Emission spectroscopy of tetraacenaphthoporphyrins

CHED 1401

Brian M. Bennett, bmbenne@ilstu.edu and David L. Cedeņo, dcedeno@ilstu.edu. Department of Chemistry, Illinois State University, Campus Box 4160, Normal, IL 61790
Tetraacenaphtoporphyrins are porphyrin derivatives in which a naphthalene moiety has been fused to the beta positions of each of the pyrrole rings. This work presents emission studies of two tetraacenaphthoporphyrins that differ in the substituent in the meso position: TPTAP that contains phenyl substituents, and TPATAP that contains phenyacetylene substituents. Molecular modeling of the compounds indicate that the presence of these substituents induces steric crowding that forces the porphyrin macrocycle out of the typical planar conformation. This results in a significant shift of the absorption bands and a decrease of the fluorescent yields relative to tetraphenylporphyrin (TPP). The near infrared emission spectrum (800-1400 nm) of the compounds was acquired in a home-built instrument using a cooled germanium detector. The dependence of the emission on oxygen concentration was also studied.