Supramolecular Assembly of Multicomponent Photoactive Systems via Cooperatively Coupled Equilibria

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• 作者：Miguel Garcı ; ́ ; a-Iglesias ; Katrin Peuntinger ; Axel Kahnt ; Jan Krausmann ; Purificación Vázquez ; David González-Rodrı ; ́ ; guez ; Dirk M. Guldi ; Tomás Torres
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：December 26, 2013
• 年：2013
• 卷：135
• 期：51
• 页码：19311-19318
• 全文大小：520K
• ISSN：1520-5126

文摘

Here, we show that the synergistic interplay between two binding equilibria, acting at different sites of a (Zn)phthalocyanine-amidine molecule (Pc1), enables the dissociation of the photoinactive phthalocyanine dimer (Pc1)₂ into a three-component system, in which a sequence of light harvesting, charge separation, and charge shift is successfully proven. The aforementioned dimer is assembled by dual amidine-Zn(II) coordination between neighboring Pc1 molecules and gives rise to high association constants (K_D 鈮?10¹¹ M^鈥?). Such extraordinary stability hampers the individual binding of either carboxylic acid ligands through the amidine group or pyridine-type ligands through the Zn(II) metal atom to (Pc1)₂. However, the combined addition of both ligands, which cooperatively bind to different sites of Pc1 through distinct noncovalent interactions, efficiently shifts the overall equilibrium toward a photoactive tricomponent species. In particular, when a fullerene-carboxylic acid (C₆₀A) and either a dimethylamino-pyridine (DMAP) or a phenothiazine-pyridine ligand (PTZP) are simultaneously present, the photoactivity is turned on and evidence is given for an electron transfer from photoexcited Pc1 to the electron-accepting C₆₀A that affords the DMAP-Pc1^鈥?-C₆₀A^{鈥⑩€?/sup> or PTZP-Pc1鈥?-C₆₀A鈥⑩€?/sup> radical ion pair states. Only in the latter case does a cascade of photoinduced electron transfer processes afford the PTZP鈥?-Pc1-C₆₀A鈥⑩€?/sup> radical ion pair state. The latter is formed via a thermodynamically driven charge shift evolving from PTZP-Pc1鈥?-C₆₀A鈥⑩€?/sup> and exhibits lifetimes that are notably longer than those of DMAP-Pc1鈥?-C₆₀A鈥⑩€?/sup>.}