Planetary nebulae (PNe) are known to be extreme radiation environments. However, these extreme conditions do not preclude the presence of different types of molecules. PNe appear as unique laboratories where atoms and simple and complex molecules, including radicals and ions, coexist. Our recent high-resolution radio observations of the C-rich PNe IC 418 and NGC 7027 and proto-PN (pPN) IRAS 22272+5435 have provided us with a precise database of the molecular content of these three objects. In our aim to study the organic molecules in the radio domain, we have found very deep radio recombination lines (RRLs) of neutral and ionized atoms never observed before. These new detected RRLs, along with the molecular content, will give information on the evolutionary state of the sources, as well as the chemical reactions taking place in such complex astrophysical environments.