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Cyclic azobenzene-BODIPY hybrids were synthesized via cyclization by 1) acid-catalysed condensation of azobenzene-bridged dipyrroles with 3,5-di-tert-butylbenzaldehyde, 2) oxidation with DDQ, and 3) metalation with BF 3  ⋅ Et 2 O. The structures of many cyclic hybrids have been confirmed by single crystal X-ray analysis. The absorption spectra of the hybrids reveal the effective cyclic conjugation. The ultrafast measurements reveal that the photoexcited decays of these cyclic hybrids depend upon the ring size and connectivity., (© 2023 Wiley-VCH GmbH.)

Dithienylethene (DTE)-embedded expanded porphyrins were synthesized and confirmed to be photochemically inactive due to the lowest excited state of the expanded porphyrins. On the other hand, DTE-embedded expanded calixphyrins exhibited reversible photochromism upon UV-irradiation to form colored closed forms, which reverted to colorless open forms upon red-light irradiation. The closed forms were oxidized with DDQ or the air to lock the recorded information by converting to photochemically inactive expanded porphyrins. This was unlocked by reduction with NaBH 4 to restore expanded calixphyrins with photochromism activity. These gated photochromic behaviors were demonstrated in PMMA (polymethyl methacrylate) film., (© 2023 Wiley-VCH GmbH.)

Fused-benzoheptagon-installed Ni II porphyrins were synthesized by a protocol consisting of (2-formyl)arylation at the meso-position(s) of Ni II porphyrins, conversion of formyl group to methoxyethene group by Wittig reaction, and final Bi(OTf) 3 -catalyzed cyclization. The structures of these porphyrins have been revealed by X-ray analysis. Owing to the installed heptagon ring(s), these porphyrins show curved structures with conformational flexibility. Dimer has been shown to have a small activation barrier for inversion and to capture C 60 and C 70 with large association constants with adjustable conformational changes., (© 2023 Wiley-VCH GmbH.)

m-Benziporphyrin(1.1.0.0) and m-pyreniporphyrin(1.1.0.0) were prepared as ring-contracted carbaporphyrins. While m-Benziporphyrin(1.1.0.0) was unstable, m-pyreniporphyrin(1.1.0.0) was fairly stable. Both of their Pd II complexes showed distorted coordination structures with extremely short Pd-C bonds. As compared with the reported m-benziporphyrin Pd II complexes, these Pd II complexes showed considerably small HOMO-LUMO gaps, despite their smaller molecular size. Pd II metalation of the m-pyreniporphyrin(1.1.0.0) dimer gave the corresponding Pd II complex, which showed similar distorted coordination and a smaller HOMO-LUMO gap. Finally, Pd II metalation of a pyrene-sharing formal p-benziporphyrin(1.1.1.1) dimer gave a nonaromatic Pd II dimer, which rearranged to an aromatic Pd II complex upon treatment with alumina., (© 2022 Wiley-VCH GmbH.)

meso-Trimesityl-substituted [20]smaragdyrin freebase was synthesized by p-toluenesulfonic acid catalyzed reaction of 5-mesityldipyrromethane and 2,14-dibromodipyrrin in an improved yield of 63 %. Unexpectedly, treatment of the [20]smaragdyrin freebase with BF 3  ⋅ OEt 2 and triethylamine (TEA) gave a stable radical species, in which the BF 2 unit is coordinated at the tripyrrin site, probably by ready release of a hydrogen atom of a [22]smaragdyrin BF 2 complex. Similar treatment of [22]smaragdyrin free base produced another [22]smaragdyrin BF 2 complex, in which the BF 2 unit is coordinated at the dipyrrin site. The tripyrrin site coordinated neutral radical was oxidized with AgSbF 6 to give a stable antiaromatic cation; this was reduced with NaBH 4 to its 22π congener, which was easily oxidized back to the neutral radical in the air and rearranged to thermodynamically stable dipyrrin site coordinated [22]smaragdyrin BF 2 complex upon treatment with BF 3  ⋅ OEt 2 and TEA. Further, the dipyrrin site coordinated [22]smaragdyrin BF 2 complex was similarly oxidized to a stable neutral radical and a stable cation in a stepwise manner. This work demonstrates a rare ability of smaragdyrin BF 2 complexes to exist in multiple redox states, particularly forming a stable neutral radical by facile release of a hydrogen atom., (© 2022 Wiley-VCH GmbH.)

A meso-free β-bromodecaphyrin has been constructed by [2+3+2+3] type acid-catalyzed cross-condensation and subsequent oxidation. Hydrodebromination of this tetrabromodecaphyrin with NaBH 4 in the presence of TMEDA and palladium catalyst afforded β-unsubstituted doubly meso-free [46]decaphyrin(1.1.1.1.1.1.1.1.1.1) as the first example of β-unsubstituted meso-free regular expanded porphyrins with the number of pyrrole units larger than eight. It exhibits distinct aromaticity originating from its 46π-conjugated electronic circuit and flexible conformational change between non-twisted and doubly twisted forms depending on the solvent-polarity. Their distinct conformations have been analyzed by combined experimental and theoretical investigations., (© 2022 Wiley-VCH GmbH.)

