Phenylene oligomers have been prepared by ship-in-a-bottle synthesis inside palladium containing basic zeolites by homo-coupling of 1,4-phenylenediboronic acid. Product analysis and "in situ" IR spectroscopy support the formation of oligomers of three to five phenylene rings. The encapsulated oligomers emit the characteristic blue light upon excitation and laser flash photolysis reveals the formation of long-lived transient decaying in hundreds of mus that has been attributed to the corresponding triplet excited state.