Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations

Photodissociation of the complex between protonated tryptamine, TryH+, and 18-crown-6 ether (CE) was investigated. Absorption maxima of TryH+ and TryH+(CE) are at 249 and 273 nm, respectively. Ions decay exponentially on a microsecond timescale, and mass spectra reveal that NH3 loss is an important channel even though CE targets this group. TD-DFT calculations identified an electronically excited state, where the photoactive electron is located in an antibonding orbital between C and NH3. Dissociation along this coordinate and CE rearrangement to the new charge site accounts for ammonia loss. Photodissociation in an electric field and time-of-flight measurements corroborate such a non-statistical bond-breakage.