Guo-Ping Yong

Direct arylation of unactivated aromatic C–H bonds catalyzed by a stable organic radical

A stable zwitterionic radical can catalyze direct arylation of unactivated aromatic C-H bonds via a chain homolytic aromatic substitution mechanism in the presence of potassium tert-butoxide.

An improved Stöber method towards uniform and monodisperse Fe3O4@C nanospheres

Significant progress has recently been made in the synthesis of Fe3O4@C nanospheres with uniform, monodisperse and tunable carbon shells. Fe3O4@C nanospheres were obtained by directly carbonizing Fe3O4@polymer which was synthesized by a versatile and economical Stober method with resorcinol and formaldehyde as precursors. The synthesis conditions in the formation of Fe3O4@polymer were systematically investigated. It was found that the yield of the Fe3O4@polymer is highly influenced by the concentration of ammonium hydroxide, and the monodispersity is mainly affected by the concentration of ammonium hydroxide and the citrate group sites outside the surfaces of the Fe3O4 nanospheres. Interestingly, carbonization of Fe3O4@polymer at high temperature makes the grain sizes of Fe3O4 in Fe3O4@C samples larger than those in the Fe3O4 sample, which makes the saturation magnetization value for the Fe3O4@C samples higher than those of common obtained materials. The adsorption performance of Fe3O4@C for anthracene was tested both in water and in cyclohexane solution; it shows fast adsorption rates (about 1 h to reach equilibrium in water and 3 h in cyclohexane solution) and high adsorption capacities (31.5 mg g−1 in water and 2 mg g−1 in cyclohexane solution), which are ascribed to its high uniformity and monodispersity. These make Fe3O4@C an ideal adsorption and enrichment material, especially for polycyclic aromatic hydrocarbons in water and in organic solvents.

Stacking-induced white-light and blue-light phosphorescence from purely organic radical materials

The internal salt and the sodium salt based on a new purely organic radical material exhibit stacking-induced white-light and blue-light phosphorescence, respectively, and possess moderate quantum yields. The high solubility in water makes them promising candidates for potential applications in OLEDs, especially as white-LEDs.

New zwitterionic radical salts: dimers in solution and unusual magnetic and luminescent properties in the solid state

A new and stable zwitterionic (neutral) radical and its perchlorate salts exist as diamagnetic pi-dimers in solution, and pi-stacking 1D chains with interesting magnetic and luminescent properties in solid state.

Anion–π interactions in new electron-deficient π systems: the relevance to solid phosphorescent colors

We herein report a new electron-deficient π system, namely carboxycarbonyl substituted imidazo[1,2-a]pyridinium, which exhibits various noncovalent interactions (hydrogen bonding, anion–π and η1-type anion–π) with chloride or perchlorate anion. Crystallographic results demonstrate that the interaction types of chloride anion and π receptor systems can be tuned: from anion–π interactions (with guest methanol molecule in crystal) to η1-type anion–π interactions (without guest methanol molecule in crystal). These carboxycarbonyl substituted imidazo[1,2-a]pyridinium salts also exhibit different phosphorescent colors in the solid state induced by crystal stacking structures or anion–π interactions that can influence the charge transfer to electron-deficient carboxycarbonyl substituted imidazo[1,2-a]pyridinium. Especially, the solid phosphorescent color changes induced by anion–π interactions are very interesting. The high solubility in water makes these purely organic phosphorescent materials promising candidates for potential applications.

One-pot synthesis of yolk–shell mesoporous carbon spheres with high magnetisation

A simple and novel route for the synthesis of monodisperse yolk–shell magnetic mesoporous carbon spheres (Fe3O4@void@C) via a ‘one-pot’ strategy for direct carbonisation and etching was developed. The synthesised materials were characterised by XRD, TEM, SEM, FT-IR, EDS, TGA, N2 sorption, and magnetic susceptibility measurements, and the ideal conditions for the synthesis of the Fe3O4@void@C spheres were systematically investigated. The morphologies and the saturation magnetisation values were observed to be strongly influenced by the composition of the solvent (ethanol–water) and the proportions of TEOS and formaldehyde used in the synthesis. The synthesised materials possessed a large average pore diameter (4.5 nm) and a magnetisation strength (62 emu g−1) greater than that of Fe3O4 itself. The performance of Fe3O4@void@C in the adsorption of pyrene was tested in aqueous solution, and fast adsorption rates (approximately 40 min to reach equilibrium) and high adsorption capacities (77.1 mg g−1) were observed. In addition, Fe3O4@void@C exhibited excellent reusability for the adsorption of pyrene over six adsorption–desorption cycles.

