Robert West and co-workers have synthesized a group of stable, cyclic carbenes, silylenes, and germylenes. West and co-workers have suggested that these molecules may possess aromatic character based on experimental evidence that they have obtained. William Herndon and Nancy Mills have recently utilized Isotopological Homodesmotic Reactions (IHR) to determine the Aromatic Stabilization Energy (ASE) of a flourenyl cation. The advantage of employing an IHR for the ASE calculation is that the strain energy contribution from the sigma framework of the cyclic compound can be strategically canceled-out. The following diagram demonstrates one sample of the various Isotopological Homodesmotic Reactions examined in the present work:

A

B

+

→

C

D

+

	Aromatic
DFT/B3LYP	Compund	Reference	Reference	Reference	DE	ASE
6-31+G(d,p)	A	B	C	D	(Hartrees)	(kcal/mol)
X = C	-540.7294629	-581.2506242	-580.0220427	-541.9329119	0.0251325	15.77
X = Si	-792.1829124	-832.6885311	-831.4735859	-793.3771357	0.0207219	13.003
X = Ge	-2577.7275553	-2618.2073014	-2617.0189819	-2578.8931865	0.0226883	14.24

All the structures of the molecules contained in this work were each optimized in Gaussian 03 using HF/6-31+G(d,p) and B3LYP/6-31+G(d,p) levels of ab initio theory. Another computational chemistry technique utilized to probe the aromatic behavior of the compound in question and its corresponding reference molecules is the Nucleus Independent Chemical Shift (NICS) methodology developed by Schleyer. The NICS value of a probe (Bq) atom centered at one angstrom above the molecular plane measures the shielding or deshielding tendency of a molecule exposed to a magnetic field due to aromatic pi-electron delocalization. Amnon Stanger's suggestion that performing a NICS scan may further elucidate the aromatic behavior of a compound was also examined for each molecule in every Isotopological Homodesmotic Reaction.