Fullerene- and Pyromellitdiimide-Appended Tripodal Ligands Embedded in Light-Harvesting Porphyrin Macrorings

Synthesis and Photocatalytic CO2 Reduction of a Cyclic Zinc(II) Porphyrin Trimer with an Encapsulated Rhenium(I) Bipyridine Tricarbonyl Complex

We previously reported a cyclic Zn(II) porphyrin trimer in which three Zn porphyrins are alternately bridged by three 2,2'-bipyridine (bpy) moieties, enabling the encapsulation of metal complexes within the nanopore formed by the Zn porphyrins. In this study, we introduced a [Re(CO)3 Br] fragment into one of the bpy moieties of the cyclic trimer to form the catalytic Re(4,4'-R2 -bpy)(CO)3 Br center (R=methyl ester). The ester groups (R) play an important role in the synthesis of the cyclic structure. However, it was observed that these ester groups significantly deactivated the photocatalytic CO2 reduction reaction. Therefore, we converted the ester groups with a suitable reducing reagent into hydroxymethyl groups, followed by acetylation to form acetoxymethyl groups. This modification remarkably enhanced the photocatalytic activity of the cyclic trimer=Re complex system for CO2 reduction. Moreover, in the modified system, the presence of the Re complex induced room-temperature phosphorescence of the Zn porphyrin. The phosphorescence was significantly quenched by 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole, indicating that efficient electron transfer mediated by the excited triplet state of the Zn porphyrin occurs during the photocatalytic CO2 reduction.

Photocatalytic CO2 reduction sensitized by a special-pair mimic porphyrin connected with a rhenium(i) tricarbonyl complex

Zn porphyrins with an imidazolyl group at the meso position generate a highly stable porphyrin dimer by complementary coordination from the imidazolyl to the Zn ion in noncoordinating solvents such as chloroform, which mimics the natural special pair in photosynthesis. In this work, we have synthesized an imidazolyl-substituted Zn porphyrin connected with a Re 2,2-bipyridine tricarbonyl complex as a CO₂ reduction catalyst via a p-phenylene linker, affording a homodimer with two Re complexes on both sides (ReDRe). The dimeric structure is easily dissociated into the corresponding monomers in coordinating solvents. Therefore, we prepared a mixture containing a heterodimer with the Re carbonyl complex on one side (ReD) by simple mixing with an imidazolyl Zn porphyrin and evaporating the solvent. Using the Grubbs catalyst, the subsequent olefin metathesis reaction of the mixture gave covalently linked porphyrin dimers through the allyloxy side chains, enabling the isolation of the stable hetero- (ReD′) and homo-dimers (ReD′Re) with gel permeation chromatography. The Zn porphyrin dimers have intense absorption bands in the visible light region and acted as good photosensitizers in photocatalytic CO₂ reduction in a mixture of N,N-dimethylacetamide and triethanolamine (5 : 1 v/v) containing 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole as the electron donor, giving CO with high selectivity and durability. Under irradiation with strong light intensity, the reaction rate in ReD′ exceeded that of the previous porphyrin Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Re complex dyad, ZnP-phen=Re. For instance, after irradiation at 560 nm for 18 h, the turnover number (TON_CO) of ReD′ reached 2800, whereas the TON_CO of ZnP-phen=Re was 170. The high activity in the system using the porphyrin dimer originates from no accumulation of the one-electron reduced species of the porphyrin that inhibit light absorption due to the inner-filter effect.

An artificial special pair was connected with a Re 2,2-bipyridine tricarbonyl complex. The special pair derivative acted as a good photosensitizer in photocatalytic CO₂ reduction, giving CO with high selectivity and durability.

Photocatalytic CO2 Reductions Catalyzed by meso-(1,10-Phenanthrolin-2-yl)-Porphyrins Having a Rhenium(I) Tricarbonyl Complex

We have prepared Zn and free-base porphyrins appended with a fac-Re(phen)(CO)3 Br (where phen is 1,10-phenanthroline) at the meso position of the porphyrin, and performed photocatalytic CO2 reduction using porphyrin-Re dyads in the presence of either triethylamine (TEA) or 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. The Zn porphyrin dyad showed a high turnover number for CO production compared with the free-base porphyrin dyad, suggesting that the central Zn ion of porphyrin plays an important role in suppressing electron accumulation on the porphyrin part and achieving high durability of the photocatalytic CO2 reduction using both TEA and BIH. The effect of acids on the CO2 reduction was investigated using the Zn porphyrin-Re dyad and BIH. Acetic acid, a relatively strong Brønsted acid, rapidly causes the porphyrin's color to fade upon irradiation and dramatically decreases CO production, whereas proper weak Brønsted acids such as 2,2,2-trifluoroethanol and phenol enhance the CO2 reduction.

