Noncovalent Interactions in 2-Mercapto-1-methylimidazole Complexes with Organic Iodides

2-Mercapto-1-methylimidazole (mmim) forms complexes with organic iodides, 1,4-diiodotetrafluoro-benzene (p-F₄DIB), tetraiodoethylene (TIE), and 1,2-diiodotetrafluorobenzene (o-F₄DIB), in which there are remarkably similar N-H⋯S hydrogen bonding and S⋯I halogen bonding patterns. Extended chains of alternating donor (mmim) and acceptor (p-F₄DIB and TIE) molecules are formed through divalent I⋯S⋯I interactions. These chains are joined into double strands through N-H⋯S interactions that link two mmim molecules into a dimer. In the third complex, N-H⋯S bound dimers are linked into infinite chains through S⋯I interactions involving a pair of o-F₄DIB molecules. Thermal analysis indicates that decomposition in both of the F₄DIB complexes proceeds through total loss of acceptor, while decomposition of the TIE complex involves a combination of acceptor loss and acceptor reaction. Melting in the o-F₄DIB complexes appears to be preceded by a solid-state rearrangement or premelting phenomenon that is not observed in the other two complexes. Crystal data for mmim·p-F₄DIB: monoclinic space group, C2/c (no. 15), α = 26.915(3) Å, b = 7.9216(6) Å, c = 14.2630(4) Å, β= 105.618(1)°, V = 2928.7(4) ų, Z = 8, p_calc = 2.34 g/cm³. Crystal data for mmim·TIE: monoclinic space group, C2/c (no. 15), a = 20.1789(12) Å, b = 10.7824(10) Å, c = 14.5072(2) Å, β= 118.767(1)°, V= 2766.9(3) ų, Z = 8, p_calc = 3.10 g/cm3. Crystal data for mmim· 0-F4DIB: triclinic space group, P1 (no. 2), α = 7.4987(7) Å, b = 8.1906(12) Å, c = 11.6512(12) Å, α = 83.245(4)°, β = 84.695(3)°, γ = 86.135(3)°, V = 706.35(14) ų, Z = 2, p_calc = 2.43 g/cm³.