Self-assembly of double-decker cages induced by coordination of perylene bisimide with a trimeric Zn porphyrin: study of the electron transfer dynamics between the two photoactive components

Abstract

We describe the thermodynamic characterization of the assembly process of a covalently connected trimeric Zn porphyrin induced by coordination to a bispyridyl functionalized perylene bisimide . The perylene bisimide ligands act as pillars via two axial coordination bonds with the porphyrinic Zn(ii) ions fixing the planes of the porphyrin units in a nearly co-facial orientation and inducing the formation of trigonal prism-like structures. The fully assembled (2).(3) aggregate and the partially assembled one, (2).(2), in which only two zinc porphyrin sites of trimeric are axially coordinated to , are present in solution in equilibrium with freely diffusing species and . The strong quenching observed in the mixture for the luminescence of the components and is ascribed to an efficient photoinduced electron transfer from the Zn porphyrin units of to coordinated occurring upon excitation of both components within the assemblies. In the formed assemblies, the Zn porphyrin units of the trimer behave independently. Thus, the porphyrin units that are not coordinated with in the partially assembled complex, (2).(2), display the same photophysical behaviour registered for freely diffusing . The rate of charge separation within the cage is nearly independent on the polarity of the solvent (ca. 10(10) s(-1)) whereas the charge recombination process, leading to the ground state, has a lifetime of 110 ps in dichloromethane and ca. 6 ns in toluene, in agreement with a Marcus inverted behaviour.

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

“…Their first oxidation potentials are at +0.27 and +0.28 V (versus ferrocene/ferrocenium (Fc/Fc + )), respectively, which are close to the value reported for a similar bis‐porphyrin . Pyrrolidinofullerene 5 showed four reduction waves with potentials at −1.08, −1.46, −1.87, and −2.01 V. The first oxidation potential of the complex 2⋅5 , attributable to porphyrin oxidation, is slightly less positive (+0.21 V) than that in the free component, as already observed for zinc–porphyrins bound to amine ligands . The reduction potentials comprise porphyrin and fullerene peaks, with small variations relative to the free components (Table S4 in the Supporting Information).…”

Sawhorse‐Type Tetracarbonyldiruthenium Tweezers

“…The related association constants were derived from Benesi-Hildebrand equations [28] and, as expected, are in the order of 10 3 m -1 ( Table 1). On the other hand, analogous bis(porphyrin)-based host systems [19,25,26] display association constants 2-3 times higher compared with those of the present case, which indicates a nonoptimal match between the host cavities of 3 and 4 and the length of these bis(pyridyl) guests. Taking these values as a benchmark for monodentate coordination, 3 and 4 were then titrated with bpy and bpe in CCl 4 .…”

“…Therefore, 3 and 4 were titrated with molecules bearing two pyridine units, [19,[24][25][26] namely, 4,4Ј-bipyridine (bpy), 1,2-bis(4-pyridyl)ethylene (bpe), 5,10-bis(4-pyridyl)-15,20-diphenyl-21H,23H-porphyrin (5,10-dpp), and 5,15-bis(4-pyridyl)-10,20-diphenyl-21H,23H-porphyrin (5,15-dpp) ( Figure S5), which can afford a bridging bidentate coordination to the Zn II ions of the bis(porphyrin) tweezers 3 and 4. Therefore, 3 and 4 were titrated with molecules bearing two pyridine units, [19,[24][25][26] namely, 4,4Ј-bipyridine (bpy), 1,2-bis(4-pyridyl)ethylene (bpe), 5,10-bis(4-pyridyl)-15,20-diphenyl-21H,23H-porphyrin (5,10-dpp), and 5,15-bis(4-pyridyl)-10,20-diphenyl-21H,23H-porphyrin (5,15-dpp) ( Figure S5), which can afford a bridging bidentate coordination to the Zn II ions of the bis(porphyrin) tweezers 3 and 4.…”

Supramolecular Coordination: Self-Assembly of Finite Two- and Three-Dimensional Ensembles

“…The analogous trigonal prisms having ditopic N-donor ligands based on perylene tetracarboxylic acid bisimide also showed efficient photoinduced electron transfer from the Zn porphyrin units to the axially coordinated bisimide pillars, occuring from the singlet excited states localized on both chromophores. 437 …”