Noncovalent interactions in 2-mercapto-1-methylimidazole complexes with organic iodides

2-Mereapto-1-methylimidazole (mmim) forms complexes with organic iodides, 1,4-diiodotetrafluorobenzene (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), a=26.915(3) Angstrom, b=7.9216(6) Angstrom, c=14.2630(4) Angstrom, beta=105.618(1)degrees, V=2928.7(4)Angstrom(3), Z=8, rho(calc)=2.34 g/cm(3). Crystal data for mmim.TIE: monoclinic space group, C2/c (no. 15), a=20.1789(12) Angstrom, b=10.7824(10) Angstrom, c=14.5072(2) Angstrom, beta=118.767(1)degrees, V=2766.9(3) Angstrom(3), Z= 8, rho(calc) g/cm(3). Crystal data for mmim. o-F4DIB: triclinic space group, P (1) over bar (no. 2), a=7.4987(7) Angstrom, b=8.1906(12) Angstrom, c=11.6512(12) Angstrom, alpha=83.245(4)degrees, beta=84.695(3)degrees, gamma=86.135(3)degrees, V=706.35(14) Angstrom(3), Z= 2, rho(calc) = 2.43g/cm(3).