Directly meso-meso linked porphyrin-tetrabromo[36]octaphyrin-porphyrin hybrid trimer 10 was successfully synthesized via acid-catalyzed condensation reaction and subsequent oxidation. Zn II -metalation of 10 induced transannular meso-meso bond formation to give Möbius aromatic bis-Zn II octaphyrin 11, which was oxidized by DDQ/Sc(OTf) 3 to provide fully conjugated porphyrin-[36]octaphyrin-porphyrin hybrid tape 12 as the first example of porphyrin tape exhibiting Möbius aromaticity. Hybrid tape 12 displays significantly red-shifted absorption and small electrochemical HOMO-LUMO gap, indicating the effective conjugation through the whole chromophores., (© 2022 Wiley-VCH GmbH.)

We report the synthesis, characterization, and reactivities of two stable Ni III N-confused porphyrin (NCP) complexes. Metalation of 3-OEt NCP 1 with NiCl 2  ⋅ 6H 2 O in CHCl 3 /EtOH gave 3-OEt Ni II NCP 3 initially, which was easily oxidized in air to form the Ni III complex of NCP inner C-oxide 4. Bis-ethoxy-modified Ni III complex 5 was synthesized by oxidation of 3 with PIFA in ethanol and CHCl 3 . The structures of 4 and 5 were determined by single-crystal X-ray diffraction analysis. An unusually long Ni III -C bond (2.170(9) Å) was observed in 4. The g-factor (g>2.1) observed in the EPR spectra of 4 and 5 further confirmed that they are paramagnetic Ni III complexes. Comparative experiments showed that the 3-ethoxy group plays an important role in the formation of 4 and 5. Reduction of 4 and 5 with NaBH 4 regenerated complex 3., (© 2021 Wiley-VCH GmbH.)

In contrast to the extensive development of the meso-functionalization of porphyrins, that of corroles had rarely been explored until the development of practical synthetic methods for meso-free corroles in 2015. The ready availability of meso-free corroles opened up meso-functionalization chemistry of corroles, giving rise to successful synthesis of various meso-substituted corroles such as meso-halogen, meso-nitro, meso-amino, meso-oxo, and meso-iminocorroles as well as meso-meso-linked corrole dimers and corrole tapes. In some cases, 2NH corroles exist as stable or transient radical species. The impact of meso-functionalization on the structures, electronic properties, optical characteristics, and aromaticity of corroles are highlighted in this Minireview., (© 2021 Wiley-VCH GmbH.)

Triple helicene-like semi-fused trimeric Ni II porphyrins were constructed by alkyne trimerization of an ethynyl-substituted porphyrin and subsequent three-fold Grignard addition to the formyl groups and acid-catalyzed intramolecular cyclization. The presence of stereogenic sp 3 carbons in the central bridge leads to small inter-porphyrin conjugative interactions as was revealed by electrochemical and optical properties. Two diastereomers with stable chiral conformations were optically resolved, and the separated enantiomers displayed considerably intense circular dichroism. Importantly, the chiroptical response of C 3 -symmetric helical isomer (|Δϵ|=830 m -1  cm -1 ) is 1.8 times amplified from that of C 1 -symmetric one (|Δϵ|=470 m -1  cm -1 ). The observed amplification has been interpreted in terms of different spatial arrangements of the three porphyrins., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

N,N'-Diarylated tetrabenzotetraaza[8]circulenes 3 a and 3 b were synthesized in good yields by a reaction sequence involving oxidation of tetrabenzodiazadithia[8]circulene 5-Oct and S N Ar reaction with aniline derivatives. The obtained aza[8]circulenes 3 a and 3 b were easily oxidized to give their radical cations 3 a + and 3 b + , which are highly stable under ambient conditions. X-ray diffraction analysis of radical cation 3 a + showed a face-to-face dimer arrangement with an interplanar separation of 3.320 Å. The spin density of 3 a + was calculated to be delocalized over the whole circulene π-systems with spin-spin exchange integral (J=-144 cm -1 ) in the dimeric part. These radical cations displayed far red-shifted absorption bands reaching to 2000 nm. Thus this study has proved the hetero[8]circulene scaffold to be a new entry of promising electronics and spin materials., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

