Crystallographic identification of a novel 2,4,5-tri(N-methyl-4-pyridinium)-1,3-thiazole with a complex network of polyiodide/iodine counter ions and co-crystallized cyclododecasulfur (S12)

Abstract

The crystals of an unprecedented 2,4,5-tri(N-methylpyridinium)-1,3-thiazole are monoclinic and belong to the space group P2₁/c as determined by single-crystal XRD. Crystal data for C₂₁H₂₁I₁₃N₄S_5.98: monoclinic, a = 7.5627(5) Å, b = 30.6764(19) Å, c = 20.8848(15) Å, β = 91.632(6)°, V = 4843.2(6) Å³, Z = 4, T = 100.01(10) K, μ(Cu Kα) = 67.840 mm^-1, Dcalc = 2.977 g/cm³, 17906 reflections measured (7.152° ≤ 2Θ ≤ 162.94°), 17906 unique (R_sigma = 0.0607) which were used in all calculations. The final R₁ was 0.1366 (I > 2σ(I)) and wR₂ was 0.3926 (all data). The crystal lattice contains 2,4,5-tri(N-methylpyridinium)-1,3-thiazole, molecular iodine and triiodide counterions which interact with one another to coordinatively form polyiodides, as well as a surprising co-crystallized neutral molecule of cyclododecasulfur (S₁₂). Close monitoring of the synthetic procedure reveals chemical condensation and decomposition of the thioamide reagent to be the impetus for the formation of individual components of the crystal lattice. Analysis of the XRD, including a Hirshfeld surface analysis, shows that (a) the crystal lattice has a number of stabilizing Coulombic short contacts such as I∙∙∙I, I∙∙∙S, I∙∙∙C, and C∙∙∙S and non-classical C-H∙∙∙I and C-H∙∙∙S hydrogen bond interactions (b) the iodine/iodide network are major determinants in the stability of its crystal lattice despite the reduced occupancies of sulfur and (c) the Hirshfeld analysis in comparison with the conventional Mercury visualization program was able to simplify, identify and quantify complex atom-atom interactions such as H∙∙∙H and N∙∙∙I in its crystal lattice. Herein, it is reported, for the first time, the formation of co-crystallized, neutral cyclododecasulfur (S₁₂) from thioamide as the sulfur source. S₁₂ displays a consistent geometry and comparable average S-S distances, S-S-S angles and torsion angles with previously reported crystal structures of S₁₂. The complex network facilitated by the formation of polyiodides via the interaction of symmetric and asymmetric triiodides and iodine has resulted in quite strong interactions that are less than the sums of the van der Waals radii of two connected atoms as well as an array of fascinating geometrical alignments such as T-shape, trigonal pyramidal and L-shape.