Re. Hoffman et al., ACIDITY OF DIBASIC CARBON ACIDS .3. ION SOLVATION STATE OF MONOMETALLIC SALTS OF 9,10-DIHYDROANTHRACENE AND ITS DERIVATIVES IN THF, Perkin transactions. 2, (6), 1996, pp. 1225-1232
The ion solvation state of monometallic salts of 9,10-dihydroanthracen
e (DHA) and its 9,10-disubstituted derivatives in THF has studied by W
-VIS and H-1 and C-13 NMR spectroscopy, At room temperature, lithium 9
-phenyl-9,10-dihydroanthracen-9-ide, lithium 9,10-dimethyl-9,10-dihydr
oanthracenide and lithium 9,10-diphenyl-9,10-dihydroanthracenide exist
as solvent separated ion pairs (SSIP). Lithium 9, 10-dihydroanthracen
e, lithium 9-methyl-9,10-dihydroanthracen-10-ide and sodium, potassium
and rubidium 9-phenyl-9,10-dihydroanthracen-9-ides, 9,10-dimethyl-9,1
0-dihydroanthracenides and 9,10-diphenyl-9,10-dihydroanthracenides exi
st as a mixture of SSIP and contact ion pairs (CIP). Sodium, potassium
, rubidium and caesium 9,10-dihydroanthracenides, 9-methyl-9,10-dihydr
oanthracen-10-ides and 9-cyano-9,10-dihydroanthracenides exist as CIP
in solution. The stabilizing effect of the methyl and phenyl substitue
nts is more significant for SSIP than for CIP. The thermodynamics for
SSIP to CIP conversion is determined for the sodium salts: of DHA and
its; derivatives. Delta S-degrees is 27 +/- 2 cal mol(-1) K-1 Delta H
degrees increases with substituent size and charge dispersion. A model
for the transition of CIP of alkali-metal salts of DHA and its deriva
tives into SSIP is suggested. The model takes into account the geometr
y and charge distribution in anions.