Unexpected NMR shieldings of sp- and sp²-hybridized carbon atoms in graphyne systems

Abstract

Graphynes (GYs) are two-dimensional alloptropic forms of carbon consisting of periodically arranged sp- and sp2-hybridized carbon atoms in a planar structure. Graphynes can be formally created from graphene by inserting...

NMR chemical shift of confined 129Xe: coordination number, paramagnetic channels and molecular dynamics in a cryptophane-A biosensor

“…Similar reasoning was also used to gain insight into CS trends in differently hybridised graphyne structures. 135 However, in our present case involving dynamic and flexible, H 2 O-dissolved cage structures, no similarly easily analysable trends of the electron-density differences between system configurations corresponding to high or low/negative Xe CS could be observed, which renders the analysis by density differences less appealing than in the referenced cases of rigid molecular structures.…”

“…For interpreting chemical-shift trends, one may also choose to look at the electron-density difference maps 134,135 between the ground and the magnetically allowed excited states in the vicinity of the NMR nucleus. This would in principle make it possible to take into account the r −3 -dependence on the electron-nucleus distance of the PSO operator, in eqn (4).…”

Pyrolytic Modification of Heavy Coal Tar by Multi-Polymer Blending: Preparation of Ordered Carbonaceous Mesophase

“…The carbonaceous mesophase contains various aromatic formats with many sp 2 -hybridized carbon atoms, and the aromatic molecules are highly analogous to the ortho-hexagonal arrangement of carbon atoms in the graphite lattice. Therefore, the mesophase has the potential to be transformed into graphitic carbon materials [26][27][28]. In recent years, there has been research on adjusting mesophase to enhance material properties.…”