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Synthesis and reversible redox switching of novel linear π-conjugated meso-aminoporphyrin oligomers analogous to polyanilines are reported. The oligomers exhibit characteristic near-infrared (NIR) absorption/emission properties.

A pair of chiral Pt(ii) complexes exhibiting aggregation-induced phosphorescence and circularly polarized luminescence have been synthesized and characterized.

Drop-casting of gold nanoparticle (AuNP) with radical cation moiety of a quaterthiophene derivative provided a conductive film. The interparticle π-dimer was considered to act as effective conduction paths in the AuNP assembly.

Oxidation reactions of 1,2-diarylbenzenes induce intramolecular C-C bond formation. The substrates studied here were prepared by the stepwise Suzuki-Miyaura coupling reaction that introduced 2-naphthyl, 2-anthranyl, and 2-pyrenyl groups on the ortho positions of benzene. The subsequent oxidation reaction with FeCl3 induced an oxidative C-C bond formation reaction in the interior regions of the molecules. In marked contrast to our previous observations, two C-C bonds were formed. Theoretical calculations indicated that large spin densities at the reaction positions of the bis(cation radical) and/or cation radical species are needed for the C-C bond formation. The π-expanded molecules obtained here showed bathochromic shifts in the absorption spectra and amphoteric multi-redox behavior in electrochemistry.

Considering the widespread interest in the chiroptical properties of materials, especially circularly polarized luminescence (CPL), the functionalization of bipyrenol (BPy) was carried out aiming at future advanced chiral materials (ACMs) in which BPy shows a high quantum yield and clear CPL spectra. To create ACMs using BPy units that contain nucleophilic substituents, amine and thiol were selected as the functional group and attached to BPy by means of alkyl linkages. The obtained thiol and amine derivatives are stable under ambient conditions. To demonstrate the potential of these molecules, photoinduced electron-transfer systems were synthesized.

Treatments of dihydroxyporphyrinato Sn(IV) with 1- and 2-hydroxypyrenols afforded 1- and 2-hydroxypyrene-coordinated Sn(IV) porphyrins. Because of their stability, these complexes enable conventional chemical manipulations, such as SiO2 column chromatography. Single-crystal diffraction studies revealed that the dihedral angles between the porphyrin and the pyrenolato ligand are small. The large high-field shifts of 1H NMR signals attributable to the pyrenolato ligand support the parallel alignment of the porphyrin and the pyrenolato ligand. Singlet signals of the β-hydrogens of porphyrin suggest the free rotation of the pyrenolato ligand around the Sn-O coordination bond. In addition, low-field shifts were observed for these β-hydrogens. These phenomena suggest the free rotation of the pyrenolato ligand around the pyrenolato O-C bond. Because these two rotation axes are positioned at an angle of 120°, this moiety could be regarded to show the transmission-like motion in molecular machines.

The molecular structure of 9,10-bis[bis(4-tert-butylphenyl)methylene)-9,10-dihydroanthracene, an anthraquinodimethane derivative having four aryl groups on exocyclic methylene positions, was experimentally and theoretically characterized. Single-crystal diffraction study revealed that the title molecule takes a butterfly shape, i.e., two exocyclic carbons rise from the molecular plane, defined by four carbons of central quinoidal ring, by 1.257(3) A (average). The dihedral angle of the butterfly wing, i.e., the angle between the two annulated benzenes is 137.71(5)°. Characteristic bond alternation was observed for the central quinoidal moiety and the exocyclic double bond. Theoretical study indicated that this butterfly shape is the stable structure. The two optimized structures nearly reproduced the experimentally observed molecular structures, bond distances, and angles.

Treatment of a meso-diarylporphyrin with PhI(OAc)2 in the presence of BF3·OEt2 and propionic acid affords the corresponding porphyrinquinone in a high yield (91%). A novel quinone derived from meso-meso β-β doubly-fused diporphyrin was obtained as the sole byproduct (16% yield), which exhibited strong panchromatic absorption between 300 and 1000 nm. It had a low HOMO-LUMO gap owing to the expanded and low-symmetry π-planes.

An innovative π-expanded ligand derived from salicylaldimine ligand representing pyrene ring as a substitute for benzene ring was synthesized in 5 steps from commercially available pyrene. This unique bidentate ligand (1) was coordinated to Cu(II) metal centre for affording complex 2, which was characterized by IR, elemental, X-ray diffraction analyses, and magnetic susceptibility. Its coordination geometry is a trans-square plane with an obvious stair-step structure which is formed by two pyrene moieties and the coordination plane (CuN2O2). In addition, the dihedral angle between the coordination plane and the pyrene ring is 34.9o and the plane of seven carbon atoms of the long alkyl chains were arranged nearly parallel to the pyrene rings. The electronic properties of this novel complex 2 were examined via cyclic voltammetry and absorption spectroscopy to show the narrower HOMO-LUMO gap than those of the complex 4. Moreover, the particular behavior of both complexes 2 and 4 was investigated through DFT studies.

