A supersonic free jet expansion has been used to prepare small clusters of aromatic organic compounds, and their structure and energy-transfer properties have been studied by laser-induced fluorescence. The dimer of s-tetrazine was found to have two observable conformations. In the first, the two monomer units were side by side in a planar configuration. In the second, the two molecules were in a T-shaped configuration. In the T-shaped geometry the two rings are not equivalent, and spectra resulting from excitation of one or the other ring could be distinguished. A mixed-gas expansion of tetrazine and benzene in helium produced a mixed tetrazine–benzene dimer, a trimer consisting of two tetrazines and one benzene, and bands that were attributed to larger clusters. The benzene–tetrazine dimer had a stacked, parallel-plate geometry, while the T2B trimer had a benzene stacked parallel over a planar tetrazine dimer. Dimers of dimethyl tetrazine were found to be more tightly bound in the excited electronic state. Excitation of the 6a1 ring mode in the dimethyl tetrazine dimer led to intramolecular vibrational relaxation into the cluster modes. Dissociation was observed following excitation of the 6a20 transition of the tetrazine–benzene dimer.