1,2,4,6-Thiatriazinyl Radicals and Dimers: Structural and Electronic Tuning through Heteroaromatic Substituent Modification

Abstract

The functionalization of thiatriazinyl (TTA) radicals with pyridyl and thienyl moieties is described, and their influence at both the molecular and solid-state level has been investigated. Comparative electron paramagnetic resonance studies of 3,5-bis-(2-pyridyl)-1,2,4,6-thiatriazinyl (Py 2 TTA) and 3,5-bis-(2-thienyl)-1,2,4,6-thiatriazinyl (Th 2 TTA) reveal the impact of heteroaromatic substitution on the electronic structure, which is supported by density functional theory calculations. Single crystal X-ray analysis emphasizes the importance of intermolecular contacts on the crystal packing and demonstrates the potential for structural control through S---N′ and N---HC′ interactions, which are enhanced in Py 2 TTA and Th 2 TTA by the presence of the pyridyl and thienyl groups, respectively. This work represents a fundamental study of heterocyclic aromatic substitution in thiazyl-based radicals and investigates how varying these functional groups influences the molecular properties and long-range order within the supramolecular structure.

Ambivalent binding between a radical-based pincer ligand and iron

“…Based on single crystal X-ray analysis, Py 2 TTA • selfassociates in the solid state to form a sulphur-sulphur bridged co-facial dimer. 29 Such structural features have also been reported for other TTA derivatives. 35,36 Although dimerization occurs, stabilization of the radical may be accomplished through metal coordination, as has been shown to work with other radical based ligand systems.…”

“…This challenge was overcome by changing the oxidant to N-chlorosuccinimide (NCS), affording Py 2 TTA • as a microcrystalline copper coloured solid (Scheme 1). 29 Purification can be accomplished by sublimation under vacuum or recrystallization in hot acetonitrile (MeCN). Based on single crystal X-ray analysis, Py 2 TTA • selfassociates in the solid state to form a sulphur-sulphur bridged co-facial dimer.…”

“…28 Not only does this ligand design maintain the topology of terpy, but it also affords ambiguity in regards to oxidation states as both the anionic and neutral states are isolatable. 29 In other words, Py 2 TTA enables coordination of the neutral radical (Py 2 TTA • ) in a manner comparable to terpy, as well as the anionic form (Py 2 TTA − ), which is similar to the monoanionic 2,5-bis(2-pyridyl)pyrrolide (bpp) ligand. While bpp has been recognized as an anionic analogue of terpy, this ligand system is relatively underdeveloped compared to the ubiquitous application of terpy ligands in coordination chemistry.…”

Strategy for Stimuli-Induced Spin Control Using a Liquescent Radical Cation

“…The intermolecular distance of the S–S contact in the π-dimer was estimated to be 2.98 Å, which is significantly shorter than the sum of the van der Waals radii. 16,17 The crystal packing structure revealed that no significant dimer–dimer interactions were present in any of the axis projections (Figures 3a and S9). Powder XRD measurements (Figures 3b, S10, and S11) revealed that the sharp diffraction peaks in the DM-GC state nearly disappeared in the PM-OL state, changed to a distinctly sharp pattern in the PM-OS state, and finally returned back to the original crystal pattern in the DM-GS state.…”

Connecting mononuclear dysprosium single-molecule magnets to form dinuclear complexes via in situ ligand oxidation

“…6 Since Py 2 TTA can exist as a neutral radical in solution, the generation of the oxide may be attributed to the generation of the radical, which is known to be susceptible to oxidation. 8 Alternatively, the generation of the oxide may occur following coordination to the metal ion, which pulls electron density of the anionic charge towards the metal centre leaving the sulphur atom of the TTA ring susceptible to oxidation. In order to elucidate the reaction process, time dependent 1 H NMR studies were carried out on the in situ reaction between Y(NO 3 ) 3 Á6H 2 O (2 equiv.)…”