Tris-(8-hydroxyquinoline) metal complex Znq 2 , used as light-emitting layer in electroluminescent (EL) devices was synthesized and optical properties of as-deposited Znq 2 in thin films were studied. Interesting phenomenon was observed while studying the ageing and degradation behavior of Znq 2 films and consequently a stable form having strong blue photoluminescence (peak 465nm) was discovered. This converted (from green to blue emitting) film has higher molecular packing density and comparable photoluminescence intensity with Znq 2 film. Here, we report on the production of this blue material under controlled conditions and its optical properties.The thin films have been deposited by thermal evaporation on quartz and silicon substrates. The optical constants (n and k) of green Znq 2 film and converted (to blue) thin films have been determined using spectroscopic ellipsometry. Environment induced effects on optical properties of films have been studied using ellipsometry, photoluminescence and UV–vis transmission measurements.