Magnetic and luminescent properties of Cd(II)- and Fe(II)-anion radical frameworks: various networks or structures influenced by metal ion sizes or in situ forming mechanisms of anion radical ligand

The preparation, X-ray crystallography, EPR, and magnetic and luminescent properties of three new metal–anion radical frameworks are described herein. The anion radical ligand (bipo−˙) and co-ligand, 1,4-benzenedicarboxylate (BDC2−), coordinate to Cd(II) centers, leading to an interpenetrated three-dimensional (3D) metal–organic frameworks (MOF), [Cd3(bipo−˙)4(BDC)]n (1). Although [Fe3(bipo−˙)4(BDC)]n (2) and 1 possess the same space group (tetragonal, P42/nbc), and similar rigid spirocycle-like chain and powder X-ray diffraction (PXRD) patterns, 2 exhibits an interesting spirocycle-like one-dimensional (1D) chain network, in which BDC2− behaves not as bridging co-ligand but as a counteranion, according to smaller Fe(II) ion size and long Fe1⋯Fe1′ distance between rigid chains. Thus, metal ion sizes induce different networks of isomorphous 1 and 2. Moreover, the different forming mechanisms of bipo−˙ ligand also result in different structural MOFs: the in situ deprotonation of initial Hbipo−˙ leads to an 1D Fe(II) MOF (2); the in situaldol condensation and then deprotonation of initial hydrochloride salt of imidazo[1,2-a]pyridin-2(3H)-one results in a two-dimensional (2D) Fe(II) MOF, [Fe3(bipo−˙)2(μ2-OH)2(μ2-H2O)(BDC)]n (3). More noteworthy, in 2, BDC2− suffers large distortion, mainly attributed to its strong electrostatic interaction with the Fe(II) cation on the rigid spirocycle chain. Compounds 2 and 3 exhibit broad EPR signals, ascribed to the strong iron–anion radical antiferromagnetic coupling. 1 shows an unusual magnetic phase transition at ∼70 K, and intense fluorescence emission which can even be excited by visible light (460 nm). Both 2 and 3 show strong antiferromagnetic interaction between Fe(II) cation and radical. Compared to 1, two Fe(II) MOFs exhibit obvious blue-shift fluorescence emissions.

Stacking-induced broadband near-infrared absorption beyond 2500 nm and deep-red phosphorescence from purely organic radicals

Herein, we present two new purely organic radicals which exhibit unusual stacking-induced broadband near-infrared (NIR) absorption beyond 2500 nm and deep-red phosphorescence. These interesting properties make them promising light harvesting and solid-state NIR phosphorescent materials.

Excitation-light-responsive phosphorescent color changes in a β-cyclodextrin inclusion complex

Herein, we report a novel supramolecular phosphorescent material based on a β-cyclodextrin inclusion complex. This inclusion complex exhibits unprecedented excitation-light-responsive phosphorescent color changes, which is a promising candidate for dynamically photofunctional material.

Morphology-controllable fabrication of organic microcrystals by solid-phase reactions: revealing morphology-sensitive highly efficient phosphorescence and enhanced near-infrared absorption

The vapor-solid and solid-phase anion exchange reactions provide useful strategies for the morphology-controllable fabrication of organic microcrystals. The changes in morphology induce interesting changes in the photophysical properties of organic microcrystals. Significantly, hexangular microflakes exhibit higher phosphorescence quantum yield (up to 57.5%) and enhanced near-infrared absorption.