Self-assembly of coordination molecular baskets as inorganic analogues of cyclotriveratrylenes (CTV)

A [3 + 3] modular self-assembly gives rise to the formation of basket-shaped, crown ether-functionalized, nano-sized trimetallo-macrocycles, which function as structural analogues of cyclotriveratrylenes (CTV).     

Gradient modeling for multivariate quantitative data

We propose a new parametric model for continuous data, a “g-model”, on the basis of gradient maps of convex functions. It is known that any multivariate probability density on the Euclidean space is uniquely transformed to any other density by using the gradient map of a convex function. Therefore the statistical modeling for quantitative data is equivalent to design of the gradient maps. The explicit expression for the gradient map enables us the exact sampling from the corresponding probability distribution. We define the g-model as a convex subset of the space of all gradient maps. It is shown that the g-model has many desirable properties such as the concavity of the log-likelihood function. An application to detect the three-dimensional interaction of data is investigated.     

Using End Groups to Tune the Linear and Nonlinear Optical Properties of Bis(dioxaborine)‐Terminated Polymethine Dyes

Six anionic pentamethine dyes with different 2,2‐difluoro‐4‐aryl‐1,3,2(2 H)‐dioxaborin‐6‐yl termini were synthesized and isolated as tetra‐n‐octylammonium salts with a variety of aryl groups appended to increase conjugation beyond the dioxaborine termini. The increased conjugation was expected to decrease the energy of the lowest‐lying excited state, and increase the transition dipole moment linking this state to the ground state, which would be anticipated to result in an increase in the real part of the third‐order polarizability, Re(γ). UV/Vis‐NIR absorption spectroscopy indicates that the absorption maxima in DMSO vary from 691 to 761 nm, with the longest wavelength transitions observed for a derivative where the aryl group is 4‐nitrophenyl. Closed‐aperture Z‐scan measurements at 1.3 μm in DMSO indicate that Re(γ) varies from ?2.9×10^?33 to ?5.4×10^?33 esu in these systems. The largest magnitude of Re(γ) was observed for a dye with E‐4‐styrylphenyl aryl groups. This result can be rationalized using a two‐state expression which relates Re(γ) to the energy and transition dipole moment of the transition from the ground state to the lowest‐lying excited state. A nonamethine analogue of this compound was also synthesized and exhibits a slightly larger Re(γ) with respect to a previously reported bis(dioxaborine)‐terminated nonamethine. The extension of conjugation beyond the dioxaborine termini seems to result in an overall increase in Re(γ). However, the effects are smaller than those found by increasing conjugation in the polymethine bridge due to reduced participation of terminal groups in the HOMO.     

Near-infrared storage ring free electron laser experiments at AIST

The development of free electron lasers (FELs) with a compact storage ring NIJI-IV in the near- and middle-infrared regions has been advanced at the National Institute of Advanced Industrial Science and Technology. The optical klystron ETLOK-III was installed in one of the long straight sections of the NIJI-IV, and spontaneous emission spectra were observed in the visible and near-infrared regions. Optical cavity chambers for infrared FELs were installed this February, and it was confirmed that the vibration amplitude of the optical cavity chambers was below 0.5 μm in an optical beam axis. FEL experiments in the near-infrared region will be performed this winter.     

Cyclic monoterpenes trapped in a polyaromatic capsule: unusual selectivity,isomerization, and volatility suppression

Cyclic monoterpenes (CMTs) are intractable natural products with high volatility and strong odors so that there has been no molecular receptor capable of selectively and tightly trapping CMTs in both solution and the solid state. We herein report that a polyaromatic capsule acts as a functional nanoflask for CMTs with the following five features: (i) the capsule can selectively bind menthone from mixtures with other saturated CMTs in water. In contrast, (ii) treatment of the capsule with mixtures of menthone and π-conjugated CMTs gives rise to ternary host–guest complexes with high pair-selectivity. Notably, (iii) the encapsulated menthone displays unusual isomerization from a typical chair conformer to otherwise unstable conformers upon heating. (iv) The selective binding of volatilized CMTs is demonstrated by the capsule even in the solid state at atmospheric pressure. Furthermore, (v) the volatilities of CMTs are significantly suppressed at elevated temperatures by the capsule upon encapsulation in solution as well as in the solid state.

