Although 3 and 4 retained the icosahedral structure of 2, the former two NCs displayed considerable distortion from an ideal icosahedral structure because of John-Teller effects originating in the partially filled non-degenerate P orbitals of the superatom electron configuration (1S 2 1P 4 ) of each NC. The extent of distortion from an ideal icosahedron was assessed using the continuous symmetry measure (CSM) method implemented in SHAPE V2. which provided CSM values of 0.073, 0.249, and 0.244 for 2, 3, and 4, respectively (Figure ). These data suggested that the latter two NCs comprised more distorted cores than 2.