Organobismuth compounds have been studied in various fields, including electronic states, pnictogen bonds, and catalysis. Among them, one of the unique electronic states of the element is the ...hypervalent state. So far, many issues regarding the electronic structures of bismuth in hypervalent states have been revealed; meanwhile, the influence of hypervalent bismuth on the electronic properties of π-conjugated scaffolds is still vailed. Here, we synthesized the hypervalent bismuth compound, BiAz, by introducing hypervalent bismuth into the azobenzene tridentate ligand as a π-conjugated scaffold. The influence of hypervalent bismuth on the electronic properties of the ligand was evaluated from optical measurements and quantum chemical calculations. The introduction of hypervalent bismuth revealed three significant electronic effects: first, hypervalent bismuth shows position-dependent electron-donating and electron-accepting effects. Second, BiAz can have a larger effective Lewis acidity than the hypervalent tin compound derivatives reported in our previous research. Finally, the coordination of dimethyl sulfoxide transformed the electronic properties of BiAz, similar to the hypervalent tin compounds. The data from quantum chemical calculations showed that the optical properties of the π-conjugated scaffold were able to be changed by introducing hypervalent bismuth. To the best of our knowledge, we first demonstrate that the introduction of hypervalent bismuth should be a new methodology for controlling the electronic properties of π-conjugated molecules and developing sensing materials.
In this paper, we develop an articulated mobile robot that can climb stairs, and also move in narrow spaces and on 3-D terrain. This paper presents two control methods for this robot. The first is a ...3-D steering method that is used to adapt the robot to the surrounding terrain. In this method, the robot relaxes its joints, allowing it to adapt to the terrain using its own weight, and then, resumes its motion employing the follow-the-leader method. The second control method is the semi-autonomous stair climbing method. In this method, the robot connects with the treads of the stairs using a body called a connecting part, and then shifts the connecting part from its head to its tail. The robot then uses the sensor information to shift the connecting part with appropriate timing. The robot can climb stairs using this method even if the stairs are steep, and the sizes of the riser and the tread of the stairs are unknown. Experiments are performed to demonstrate the effectiveness of the proposed methods and the developed robot.
The development of a heat‐resistant mechanoluminescent chromic (MLC) dye based on an organic–inorganic hybrid molecular scaffold is reported. Luminescent organoboron complexes were introduced into ...polyhedral oligomeric silsesquioxane (POSS) at each vertex through the rigid linker structure in the Suzuki–Miyaura cross‐coupling reaction. From optical measurements, it was found that the crystalline state of the modified POSS showed orange emission. By adding mechanical forces to the sample, regular structures collapsed. Correspondingly, the emission color turned to yellow. Interestingly, the yellow‐emissive amorphous state can be preserved during heating. By radially distributing luminescent chromophores on the rigid cube, both optical and thermal properties can be modulated to realize heat‐ resistant MLC behavior. POSS can contribute not only to expressing the MLC behavior, but also to improving thermal stability in the amorphous state. This is the first example, to the best of our knowledge, to offer the rational design of a heat‐resistant MLC material.
Emitting under pressure: The development of a heat‐resistant mechanoluminescent chromic (MLC) dye based on an organic–inorganic hybrid molecular scaffold, composed of luminescent organoboron complexes introduced into polyhedral oligomeric silsesquioxane, is reported. By adding mechanical forces to the sample, regular structures collapsed, and correspondingly, the emission color turns from orange to yellow (see figure).
This paper proposes control method for a snake robot to ascend and descend steps. In a multiplane step environment, it is necessary for locomotion to transfer from one plane to another. When a snake ...robot moves, it touches several planes as its body is long and thin. In this paper, we propose a control method to track the trajectory of a snake robot in a step environment. We decomposed the 3-D motion of the robot into two simple models by introducing an assumption that simplifies the model and controller, and derive a model of the robot as a hybrid system with switching. The control method consists of a tracking controller, a method for shifting the robot's part connecting the planes, and active lifting to control the shape of the robot. Ascent and descent experiments confirm the effectiveness of the proposed controller and the method for shifting the connecting part of the robot's body.
