Transient chirality inversion during racemization of a helical cobalt(III) complex.

SignificanceWe first observed a transient chirality inversion on a simple unimolecular platform during the racemization of a chiral helical complex [LCo3A6]3+, i.e., the helicity changed from P-rich (right-handed) to M-rich (left-handed), which then racemized to a P/M equimolar mixture in spite of the absence of a reagent that could induce the M helix. This transient chirality inversion was observed only in the forward reaction, whereas the reverse reaction showed a simple monotonic change with an induction time. Consequently, the M helicity appeared only in the forward reaction. These forward and reverse reactions constitute a hysteretic cycle. Compounds showing such unique time responses would be useful for developing time-programmable switchable materials that can control the physical/chemical properties in a time-dependent manner.

Effects of Interviewer Age on the Reminiscence Bump in Older adults' Autobiographical Memories.

INTRODUCTION: This study aims to investigate whether the reminiscence bump in older adults' autobiographical memory is influenced by the interviewer's age. Methods: I arranged four interviewer. CONDITIONS: child, university student, middle-aged adult, and older adult. The participating older adults were asked individually to describe three memories and the age at which the event occurred. I analyzed the temporal distribution of the bumps and the recall order. RESULTS: The results indicate that the interviewer's age, especially the child interviewers were influenced the temporal location of the reminiscence bump. Conclusion: This study discusses the implications of these findings for older adults' social communication processes.

Speed Tuning of the Formation/Dissociation of a Metallorotaxane.

Switching between the formation/dissociation of rotaxanes is important to control the function of various types of rotaxane-based materials. We have developed a convenient and simple strategy, the so-called "accelerator addition", to make a static rotaxane dynamic without apparently affecting the chemical structure. As an interlocked molecule that enables tuning of the formation/dissociation speed, a metallorotaxane was quantitatively generated by the complexation of a triptycene-based dumbbell-shaped mononuclear complex, [PdL2 ]2+ (L=2,3-diaminotriptycene), with 27C9. As a result of the inertness of the Pd2+ -based coordination structure, the metallorotaxane was slowly formed (the static state). This rotaxane formation was accelerated 27 times simply by adding Br- as an accelerator (the dynamic state). A similar drastic acceleration was also demonstrated during the dissociation process when Cs+ was added to the metallorotaxane to form the free axle [PdL2 ]2+ and the 27C9-Cs+ complex.

Guest Recognition Control Accompanied by Stepwise Gate Closing and Opening of a Macrocyclic Metallohost.

Host-guest binding behavior of macrocyclic hosts is significantly influenced by the shapes and sizes of the hosts. In particular, closing/opening the apertures of the hosts controls the guest uptake/release. A post-metalation modification method was used to achieve the open/close conversions. The starting open complex, [LCo2 (pip)4 ](OTf)2 , was efficiently converted to the closed complex, [LCo2 (hda)2 ](OTf)2 , which has a doubly bridged structure. The conversion of this closed complex to the open complex [LCo2 (hda)2 (OAc)]+ was too slow to be completed, but this gate-opening was dramatically accelerated by the addition of Na+ . The Na+ binding was also significantly enhanced by the gate-opening, that is, conversion of [LCo2 (hda)2 ]2+ to [LCo2 (hda)2 (OAc)]+ .

Rhodium(I) Complexes Bearing an Aryl-Substituted 1,3,5-Hexatriene Chain: Catalysts for Living Polymerization of Phenylacetylene and Potential Helical Chirality of 1,3,5-Hexatrienes.

Unique bench-stable rhodium(I) complexes bearing an aryl-substituted 1,3,5-hexatriene chain have been synthesized by reactions of (bicyclo[2.2.1]hepta-2,5-diene)rhodium(I) chloride dimer ([Rh(nbd)Cl]2 ) with aryl boronic acids and diphenylacetylenes in the presence of a 50 % aqueous solution of KOH. X-ray crystallographic analysis of the isolated complexes indicated a square-planar structure stabilized by a strong interaction with one of the aryl groups on the 1,3,5-hexatriene chain, which has a helical structure. The helical chirality of the isolated rhodium complexes was confirmed to be sufficiently stable to be resolved into enantiomers by HPLC on a chiral stationary phase at room temperature. It was confirmed that the isolated rhodium complexes functioned as initiators for living polymerization of phenylacetylene to give cis-stereoregular poly(phenylacetylene) with a well-controlled molecular weight.

