Solid-State NMR Spectra and Long, Intra-Dimer Bonding in the π-[TTF]22+ (TTF = Tetrathiafulvalene) Dication

The 13C chemical-shift tensor principal values for TTF and π-[TTF]22+ (TTF = tetrathiafulvalene) dimer dications have been measured in order to better understand the electronic structure and long intradimer bonding of these TTF-based dimer structures. The structure of π-[TTF]22+ is abnormal due to its two C−C and four S−S ca. 3.4 A intradimer separations, which is less than the sum of the sulfur van der Waals radii, and has a singlet 1A1g electronic ground state. This study of TTF and [TTF]22+ was conducted to determine how the NMR chemical-shift tensor principal values change as a function of electronic structure. This study also establishes a better understanding of the interactions that lead to spin-pairing of the monomeric radical units. The density functional theory (DFT) calculated nuclear shielding tensors are correlated with the experimentally determined principal chemical-shift values. The embedded ion method (EIM) was used to investigate the electrostatic lattice potential in [TTF]22+. These the...