Photoinduced Electron Transfer within Porphyrin‐Anthra‐quinone Dyads Connected by Hamilton Hydrogen Bonding

Abstract

Porphyrin-or zinc-porphyrin-cyanuric acid conjugants (TPP-CA or ZnTPP-CA) and anthraquinone connected with the known "Hamilton receptor" (AQ-H) were synthesized. The supramolecular dyads constructed via the AQ-H and TPP-CA/ZnTPP-CA exhibit six hydrogen bonds, which provide the association constant K APP approximately (2.8±0.3)×10 3 mol -1 •L in toluene. Selective excitation of the porphyrin/zinc porphyrin chromophores results in an electron transfer between TPP-CA/ZnTPP-CA and AQ-H within the supramolecular assemblies, leading to an efficient quenching of the TPP-CA/ZnTPP-CA fluorescence. The singlet electron transfer from porphyrin/ zinc-porphyrin to anthraquinone proceeds mainly via a 'through space' mechanism with efficiencies of 43%, 58%, and rate constants of 7.6×10 7 , 7.0×10 8 s -1 , respectively.

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“…The rst step of the Scheme 2 involved the synthesis of 4-formylphenyl 4-(bromomethyl)-3-nitrobenzoate (-CHO-ONB-Br) through esterication of 4-(bromomethyl)-3-nitrobenzoic acid with 4-hydroxybenzaldehyde using DCC and DMAP. 34 The resultant bromo-product (-CHO-ONB-Br) acts as a reactant for the next step which reacts with 4-hydroxybenzaldehyde in a nucleophilic substitution reaction in presence of K 2 CO 3 . 35 The products of both steps were conrmed by 1 H-NMR and LCMS ( Fig.…”

“…Then DCC (2.2 g, 10.66 mmol) was added and further stirred for 10 min. Finally, 4-hydroxybenzaldehyde (1.0 g, 8.19 mmol), was added to the reaction mixture and stirred at room temperature for 16 h. 34 Aer con-rming the completion of reaction by TLC, the reaction mixture was quenched with water (100 mL) and transferred into a glass separating funnel and the compound was extracted into ethyl acetate (2 Â 100 mL). The combined organic layers were washed with NaCl solution (100 mL) and it was dried on anhyd.…”