A polyaromatic capsule demonstrated its unique host functions toward cyclic monoterpenes, i.e., selective binding in water, pair-selective encapsulation, unusual isomerization, selective binding in the solid state, and remarkable volatility suppression.     

Assembly state of catalytic modules as chiral switches in asymmetric Strecker amino acid synthesis

Self-assembled chiral polymetallic complexes often demonstrate novel properties as asymmetric catalysts. We report the three-dimensional structures of two such asymmetric catalysts (crystals A and B) for Strecker alpha,alpha-disubstituted amino acid synthesis. These complexes are constructed via assembly of the same chiral modules derived from d-glucose, but their assembly modes differ. The enantioselectivity in the Strecker reaction was dramatically switched, depending on which assembly mode was used: the catalyst generated in situ whose structure is represented by crystal B, or by crystal A. These findings provide insight into the functional importance of higher-order structures of an artificial catalyst.     

Selective formation of a self-assembling homo or hetero cavitand cage via metal coordination based on thermodynamic or kinetic control

The selective formation of a homo or hetero cavitand cage composed of two molecules of tetra(4-pyridyl)-cavitand (1), tetrakis(4-cyanophenyl)-cavitand (2), or tetrakis(4-pyridylethynyl)-cavitand (3), and four molecules of Pd(dppp)(OTf)(2) (4) or Pt(dppp)(OTf)(2) (5) has been studied. A 1:1:4 mixture of 1 with more steric restriction, 2 with less coordination ability, and 4 or 5 specifically self-assembled into a hetero cavitand cage 6 or 7, respectively. In contrast, a 1:1:4 mixture of 2, 3, and 4 in CDCl(3) at room temperature assembled into the most labile homo cyanophenyl cavitand cage 8 and the most stable homo pyridylethynyl cavitand cage 9 in a 1:1 ratio. Upon heating at 50 degrees C, the thermodynamic equilibrium was shifted to a 1:1:1 mixture of 8, 9, and a hetero cavitand cage 10. When 1 equiv of 3 was added to 8 at room temperature, 8, 9, and 10 were formed initially in a 1:1:3 ratio and finally shifted to a 1:1:1 ratio. In the Pt-system, upon addition of 1 equiv of 3 to homo cyanophenyl cavitand cage 11 in CDCl(3) at room temperature, the ratio of hetero to homo cavitand cage (13/12) initially attained was 8.7 and remained above 5.6 at room temperature. Upon heating at 50 degrees C, 13 was finally converted to 11 and 12. Thus, the selectivity for the self-assembly of the homo or hetero cavitand cage is controlled by the balance between kinetic and thermodynamic stabilities of cages based on a combination of factors such as coordination ability and steric demand of the cavitands.     

Mixed La-Li heterobimetallic complexes for tertiary nitroaldol resolution

A kinetic resolution of tertiary nitroaldols derived from simple ketones is described. Mixed BINOL/biphenol La-Li heterobimetallic complexes gave the best selectivity in retro-nitroaldol reactions of racemic tertiary nitroaldols. By using a mixture of La-Li3-(1a)3 complex (LLB 2a) and La-Li3-(1b)3 (LLB* 2b) complex in a ratio of 2/1, chiral tertiary nitroaldols were obtained in 80-97% ee and 30-47% recovery yield.     

A Solvato‐Fluorochromic Macrocycle of Multiple Anthracene Fluorophores in Close Proximity

A fluorescent macrocycle containing four anthracene panels linked by meta‐phenylene spacers and amino hinges was synthesized. The macrocycle adopts a twisted, compressed conformation that places embedded anthracene fluorophores in close contact. Emission from the convoluted macrocycle is highly solvatochromic and significantly enhanced as compared with that of the partial structures.