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A three-fold symmetric trioxotriangulene derivative with three pyridyl groups as coordinating sites was designed and synthesized. In a cyclic voltammetry measurement, the trioxotriangulene skeleton exhibited a multi-stage redox ability from neutral radical to radical tetra-anion species. In the zinc complex of monoanion species, three pyridyl groups coordinated to the zinc ion to build up a two-dimensional coordination network with a cavity larger than 12 &Aring, in diameter. This complex was utilized as a cathode active material of a lithium ion battery, and it exhibited a capacity of ca. 60 mAh g&minus, 1 per the weight of the active material with a stable cycling performance up to 1000 cycles. This work shows that the coordination network formed by the trioxotriangulene-based ligand was effective in the improvement of cycle performance of the organic rechargeable battery.

Despite recent advances in the carbonization of organic crystalline solids like metal-organic frameworks or supramolecular frameworks, it has been challenging to convert crystalline organic solids into ordered carbonaceous frameworks. Herein, we report a route to attaining such ordered frameworks via the carbonization of an organic crystal of a Ni-containing cyclic porphyrin dimer (Ni2-CPDPy). This dimer comprises two Ni–porphyrins linked by two butadiyne (diacetylene) moieties through phenyl groups. The Ni2-CPDPy crystal is thermally converted into a crystalline covalent-organic framework at 581 K and is further converted into ordered carbonaceous frameworks equipped with electrical conductivity by subsequent carbonization at 873–1073 K. In addition, the porphyrin’s Ni–N4 unit is also well retained and embedded in the final framework. The resulting ordered carbonaceous frameworks exhibit an intermediate structure, between organic-based frameworks and carbon materials, with advantageous electrocatalysis. This principle enables the chemical molecular-level structural design of three-dimensional carbonaceous frameworks., Carbon-based materials are promising alternatives to noble metal catalysts, but their structures are typically disordered and difficult to control. Here, the authors obtain ordered carbonaceous frameworks with advantageous electrocatalytic properties via the carbonization of nickel-containing porphyrin dimer networks.

Free-bases and a nickel(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M2-Ptz-CPDPy(OCn); M = H2 or Ni, OCn = OC6 or OC3) at opposite meso-positions have been prepared as host molecules for fullerenes. The free-base dimer (H4-Ptz-CPDPy(OC6)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 10(6) M(-1) for C60 and 7.4 ± 0.8 × 10(7) M(-1) for C70 in toluene. This C60 affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni2-Ptz-CPDPy(OC6)) also shows high affinities for C60 (1.3 ± 0.2 × 10(6) M(-1)) and C70 (over 10(7) M(-1)). In the crystal structure of the inclusion complex of C60 within H4-Ptz-CPDpy(OC3), the C60 molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C60 inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C-H···N hydrogen bonds between porphyrin β-CH groups and pyridyl nitrogens as well as π-π interactions of the pyridyl groups. The C60 molecules are linearly arranged in the inner channel of this nanotube.

We have studied the supramolecular structures and photoelectronic properties of inclusion complexes of cyclic porphyrin dimers (M2-CPDPy, M = Ni, 2H) and fullerenes (C60, C70, PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) and Li+@C60). The porphyrin dimers have self-assembling 4-pyridyl groups at the meso positions and include fullerenes in their cavities with high affinities (Kassoc ≈ 105M−1). In crystals, C60 ⊂ Ni2-CPDPy and PCBM ⊂ Ni2-CPDPy give self-assembled porphyrin nanotubes containing the linear arrays of fullerene molecules. These self-assemblies are induced mainly by the non-classical hydrogen bonds between pyridyl nitrogens and porphyin β C–H groups. On the other hand, in the crystals of C60 ⊂ H4-CPDPy and C70 ⊂ H4-CPDPy, the included fullerene molecules show zigzag chains through van der Waals contacts with each other. Due to these well-ordered arrays of C60, both crystals of C60⊂ Ni2-CPDPy and C60 ⊂ H4-CPDPy have high charge mobilities (Σμ > 0.1 cm2 V−1 s−1). C60 ⊂ H4-CPDPy shows photoinduced electron transfer from the porphyrin moieties to C60 and photovoltaic activity with IPCEmax = 17% in photoelectrochemical cells. Moreover, the inclusion complexes of lithium-ion-encapsulated C60(Li+@C60) and M2-CPDPy exhibit photoinduced charge separation with very long lifetimes reaching submillisecond order. [TANSO 2013 (No. 260) 284–91.]

Lithium ion encapsulated [60]fullerene (Li+@C60) is included within a free base and nickel complex of a cyclic porphyrin dimer (M-CPDPy, M = H4 and Ni2) to afford supramolecules (Li+@C60⊂M-CPDPy) in a polar solvent (benzonitrile) with the association constants of 2.6 × 105 M−1 and 3.5 × 105 M−1, respectively. From the electrochemical analysis, the energies of the charge-separated (CS) states are estimated to be 1.07 eV for Li+@C60⊂H4-CPDPy and 1.20 eV for Li+@C60⊂Ni2-CPDPy. Both values are lower than the triplet excited energies of the fullerene and porphyrin. Upon the photoexcitation at the Q-band of the porphyrin chromophore of Li+@C60⊂H4-CPDPy, electron transfer from the triplet excited state of the free base porphyrin to Li+@C60 occurs to produce the CS state. Li+@C60⊂Ni2-CPDPy also undergoes photoinduced electron transfer to produce the CS state. The lifetimes of the resulting CS states are 0.50 ms for Li+@C60⊂H4-CPDPy and 0.67 ms for Li+@C60⊂Ni2-CPDPy. These remarkably long CS lifetimes are the best values ever reported for non-covalent porphyrin-fullerene supramolecules in solution and are attributable to the lower CS energies than the triplet energy of each chromophore.

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