Mechanistic Insights on the Impact of Long Alkyl Chain and Bromine Substitution on the Molecular Packing and Phosphorescence Behavior in Naphthalimides

Abstract This article investigates the role of heavy halogen atom introduction and alkyl chain modification in organic room temperature phosphorescence (RTP) materials. The study compares the effects of heavy halogen atom introduction on RTP and the influence of alkyl chain modification in two luminogens, viz. ODNI and BrODNI. ODNI, which lacks a heavy halogen atom exhibits a phosphorescence lifetime of ∼212 ms at 77 K, whereas BrODNI containing bromine atom shows significantly shorter phosphorescence lifetime of ∼4.5 ms. The crystal structure of ODNI and theoretical calculations for ODNI and BrODNI are performed to understand the roles of alkyl chains and heavy halogen atoms in RTP. These results provide valuable insights for the design of sustainable energy and optoelectronic materials.