I'm doing some background reading before conducting an experiment, but am getting a little confused. What serves as evidence for the formation of a host-guest complex when conducting analysis through UV-visible absorption?
From the sources that I have read and have personally observed in the lab, formation of host-guest complexes can push equilibrium to favour a specific species, like an acidic form or a basic form of the guest molecule due to stabilizing interactions within the host (think cyclodextrins + phenolphthalein). This is reflected in absorption spectra as an increase/decrease in absorbance of the peaks to reflect the increasing/decreasing proportion of acidic/basic species of the guest molecule.
Another way of telling if the host-guest complex is formed is if the there is an increase in the molar absorption coefficient or a shift in the absorption peaks of the guest molecule. Another conflicting source tells me that when a guest molecule is complexed, absorption of the guest molecule should decrease. Can anybody clarify which of these changes serves as evidence for formation of a host-guest complex?