AB INITIO IGLO STUDY OF SANDWICHED BISHOMOAROMATIC ANTI-TRICYCLE [4.2.1.1(2,5)]DECA-3,7-DIENE-9,10-DIYL DICATION AND THE TRISHOMOAROMATIC TRISHOMOCYCLOPROPENIUM ION/

The structure of the nti-tricyclo[4.2.1.1(2,5)]deca-3,7-diene-9,10-diy l dication, 6, has been investigated by ab initio calculations at the HF/6-31G and MP2/6-31G* levels of theory. The optimized geometry of 6 is in accord with the presence of homoconjugative interactions. Isode smic reactions based upon HF/6-31G//HF/6-31G*+ZPE (HF/6-31G*//HF/6-31 G) and MP2/6-31G*//6-31G*+ZPE (HF/6-31*G//HF/6-31G*) energies have be en used to investigate the relative stability of dication 6 and a mode l bishomoaromatic anti-tricyclo[4.2.1.1(2,5)]deca-3-ene-9-yl monocatio n, 8. The C-13 NMR chemical shifts of 6 were calculated using the IGLO method (at DZ//HF/6-31G and DZ//MP2/6-31G* levels). The calculated c hemical shifts closely match the experimental data on 6. The trishomoc yclopropenium ion was also restudied by ab initio/IGLO method and its highly symmetrical C-3v structure was confirmed.