B-Phenyl B III subporphyrin-α-diones prepared in a three-step reaction sequence from the parent subporphyrin were condensed with 1,2-diaminobenzenes to give the corresponding quinoxaline-fused subporphyrins in variable yields. Quinoxaline-fused B-phenyl-5,10,15-triphenyl B III subporphyrin was transformed to the corresponding subporphyrin-α-dione in the same three-step reaction sequence, which was then condensed with 1,2-diaminobenzene to give doubly quinoxaline-fused subporphyrin. These quinoxaline-fused subporphyrins exhibit redshifted absorption and fluorescence spectra compared with the parent one. A singly quinoxaline-fused subporphyrin bearing three meso-bis(4-dimethylaminophenyl)aminophenyl substituents shows blueshifted fluorescence in less polar solvent, which has been ascribed to emission associated with charge recombination of intramolecular charge transfer (CT) state., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Internally 3,3'-biphenyl-, 2,2',5,5'-bithiophene-, and 2,5-thieno[3,2-b]thiophene-bridged [46]decaphyrins were prepared. In addition to the global 46π-conjugated circuits, the internal core-modified [32]heptaphyrin- and [30]hexaphyrin moieties in 2,2',5,5'-bithiophene- and 2,5-thieno[3,2-b]thiophene-bridged [46]decaphyrins also possess doubly twisted topologies (|L k |=2) and are regarded as (doubly-twisted-annuleno)doubly-twisted-annulene variants. All these decaphyrins display distinct Hückel aromaticity owing to the global 46π-electronic networks but the contributions of the local half circuits were almost negligible due to the perpendicular orientation of the bridges., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Oxidation of β-to-β directly linked and sulfur-bridged meso-amino Ni II -porphyrin dimers with PbO 2 gave helical tetrapyrrin (biliverdin analogue)-fused Ni II -porphyrins. These ring cleaving reactions differ markedly from the previously reported oxidation of a β-β linked Ni II -porphyrin dimer carrying one amino group, which gave an azepine-fused porphyrin dimer. The tetrapyrrin-fused Ni II -porphyrins display intense NIR absorption bands at 1200-1400 nm and reversible redox processes because of the highly π-conjugated networks and rigid structures. These tetrapyrrin-fused Ni II -porphyrins were separated to stable enantiomers, which showed clear Cotton effects in their CD spectra with Δϵ of 10 2 order., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Stable B III -subporphyrin-substituted dicyanomethyl radicals were synthesized by S N Ar reaction of meso-bromo- or meso-chlorosubporphyrins with malononitrile followed by oxidation with PbO 2 . Different from previously reported dicyanomethyl radicals that underwent σ- or π-dimer formation both in the solid state and in solutions, subporphyrin-stabilized dicyanomethyl radicals exist as monomers in solutions even at low temperature. DFT calculations revealed efficient spin delocalization over the entire subporphyrin. In the solid state, these radicals form weak π-dimers with antiferromagnetic interactions depending on the crystal packing structures., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An azepine-fused Ni II -porphyrin dimer was synthesized by oxidative amination of β-β linked Ni II -porphyrin dimer, and its N-aryl congener was synthesized by twofold Buchwald-Hartwig amination of β-to-β linked and dichlorinated Ni II -porphyrin dimer. Oxidation of the NH congener gave neutral aminyl radical and nitrenium ion successively in a similar manner to the previously reported NH-bridged Ni II -porphyrin dimer. Oxidation of the N-aryl congener afforded formal nitrenium dication in a single-step two-electron oxidation. Stable nitrenium dications that are isoelectronic to neutral trivalent boron compounds and tertiary carbocations are rare. The chemical stability of the nitrenium dication was improved by chlorine substitution at the most reactive β-position. The structural, optical, magnetic, electrochemical properties of these compounds were fully characterized., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Boron(III) 5-arylsubporphyrins and B III subporphine are promising precursors for functional B III subporphyrins bearing asymmetric meso-substituents. Herein, we report the first synthesis of these molecules. Among many aryl acid chlorides examined, 4-nitrobenzoyl chloride gave B III 5-(4-nitrophenyl)subporphyrin in 10 % yield in condensation with triethylamine-tri-N-tripyrromethene-borane. The nitro group of this B III subporphyrin was reduced with NaBH 4 to prepare B III 5-(aminophenyl)subporphyrin, which was converted into B III 5-phenylsubporphyrin via the corresponding diazonium salt. B III subporphine was synthesized by condensation of triethyl orthoformate with triethylamine-tri-N-tripyrromethene-borane. Progressive removal of meso-phenyl substituents leads to continuous changes in the optical properties, whereas the B III subporphine deviates from this trend in some properties., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 triple linkages. This Minireview first discusses the fundamental properties of the parent porphyrin tapes and the peripherally functionalized porphyrin tapes. Then, a focus has been placed on the syntheses, structures, and unique properties of the recently explored porphyrin tape variants., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Boron(III) meso-lithiosubporphyrin was prepared by bromine-lithium exchange of B-tolyl B III meso-bromosubporphyrin with n-butyllithium at -98 °C. The resulting subporphyrinyllithium was treated with various electrophiles such as benzophenone, N,N-dimethylformamide, CO 2 , chlorotrimethylsilane, N-fluorobenzenesulfonimide, and dimesitylboryl fluoride to give the corresponding meso-functionalized B III subporphyrins. The nucleophile was also used to construct B III subporphyrin dimers such as bis(B III subporphyrinyl)ketone, bis(B III subporphyrinyl)carbinol, and disilane-bridged B III subporphyrin dimer. The structural, optical, and electrochemical properties of these meso-functionalized B III subporphyrins were examined by UV/Vis absorption and fluorescence spectroscopy, electrochemical studies, and DFT calculations., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diarylamine-fused subporphyrins 1 a and 1 b were synthesized from β,β-diiodo-meso-chloro subporphyrin 2 through a one-pot procedure involving nucleophilic aromatic substitution and S RN 1-type intramolecular fusion reaction as the first example of meso-nitrogen-embedded subporphyrin. While non-fused counterparts 3 b and 4 