High-resolution electronic spectroscopy of buffer-gas-cooled metal-phthalocyanines

High-resolution absorption spectra of the S1←S0000 transition of buffer-gas-cooled magnesium-phthalocyanine, zinc-phthalocyanine, and chloroaluminum-phthalocyanine are presented. The low temperature achieved through buffer gas cooling allowed the observation of a partially resolved rotational structure in each spectrum. We compare these structures with the previously observed high-resolution spectrum of free-base phthalocyanine. Despite the similar molecular structures of these molecules, the spectral characteristics of the rotational envelope vary depending on the individual molecular structures.