Molecular Iodine Stabilization in an Extended N···I–I···N Assembly

The adduct [bis(quinoxaline)‐2,2′,3,3′‐disulfide · I 2 ] ∞ (Q 2 S 2 · I 2 ) ∞ ( 1 ) can be easily synthesised from the reaction of Q 2 S 2 and I 2 in CH 2 Cl 2 or, in the absence of any solvent, through diffusion of I 2 vapours at 60 °C. X‐ray diffraction analysis shows the presence of an extended N ··· I–I ··· N assembly in which each I 2 molecule links a Q 2 S 2 molecule at both ends through a nitrogen atom to form a polymeric species; the d (I–I) and d (N–I) bond lengths confirm a very weak nitrogen–iodine interaction at the base of the N ··· I–I ··· N assembly. DFT calculations provide optimised distances for the N ··· I and I–I bonds and explanation for the zigzag chain formation: the mPW1PW functional and the B3LYP hybrid functional with a variety of basis sets for the I atomic species [CRENBL, LANL2DZ, LANL2DZ(d,p), LANL08(d), SBKJC, SBKJC polarised‐LFK and Stuttgart RLC] have been tested. Compound 1 proved stable up to nearly 100 °C, and the stability is to be mainly attributed to the lattice energy of its polymeric structure then to donor–acceptor stabilisation. The facile insertion of molecular iodine into the Q 2 S 2 network makes this compound an interesting iodine sponge, suitable for I 2 storage; moreover, Q 2 S 2 can easily collect and release I 2 (g) by a temperature‐controlled process (60 and 97 °C, respectively). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)