ic8b02416_si_001.pdf (1.48 MB)
Non-Innocent Base Properties of 3- and 4‑Pyridyl-dithia- and Diselenadiazolyl Radicals: The Effect of N‑Methylation
journal contribution
posted on 2018-10-11, 14:07 authored by Anni I. Taponen, Joanne W. L. Wong, Kristina Lekin, Abdeljalil Assoud, Craig M. Robertson, Manu Lahtinen, Rodolphe Clérac, Heikki M. Tuononen, Aaron Mailman, Richard T. OakleyCondensation of persilylated
nicotinimideamide and isonicotinimideamide
with sulfur monochloride affords double salts of the 3-, 4-pyridyl-substituted
1,2,3,5-dithiadiazolylium DTDA cations of the general formula [3-,
4-pyDTDA][Cl][HCl] in which the pyridyl nitrogen serves as a noninnocent
base. Reduction of these salts with triphenylantimony followed by
deprotonation of the intermediate-protonated radical affords the free
base radicals [3-, 4-pyDTDA], the crystal structures of which, along
with those of their diselenadiazolyl analogues [3-, 4-pyDSDA], have
been characterized by powder or single-crystal X-ray diffraction.
The crystal structures consist of “pancake” π-dimers
linked head-to-tail into ribbonlike arrays by η2-S2---N(py) intermolecular secondary bonding interactions. Methylation
of the persilylated (iso)nicotinimide-amides prior to condensation
with sulfur monochloride leads to N-methylated double
chloride salts Me[3-, 4-pyDTDA][Cl]2, which can be converted
by metathesis into the corresponding triflates Me[3-, 4-pyDTDA][OTf]2 and then reduced to the N-methylated radical
triflates Me[3-, 4-pyDTDA][OTf]. The crystal structures of both the N-methylated double triflate and radical triflate salts
have been determined by single-crystal X-ray diffraction. The latter
consist of trans-cofacial π-dimers strongly
ion-paired with triflate anions. Variable temperature magnetic susceptibility
measurements on both the neutral and radical ion dimers indicate that
they are diamagnetic over the temperature range 2–300 K.