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

Abstract

Triplet photosensitizers that generate singlet oxygen efficientlya re attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to an ear-infrared (NIR) region (700 nm %)w ith reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared as eries of mono-and bis-palladium complexes (1-Pd-H 2 , 2-Pd-H 2 , 1-Pd-Pd,a nd 2-Pd-Pd)b ased on modified calix[6]phyrins as photosensitizers for singlet oxygen generation.T hese palladium complexes showed intense absorption profiles in the visible-to-NIR region (500-750nm) depending on the number of central metals. Upon photoirradiation in the presence of 1,5-dihydroxynaphthalene (DHN) as as ubstrate for reactiveo xygen species, the bis-palladium complexes generated singlet oxygen with high efficiency and excellent photostability.S inglet oxygen generation was confirmed from the characteristics pectral feature of the spin trapped complex in the EPR spectrum and the intact 1 O 2 emission at 1270 nm.

Near‐Infrared‐III‐Absorbing and ‐Emitting Dyes: Energy‐Gap Engineering of Expanded Porphyrinoids via Metallation

“…The observed downfield shifts of the peripheral proton signals indicated the presence of distinct 26π aromatic electronic structures, as seen in c ‐Pd 2 ‐3 . Critically, the 19 F NMR spectrum of t ‐Pd 2 ‐3 showed a specific 2F:2F:2F integral pattern for the para ‐fluoro moiety of the meso ‐pentafluorophenyl groups, thereby supporting the proposed C 2 ‐symmetrical structure of the rectangular t ‐Pd 2 ‐3 (Figure S4) . On the contrary, discrete 2F:1F:2F:1F integral signals were observed for the congener, c ‐Pd 2 ‐3 (Figure S5) …”

“…Forschungsartikel field shifts of the peripheral proton signals indicated the presence of distinct 26p aromatic electronic structures,a s seen in c-Pd 2 -3.C ritically,t he 19 FNMR spectrum of t-Pd 2 -3 showed as pecific 2F:2F:2F integral pattern for the parafluoro moiety of the meso-pentafluorophenyl groups,thereby supporting the proposed C 2 -symmetrical structure of the rectangular t-Pd 2 -3 ( Figure S4). [35] On the contrary,d iscrete 2F:1F:2F:1F integral signals were observed for the congener, c-Pd 2 -3 ( Figure S5). [29] Asimilar protocol was applied to the bis-Pt II complexes in which the salt PtCl 2 (PhCN) 2 was used as the metal source to afford a trans-configured bis-Pt complex (that is, t-Pt 2 -3)i n 2% yield (Scheme 1).…”

Near‐Infrared‐III‐Absorbing and ‐Emitting Dyes: Energy‐Gap Engineering of Expanded Porphyrinoids via Metallation

“…Chemie field shifts of the peripheral proton signals indicated the presence of distinct 26p aromatic electronic structures,a s seen in c-Pd 2 -3.C ritically,t he 19 FNMR spectrum of t-Pd 2 -3 showed as pecific 2F:2F:2F integral pattern for the parafluoro moiety of the meso-pentafluorophenyl groups,thereby supporting the proposed C 2 -symmetrical structure of the rectangular t-Pd 2 -3 ( Figure S4). [35] On the contrary,d iscrete 2F:1F:2F:1F integral signals were observed for the congener, c-Pd 2 -3 ( Figure S5). [29] Asimilar protocol was applied to the bis-Pt II complexes in which the salt PtCl 2 (PhCN) 2 was used as the metal source to afford a trans-configured bis-Pt complex (that is, t-Pt 2 -3)i n 2% yield (Scheme 1).…”

Synthesis, Structure, Photophysics, and Singlet Oxygen Sensitization by a Platinum(II) Complex of Meso‐Tetra‐Acenaphthyl Porphyrin

“…[13] Photosensitized singlet oxygen generation is an emerging research area with versatile applications in organic synthesis of fine chemicals, [14] pollution controls, [15] and photodynamic therapy. [16][17][18][19] In this regard, Ru(II) polypyridyl complexes, [20] iridium(III), [21][22] gold(I) complexes, [23] and platinum(II) porphyrin complexes [24][25][26][27][28] are well known as the photosensitizer. Platinum porphyrin complexes show intense phosphorescence at room temperature due to high yields of population of the triplet state and high yield of emission quantum yield.…”