NBu4Br was chosen because it is a simple aliphatic
salt whose interionic distance (ca. 5.3 A°
) is smaller than
the Stokes radius (ca. 5.8 A°
) [13] and is supposed to
form tight ion pairs with a partial compenetration of
the anion between the aliphatic chains [14]. The ionpair
dissociation constant is 2.7 (90.2)105.