b display effective fluorescence quenching due to twisted intramolecular charge transfer (TICT) in CH 2 Cl 2 at room temperature, 1 b emits fluorescence with Φ F =0.18 under the same conditions, because conformational twisting is not allowed due to the fused structure. In addition, the oxidative titration with tris(4-bromophenyl)ammoniumyl hexachloroantimonate gave cation radical 7 for 1 a and cation radical and dication for 1 b. Actually, cation radical 7 was isolated through separation over silica gel column but was found to slowly decompose in concentrated solutions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first Si IV corrole complexes were synthesized in good yields by treatment of meso-triarylcorroles with tetrachlorosilane in 1,2-dichloroethane at 60 °C. The central silicon atom possesses a square-pyramidal coordination geometry with slightly longer Si-N bond lengths as compared with those of known triazacorrole Si IV complexes. The Si IV corrole complexes exhibit sharp and blue-shifted absorption spectra and larger fluorescence quantum yields as compared with the corresponding free-base corroles. A μ-oxo dimer of a Si IV corrole was synthesized upon treatment with methanesulfonyl chloride in pyridine at 100 °C. This dimer shows a face-to-face structure with a 90° twist in the solid state. Although the dimer exhibits a blue-shifted Soret band, reflecting the face-to-face geometry, it displays a largely red-shifted and broad fluorescence spectrum with a large Stokes shift, suggesting a large structural change in the S 1 state. These intriguing optical properties have been comprehensively studied by magnetic circular dichroism (MCD) spectroscopy, femtosecond transient absorption (fs-TA) measurements, and theoretical calculations., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 moieties, we obtained aza[7]helicenes 10 a-c and azahepta[8]circulenes 11 a,c selectively in moderate to good yields. Their solid-state structures have been revealed by X-ray diffraction analysis. UV/Vis absorption, emission, and cyclic voltammetry of these compounds were studied in comparison with those of previously reported tetraaza[8]circulene (TA8C), a symmetric and planar molecule. Furthermore, the enantiomeric separation of dimethyl-substituted aza[7]helicene 10 b was achieved, and the racemization kinetics have been elucidated both theoretically and experimentally. This work illustrates a wealth of advantages of pyrrole incorporation into the polycyclic aromatic scaffolds in terms of synthetic aspects, structural variation, and optical tuning., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Pt II -catalyzed cyclization of β-to-β ethynylene-bridged meso-amino Ni II porphyrin dimer 4 followed by oxidation with PbO 2 afforded 1,5-naphthyridine-fused porphyrin dimer 5 in good yield. This dimer possesses a redox-active 1,4-diazabutadiene linkage that is interconvertible with its reduced 1,2-diaminoethene linkage upon treatments with NaBH 4 or PbO 2 . The dimer 5 exhibits an intense NIR absorption and a narrow HOMO-LUMO gap with a remarkably low reduction potential mainly due to effective bonding interactions in the LUMO through the 1,4-diazabutadiene linkage. In contrast, the reduced dimer 7 is fairly electron-rich with high HOMO energy and shows a relatively large HOMO-LUMO gap compared to that of 5., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Control of open-shell character of meso-meso linked porphyrin meso-oxy radical dimers has been demonstrated by core metalation. Namely, Ni II -porphyrin dimer 6Ni exhibits a clear 1 H NMR spectrum and a distorted but rather coplanar quinonoidal structure consisting of two ruffled porphyrin rings, in accordance with the previous report. Freebase dimer 6H 2 shows a similar quinonoidal structure in the solid state but displays slightly broader and temperature-dependent 1 H NMR spectra, indicating a partial diradical character in solution that increases at high temperature. In sharp contrast, bis-imidazole-coordinated Zn II -porphyrin dimer 6ZnIm 2 exhibits a perpendicular structure consisting of two planar Zn II -porphyrins and has been characterized as a distinct open-shell diradical on the basis of its non-observable 1 H NMR signals, a clear ESR signal, and a characteristic absorption spectrum reaching about 1700 nm. Despite the distinct diradical character, 6ZnIm 2 is an extremely stable molecule., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Stable helical radicals are promising multi-functional molecules in light of intriguing magnetic and chiroptical properties. Attempts were made to extend diphenylmethyl-fused Ni II porphyrin radical to helical system as the first air-stable organic neutral helical radicals. Intramolecular Pd-catalyzed twofold C-H arylation of methyl- or methoxy-introduced meso-diphenylmethyl Ni II porphyrins gave a mixture of the target and rearranged radicals. Oxidative fusion reaction of meso-(bis(1-naphthyl)methyl) Ni II porphyrins provided doubly fused Ni II porphyrin radicals. One of the helical radicals was separated into enantiomers that showed mirror-image circular dichroism (CD) spectra up to 1300 nm. The helical dinaphthylmethyl-fused Ni II porphyrin radical displayed solid-state magnetic property mostly arising from monomeric radicals, different from the parent diphenylmethyl-fused Ni II porphyrin radical that showed antiferromagnetic coupling due to π-stacked pairing., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To explore stable organic diradicaloids, meso-thienylquinonoid-substituted porphyrins Pn and hexaphyrins Hn, where "n" denotes the number of thienyl units in the meso-substituents, were synthesized. P0 was identified as a closed-shell quinonoid, whereas P1 was shown to possess significant diradical character with diradical character index (y) of 0.99 and quite small singlet-triplet energy gap (ΔE S-T ) of -0.13 kcal mol -1 . P1 was certainly stable, allowing its isolation, but decomposed gradually in solution. In the hexaphyrin series, it was shown that H0 and H1 were closed-shell quinonoids, but H2 was a highly stable diradicaloid with y=0.85 and ΔE S-T of -3.72 kcal mol -1 . The high stability of H2 was ascribed to effective spin delocalization over the entire conjugated network. Characteristically, H2 displays an intense absorption band in NIR region at λ max =1175 nm with molar absorption coefficient (ϵ) of 8.81×10 4  mol -1  L cm -1 , a narrow HOMO-LUMO gap of 0.69 eV, and nine reversible redox potential waves., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

