We present the third order nonlinear optical study of tetrathiafulvalene-based molecular corners. Degenerate four-wave mixing measurements have been done to provide information about the magnitude and the origin of the nonlinearity, while the nonlinear absorption has been separately measured by performing "open aperture" Z-scan measurements. The response has been found to be strongly dependent upon the structure of the molecular corners. (C) 2010 American Institute of Physics. [doi:10.1063/1.3482943]