Post-Metalation Modification of a Macrocyclic Dicobalt(III) Metallohost by Site-Selective Ligand Exchange for Guest Recognition Control.

We propose post-metalation modification as a useful strategy to control the guest recognition behavior of a metal-containing macrocyclic host. This is based on the ligand exchange of the axial ligands of a cobalt(III) dinuclear macrocyclic host, [LCo2 X4 ]2+ (X=axial amine ligand). Four piperidine ligands in [LCo2 (pip)4 ]2+ (pip=piperidine) were site-selectively replaced with primary amines. The competitive experiments revealed that the order of the affinity toward the cobalt centers in [LCo2 X4 ]2+ is primary amine > secondary amine > tertiary amine and that the piperidine-coordinating complex, [LCo2 (pip)4 ]2+ , was reasonably reactive among the isolable complexes. Indeed, two piperidine ligands at the diagonal positions in [LCo2 (pip)4 ]2+ were site-selectively replaced with pyridine or acetate ion. The replacement of piperidine with acetate ion significantly enhanced the recognition ability towards Na+ .

Non-Covalent Interactions Enable the Length-Controlled Generation of Discrete Tubes Capable of Guest Exchange.

Supramolecular chemistry in confined spaces constructed from macrocyclic molecules has attracted much attention because it can utilize the specific binding properties of macrocyclic cavities. Herein we report the preparation of length-controlled discrete tubular structures by homo-/co-assembly of rim-differentiated and peralkylamino-substituted pillar[5]arenes via hydrogen bonds and salt bridges. By dimerization and trimerization, the expanded tubes show a fivefold helical structure and stepwise binding, respectively. We found that the exchange speed of guest molecules in the tubes could be controlled by varying the tube length.

Switching of Recognition First and Reaction First Mechanisms in Host-Guest Binding Associated with Chemical Reactions.

Host-guest binding sometimes triggers the subsequent chemical reactions of the host framework as well as changes in the physical properties. Since the host-guest binding generally occurs very quickly, it is sometimes difficult to differentiate the mechanism from the alternative one in which the guest binding occurs after the reaction. However, it is important to differentiate the two mechanisms when we develop new molecules based on time-dependent functions. Thus, we propose two distinct mechanisms, recognition first and reaction first, in a slowly reacting host system. We designed and synthesized a new cobalt(III) metallohost, [LCo2(pip)4](OTf)2 (pip = piperidine), which can take up a guest cation into its 18-crown-6-like cavity causing concomitant exchange of the axial piperidine ligands under solvolytic conditions. We investigated the mechanism to elucidate whether the guest recognition or ligand exchange occurs first. When Na+ (5-10 equiv) was present, the guest recognition occurred by the recognition first mechanism; i.e., Na+ was initially taken up into the cavity, then the axial piperidine ligands were replaced with methoxo ligands. On the other hand, when 1 equiv of M+ (= K+, Rb+) was present, the guest recognition occurred by the reaction first mechanism; i.e., M+ was taken up after one of the piperidine ligands was replaced with a methoxo ligand. Therefore, the recognition pathway can be switched by changing the guest cations.

Ligand Exchange Strategy for Tuning of Helicity Inversion Speeds of Dynamic Helical Tri(saloph) Metallocryptands.

We developed a new strategy, ligand exchange strategy, for tuning the response speeds of helicity inversion of a metal-containing helical structure. This is based on the exchange of the two axial amine ligands of the octahedral Co3+ centers in the metallocryptands [LCo3 X6 ] (X=axial amine ligand). The response speeds of the helicity induction were controlled by using different combinations of achiral and chiral amines as the starting and entering ligands, respectively. The response speeds of the helicity inversion from P to M were also tuned by using different combinations of chiral amines.

