Effects of fluorine and phenyl substituents on oxygen sensitivity and photostability of cyclometalated platinum(II) complexes

Abstract

Fluorinated cyclometalated Pt(II) complexes Pt(Fppy)(acac) and Pt(dFppy)(acac), phenyl-substituted LA1, and 2,4-difluorophenyl-substituted LA2 were synthesized and applied as phosphorescent probes for monitoring of molecular oxygen compared with a model complex Pt(ppy)(acac). The phosphorescence of all Pt(II) complexes in tetrahydrofuran (THF) or immobilized in ethyl cellulose (EC) films was gradually quenched with the increase of the oxygen concentration. The intensity ratio I0/I9.61 and I0/I100 were used to evaluate oxygen sensitivities of the Pt(II) complexes in THF and in EC film, respectively. LA1 demonstrates the highest oxygen sensitivity with I0/I9.61 of 19.5 in THF, and I0/I100 of 13.5 and a KSVapp of 16.9 bar–1 in EC film. The photostability tests of the Pt(II) complexes immobilized EC films show that, phenyl and fluorine substituents have a synergistic effect on improving the photostability of the complexes. The LA2-immobilized EC film demonstrates the highest photostability and excellent operational stability (3.8 s on going from 100% N2 to 100% O2 and 4.5 s on going from 100% O2 to 100% N2), which is a potential photostable probe for online monitoring of molecular oxygen.