Planar and twisted cyanine dyes with different pK(a) values are examin
ed concerning their protonation equilibrium in sol-gel matrices. In th
e sol-gel matrix the equilibrium between the cation and the dicationic
form shifts to the dication pointing to acid-base reactions of sol-ge
l walls with cyanine dyes. The colorless dicationic species is not fou
nd for pseudoisocyanine and in sol-gel bulks prepared with drying cont
rol chemical agents (DCCA) indicating the absence of the responsible i
nteraction, The fluorescence lifetimes of cyanine molecules are used t
o compare the pore size and distribution in sol-gel matrices prepared
with and without DCCA. J-aggregation, examined for one dye, depends st
rongly on environment polarity and pore size.