Photoinduced Processes in Self‐Assemblies of Bis‐Porphyrinic Tweezers with an Axially Coordinated Bispyridinofullerene

Abstract

Self‐assembled bis(zinc porphyrin)–bispyridinopyrrolidinofullerene coordination complexes were obtained in solution. Two [5]polynorbornane‐bridged bis‐porphyrins were used that differed in the arms containing porphyrin units: whereas 1 has rigid [5]polynorbornane linkers, compound 2 has additional flexible propyl chains. The different geometries of the two hosts affect both the complexation process and the photoreactivity of the final product. Formation of the complexes, characterized by absorption, emission, and NMR spectroscopy, occurs with association constants in the order of 104 and 106 m−1 for bis‐porphyrin tweezers 1 and 2, respectively. The higher flexibility of tweezers 2 accounts for the greater association ability. Full photophysical characterization of the complexes, as well as of suitable models, has been performed by means of steady‐state and time‐resolved optical spectroscopy. Ultrafast luminescence detection and pump–probe transient absorption analysis were used to investigate photoinduced processes within the complexes. The results provide evidence that an electron‐transfer process from the bis‐porphyrin host to the fullerene guest occurs in both complexes, and a slightly longer lifetime of the charge‐separated state is observed in the complex with more flexible host 2.

Photophysical properties of porphyrinic covalent cages endowed with different flexible linkers

“…Fluorescence lifetimes in the ps regime were measured by means of a Hamamatsu synchroscan streak-camera apparatus (C10910-05 main unit and M10911-01 synchroscan unit) equipped with an ORCA-Flash 4.0 V2 charge-coupled device (CCD) and an Acton spectrograph SP2358. As excitation source, a Newport Spectra Physics Solstice-F-1K-230 V laser system, combined with a TOPAS Prime (TPR-TOPAS-F) optical parametric amplifier (pulse width: 100 fs, 1 kHz repetition rate) [42] was used, tuned at 560 nm. To reduce photo-degradation, the pump energy on the sample was reduced to 26 mJ/ pulse.…”

Mechanochemical N-alkylation of imides

“…The reaction of the norbornene endo -succinimide 1 [25] with 1,3-dibromopropane ( 2 ) was used as a model system for the optimization of the reaction conditions [26]. Here, imide 1 is a solid, while dibromopropane is a liquid reagent.…”

Cooperativity in Binding of Aliphatic Diamines by Bis(Zn(II)porphyrin) Receptor with Moderately Flexible Linkers

“…Synthesis of compounds 9, 10 and 11 was reported previously. [15] In all titration experiments the exact volume of the solvent was weighed on the analytical scale with an accuracy of 0.1 mg. UV-Vis titrations were carried out at a concentration of porphyrin solution of 10 -6 mol dm -3 . Used solvents were of spectroscopic grade (Fluka).…”

“…The same spacer was also used for determination of relative stereochemistry. [14] Here we present results of supramolecular selfassembly of bis-porphyrin 9 [15] and a series of ditopic guests such as diamines. The aim of this study was to investigate hostguest interactions of diamines, wanting to establish if there is any size selectivity as for the specific recognition of diamines and other interesting molecular recognition properties.…”