Supramolecular Wiring of Benzo-1,3-chalcogenazoles through Programmed Chalcogen Bonding Interactions

The high‐yielding synthesis of 2‐substituted benzo‐1,3‐tellurazoles and benzo‐1,3‐selenazoles through a dehydrative cyclization reaction has been reported, giving access to a large variety of benzo‐1,3‐chalcogenazoles. Exceptionally, these aromatic heterocycles proved to be very stable and thus very handy to form controlled solid‐state organizations in which wire‐like polymeric structures are formed through secondary N⋅⋅⋅Y bonding interactions (SBIs) engaging the chalcogen (Y=Se or Te) and nitrogen atoms. In particular, it has been shown that the recognition properties of the chalcogen centre at the solid state could be programmed by selectively barring one of its σ‐holes through a combination of electronic and steric effects exerted by the substituent at the 2‐position. As predicted by the electrostatic potential surfaces calculated by quantum chemical modelling, the pyridyl groups revealed to be the stronger chalcogen bonding acceptors, and thus the best ligand candidate for programming the molecular organization at the solid state. In contrast, the thiophenyl group is an unsuitable substituent for establishing SBIs in this molecular system as it gives rise to chalcogen–chalcogen repulsion. The weaker chalcogen donor properties of the Se analogues trigger the formation of feeble N⋅⋅⋅Se contacts, which are manifested in similar solid‐state polymers featuring longer nitrogen–chalcogen distances. Building benzo‐1,3‐chalcogenazoles: A versatile four‐step synthesis of 2‐substituted benzo‐1,3‐selenazoles and ‐tellurazoles starting from 2‐bromoaniline is reported (see figure; R=alkyl, alkenyl, phenyl, furanyl, thiophenyl, pyridyl and ferrocenyl groups). The solid‐state arrangement shows that, depending on the electronic and geometrical properties of the substituent at the 2‐position, one can control the wiring organization through two‐ (X⋅⋅⋅Y) or three‐atoms (X⋅⋅⋅Y⋅⋅⋅X) secondary bonding interactions.