Takayuki Tanaka

Since the discovery of its facile synthesis in 2001, meso-aryl-substituted expanded porphyrins have been developed as a new class of azaannulenes in light of their facile redox interconversions, conformational flexibilities involving flipping of the constitutional pyrroles, rich metal coordination behaviors, unprecedented chemical reactivities, effective platforms to realize versatile electronic states including Möbius aromatic and antiaromatic species, and abilities to stabilize organic radical

Tetrabenzotetraaza[8]circulene (1) has been synthesized in good yield by a "fold-in" oxidative fusion reaction of a 1,2-phenylene-bridged cyclic tetrapyrrole. X-ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic-like character, such as sharp absorption bands, high fluorescence quantum yields (Φ(F)=0.55 in THF), and a single exponenti

Twist and sort out! Chiral separation of PdII, NiII, and PtII complexes of [28]hexaphyrin(1.1.1.1.1.1) was achieved by HPLC on a chiral stationary phase (see inset for CD trace). The absolute configuration for the PdII complex was determined by X-ray crystallography. Asymmetric metalation of hexaphyrin, achieved with a PdII binap salt, resulted in 23 % ee. This is the first example of asymmetric synthesis of Möbius-twisted molecules. Detailed facts of importance to specialist readers are publish

Triply linked porphyrin arrays, so called porphyrin tapes, are intriguing molecules in terms of their planar structures, far red-shifted absorption bands, multi-charge storage abilities, and high conductivities. Recently, porphyrin tape variants such as porphyrin-expanded porphyrin hybrid tapes, porphyrin arch-tapes, corrole tapes, and a subporphyrin tape have been explored as novel π-conjugated materials. These new molecules exhibit electronic and structural characteristics owing to direct trip

Hybrid porphyrin tapes 3 and 4, consisting of a mixture of 3,5-di-tert-butylphenyl-substituted donor-type Zn(II)-porphyrins and pentafluorophenyl-substituted acceptor-type Zn(II)-porphyrins, were prepared by a synthetic route involving cross-condensation reaction of a Ni(II)-porphyrinyldipyrromethane and pentafluorophenyldipyrromethane with pentafluorobenzaldehyde followed by appropriate demetalation, remetalation, and oxidative ring-closure reaction. The Ni(II)-substituted porphyrin tapes 5 (Ni

A meso-meso linked porphyrin–hexaphyrin hybrid was synthesized by the cross condensation using meso-porphyrinyl-dipyrromethane and was oxidized with DDQ-Sc(OTf)3 to afford a porphyrin–[26]hexaphyrin hybrid tape that was reduced with NaBH4 to give a porphyrin–[28]hexaphyrin hybrid tape. Fully electronic conjugations in the hybrid tapes are observed in the UV/vis/NIR absorption spectra, electrochemistry, and excited-state dynamics.

Oxidative fusion reactions of ortho-phenylene-bridged cyclic hexapyrroles and hexathiophenes furnished novel closed helicenes in a selective manner. X-Ray diffraction analysis unambiguously revealed the structures to be a closed pentaaza[9]helicene, the longest azahelicene reported so far, and an unexpected double-helical structure of hexathia[9]/[5]helicene, whose formation was assumed to result from multiple oxidative fusion along with a 1,2-aryl shift. The pentaaza[9]helicene exhibited well-d

The oxidation of 10-10' singly linked corrole dimers with DDQ at low concentration in CHCl3 afforded meso-meso, β-β, β-β triply linked 2H-corrole dimers (with two inner NH groups in each corrole unit), which exhibited characteristic (1) H NMR and absorption spectra attributable to their nonaromatic electronic networks. These 2H-corrole dimers were reduced with NaBH4 to aromatic 3H-corrole dimers, which were unstable and easily oxidized back to the 2H-corrole dimers upon exposure to air. Bis(zinc

A singly linked corrole dimer was synthesized by condensation of a dipyrromethane-1-carbinol with 1,1,2,2-tetrapyrroethane. Oxidation of the dimer gave doubly linked corrole dimers 9 and 10 as the first examples of fused corrole dimers involving a meso-meso linkage. Dimers 9 and 10 exhibit characteristic (1)H NMR spectra, absorption spectra, excited-state dynamics, and two-photon absorption (TPA) values, which indicate the nonaromatic nature of 9 and the aromatic nature of 10. Interestingly, 9 i

Hetero[8]circulenes are an interesting class of polycyclic heteroaromatic molecules having rigid and planar structures, which are promising in light of their potential applications for OLEDs, OFETs and so forth. Although their synthetic methods have been developed in some specific cases, a facile synthetic protocol of novel hetero[8]circulenes with tunable properties is highly desirable. We herein report the unexpected formation of methoxy-substituted quasi-aza[8]circulene and its conversion int

5,10-Bis(pentafluorophenyl)corrole (5) and 5,15-bis(pentafluorophenyl)corrole (9) have been synthesized as meso-free corroles by rational synthetic routes. Both the structures of these corroles have been unambiguously revealed by X-ray diffraction analysis and their optical and electrochemical properties have been studied. Chlorination and oxidative dimerization of 5 and 9 have been explored, which revealed a marked different reactivity of the free meso-positions in 5 and 9. 10-Chlorinated corro

Polycyclic heteroaromatic compounds including pyrrole units are promising functional scaffolds owing to their electron-rich nature, bright fluorescence, and applicability to anion recognition at the pyrrolic hydrogen atom. We report herein the effective synthesis of pseudo-aza[5]helicene and aza[7]helicene derivatives, and unexpected formation of azahepta[8]circulenes by oxidative fusion reactions. By choosing reaction conditions and peripheral substituents attached at the terminal indole moieti

Synthetic challenges toward anomalous structures and electronic states often involve handling problems such as insolubility in common organic solvents and oxidative degradation under aerobic conditions. We designed benzo-annulated aza[<i>n</i>]helicenes, which benefit from both the suppressed elevation of highest occupied molecular orbital (HOMO) energies and high solubility due to hydrogen bonding with solvent molecules to overcome these challenges. This strategy enabled the synthesis of six ne

Abstract Tetrabenzotetraaza[8]circulene ( 1 ) has been synthesized in good yield by a “fold‐in” oxidative fusion reaction of a 1,2‐phenylene‐bridged cyclic tetrapyrrole. X‐ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic‐like character, such as sharp absorption bands, high fluorescence quantum yields ( Φ F =0.55 in THF), and a sing

Double ring expansion from a 5,15-diarylporphyrin to a 5,16-diaryl-10,11,21,22-tetradehydro[20]porphyrin(2.1.2.1) occurred through a reaction sequence consisting of oxidation with PbO2 to 5,15-dioxoporphodimethene, a Corey-Fuchs reaction with tetrabromomethane in the presence of triphenylphosphine, and Fritsch-Buttenberg-Wiechell rearrangement triggered by tert-butyllithium. The obtained tetradehydro[20]porphyrin(2.1.2.1) and its mono- and dihydrogenated congeners exhibited 20 π antiaromatic cha