Kosuke Ono

Spin Crossover by Encapsulation

Encapsulation by synthetic hosts can transform the spin states of square planar Ni(II)(acen) and Co(II)(tap) complexes. Upon encapsulation, the red Ni(II) diamagnetic state was converted into a green paramagnetic state, whereas the Co(II) low spin (S = 1/2) state was changed into a coupled (S = 1/2 and S = 3/2) state. The host cages are noninnocent and host-guest interactions within the confined cavity influence the resultant properties of the enclathrated metal complexes.

[m × n] Metal Ion Arrays Templated by Coordination Cages

Three-dimensional m × n arrays of metal ion clusters can be assembled as aromatic stacks of planar polynuclear metal complexes within columnar coordination cages. The polynuclear complexes and cage height program the final array structures of the metal ion clusters. Cyclic trinuclear Au(I) complexes (m = 3) assembled into trigonal prismatic arrays (n = 1-3) within the cages and the array structures were clearly shown by X-ray crystallographic analysis. A silver-sandwiched hetero-Au(3)-Ag-Au(3) cluster was also prepared by treating a hexanuclear Au(3)-Au(3) cluster with Ag(I) ion.

ON/OFF red emission from azaporphine in a coordination cage in water.

Red-emissive molecules have important applications as chemosensors, biological tags, and new light source materials but are severely limited by solubility and the tendency to form nonemissive aggregrates. Here we present an unusual example where a coordination cage sequesters and maintains the red-emissive properties of tetraazaporphine (TAP) in aqueous solution. Additionally, encapsulation within the highly cationic host lowers the pK(a) of the TAP interior protons, leading to the formation of an acid/base ON/OFF fluorescent switch.

Self-Assembly of Nanometer-Sized Boroxine Cages from Diboronic Acids

By use of the reversible trimerization of boronic acids, the series of boroxine cages 3-mer, 6-mer, and 12-mer were constructed from rationally designed diboronic acids whose bond angles between two C-B bonds are 60°, 84°, and 117°, respectively. Boroxine cages 6-mer and 12-mer have 1.5 and 2.5 nm sized cavities, respectively.

Controlled Self-Assembly of Multiple Diastereomeric Macrocyclic Boronic Esters Composed of Two Chiral Units

Controlled construction of four out of five diastereomers of macrocyclic boronic ester was achieved in high yield by utilizing the self-assembly of two chiral components with the proper choice of reaction conditions. Three diastereomers could be constructed as enantiopure forms by properly changing the chirality combination between the two building blocks. Furthermore, the methodology could be applicable to the three-component self-assembly of enantiopure macrocyclic boronic esters having two different diboronic acid moieties.

Release and Recovery of Guest Molecules during the Reversible Borate Gel Formation of Guest‐Included Macrocyclic Boronic Esters

Borate gel formation from guest-encapsulated macrocyclic boronic esters was realized by the addition of a diamine to the suspension of the boronic esters in various organic solvents, which triggered the release of the guest compounds. The guest molecules could be recovered from the borate gel by addition of an acid to remove the diamine, which facilitated the reconstruction of the initial guest-encapsulated macrocyclic boronic esters.

Using Coq in specification and program extraction of hadoop mapreduce applications

Hadoop MapReduce is a framework for distributed computation on key-value pairs. The goal of this research is to verify actual running code of MapReduce applications. We first constructed an abstract model of MapReduce computation with the proof assistant Coq. In the model, mappers and reducers in MapReduce computation are modeled as functions in Coq, and a specification of a MapReduce application is expressed in terms of invariants among functions involving its mapper and reducer. The model also provides modular proofs of lemmas that do not depend on applications. To achieve the goal, we investigated the feasibility of two approaches. In one approach, we transformed verified mapper and reducer functions into Haskell programs and executed them under Hadoop Streaming. In the other approach, we verified JML annotations on Java programs of the mapper and reducer using Krakatoa, translated them into Coq axioms, and proved Coq specifications from them. In either approach, we were able to verify correctness of MapReduce applications that actually run on the Hadoop MapReduce framework.

Inclusion of Two Different Guest Molecules within a Rationally Designed Macrocyclic Boronic Ester in Organic Solvent

The inclusion of two different guest molecules in a macrocyclic boronic ester in organic solvent utilizing only π-stacking interactions has been successfully realized. For this purpose, a new tetrol which has an appropriate distance between two 1,2-diol units for the inclusion of two aromatic molecules is designed and synthesized. Simple mixing of the new tetrol with 2,7-pyrenediboronic acid in the presence of pyrene-4,5-quinone efficiently affords the desired macrocyclic boronic ester, which is found by (1)H NMR spectroscopy, ESI-MS, and isothermal titration calorimetry studies to include one molecule each of a dinitronaphthalimide derivative and pyrene. Furthermore, inclusion of two planar molecules within the macrocyclic boronic ester is revealed by X-ray analysis.

Enhancement of host-guest interactions using rationally designed macrocyclic boronic esters with a naphthalene core.

Efficient inclusion of electron-deficient aromatic guest molecules in an organic solvent utilizing π-stacking interactions was achieved by using two kinds of macrocyclic boronic esters, 1,4-naph-[2+2] and 1,5-naph-[2+2], which were easily prepared by self-assembly of 1,4-naphthalenediboronic acid (3) or 1,5-naphthalenediboronic acid (4) and racemic tetrol 1 with an indacene framework in a protic solvent. The X-ray crystallographic analyses revealed that the tilt angles of the two naphthalene rings are different: that of 1,4-naph-[2+2] is about 15° and that of 1,5-naph-[2+2] is about 0°. Owing to the parallel alignment of two aromatic rings, 1,5-naph-[2+2] has a much higher binding ability than 1,4-naph-[2+2]. This knowledge could be useful for the design of the new host molecules in organic solvents.

Dynamic Behavior of Covalent Organic Cages

Discrete, large, covalent organic cages have recently been constructed by utilizing various types of dynamic covalent bond formation. The reversibility of bond formation can provide an opportunity to exhibit unique dynamic behavior; however, the transformation of such rigid cages to other structures remains challenging. To clarify the current status of this emerging research field, this Concept article gives an overview of recent progress of the dynamic behavior of covalent organic cages by classifying them into four types of transformation, namely, dimerization into the interlocked cages, transformation into different cage structures, exchange of components, and disassembly. The driving forces of such dynamic behavior and problems to be solved are also highlighted.