10,15,20-Tris(pentafluorophenyl)-substituted Ni II -porphyrin meso-oxy radical bearing two coordinating pyridines was synthesized as a stable radical with a quartet ground state (S=3/2). X-ray structural analysis revealed that the Ni II porphyrin moiety is fairly planar and the Ni-N bond lengths are considerably longer, indicating the high-spin state of the Ni II center. The radical exhibited a quartet ground state, indicating the ferromagnetic interaction between the high-spin Ni II center (S=1) and the porphyrin meso-oxy radical (S=1/2)., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diphenylphosphine-oxide-fused Ni II porphyrin 8 was synthesized from 3,5,7-trichloroporphyrin 5 via a reaction sequence of nucleophilic aromatic substitution with lithium diphenylphosphide, oxidation with H 2 O 2 , and palladium-catalyzed intramolecular cyclization. Reduction of 8 with HSiCl 3 gave diphenylphosphine-fused Ni II porphyrin 9. The embedded P=O and P moieties serve as a strong electron-accepting and electron-donating group to perturb the optical and electrochemical properties of the Ni II porphyrin. Ni II porphyrin 9 is diamagnetic with a low-spin Ni II center in solution but becomes paramagnetic with a five-coordinated Ni II center with high-spin (S=1) state in the solid state. Diphenylphosphine-oxide-fused Zn II porphyrin 10 was also synthesized and shown to form a face-to-face dimer with mutual O-Zn bonds in the crystal and in nonpolar and moderately polar solvents. The dimerization of 10 in CDCl 3 has been revealed to be an entropy-driven process with a large entropy gain (ΔS D =207 J K -1  mol -1 )., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A meso-meso-linked diphenylamine-fused porphyrin dimer and its methoxy-substituted analogue were synthesized from a meso-meso-linked porphyrin dimer by a reaction sequence involving Ir-catalyzed β-selective borylation, iodination, meso-chlorination, and S N Ar reactions with diarylamines followed by electron-transfer-mediated intramolecular double C-H/C-I coupling. While these dimers commonly display characteristic split Soret bands and small oxidation potentials, they produced different products upon oxidation with tris(4-bromophenyl)aminium hexachloroantimonate. Namely, the diphenylamine-fused porphyrin dimer was converted into a dicationic closed-shell quinonoidal dimer, while the methoxy-substituted dimer gave a meso-meso, β-β doubly linked porphyrin dimer., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Treatment of nonaromatic N-fused [24]pentaphyrin with trichloromethylsilane in the presence of a base afforded doubly N-fused [24]pentaphyrin and its silicon complex. Addition of fluoride ion to the silicon complex led to the formation of its fluorosilicate as an unprecedented monoanionic six-coordinated Si IV complex of porphyrinoid. Treatment of the fluorosilicate with acid led to the recovery of the silicon complex. The doubly N-fused pentaphyrin, the silicon complex, and the fluorosilicate were all characterized as distinct Möbius aromatic molecules by spectroscopic measurements and X-ray crystallographic analyses. Importantly, the second N-fusion reaction, Si-incorporation and fluoride addition to the Si-atom enhanced the aromaticity of doubly N-fused [24]pentaphyrins in this order. Tamao-Fleming oxidation of the silicon complex gave β-keto doubly N-fused pentaphyrin and triply fused [24]pentaphyrin, which were nonaromatic and Hückel anti-aromatic, respectively., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A coiled structure of meso-pentafluorophenyl-substituted [62]tetradecaphyrin 1 was revealed by X-ray structural analysis. Synthetic protocols were devised to form mono- and bis-Zn(II) complexes, 1 Zn and 1 Zn2 , selectively. The former displayed a trigonal-bipyramidal pentacoordinated Zn(II) ion as a rare case and a cyclic voltammogram exhibiting eleven reversible redox waves. The latter showed a Ci-symmetric structure with modest Hückel aromaticity owing to a 62 π-electronic circuit as the largest aromatic molecule to date., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cross-coupling reactions of unactivated aryl sulfides with alkynylmagnesium chloride have been invented to afford 1-aryl-1-alkynes with the aid of a palladium/N-heterocyclic carbene complex. This reaction has by far the widest scope of all transformations utilizing aryl sulfides and alkynes, while known cross-coupling alkynylations of aryl-sulfur electrophiles require activated azaaryl sulfides, thiolactams, or arenesulfonyl chlorides. The alkynylation of aryl sulfides is compatible with typical protecting functional groups. The alkynylation is applied to the synthesis of benzofuran-based fluorescent molecules by taking advantage of characteristic organosulfur chemistry., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

