AbstractIn 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 π‐π* absorption 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.
摘要 在继续以前对外围具有 2,7 芴单元的富碳中四芳基卟啉的研究的基础上,现在分析了将外围树枝状臂换成线状臂对其氧光敏能力、荧光和双光子吸收(2PA)特性的影响。因此,我们分离并研究了拥有多达二十个共轭芴基单元的星光卟啉。更确切地说,我们合成了一系列五种新的自由基卟啉及其 Zn(II) 复合物,这些卟啉具有完全共轭的臂,通过 1,2- 烯基间隔连接着越来越多的芴基。在以臂为中心的 π-π* 吸收带受到激发时,外围的芴基单元向中心的卟啉核心进行有效的能量转移,导致后者发出强烈的红光并使氧气光敏化。更有趣的是,与用于光动力疗法(PDT)或荧光成像的树枝状聚合物类似物相比,这些卟啉的线性光学特性只是略有改善,但它们的 2PA 截面却得到了更显著的提高,这证明了不同结构对非线性光学特性所起的关键作用。最后,通过与文献中报道的其他基于卟啉的双光子光敏剂进行比较,我们发现这些新的 "半断开 "星爆系统在本征 2PA、荧光和氧光敏之间表现出显著的权衡。