2,4,6-Tris(4-Iodophenyl)-1,3,5-trimethylbenzene

2,4,6-Tris(4-iodophenyl)-1,3,5-trimethylbenzene was synthesized from 2,4,6-triphenyl-1,3,5-trimethylbenzene, using [bis(trifluoroacetoxy)iodo]benzene as the iodinating agent. The title compound was characterized by means of NMR, IR, and mass spectrometry, as well as TG analysis.

Visualization of nonemissive triplet species of Zn(ii) porphyrins through Cu(ii) porphyrin emission via the reservoir mechanism in a porphyrin macroring

A macroring shows long-lived near-IR emission from Cu(ii) porphyrin via the reservoir mechanism. The significant emission quenching by O₂ suggests that the T₁ state of Zn(ii) porphyrin can be monitored by the near-IR emission.

Synthesis and Photophysical Properties of Porphyrin Macrorings Composed of Free-Base Porphyrins and Slipped-Cofacial Zinc Porphyrin Dimers

The self-assembled macroring N-(Zn-Fb-Zn)₃ has been constructed by intermolecular complementary coordination among three trisporphyrin Zn-Fb-Zn molecules, each of which consists of a central free-base porphyrin and two imidazolyl-zinc-porphyrin ends. Thus, N-(Zn-Fb-Zn)₃ has three slipped-cofacial zinc porphyrin dimers ("special pair model") and three free-base porphyrins, alternately. The zinc porphyrin dimers in N-(Zn-Fb-Zn)₃ are covalently connected by a ring-closing olefin metathesis reaction between the allyl ether groups substituted on the zinc porphyrin dimers, giving a covalently linked macroring C-(Zn-Fb-Zn)₃. The fluorescence spectra of C-(Zn-Fb-Zn)₃ in several solvents show that the photoinduced energy transfer from one of the zinc porphyrin dimers to a free-base porphyrin occurs intramolecularly in toluene, whereas the photoinduced electron transfer predominantly occurs intramolecularly in N,N-dimethylformamide. Treatment of C-(Zn-Fb-Zn)₃ with copper(II) acetate gives a Cu-containing heteromultinuclear porphyrin macroring C-(Zn-Cu-Zn)₃, demonstrating that C-(Zn-Fb-Zn)₃ could be a good precursor to construct various heteromultinuclear porphyrin macrorings.

Hierarchical Corannulene-Based Materials: Energy Transfer and Solid-State Photophysics

We report the first example of a donor-acceptor corannulene-containing hybrid material with rapid ligand-to-ligand energy transfer (ET). Additionally, we provide the first time-resolved photoluminescence (PL) data for any corannulene-based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor-acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand-to-ligand ET rate calculated using two models is comparable with that observed in fullerene-containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π-bowls, specifically corannulene derivatives, with the versatility of crystalline hybrid scaffolds, but could also foreshadow the engineering of a novel class of hierarchical corannulene-based hybrid materials for optoelectronic devices.

Core expanded, 21,23-dithiadiacenaphtho[1,2-c]porphyrin interactions with [60]fullerene

Saddle-shaped 21,23-dithiadiacenaphtho[1,2-c]porphyrin exhibits binding interaction with [60]fullerene in addition to photon absorption bands extending to 1000 nm.

A supramolecular photosynthetic model made of a multiporphyrinic array constructed around a C60 core and a C60-imidazole derivative

The photophysical properties of a supramolecular fullerene-porphyrin ensemble resulting from the self-assembly of a pyrrolidinofullerene-imidazole derivative (F1) with a multimetalloporphyrin array constructed around a hexasubstituted fullerene core (F(ZnP)12) have been investigated. The fullerene hexa-adduct core of the host system does not play any active role in the cascade of photoinduced events of the supramolecular ensemble, indeed no intercomponent photoinduced processes could be observed in host F(ZnP)12. In contrast, upon axial coordination with the monosubstituted fullerene guest F1, a quantitative quenching of the fluorescence signal of the metalloporphyrins was observed for the supramolecular complex [F(ZnP)12(F1)n] both in polar and nonpolar solvents. In toluene, the supramolecular ensemble exhibits a charge transfer emission centered around nm, suggesting the occurrence of intramolecular face-to-face interactions of F1 with neighboring metalloporphyrin moieties within the self-assembled photoactive array. This mechanism is supported by the fact that a one order of magnitude increase in the binding constant was observed for the supramolecular complex [F(ZnP)12(F1)n] when compared with a reference system lacking the pyrrolidinofullerene unit. In benzonitrile, a long-lived charge-separated state (τ=0.3 μs) has been detected for the supramolecular adduct.