loop policy is globally asymptotically stabilizing with state feedback. Both policies were validated with hardware experiments using up to 15 robots. These experimental results suggest that similar policies might be applied to control micro- and nanoscale robotic systems, which are often subject to similar constraints.

Remarkable cage deboronation and rearrangement of a closo-1,12-dicarbadodecaborane to form a neutral nido-7,9-dicarbaundecaborane

Deboronation and cage rearrangement of the closo-1,12-carborane salt [1,12-(PPh2Me)2-1,12-C2B10H10]I2 occurs in refluxing methanol to give the zwitterionic nido-7,9-carborane 7,9-(PPh2Me)2-7,9-C2B9H9. Notably, deboronation and cage substitution of the isomeric closo-1,7-carborane salt [1,7-(PPh2Me)2-1,7-C2B10H10]I2 takes place in methanol to afford the salt [10-OMe-7,9-(PPh2Me)2-7,9-C2B9H9]I.

Theoretical study of topographical features around the conical intersections of fluorene-based light-driven molecular rotary motor

Topographical features around the conical intersection (CIX) of a fluorene-based light-driven molecular rotary motor have been examined by means of ab initio molecular orbital calculations. The model molecule is a derivative of 9-(2-phenyl-2-cyclopenten-1-ylidene)-9H-fluorene (PCPF) where PCPF is bridged by a pentamethylene chain between the 2 position of the phenyl group and the pseudoaxial position of the C(5) atom in the 2-cyclopenten-1-ylidene ring. This model molecule (denoted by M5-PCPF) has been very recently reported as a candidate for a light-driven molecular motor with constant rotation. The conical intersection for the photoprocess of the ethylenic C═C torsion reported there (denoted by CIX1), which exclusively leads to a product of P'-M5-PCPF, is found to be classified as a sloped-type CIX. Another CIX reported at the present time (CIX2) exclusively goes back to a reactant of P-M5-PCPF, whereas CIX2 is also classified as a sloped-type CIX. At the stable geometry in S1 around the CIX region (S1-geometry), the 2-cyclopenten-1-ylidene rotor takes a perpendicular twist against the fluorene stator, but the fluorene stator does not wag so much against the C═C rotary axis. The wagging motions of the fluorene stator from S1-geometry to the opposite directions lead to CIX1 and CIX2, respectively.

Molecule concept nanocars: chassis, wheels, and motors?

The design, synthesis, and running of a molecular nanovehicle on a surface assisted by proper nanocommunication channels for feeding and guiding the vehicle now constitute an active field of research and are no longer a nano-joke. In this Perspective, we describe how this field began, its growth, and problems to be solved. Better molecular wheels, a molecular motor with its own gears assembling for torque transmission must be mounted on (i.e., chemically bonded to) a good molecular chassis for the resulting covalently constructed molecular nanovehicle to run on a surface in a controlled manner at the atomic scale. We propose a yearly molecule concept nanocar contest to boost molecular nanovehicle research.

Synthesis and single-molecule imaging of highly mobile adamantane-wheeled nanocars

The synthesis and single-molecule imaging of two inherently fluorescent nanocars equipped with adamantane wheels is reported. The nanocars were imaged using 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as the chromophore, which was rigidly incorporated into the nanocar chassis via Sonogashira cross-coupling chemistry that permitted the synthesis of nanocars having different geometries. In particular, studied here were four- and three-wheeled nanocars with adamantane wheels. It was found that, for the four-wheeled nanocar, the percentage of moving nanocars and the diffusion constant show a significant improvement over p-carborane-wheeled nanocars with the same chassis. The three-wheeled nanocar showed only limited mobility due to its geometry. These results are consistent with a requisite wheel-like rolling motion. We furthermore developed a model that relates the percentage of moving nanocars in single-molecule experiments with the diffusion constant. The excellent agreement between the model and the new results presented here as well as previous single-molecule studies of fluorescent nanocars yields an improved understanding of motion in these molecular machines.

Island formation and manipulation of prochiral azobenzene derivatives on Au(111)

Based on previous work with very similar azobenzene derivatives, this study of para-TBA (2,2',5,5'-tetra-tert-butylazobenzene) molecules aims to identify single intact molecules and investigate their adsorption behavior on a Au(111) surface. The molecules are found to be mobile on the surface at the deposition temperature, leading to highly ordered and enantiomerically pure molecular islands. Voltage pulses between the surface and the tip of a scanning tunneling microscope are used to change the chirality of the adsorbate molecules. On the Cu(111) surface instead, single molecules are found on the terraces, which points to a stronger molecule-substrate interaction.