Room-Temperature Phosphorescence and Cellular Phototoxicity Activated by Triplet Dynamics in Aggregates of Push–Pull Phenothiazine-Based Isomers

Abstract

In this study, we report a comprehensive timeresolved spectroscopic investigation of the excited-state deactivation mechanism in three push−pull isomers characterized by a phenothiazine electron donor, a benzothiazole electron acceptor, and a phenyl π-bridge where the connection is realized at the relative ortho, meta, and para positions. Spin−orbit charge-transferinduced intersystem crossing takes place with high yield in these all-organic donor−acceptor compounds, leading also to efficient production of singlet oxygen. Our spectroscopic results give clear evidence of room-temperature phosphorescence not only in solidstate host−guest matrices but also in highly biocompatible aggregates of these isomers produced in water dispersions, as rarely reported in the literature. Moreover, aggregates of the isomers could be internalized by lung cancer and melanoma cells and display bright luminescence without any dark cytotoxic effect. On the other hand, the isomers showed significant cellular phototoxicity against the tumor cells due to light-induced reactive oxygen species generation. Our findings strongly suggest that nanoaggregates of the investigated isomers are promising candidates for imaging-guided photodynamic therapy.

Effects of the nature of donor substituents on the photophysical and electroluminescence properties of derivatives of perfluorobiphenyl: donor–acceptor versus donor–acceptor–donor type AIEE/TADF emitters

“…Phenothiazine and phenoxazine are strong electron donors. 35,36 The lowest energy absorption bands of furoindole containing compounds FurInd-PFBP and 2FurInd-PFBP are hypsochromically shifted when compared to those of PTZ-PFBP, 2PTZ-PFBP, PXZ-PFBP and 2PXZ-PFBP. 37 The number of donating moieties present in the structures of the compounds has a small impact on the absorption spectra.…”

N^N^C-Cyclometalated rhodium(iii) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity

“…the ability of compounds with identical molecular formulae to exist in spatially different forms is one of the most fundamental ideas in chemistry. [1][2][3] Revealing the impact of isomerism on crystal structures, [4][5][6][7][8][9][10][11][12] and chemical properties, [13][14][15][16][17][18][19][20][21] as well as physical [22][23][24][25][26][27][28][29][30][31][32][33][34] and biological properties [35][36][37][38][39] is of particular importance for establishing structure-property relationships which pave the way toward the more predictable design of substances with desirable properties. Despite various kinds of constitutional and configurational isomerism of metal complexes being well known, 40 ligand isomerism, which belongs to constitutional isomerism, is documented in literature to a considerably lesser extent than other types of the isomerism of complexes.…”