A photoelectron spectrum of an acrylonitrile (AN:CH2CHCN) trimer anion, (AN)3-, produced by electron impact on an acrylonitrile cluster was measured, and was compared with that of a molecular anion of 1,3,5-cyclohexanetricarbonitrile (c-HTCN) in the triequatorial form, which was first synthesized in the present experiment. A comparison of the vertical detachment energies of (AN)3- and the molecular anion lead us to conclude that (AN)3- is assigned as one of the stereoisomers (diaxial form) of c-HTCN (−) on the basis of our previous studies refs 13, 14, and 20−22 [Tsukuda, T.; Kondow, T. J. Chem. Phys. 1991, 95, 6989. Tsukuda, T.; Kondow, T. J. Am. Chem. Soc. 1994, 116, 9555. Ichihashi, M.; Tsukuda, T.; Nonose, S.; Kondow, T. J. Phys. Chem. 1995, 99, 17354. Fukuda, Y.; Tsukuda, T.; Terasaki, A.; Kondow, T. Chem. Phys. Lett. 1995, 242, 121. Fukuda, Y.; Tsukuda, T.; Terasaki, A.; Kondow, T. Chem. Phys. Lett. 1996, 260, 423.].