A new assembly of diiodine molecules at the 1,3-dimethylimidazole-2-thione (Me(2)ImS) template: crystal structure of (Me(2)ImS)(2)center dot(I-2)(5)

The new poly(I-2) adduct [(Me(2)ImS)(2)center dot(I-2)(5)] (Me(2)ImS = 1,3-dimethylimidazole-2-thione) has been synthesized and characterized by single crystal X-ray diffraction analysis. Units of [(Me(2)ImS)(2)center dot(I-2)(5)] are located about a crystallographic inversion center, in which five diiodine molecules display interatomic contacts in a "head-to-tail" sequence giving a -(I-2)(5)- chain interacting at each end with one Me(2)ImS molecule, CCDC 2133501. The S-bonding of Me(2)ImS to I-2 is described as a donor-acceptor interaction in which I-2 acts as an acceptor through the sigma*(I-I) orbital resulting in an electronic charge transfer from the thioamide moiety. The bond distances d(S-I(1)) (2.504(2) angstrom) and d(I(1)-I(2)) (3.133(1) angstrom) are indicative of a strong interaction. Based on the S-I and I-I bond distances, the calculated values of the electronic charge densities, and the Raman spectral data, it is reasonable to represent the compound as an extended polarised system: [(Me(2)ImS)-I(1)]delta+MIDLINE HORIZONTAL ELLIPSISI(2)delta-MIDLINE HORIZONTAL ELLIPSISI(3)-I(4)delta-MIDLINE HORIZONTAL ELLIPSIS(I(5)-I(5)(a))MIDLINE HORIZONTAL ELLIPSISI delta--IMIDLINE HORIZONTAL ELLIPSISI delta-MIDLINE HORIZONTAL ELLIPSIS[I-(Me(2)ImS)](delta+). The molecular electrostatic potential maps of the three adducts Me(2)ImS center dot I-2, Me(2)ImS center dot I-2 center dot I-2, and MeImHS center dot I-2 (MeImHS = methimazole) have been reported to clearly identify the areas of charge increment (electron belt) and depletion (sigma-hole), and thus the directionality of the noncovalent interactions.