TCT-4-i-X where bond angle B 1 -A-B i is bisected by the S4 axis (the short C2 axis), and X = R or S as for T-4 species; i ∈ {2, 3, 4}. TET-4-i-X where bond angle B 1 -A-B i is bisected by the S4 axis (the long C2 axis), and X = R or S as for T-4 species; i ∈ {2, 3, 4}. GYP-4-i-j where B i is trans to B 1 , B j is closest adjacent vertex to B 1 ; i and j ∈ {2, 3, 4}. TT-4-X where X = R or S as for T-4 species.