Heats fo Formation of Solvated Annulene and Substituted Azaannulene Dianions

Article abstract of DOI:10.1021/j150666a062

It was found that the heat of solution of the potassium salt of the cyclooctatetraene (COT) dianion in tetrahydrofuran (-11.1 kcal/mol) measured calorimetrically is very different from the heat of solution determined from solubility data.This is attributed to the existence of a partially solvated solid salt (K⁺2COT^2-*nTHF), which is the form of the COT dianion lowest in energy yet generated.This stable form of the <8>annulene dianion is lower in energy by 393.5 kcal/mol than the gas-phase dianion with two potassium cations.Both solvation and lattice effects are rsponsible for this tremendous stabilization.Substitution of a nitrogen atom for one of the carbon atoms in the eight-member ring system results in an increase in the energy of the THF solvated dianion relative to the metal and neutral organic compound due to an increase in the electron-electron repulsion energy in the dianion.