ortho-Phenylene-bridged cyclic trimeric oligopyrrole C3 and hexameric oligopyrrole C6 were synthesized by Suzuki-Miyaura coupling reactions. The twisted structures of C3 and C6 were unambiguously revealed by X-ray diffraction analysis. The optical properties of these cyclic oligopyrroles were compared with linear oligopyrrole L3 and cyclic tetramer C4. The cyclic oligopyrroles exhibited large Stokes shifts and blue fluorescence with high quantum yields in solution and in the solid state. In addition, selective N-methylation and N-tolylation of C3 were used to tune the optical and electrochemical properties by changing the molecular twists and conformational flexibilities. Throughout these studies, the structure-property relationship of these cyclic strained oligopyrroles has been illustrated as an interesting molecular motif for novel cyclic π-conjugated systems., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

β,β-(1,4-Dithiino)subporphyrin dimers 7-syn and 7-anti were synthesized by the nucleophilic aromatic substitution reaction of 2-bromo-3-(4-methoxyphenylsulfonyl)subporphyrin 4 with 2,3-dimercaptosubporphyrin 5 under basic conditions followed by axial arylation. Additions of C60 or C70 to a dilute solution of 7-anti (ca. 10(-6)  m) in toluene did not cause appreciable UV/Vis spectral changes, while similar additions to a concentrated solution (ca. 10(-3)  m) resulted in precipitation of complexes. In contrast, dimer 7-syn captured C60 and C70 in different complexation stoichiometries in toluene; a 1:1 manner and a 2:1 manner, respectively, with large association constants; Ka =(1.9±0.2)×10(6)  m(-1) for C60 @7-syn, and K1 =(1.6±0.5)×10(6) and K2 =(1.8±0.9)×10(5)  m(-1) for C70 @(7-syn)2 . These association constants are the largest for fullerenes-capture by bowl-shaped molecules reported so far. The structures of C60 @7-anti, C70 @7-anti, C60 @7-syn, and C70 @7-syn have been determined by single-crystal X-ray diffraction analysis., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

