Identifying Nanothread Structures with Experimental and Calculated Nuclear Magnetic Resonance Spectra

Well-ordered packed one-dimensional, mainly sp³, carbon nanomaterials, known as nanothreads, have recently been synthesized by slowly compressing and decompressing crystalline, solid benzene from high pressure. The atomic structure of these threads has been determined only in part. We calculated the ¹³C NMR chemical shifts, chemical shielding tensors and anisotropy of several axially ordered and disordered partially (degree-4) and fully (degree-6) saturated nanothreads within density functional theory and compared systematically with the experimental solid-state NMR spectra to assist in identifying the structures of the synthesized nanothreads. The results reveal that some degree-4 threads might contribute to the sp² carbon component, and degree-6 threads with distinct carbon sites are plausible candidates of the one-dimensional carbon nanomaterial. We further narrowed down the subset of possible degree-4 and degree-6 candidates by analyzing the calculated and measured chemical shifts anisotropy and two-dimensional solid-state NMR spectra.