The synthesis of 5,10,15,20-tetraarylporphyrins and their platinum(II) complexes as luminescent oxygen sensing materials

5,10,15,20-tetraarylporphyrins TPP, TNP and TPyP (where TPP = 5,10,15,20-tetraphenylporphyrin, TNP = 5,10,15,20-tetranaphthalporphyrin and TPyP = 5,10,15,20-tetrapyrenyl-porphyrin) and the corresponding Pt(II) complexes were prepared. The photophysical properties of the porphyrin ligands and the Pt(II) complexes were studied using UV–vis absorption and photo-luminescence spectra; the geometry and electronic structure of the ligands and the complexes were studied via DFT/TDDFT calculations. UV–vis absorption and luminescence emission spectra showed that the added aryl groups did not contribute to the π-conjugation system of either the metal-free porphyrins or the Pt(II) complexes and, therefore, all ligands (and complexes) displayed similar photophysical properties. DFT/TDDFT calculations supported the proposed photophysical process and indicated very weak involvement of the aryl appendents in the low-lying electronic excited states. The luminescent oxygen sensing properties of the Pt(II) complexes were studied in solution as well as in polymer films (monitored via emission intensity and lifetime mode). The results demonstrated that in the case of both the pyrenyl and naphthyl groups, the oxygen sensing character of the complexes could be improved (quenching constant KSV = 0.068 Torr−1 for Pt–TNP vs. KSV = 0.040 Torr−1 for the parent complex Pt–TPP).