β-to-β 2,5-Pyrrolylene linked cyclic porphyrin oligomers have been synthesized by Suzuki-Miyaura coupling of 2,5-diborylpyrrole and 3,7-dibromoporphyrin. The cyclic porphyrin oligomers exhibit roughly coplanar structures, strong excitonic coupling, small electrochemical HOMO-LUMO gaps, and ultrafast excitation energy transfer between the neighboring porphyrins via the pyrrolylene bridge., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Porphyrin-stabilized meso- or β-carbocations were generated upon treatment of the corresponding bis(4-tert-butylphenyl)porphyrinylcarbinols with trifluoroacetic acid (TFA). Bis(4-tert-butylphenyl)porphyrinylcarbinols were treated with TFA to generate the corresponding carbocations stabilized by a meso- or β-porphyrinyl group. The meso-porphyrinylmethyl carbocation displayed more effective charge delocalization with decreasing aromaticity compared with the β-porphyrinylmethyl carbocation. A propeller-like porphyrin trimer, tris(β-porphyrinyl)carbinol, was also synthesized and converted to the corresponding cation that displayed a more intensified absorption reaching over the NIR region. meso-Porphyrinylmethyl carbanion was generated as a stable species upon deprotonation of bis(4-tert-butylphenyl)(meso-porphyrinyl)methane with potassium bis(trimethylsilyl)amide (KHMDS) and [18]crown-6, whereas β-porphyrinylmethyl anions were highly unstable., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A rectangular [28]hexaphyrin bearing outer straps at the long side has been synthesized by SN Ar reaction of [26]hexaphyrin with allyl alcohol, intramolecular olefin metathesis by using Hoveyda-Grubbs second-generation catalyst, and reduction with NaBH4 . The peripheral straps enforce a rectangular conformation for the [28]hexaphyrin, which shows Hückel antiaromatic character, as confirmed by its planar X-ray structure, a strong paratropic ring current, characteristic UV/Vis/NIR absorption features, small electrochemical HOMO-LUMO gap, and very fast S1 decay., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Boron arylations of B-(methoxo)triphenylsubporphyrin have been developed with a combined use of ArZnI⋅LiCl and trimethylsilyl chloride. Aryl zinc reagents bearing bromo, cyano, amide, and ester groups can be employed for the B-arylation reaction to provide the corresponding B-arylated subporphyrins in moderate yields. Postmodifications of B-arylated subporphyrins have been demonstrated without loss of the B-C bond. These modifications include conversion of the cyano group into a benzoyl group with PhMgBr, hydrolysis of the ester group to give B-(4-carboxyphenyl)subporphyrin, and Pd-catalyzed Suzuki-Miyaura coupling of the 4-bromophenyl group to give a 1,4-phenylene-bridged subporphyrin-Zn II porphyrin hybrid that displays intramolecular excitation energy transfer from the subporphyrin to the porphyrin. The newly synthesized B-arylated subporphyrins have been fully characterized by NMR, UV/Vis absorption and fluorescence spectroscopies, mass spectrometry, electrochemical measurements, and X-ray diffraction analysis., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Directly 2,12- and 2,8-linked Zn(II) porphyrin oligomers were prepared from 2,12- and 2,8-diborylated Zn(II) porphyrin by a cross platinum-induced coupling with a 2-borylated Zn(II) porphyrin end unit followed by a triphenylphosphine (PPh3 )-mediated reductive elimination. Comparative studies on the steady-state absorption and fluorescence spectra and the fluorescence lifetimes led to a conclusion that the exciton in the S1 state is delocalized over approximately four and two Zn(II) porphyrin units for 2,12- and 2,8-linked Zn(II) porphyrin arrays, respectively., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

C-H arylation of polyfluoroarenes and heteroarenes with aryl sulfides proceeds smoothly with the aid of a palladium-N-heterocyclic carbene catalyst. A bulky zinc amide, TMPZnCl⋅LiCl, plays a key role as an effective base to generate the corresponding arylzinc species in situ. This arylation protocol is practically much easier to perform than our previous method, which necessitates preparation of the arylzinc reagents in advance from the corresponding aryl halides. Aryl sulfides that are prepared through sulfur-specific reactions, such as SN Ar sulfanylation and extended Pummerer reactions, undergo this direct arylation, offering interesting transformations that are otherwise difficult to achieve with conventional halogen-based organic synthesis., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silylation of peripherally lithiated porphyrins with silyl electrophiles has realized the first synthesis of a series of directly silyl-substituted porphyrins. The meso-silyl group underwent facile protodesilylation, whereas the β-silyl group was entirely compatible with standard work-up and purification on silica gel. The meso-silyl group caused larger substituent effects to the porphyrin compared with the β-silyl group. Silylation of β-lithiated porphyrins with 1,2-dichlorodisilane furnished β-to-β disilane-bridged porphyrin dimers. A doubly β-to-β disilane-bridged Ni(II)-porphyrin dimer was also synthesized from a β,β-dilithiated Ni(II)-porphyrin and characterized by X-ray crystallographic analysis to take a steplike structure favorable for interporphyrinic interaction. Denickelation of β-silylporphyrins was achieved upon treatment with a 4-tolylmagnesium bromide to yield the corresponding freebase porphyrins., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

B-Methoxy β-(4-methoxyphenylsulfinyl)subporphyrin and B-phenyl β-(4-methoxyphenylsulfinyl)subporphyrin were synthesized by oxidation of the corresponding β-sulfanylsubporphyrins with m-chloroperbenzoic acid and were separated into diastereomers, respectively. B-Methoxy subporphyrin diastereomers were interconverted to each other in methanol or ethanol, whereas such interconversion was not observed for B-phenyl subporphyrin diastereomers even at high temperature. Diastereomeric interconversions of B-methoxy subporphyrins were dramatically accelerated by addition of trifluoroacetic acid. These results suggest that the diastereomeric interconversions of B-methoxy subporphyrins, namely, their bowl inversions, proceed via a mechanism involving protonation-induced generation of subporphyrin borenium cations followed by nucleophilic attacks by alcohols., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

