Exclusive Hydrophobic Self-Assembly of Adaptive Solid-State Networks of Octasubstituted 9,9′-Spirobifluorenes

The Synthesis and Properties of Spirophenanthrene

Motivated by the success of 9,9'-spirobifluorene (SBF) in optoelectronic materials, we synthesized a novel spiro compound, spirophenanthrene (SP). Incorporating a phenanthrene unit as the core, we aimed to leverage the π-conjugation of SPs to surpass the limitations of SBF. Experimental and theoretical studies revealed significant advantages over SBF, including red-shifted wavelengths, tunable LUMO energy levels, and enhanced thermal stability. These advantages suggest the potential of SPs as versatile building blocks for diverse optoelectronic devices.

Diphenoquinones Redux

Benzoquinones can undergo reversible reductions and are attractive candidates for use as active materials in green carbon-based batteries. Related compounds of potential utility include 4,4'-diphenoquinones, which have extended quinonoid structures with two carbonyl groups in different rings. Diphenoquinones are a poorly explored class of compounds, but a wide variety can be synthesized, isolated, crystallized, and fully characterized. Experimental and computational approaches have established that typical 4,4'-diphenoquinones have nearly planar cores in which two cyclohexadienone rings are joined by an unusually long interannular C═C bond. Derivatives unsubstituted at the 3,3',5,5'-positions react readily by hydration, dimerization, and other processes. Association of diphenoquinones in the solid state normally produces chains or sheets held together by multiple C-H···O interactions, giving structures that differ markedly from those of the corresponding 4,4'-dihydroxybiphenyls. Electrochemical studies in solution and in the solid state show that diphenoquinones are reduced rapidly and reversibly at potentials higher than those of analogous benzoquinones. Together, these results help bring diphenoquinones into the mainstream of modern chemistry and provide a foundation for developing redox-active derivatives for use in carbon-based electrochemical devices.

Sonogashira Synthesis of New Porous Aromatic Framework-Entrapped Palladium Nanoparticles as Heterogeneous Catalysts for Suzuki-Miyaura Cross-Coupling

Palladium nanoparticles entrapped in porous aromatic frameworks (PAFs) or covalent organic frameworks may promote heterogeneous catalytic reactions. However, preparing such materials as active nanocatalysts usually requires additional steps for palladium entrapment and reduction. This paper reports as a new approach, a simple procedure leading to the self-entrapment of Pd nanoparticles within the PAF structure. Thus, the selected Sonogashira synthesis affords PAF-entrapped Pd nanoparticles that can catalyze the C-C Suzuki-Miyaura cross-coupling reactions. Following this new concept, PAFs were synthesized via Sonogashira cross-coupling of the tetraiodurated derivative of tetraphenyladamantane or spiro-9,9'-bifluorene with 1,6-diethynylpyrene, then characterized them using powder X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, high-resolution scanning transmission electron microscopy, and textural properties (i.e., adsorption-desorption isotherms). The PAF-entrapped Pd nanocatalysts showed high catalytic activity in Suzuki-Miyaura coupling reactions (demonstrated by preserving the turnover frequency values) and stability (demonstrated by palladium leaching and recycling experiments). This new approach presents a new class of PAFs with unique structural, topological, and compositional complexities as entrapped metal nanocatalysts or for other diverse applications.

Accessing new microporous polyspirobifluorenes via a C/Si switch

Microporous spirosilabifluorene networks were synthesized via Yamamoto coupling of tetrabromospirosilabifluorene precursors. They exhibit bright fluorescence that is quenched in the presence of nitroaromatics. The C/Si switch has subtle effects on the optical properties of the spirobifluorene network and provides a convenient route to 3,3',6,6'-coupled and other polybifluorenes.

Understanding how intrinsic micro-pores affect the dielectric properties of polymers: an approach to synthesize ultra-low dielectric polymers with bulky tetrahedral units as cores

Two fluoro-containing low dielectric polymers have been successfully prepared based on thermo-crosslinkable trifluorovinyl ether (TFVE) monomers with bulky tetrahedral units (adamantane and spirobifluorene).

Spiro-fused bis-hexa-peri-hexabenzocoronene

A spiro-fused hexa-peri-hexabenzocoronene dimer is first prepared, which is confirmed by X-ray crystallography, exhibiting reversible redox property.