1,3-Dithiolo[4,5-b][1,4]dithiin-1-ium,2-[4-[[3-[[5-[(2-cyanoethyl)thio]-4',5'-dimethyl[2,2'-bi-1,3-dithiol-1-ium]-4-yl]thio]propyl]thio]-5-[[3-[[4',5'-dimethyl-5-(methylthio)[2,2'-bi-1,3-dithiol-1-ium]-4-yl]thio]propyl]thio]-1,3-dithiol-1-ium-2-yl]-5,6-di