Chalcogen bond activation in cation radical salts of naphthalene peri-diselenides with S = 5/2 magnetic anions

Abstract

The activation of strong σ-holes in the oxidized form of 2,7-dimethoxynaphthalene peri-diselenide (1) is demonstrated in its radical salts with magnetic (S = 5/2) FeX₄⁻ anions as well as their diamagnetic analogs GaX₄⁻ (X = Cl, Br). All four salts exhibit short and directional Se⋯X chalcogen bonding (ChB) interactions, together with strong dimerization of the radical species into dicationic dimers along the stacks of 1˙⁺. Magnetic analysis highlights the presence of antiferromagnetic interactions between paramagnetic FeX₄⁻ anions and reveals long-range antiferromagnetic order with T_N = 5.9 K only in the FeBr₄⁻ salt, attributable to the short Br⋯Br distances induced by ChB interactions.