Giant Star‐shaped meso‐substituted Fluorescent Porphyrins with Fluorenyl‐containing Arms Designed for Two‐photon Oxygen Photosensitization

Abstract

In the continuation of previous studies on carbon‐rich meso‐tetraarylporphyrins featuring 2,7‐fluorene units at their periphery, the effect of changing the peripheral dendritic arms for linear arms on . their oxygen‐photosensitizing ability, their fluorescence and their two‐photon absorption (2PA) properties is now analyzed. Thus, starburst porphyrins possessing up to twenty conjugated fluorenyl units were isolated and studied. More precisely, a series of five new free‐base porphyrins featuring fully conjugated arms incorporating an increasing number of fluorenyl groups connected via 1,2‐alkenyl spacers were synthesized, along with their Zn(II) complexes. Upon excitation in the arm‐centred band, an efficient energy transfer takes place from the peripheral fluorenyl units to the central porphyrin core, leading to intense red‐light emission and oxygen photosensitization by the latter. More interestingly, while the linear optical properties of these porphyrins were only slightly improved compared to those of their dendrimer analogues for photodynamic therapy (PDT) or fluorescence imaging, their 2PA cross‐sections were much more significantly boosted, evidencing the key role played by different structures on nonlinear optical properties. Finally, by comparison with other porphyrin‐based two‐photon photosensitizers reported in the literature, we show that these new “semi‐disconnected” starburst systems exhibit a remarkable trade‐off between intrinsic 2PA, fluorescence and oxygen photosensitization.

Controlling Redox and Wirelike Charge-Delocalization Properties of Dinuclear Mixed-Valence Complexes with MCp*(dppe) (M = Fe, Ru) Termini Bridged by Metalloporphyrin Linkers

“…Herein, we report on the design of new MV systems [ 1 MM’ ] +• consisting of the two MCp*(dppe) fragments (M = Fe, Ru; Cp* = η 5 -C 5 Me 5 ; dppe = 1,2-diphenylphosphinoethane) bridged by the zinc- and nickel-porphyrin-containing linkers (Figure a). Porphyrin motifs with the large dimensions are widely utilized in nature and materials chemistry, − key components for charge and energy carrier transport systems, and their highly π–delocalized systems with the small HOMO–LUMO gaps bring the frontier orbitals closer to the energy levels of the metal fragments to lead to stronger long-range metal-BL interaction, i.e. a nm-order highly delocalized system (>1 nm) (Figure d).…”