Homochiral organic molecular cage RCC3-R-modified silica as a new multimodal and multifunctional stationary phase for high-performance liquid chromatography

In this work, homochiral reduced imine cage was covalently bonded to the surface of the silica to prepare a novel high-performance liquid chromatography stationary phase, which was applied for the multiple separation modes such as normal phase, reversed-phase, ion exchange, and hydrophilic interaction chromatography. The successful preparation of the homochiral reduced imine cage bonded silica stationary phase was confirmed by performing a series of methods including X-ray photoelectron spectroscopy, thermogravimetric analysis, and infrared spectroscopy. From the extracted results of the chiral resolution in normal phase and reversed-phase modes, it was demonstrated that seven chiral compounds were successfully separated, among which the resolution of 1-phenylethanol reached the value of 3.97. Moreover, the multifunctional chromatographic performance of the new molecular cage stationary phase was systematically investigated in the modes of reversed-phase, ion exchange, and hydrophilic interaction chromatography for the separation and analysis of a total of 59 compounds in eight classes. This work demonstrated that the homochiral reduced imine cage not only achieved multiseparation modes and multiseparation functions performance with high stability, but also expanded the application of the organic molecular cage in the field of liquid chromatography.     

Can Fluorinated Molecular Cages Be Utilized as Building Blocks of Hyperhalogens?

Based on the density functional theory for exchange‐correlation potential, fluorocarbon molecular cages are investigated as building blocks of hyperhalogens. By utilizing C₈F₇ as a ligand, a series of hyperhalogen anions, that is, M(C₈F₇)₂^? (M=Li, Na, and K) and M(C₈F₇)₃^? (M=Be, Mg, and Ca), are modeled. Calculations show that all the C₈F₇ moieties preserve their geometric and electronic integrity in these anions. These anionic molecules possess larger vertical electron detachment energies (5.11–6.45 eV) than that of C₈F₇^?, verifying their hyperhalogen nature. Moreover, it is also revealed that using larger fluorinated cage C₁₀F₉ as ligands can bring about hyperhalogen anions with larger vertical electron detachment energies. The stability of these studied anions is determined by their large HOMO–LUMO gaps and positive dissociation energies of predetermined possible fragmentation pathways. It is hoped this study will provide an approach for the construction of new types of hyperhalogens and stimulate more research in superatom chemistry.     

A Mixed‐Ligand Approach for a Gigantic and Hollow Heterometallic Cage {Ni64RE96} for Gas Separation and Magnetic Cooling Applications

Nanosized aggregations of metal ions shielded by organic ligands possessing both exquisite structural aesthetics and intriguing properties are fundamentally interesting. Three isostructural gigantic transition‐metal–rare‐earth heterometallic coordination cages are reported, abbreviated as {Ni₆₄RE₉₆} (RE=Gd, Dy, and Y) and obtained by a mixed‐ligand approach, each possessing a cuboidal framework made of 160 metal ions and a nanosized spherical cavity in the center. Along with the structural novelty, these hollow cages show highly selective adsorptions for CO₂ over CH₄ or N₂ at ambient temperatures. Moreover, the gadolinium analogue exhibits large magnetocaloric effect at ultralow temperatures.     

C~1~2~0O的分子结构和光谱性质的理论研究

用INDO系列方法对双笼氧化物C~1~2~0O进行了理论研究,结果表明:双笼氧化物C~1~2~0O的形成缓解了C~6~0O中环氧三元环的角张力,并形成了呋喃型五元环将两碳笼连接在一起。两碳笼的直接键连使两笼距离较近,有较弱的相互作用,但仍各自表现一定的独立性,C~1~2~0O可发生分解生成新的化合物,C~1~2~0O的电子光谱与母体分子C~6~0相似。     

An extremely stable host-guest complex that functions as a fluorescence probe for calcium ions

Herein, we report a crown ether based molecular cage that forms extremely stable supramolecular complexes with dimethyldiazapyrenium (DMDAP) ions in CD(3)CN through the collaboration of multiple weak C-HO hydrogen bonds. The very strong binding affinity in this host-guest system allows the molecular cage to bleach the fluorescence signal of DMDAP substantially in equimolar solutions at concentrations as low as 1 x 10(-5) M. Remarkably, a 1x10(-5) M equimolar solution of the molecular cage and DMDAP is highly selective toward Ca(2+) ions-relative to other biologically important Li(+), Na(+), K(+), and Mg(2+) ions-and causes a substantial increase in the fluorescence intensity of the solution. As a result, this molecular cage/DMDAP complex behaves as a supramolecular fluorescence probe for the detection of Ca(2+) ions in solution.     

A density functional computational investigation on electronic properties of the stable irregular boron fullerenes with 20–56 atoms

The various irregular B_n (n=20‐56) cages are optimized at the B3LYP/6‐311G level. The geometries and electronic properties are systemically discussed. New B₂₄ and B₂₈ geometries are revealed. The calculated results show that the number of polygonal vacancies is apparently increased as the size of irregular cages being increased and that the irregular cage configurations with uneven distribution of different sized holes enhances the stabilities of the fullerenelike cages. The magic numbers of stabilities are predicted to be B₄₈. HOMO and LUMO gaps are discussed. Furthermore, the delocalized π orbitals are mainly distributed around the polygonal vacancies of irregular cages and enhance the stabilities of the irregular boron cages. © 2015 Wiley Periodicals, Inc.     

Balancing Ligand Flexibility versus Rigidity for the Stepwise Self-Assembly of M12L24 via M6L12 Metal–Organic Cages

Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal–organic cages. Two ligands, the bend angles of which are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions, were synthesized and used for self-assembly with Pd²⁺. As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M₂( L1 )₄, M₆( L2 )₁₂, and M₁₂( L2 )₂₄ cages. By controlling the self-assembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydrogen-bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests.     

Dynamic Interconversion between Boroxine Cages Based on Pyridine Ligation

Dynamic interconversion between large covalent organic cages was achieved simply by heating or acid/base treatment. A mixture of the boroxine cages 12‐mer and 15‐mer was cleanly converted into a pyridine adduct of the 9‐mer boroxine cage upon treatment with pyridine, and the geometry of N‐coordinated boron atoms changed from trigonal to tetrahedral. The reverse reaction was achieved by heating or acid treatment. In this process, the larger boroxine cages 12‐mer and 15‐mer were found to be entropically favored owing to the release of free pyridine molecules from 9‐mer ?6 Py.