Tunable Superstructures of Dendronized Graphene Nanoribbons in Liquid Phase.

In this Communication, we report the first synthesis of structurally well-defined graphene nanoribbons (GNRs) functionalized with dendritic polymers. The resultant GNRs possess grafting ratios of 0.59-0.

Revisiting the Perfluorinated Trityl Cation.

Although ultimately not isolable for X-ray structural characterization, the free perfluorinated trityl cation was shown to be observable in neat triflic acid, which represents milder conditions than previous reports of this cation in "magic acid" or oleum. A triflate-bound species could be generated in organic solvents using stoichiometric amounts of triflic acid and was shown to be synthetically viable for hydride abstraction from Et SiH. It was demonstrated that the para-position on the -C F rings is the primary point of attack for decomposition of the cation.

Intrinsic Properties of Single Graphene Nanoribbons in Solution: Synthetic and Spectroscopic Studies.

We report a novel type of structurally defined graphene nanoribbons (GNRs) with uniform width of 1.7 nm and average length up to 58 nm. These GNRs are decorated with pending Diels-Alder cycloadducts of anthracenyl units and N- n-hexadecyl maleimide.

Highly efficient F heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation.

We present heteronuclear F refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle-spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent C-F dipolar coupling interactions while simultaneously suppressing strong anisotropic chemical shift as well as homonuclear F-F dipolar coupling effects as typically present in perfluorated compounds. In an extensive numerical and experimental analysis using a rigid, organic solid as a model compound, it becomes evident that the supercycled rCW schemes markedly improve the decoupling efficiency, leading to substantial enhancements in resolution and sensitivity when compared to previous state-of-the-art methods.

Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR.

We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization ((RESPIRATION)CP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer.

Efficient polarization transfer between spin-1/2 and ¹⁴N nuclei in solid-state MAS NMR spectroscopy.

Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as (14)N in solid-state NMR is severely challenged by the typical presence of large quadrupole coupling interactions. This has effectively prevented the use of the abundant (14)N spin as a probe to structural information and its use as an element in multi-dimensional solid-state NMR correlation experiments for assignment and structural characterization. In turn, this has been a contributing factor to the extensive use of isotope labeling in biological solid-state NMR, where (14)N is replaced with (15)N.