Optically active triple helicenes (
) were prepared via a palladium-catalyzed enantioselective cross-cyclotrimerization of two helicenyl arynes
, which are generated
from
, with dialkyl ...acetylenedicarboxylate
. Enantiomeric ratios of up to 98:2 were obtained when using
and (
)-QUINAP as the alkyne and chiral ligand, respectively. The absolute stereochemistry of
was revealed to be (
,
,
) by a single-crystal X-ray diffraction analysis. Kinetic studies of the racemization of enantiomerically pure
at elevated temperatures were conducted based on a high-performance liquid chromatography analysis. The activation energy for the racemization was found to be 29.1 kcal mol
. Density functional theory calculations revealed that the palladium-catalyzed enantioselective cross-cyclotrimerization reactions proceed via the dynamic kinetic resolution of a five-membered palladacycle
with two 5helicenes. Several initially formed stereoisomers of
eventually isomerize into the most thermodynamically stable palladacycle intermediate (
,
,
)-
by inversion of the 5helicenyl moiety. Then, the insertion of
into
to form (
,
,
)-
, followed by a reductive elimination, leads to the formation of (
,
,
)-
in a stereoselective manner. The optical properties of
were studied by circular dichroism and circularly polarized luminescence.
This paper proposes a shape control method for a snake robot, which maintains head position and orientation, and avoids joint limits and self-collision. We used a passive wheeled snake robot that can ...switch the grounded/lifted status of its wheels. We derived a kinematic model of the robot that represents its redundancy as both joint angles the shape controllable points (SCPs) and the null space of the control input. In the control method, the shape is changed by sequential control of the SCPs, and the null space of the control input is used for joint limit and self-collision avoidance. Jumps in control input do not occur, although the controlled variable and the model are switched. Simulations and an experiment were used to demonstrate the effectiveness of the proposed method.
In this paper, we analyze the conditions related to singular configurations with unconstrained links and present related theorems and lemmas for a snake robot and an articulated mobile robot. A snake ...robot and an articulated mobile robot have links that have passive or active wheels and the links are serially connected by active joints. The singular configuration should be avoided if the robots are automatically controlled because they cannot execute intended motion when they are in the singular configuration. We derive a novel necessary and sufficient condition for the singular configurations of the snake robot; this removes some limitations of the traditional condition for a snake robot without unconstrained links. We also derive the necessary and sufficient conditions for the singular configurations of the articulated mobile robot, and the structural conditions under which a real articulated mobile robot does not have a singular configuration. These conditions are proved by analyzing the elements of matrices included in the kinematic model and considering the geometrical meaning of the elements. In addition, we propose evaluation indices representing the distance from the singular configurations of a snake robot. We verify the effectiveness of these indices through simulations.
Mechanochromic luminescent molecules often suffer from critical loss of luminescence intensity during phase transitions in the solid state. In this study, we present mechanochromic luminescent ...molecules that can provide clear color changes with constant emission intensity during phase transitions. It was reported that the class of aggregation‐induced emission (AIE)‐active boron complexes can present intense emission by freezing intramolecular motions. According to this mechanism, we designed a complex with a fused ligand to preserve the enhanced emission in the aggregated state in the AIE during phase transitions between the solution, amorphous, and crystalline states. From optical measurements, it was shown that the synthesized boron complexes present bright emission in various phases. In particular, as we expected, the luminescence color was clearly altered during phase transition, whereas the emission intensity changed only slightly. Finally, we also found that diverse luminescence colors were obtained from each polymorph and for various substituents as induced by the substituent effect. The results in the series of mechanistic studies show that electronic interactions and π–π interactions can modulate the electronic conjugation system of the complexes without causing loss of emission efficiency.
Novel boron complexes were designed and synthesized for realizing constant emission during phase transitions. The synthesized complexes show bright emission in various phases. Additionally, the luminescence color changes drastically during phase transition. We also found that diverse luminescence colors were obtained for each polymorph and for different substituents.
