Aromaticity and antiaromaticity in monoheterocyclic three‐membered rings: Application of natural bond orbital theory

Using natural bond orbital theory, aromatic stabilisation energies (NBO-ASEs) were calculated for neutral and cationic monoheterocyclic three-membered rings C2H2X(R)n (X = group 14-17 elements of rows 3-5; R F, H or SiH3; n 0-2). Generally, there was a decrease in the (anti)aromatic nature molecule moving down as either stabilizing overlap (aromaticity) destabilising interactions (antiaromaticity) reduced due to larger atoms inducing longer bonds. (Anti)aromatic trends supported with dissected nucleus independent chemical shift NICS(0)π,zz values (R2 0.94), also by comparison NBO-ASEs literature selection systems including benzene, cyclobutadiene cyclopentadienyl anion. Comparisons are made other studies that have used range approaches study (anti)aromaticity some these molecules, it found non-dissected NICS homodesmotic equations often gave significantly overestimated if not misleading results.