As the most nucleophilic porphyrins, meso- or β-lithiated porphyrins were generated by iodine-lithium exchange reactions of the corresponding iodoporphyrins with n-butyllithium at -98 °C. Porphyrinyllithiums thus prepared were used for synthesis of dimesitylporphyrinylboranes through reactions with fluorodimesitylborane. The boryl groups proved to serve as an electron-accepting unit to alter the photophysical and electrochemical properties. In addition, 5-diarylamino-15-dimesitylboryl-substituted donor-accepter porphyrins showed increased intramolecular charge-transfer character in the S1 state. Furthermore, the reaction of β-lithiated porphyrin with dichloromesitylborane provided a boron-bridged porphyrin dimer, which exhibited a conjugative interaction between two porphyrin units through the vacant p-orbital on the boron center., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Invited for the cover of this issue are Takanori Soya and Atsuhiro Osuka at Kyoto University. The image depicts Group 9 metal (Co, Rh, and Ir) complexes of meso-aryl-substituted rubyrin and a meteorite approaching to the atmosphere. A large amount of Iridium is often contained in meteorites. Read the full text of the article at 10.1002/chem.201501080., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The metalation of meso-tetrakis(pentafluorophenyl)-substituted [26]rubyrin has been explored with Group 9 metal salts (Rh(I) , Co(II) , Ir(III) ), affording a Hückel aromatic [26]rubyrin-bis-Rh(I) complex with a highly curved gable-like structure, a Hückel antiaromatic [24]rubyrin-bis-Co(II) complex that displays intramolecular antiferromagnetic coupling between the two Co(II) ions (J=-4.5 cm(-1) ), and two Cp*-capped Ir(III) complexes; in one, the iridium metal sits on the [26]rubyrin frame with two IrN bonds, whereas the other has an additional IrC bond, although both Ir(III) complexes display moderate aromatic character. This work demonstrates characteristic metalation abilities of this [26]rubyrin toward Group 9 metals., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

[52]Dodecaphyrin(1.1.0.1.1.0.1.1.0.1.1.0) was quantitatively oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to the corresponding [50]dodecaphyrin. Further oxidation of [50]dodecaphyrin with MnO2 quantitatively afforded [48]dodecaphyrin. Of the three, [50]dodecaphyrin showed Hückel aromatic character as the largest aromatic molecule reported to date. Protonation of [50]dodecaphyrin with methanesulfonic acid (MSA) led to the formation of a planar tetraprotonated species that displayed a sharp and intense Soret-like band at 906 nm with ε=6.5×10(5) M(-1) cm(-1) and Q-band-like bands at 1346 and 1600 nm., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 corrole 11 was effectively prepared by the reaction of 9 with Palau'chlor in the presence of 1 % pyridine whereas 5-chlorinated corrole 12 was obtained in a trace amount from similar chlorination of 5. 5,5'-Linked corrole dimer 13 was produced by reaction of 5 with AgNO2 in a good yield, whereas 10,10'-linked corrole dimer 14 was formed in a moderate yield by the reaction of 9 with [bis(trifluoroacetoxy)iodo]benzene. Observed large electronic interaction between the two corroles in 13 as compared with that in 14 has been ascribed mainly to conformational flexibility of the former, which allows more coplanar conformation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

[26]Hexaphyrin(1.1.1.1.1.1) bearing two 5-formyl-2-pyrrolyl groups at the 5- and 20-positions was prepared by cross-condensation of 5,10-bis(pentafluorophenyl)-substituted tripyrrane with 2,5-diformylpyrrole as an effective binuclear metal-coordinating ligand, owing to the two hemiporphyrin-like NNNN pockets. In fact, metalation of this hexaphyrin with Zn(II) , Cu(II) , and Pd(II) salts proceed smoothly at room temperature to give the corresponding bismetal complexes that displayed remarkably redshifted absorption spectra reaching deep into near infrared region. These redshifted absorption bands are ascribed, through electrochemical investigations and DFT calculations, to two structural motifs: the N-metalopyrrole substructure that elevates the HOMO level due to the electron-donating property and the two coordinated metal ions that serve as Lewis acids to lower the LUMO level., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

meso-Bromosubporphyrin undergoes nucleophilic aromatic substitution (SN Ar) reactions with arylamines, diarylamines, phenols, ethanol, thiophenols, and n-butanethiol in the presence of suitable bases to provide the corresponding substitution products. The SN Ar reactions also proceed well with pyrrole, indole, and carbazole to provide substitution products in moderate to good yields. Finally, the SN Ar reaction with 2-bromothiophenol and subsequent intramolecular peripheral arylation reaction affords a thiopyrane-fused subporphyrin., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cross-coupling of general aryl alkyl sulfides with arylzinc reagents proceeds smoothly, even at room temperature or below, with a palladium-N-heterocyclic carbene (NHC) catalyst. When combined with reactions that are unique to organosulfurs, that is, the SNAr sulfanylation or Pummerer reaction, the cross-coupling offers interesting transformations that are otherwise difficult to achieve. An alkylsulfanyl group is preferentially converted whilst leaving the tosyloxy and chloro intact, which expands the variety of orthogonal cross-coupling., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)