Host-Guest Complexation Using Pillar[5]arene Crystals: Crystal-Structure Dependent Uptake, Release, and Molecular Dynamics of an Alkane Guest.

Host-guest complexation has been mainly investigated in solution, and it is unclear how guest molecules access the assembled structures of host and dynamics of guest molecules in the crystal state. In this study, we studied the uptake, release, and molecular dynamics of n-hexane vapor in the crystal state of pillar[5]arenes bearing different substituents. Pillar[5]arene bearing 10 ethyl groups yielded a crystal structure of herringbone-type 1:1 complexes with n-hexane, whereas pillar[5]arene with 10 allyl groups formed 1:1 complexes featuring a one-dimensional (1D) channel structure. For pillar[5]arene bearing 10 benzyl groups, one molecule of n-hexane was located in the cavity of pillar[5]arene, and another n-hexane molecule was located outside of the cavity between two pillar[5]arenes. The substituent-dependent differences in molecular arrangement influenced the uptake, release, and molecular dynamics of the n-hexane guest. The substituent effects were not observed in host-guest chemistry in solution, and these features are unique for the crystal state host-guest chemistry of pillar[5]arenes.

ON/OFF Control of the Flipping Motion of Diuranyl Bis(Salophen) Macrocycle by Extremely Strong Binding with Fluoride Ion.

Diuranyl bis(salophen) complex 1 features a relatively slow conformational motion, induced by an intramolecular O═U═O···UO2 binding motif, which interconverts the two nonsymmetric halves of the ligand. This flipping motion, which constitutes one of the fundamental molecular motions, can be completely halted by addition of fluoride anion, which is bound to 1, reaching one of the highest affinities reported to date. This system represents a model to study flipping dynamics in light of the possibility of developing novel types of molecular machines based on it.

Synthesis of Sterically Fixed Phytochrome Chromophore Derivatives Bearing a 15 E- Fixed or 15 E- Anti- Fixed CD-Ring Component.

To analyze the structure and function of phytochrome chromophores, we have been synthesizing natural and unnatural bilin chromophores of phytochromes. In this manuscript, we report the synthesis of sterically fixed 15 E- fixed 18Et-biliverdin (BV) and 15 E- anti-fixed 18Et-BV derivatives. The key reaction is the introduction of an sp3 carbon alkyl chain bearing a leaving group at the meso-position of the CD-ring component by using the corresponding Grignard reagents in the presence of LiCl.

Metallonanobelt: A Kinetically Stable Shape-Persistent Molecular Belt Prepared by Reversible Self-Assembly Processes.

A triptycene-based shape-persistent belt-shaped macrocycle, metallonanobelt, was synthesized by the self-assembly of 2,3,6,7-tetraaminotriptycene L and square planar Pd2+. The pentamer was selectively formed by the complexation of L with Pd2+ in the presence of the pillar[6]arene derivative P6 having triethylene glycol pendant as a template, whereas a mixture of a trimer, tetramer, and pentamer was obtained in the absence of the template. The pentamer was successfully isolated based on the solubility difference between the metallonanobelt and the template. It was also revealed that the isolated pentamer was remarkably stable in solutions such as acetonitrile or methanol thanks to the relatively inert planar chelate metal complex, [Pd( o-phenylenediamine)2] unit. Thus, we can handle the metallonanobelt almost as a static organic nanobelt that is synthesized covalently.

Alkane-Shape-Selective Vapochromic Behavior Based on Crystal-State Host-Guest Complexation of Pillar[5]arene Containing One Benzoquinone Unit.

Colored crystals of pillar[5]arene containing one benzoquinone unit were found to exhibit alkane-shape-selective vapochromic behavior. Activated pillar[5]arene crystals, prepared by removing solvated methanol from pillar[5]arene crystals, changed color from dark-brown to light-red after exposure to linear alkane vapors; however, no color changes were observed on exposure to branched or cyclic alkanes. Uptake of methanol vapor by the activated crystals induced a different color change, from dark-brown to black. This multi-vapochromism results from the different intermolecular π-stacking interactions between the benzoquinone and 1,4-diethoxybenzene units in the alkane- and methanol-containing crystals. Unlike most known vapochromic materials, these pillar[5]arene-based materials were highly stable; after uptake of n-alkanes or methanol the color of the crystals did not change after storage in air for 3 weeks. This is because the included guests were stabilized in the cavity by multiple CH/π interactions.

