Simultaneous Arrangement of up to Three Different Molecules on the Pore Surface of a Metal–Macrocycle Framework: Cooperation and Competition

Porous crystals are excellent materials with potential spatial functions through molecular encapsulation within the pores. Co‐encapsulation of multiple different molecules further expands their usability and designability. Herein we report the simultaneous arrangement of up to three different guest molecules, TTF (tetrathiafulvalene), ferrocene, and fluorene, on the pore surfaces of a porous crystalline metal–macrocycle framework (MMF). The position and orientation of adsorbed molecules arranged in the pore were determined by single‐crystal X‐ray diffraction analysis. The anchoring effect of hydrogen bonds between the hydroxy groups of the guest molecules and inter‐guest cooperation and competition are significant factors in the adsorption behaviors of the guest molecules. This finding would serve as a design basis of multicomponent functionalized nanospaces for elaborate reactions that are realized in enzymes.     

Synthesis,Structure, and Properties of α,β‐Linked Oligothiazoles with Controlled Sequence

α,β‐Linked oligothiazoles with head‐to‐tail connectivity are presented as a new family of helical scaffolds. Combinations of palladium‐catalyzed cross‐coupling reactions at the 5‐ and 4‐positions of 2‐phenylthiazole led to the synthesis of oligo(2‐phenylthiazoles) with ortho linkages with a variety of defined sequences. The secondary structures of the α,β‐linked oligo(2‐phenylthiazoles) showed a clear dependence on their sequences. X‐ray crystallography of the trimer, tetramer, and hexamer with head‐to‐tail connection revealed the formation of a helical structure, which was stabilized by a combination of intramolecular forces, including interheteroatom (S???N), CH–π, and π–π interactions. The introduction of a chiral end‐group successfully led to the induction of chirality into the helical conformations. Programmable sequences for controlled geometries and photofunctions have been demonstrated through the manifold connection pathways in α,β‐linked oligothiazoles.     

A constructive solution to a problem of ranking tournaments

A tournament is an oriented complete graph. The problem of ranking tournaments was firstly investigated by P. Erd?s and J. W. Moon. By probabilistic methods, the existence of ?? ?? unrankable” tournaments was proved. On the other hand, they also mentioned the problem of explicit constructions. However, there seems to be only a few of explicit constructions of such tournaments. In this note, we give a construction of many such tournaments by using skew Hadamard difference sets which have been investigated in combinatorial design theory.     

Direct perfluoroalkylation of non-activated aromatic C-H bonds of phenols

A simple procedure for the perfluoroalkylation of the aromatic ring of phenols under mildly basic conditions is described. Treatment of a variety of phenols with perfluoroalkyl iodide in the presence of the radical initiator V-70L and Cs₂CO₃ provided the corresponding perfluoroalkylated products in moderate to good yields. Generally, the reaction proceeded smoothly at room temperature to yield regioselectively perfluoroalkylated products.     

Shear-Force Detection by Reusable Quartz Tuning Fork without External Vibration

Many studies have reported on the use of quartz tuning forks (a type of crystal oscillator used in wristwatches) in the detection of shear force, employed to control the distance between the probe and the sample in a scanning near-field optical microscope. This study focuses on a newly-devised shear force detection method capable of simultaneous non-external oscillation and detection, which also allows for subsequent reuse of a tuning fork. The optimum configuration and tip length for inserting a probe into the slit of a tuning fork have been elucidated. The shear force was detectable in about 5 nm decay length using such conditions.     

Azafullerene encapsulated single-walled carbon nanotubes with n-type electrical transport property

Electrical transport properties of C60 and C59N encapsulated single-walled carbon nanotubes (SWNTs) are investigated by fabricating them as the channels of field effect transistor (FET) devices at room temperature. Their measurements indicate that C60@SWNTs exhibit the enhanced p-type characteristics compared with the case of pristine SWNTs, whereas C59N@SWNTs show the n-type behavior. The novel transport properties of peapods can be explained by the charge-transfer effect, which can modify the electronic structure of SWNTs.     

Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)

meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by (1)H, (13)C, and (19)F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25 degrees C exist largely as an equilibrium among several rapidly interconverting twisted M?bius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or M?bius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100 degrees C in THF, these rapid interconversions among M?bius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a M?bius conformation. Detailed analyses of the solid-state M?bius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic pi-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable M?bius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.