Singly and Doubly N-Confused Calix[4]phyrin Organoplatinum(II) Complexes as Near-IR Triplet Sensitizers

Abstract

Organoplatinum(II) complexes of calix[4]phyrin analogues, singly N-confused calix[4]phyrin (Pt-2), and doubly N-confused calix[4]phyrin (Pt-3), were synthesized and characterized. The explicit structures of these organoplatinum(II) complexes were elucidated by single-crystal X-ray diffraction and spectroscopic studies. The introduction of N-confused pyrrole rings to the parent calix[4]phyrin scaffold was found to have profound effects on the photophysical properties, such as the bathochromic shifts of both the absorption and phosphorescence maxima. The triplet excited state properties of these platinum complexes were analyzed by DFT calculations at the B3LYP level. The organoplatinum(II) complexes derived from the deformed scaffolds can serve as potent triplet sensitizers for singlet oxygen generation under aerobic conditions.

Synthesis of Water-Soluble Thioglycosylated trans-A2B2 Type Porphyrins: Cellular Uptake Studies and Photodynamic Efficiency

“…The type I mechanism generates a superoxide anion, hydrogen peroxide, and a hydroxyl radical, whereas the type II photoreaction produces singlet oxygen ( 1 O 2 ). − In general, 1 O 2 is supposed to be the dominant cytotoxic species in the PDT studies of porphyrin-based photosensitizers. , To estimate the singlet oxygen quantum yields of glycosylated porphyrins, the compounds ( 3 , 3Zn , 6 , 6Zn ) and their water-soluble derivatives were examined in methanol saturated with oxygen (Figure ). The singlet oxygen generation was monitored by a UV–vis spectrometer using 1,3-diphenylisobenzofuran (DPBF) as an oxygen scavenger in the solution having porphyrin . Rose Bengal was used as a reference compound in this assay .…”

“…The significant intersystem crossing (ISC) would lead to the energy transfer from photosensitizers ( 6 ) to the triplet ground state of oxygen molecules, which, in turn, get excited to the singlet state and react with DPBF. The decrease in the intensity of the DPBF absorption band at 324 nm was monitored over a time period of ∼1.5 min . For photoirradiation of the porphyrins, a visible light source (λ = 400–700 nm, 15 J cm –2 ) was used; as the time progressed, the intensity of the DPBF absorption band at 324 nm gradually decreased (Figure a).…”

Doubly N‐Confused Calix[6]phyrin Bis‐Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation

“…1 ) metal complexes . Despite the disrupted π‐conjugation in the parent tetrapyrrolic scaffold, the NIR light absorption was achieved by electronic perturbation through an N‐confusion modification of the platinum calix[4]phyrin complexes (Figure ) . The doubly N‐confused derivative demonstrated the lowest energy absorption and subsequently good singlet oxygen generation.…”

Luminescent iridium(iii) dipyrrinato complexes: synthesis, X-ray structures, and DFT and photocytotoxicity studies of glycosylated derivatives

“…The type II mechanism is mainly accountable for the generation of 1 O 2 , which is the dominant cytotoxic species in PDT studies of different photosensitizers. 30,45–48 To quantify the singlet oxygen quantum yields of the iridium complexes Ir5–Ir7 , the modified literature method was used. 30,48,49 50…”