Development of a One-Pot Synthetic Method for Multifunctional Oxazole Derivatives Using Isocyanide Dichloride.

A one-pot synthetic method was developed for multifunctional dihydrooxazole and oxazole derivatives. New reaction sequences were developed involving the formation of isocyanide dichloride, an aldol-type reaction with aldehydes, and a nucleophilic addition-elimination reaction, which efficiently afforded the dihydrooxazole and oxazole scaffolds.

Phosphinic acid-promoted addition reaction of isocyanides to (Z)-hydroximoyl chlorides: efficient synthesis of α-(hydroxyimino)amides.

The reaction of (Z)-hydroximoyl chlorides with isocyanides promoted by phosphinic acid in the presence of triethylamine proceeds smoothly to afford α-(hydroxyimino)amides in good to high yields. Phosphinic acid plays an important role in effectively promoting the reaction. A wide range of (Z)-hydroximoyl chlorides and isocyanides were found to be suitable for this reaction.

[Effectiveness of an executive function task with a touch panel system for young children].

The Dimensional Change Card Sort (DCCS) task is a widely used measure for the development of executive function during early childhood. In this task, children are asked to sort cards according to one rule (e.g., color) during preswitch phases, after which they are asked to sort cards according to another rule (e.g.; shape) during the postswitch phases. A computer version of the DCCS was needed to standardize the test material, but a previous study showed that children showed more difficulty in a computer version with a mouse device than the standard card version. In this study, we assessed the effectiveness of a computer version with a touch panel and compared performance with the standard card version. Three- and 4-year-old children were given the card version and computer version of the DCCS tasks. The results revealed that children showed similar performance during the preswitch and postswitch phases both in the computer version and in the card version. The results suggest that both versions of the task assessed the same underlying cognitive processes.

Host-Guest Complexation of Perethylated Pillar[5]arene with Alkanes in the Crystal State.

Activated perethylated pillar[5]arene crystals show an unexpected alkane-shape- and -length-selective gate-opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n-alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate-opening pressure. As the chain length of the n-alkanes increased, the gate pressure decreased. A transformation into a herringbone structure was induced when n-hexane was used as a guest. By contrast, cyclic and branched alkanes were not taken up and could not induce a crystal transformation because they were too large to fit in the cavities of the pillar[5]arene. Alkane-shape-selective molecular recognition of pillar[5]arenes in the solution state was translated into the vapor/crystal state.

Trapping of a spatial transient state during the framework transformation of a porous coordination polymer.

Structural transformability accompanied by molecular accommodation is a distinguished feature of porous coordination polymers (PCPs) among porous materials. Conventional X-ray crystallography allows for the determination of each structural phase emerged during transformation. However, the propagation mechanism of transformation through an entire crystal still remains in question. Here we elucidate the structural nature of the spatial transient state, in which two different but correlated framework structures, an original phase and a deformed phase, simultaneously exist in one crystal. The deformed phase is distinctively generated only at the crystal surface region by introducing large guest molecules, while the remaining part of crystal containing small molecules maintains the original phase. By means of grazing incidence diffraction techniques we determine that the framework is sheared with sharing one edge of the original primitive cubic structure, leading to the formation of crystal domains with four mirror image relationships.

Induced chirality at the surface: fixation of a dynamic M/P invertible helical Co3 complex on SiO2.

Dynamic M/P invertible helicity was successfully induced at a SiO2 surface immobilized with a dynamic helical trinuclear cobalt complex, [LCo3(NHMe2)6](OTf)3, using chiral ((R) or (S))-1-phenylethylamine. Solid-state CD spectra and theoretical calculations suggested that the fixation of the M/P helical complex on the surface via coordination interactions was the key factor of the induced chirality at the surface.