Solvent-drop assisted mechanochemical synthesis of the black and green polymorphs of the tetrathiafulvalene-chloranil charge transfer salt

This work describes the synthesis of the green and black polymorphic forms of the tetrathiafulvalene-chloranil (TTF-CA) charge transfer salt as pure phases, by solvent-assisted mechanochemistry. Both materials were characterized using laboratory and high-resolution X-ray powder diffraction (XRPD), elemental analysis and scanning electron microscopy (SEM). The high-resolution XRPD pattern of the TTF-CA black polymorph was indexed with a triclinic lattice a = 10.756(5)angstrom, b = 11.057(4)angstrom, c = 6.614(2)angstrom, alpha = 101.36(2)degrees, beta = 93.69(3)degrees, gamma = 89.37(3)degrees, V = 769.6(5) angstrom(3). The chemical stability of these phases upon heating was investigated using thermogravimetric analysis (TGA), elemental analysis and X-ray powder diffraction (XRPD), indicating that both polymorphs undergo chemical decomposition, and ruling out the transition to an air-stable high temperature polymorph. (C) 2011 Elsevier B.V. All rights reserved.