Supramolecular complex of a fused zinc phthalocyanine–zinc porphyrin dyad assembled by two imidazole-C₆₀units: ultrafast photoevents

Abstract

A new zinc phthalocyanine-zinc porphyrin dyad (ZnPc-ZnP) fused through a pyrazine ring has been synthesized as a receptor for imidazole-substituted C (CIm) electron acceptor. Self-assembly via metal-ligand axial coordination and the pertinent association constants in solution were determined by H-NMR, UV-Vis and fluorescence titration experiments at room temperature. The designed host was able to bind up to two CIm electron acceptor guest molecules to yield CIm:ZnPc-ZnP:ImC donor-acceptor supramolecular complex. The spectral data showed that the two binding sites behave independently with binding constants similar in magnitude. Steady-state fluorescence studies were indicative of an efficient singlet-singlet energy transfer from zinc porphyrin to zinc phthalocyanine within the fused dyad. Accordingly, the transient absorption studies covering a wide timescale of femto-to-milli seconds revealed ultrafast energy transfer from ZnP* to ZnPc (k ∼ 10 s) in the fused dyad. Further, a photo induced electron transfer was observed in the supramolecularly assembled CIm:ZnPc-ZnP:ImC donor-acceptor complex leading to charge separated states, which persisted for about 200 ns.

Sequential, Ultrafast Energy Transfer and Electron Transfer in a Fused Zinc Phthalocyanine‐free‐base Porphyrin‐C60 Supramolecular Triad

“…It may be pointed out here that in the ZnPc‐H 2 P dyad only ZnPc could bind C 60 Im via metal‐ligand axial coordination. This is unlike the previous study, where the investigated ZnPc‐ZnP dyad was able to bind two C 60 Im entities independently due to the presence of metal ions in both porphyrin and phthalocyanine rings . The binding constants were evaluated by analyzing the spectral data according to the Benesi‐Hildebrand method (see Figure b inset) .…”

“…A well resolved 1 H NMR spectrum of ZnPc‐H 2 P in THF‐ d 8 as solvent is shown in Figure . The proton peak assignments were carried out by a comparative study with the ZnPc(NH 2 ) 2 , the dioxoporphyrin H 2 P and the ZnPc‐ZnP dyad previously reported . This type of molecules have the disadvantage of forming aggregates due to the π‐π stacking.…”

“…First, the interaction between C 60 Im and ZnPc was studied by adding increasing amounts of ZnPc (guest) to a solution of C 60 Im (host) . The analysis of NMR spectra, with no significant changes in the chemical shift of monitored C 60 Im signals upon addition of more than 1 equivalent of ZnPc suggested a 1 : 1 stoichiometry of C 60 Im:ZnPc.…”

“…A supramolecular triad formed by assembling a distorted ZnP–ZnPc dyad and pyridyl fullerene was also described, and intramolecular electron transfer to yield ZnP‐(ZnPc)⋅ + −(C 60 )⋅ − species was demonstrated. Recently, we reported on ultrafast energy transfer in a fused ZnP‐ZnPc dyad that, when assembled to C 60 , led to electron transfer . Additionally, a number of examples where either porphyrin dimers or phthalocyanine dimers connected to C 60 were also reported .…”

N-Confused Porphyrin Immobilized on Solid Supports: Synthesis and Metal Ions Sensing Efficacy

“…Porphyrins and analogues, well known by their impressive applications in several areas such as catalysis [ 25 , 26 , 27 , 28 ], photocatalysis [ 29 , 30 ] electronic materials [ 31 , 32 , 33 ], supramolecular chemistry [ 34 , 35 ], biomimetic models [ 36 , 37 ] , and medicine [ 25 , 38 , 39 , 40 , 41 , 42 , 43 ], are also often used as sensor probes due to their unique photophysical and photochemical properties [ 25 , 35 , 44 , 45 , 46 ]. In fact, porphyrins as free-bases or as metallo complexes have been used to create the so-called artificial noses and tongues for gas, cations, anions, and neutral species detection [ 47 ].…”