%0 Journal Article
%A Shultz, David A.
%A Boal, Andrew K.
%A Campbell, Neil P.
%D 1998
%T Effect of Aliphatic Amine Bases on the Aggregation of Alkali Metal Salts of
3,5-Di-tert-butylsemiquinone (3,5-DBSQ)
%U https://acs.figshare.com/articles/journal_contribution/Effect_of_Aliphatic_Amine_Bases_on_the_Aggregation_of_Alkali_Metal_Salts_of_3_5-Di-_i_tert_i_-butylsemiquinone_3_5-DBSQ_/3620310
%R 10.1021/ic971113v.s001
%2 https://acs.figshare.com/ndownloader/files/5708940
%K EPR
%K absence
%K aggregation
%K THF
%K toluene
%K butylsemiquinone
%K tert
%K Alkali Metal Salts
%K Lewis acidic metal ion
%K presence
%K solution spectra
%K amine
%K PMDTA
%K Na 2 1
%K amines
%K TMEDA
%K Li
%K Aliphatic Amine Bases
%K alkali metal salts
%K DBSQ
%X The alkali metal salts (Li+, Na+,
K+) of 3,5-di-tert-butylsemiquinone anion
(3,5-DBSQ) have been prepared in
the presence of three amine bases, triethylamine (TEA),
tetramethylethylenediamine (TMEDA), and pentamethyldiethyltriamine (PMDTA), as well as in the absence of amine in two
solvents, toluene and THF. EPR spectral
evidence shows that for M(3,5-DBSQ), aggregation of the lithium and
sodium salts is effectively prohibited by
Lewis basic amines PMDTA and TMEDA, with the former being more
effective than the latter. The EPR spectra
of the least Lewis acidic metal ion, K+, are unaffected
by addition of amines. In the absence of amines, the
coordinating solvent, THF, is effective at preventing aggregation,
while substantial aggregation occurs in the
noncoordinating solvent, toluene. The effectiveness of PMDTA is so
great that M(3,5-DBSQ) (M = Li+ and
Na+) aggregation is prevented even in toluene. The
combination of solution and frozen solution spectra is
best
for determining the presence of aggregates due to aggregation-induced
line broadening in solution spectra and
fine structure in spectra of S >
1/2 species. The results of the frozen
solution spectral studies indicates that, for
the amines studied, PMDTA is singular in its ability to prevent
aggregation and Li+ and Na+ salts are best
chelated
by PMDTA. Finally, we show the success of this method by preparing
a solution of Na21 that is stable
for
several hours and is amenable to EPR spectral
characterization.
%I ACS Publications