Unsymmetrically substituted biphenoquinones, 3,5-dimethyl-3′,5′-diphenylbiphenoquinone and 3,5-di-tert-butyl-3′,5′-diphenylbiphenoquinone, were prepared by a mixed oxidative coupling reaction of the corresponding phenols with potassium permanganate in CHCl3. The properties of the quinones such as reduction potential and visible light absorption were measured and positively shifted reduction potentials and bathochromic shifts as a result of light absorption were found to be characteristic of the π-expanded quinones. We also carried out single-crystal diffraction study and uncovered a unique packing motif attributable to their unsymmetrical structures.

Six-coordinated tungsten(VI) complexes with one rigid chiral bidentate ligand, 1,1′-bi-2-naphthol (bino) 1, and two flexible bidentate ligands (f-bls), pinacol (pin) or ethylene glycol (en), were prepared, and their stereochemistry was discussed. Generally, metal complexes with three f-bls produce enantiomeric Δ- and Λ-forms. Other types of isomerism are produced by f-bls, which are attributable to their conformation, i.e., δ- and λ-forms. Although the conformational isomerism of Δ- and Λ-enantiomers produces diastereomers, the energy differences between the diastereomers are small, less than several kcal mol−1. Therefore, the conformational isomerism of f-bls is not significant in coordination chemistry. We found that the introduction of one rigid chiral bidentate ligand controls the Δ- and Λ-stereochemistry of the complex. The conformation of (R)-bino produces the Δ-isomer, and that of (S)-bino affords the Λ-isomer. We also performed theoretical studies to support our observations.

Tetra(thienyl)biphenoquinones were designed and synthesized. An oxidative coupling of 2,6-bis(3-thienyl)phenol with PbO2 in acetic acid afforded the corresponding biphenoquinone along with 2,6-bis(3-thienyl)-p-benzoquinone. This biphenoquinone showed properties characteristic of a pai-expanded quinone, i.e., positively shifted reduction potential and light absorption in the visible region. In contrast to kinetically protected biphenoquinones having bulky substituents at the ortho-positions of carbonyls, the title compounds take a planar structure because of the small steric repulsion of the five-membered thiophene rings. Its charge transfer complex with perylene is characterized by a well-overlapped mixed stack.

An alternative synthesis has been developed with the objective of extending the applications of bipyrenol in mind. The key reaction involves the oxidative coupling of 2-hydroxypyrene menthyl carbonate to afford the corresponding pyrene dimer. In marked contrast to our previous method, i.e., the oxidation of 2-hydroxypyrene, the revised method is a clean and high-yielding reaction. By optimizing the reaction conditions, the yield of the alternative synthesis is increased to 88%.

The Suzuki–Miyaura coupling reaction of pyren-2-yl boronic acid ester with a meso-dibromodiphenylporphyrin derivative was carried out to give another pyrene-substituted porphyrin. The electrophilic substitution reaction occurred selectively on the porphyrin nucleus of this molecule. The introduced pyrenes acted as a light-harvesting antenna.

The reactions of Co(OAc)2 with two equivalents of 1-hydroxy-2-[(octylimino)methyl-pyrene L, performed in air, lead to the formation of the cobalt(III) complex, tris[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(III) CoL3, accommodating three chelating pyrene-based salicylaldiminato-type ligands. The complex CoL3 and the referent tris(salicylaldiminato) cobalt(III) 1’(CoIII) were obtained in excellent yields, and their characterisation by 1H NMR, IR, mass spectroscopy, elemental analysis and X-ray diffraction revealed that they were of diamagnetic nature, octahedral geometry with the cobalt centre and meridional configuration. The redox behaviour of these complexes shows an irreversible reduction wave with a peak potential in the range -1.9 to -1.2 V. Upon reduction, the complexes decompose, giving rise to a redox pattern compatible with the formation of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(II). Keywords: Coordination chemistry, Cobalt, Pyrene, π-Expanded ligand, Salicylaldimine. References: [1] Luong Xuan Dien, Ken-ichi Yamashita, Motoko S. Asano, Ken-ichi Sugiura, Synthesis of a pyrene-based π-expanded ligand and the corresponding platinum(II) complex, Bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] platinum(II), Inorganica Chimica Acta, 432 (2015) 103-108. https://doi.org/10.1016/j.ica. 2015.03.038.[2] Luong Xuan Dien, Ken-ichi Yamashita, Ken-ichi Sugiura, Metal Complexes of π-Expanded Ligands (2): Synthesis and characterizations of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] palladium(II) and the stabilized vacant dx2-y2 orbital, Polyhedron, 102 (2015) 69-74. https://doi.org/10.1016/j.poly.2015.07.043.[3] Luong Xuan Dien, Nguyen Xuan Truong, Ngo Duc Quan, Ken-ichi Yamashita, Ken-ichi Sugiura, Syntheses and structures of Ni(II) complexes containing 2 alkyliminomethyl pyrene ligands, VNU Journal of Science, 34 (4) (2018) 16-20. https://doi.org/10.25073/2588-1140/vnunst.4809.[4] Robert D. Jones, David A. Summerville, Fred. Basolo, Synthetic oxygen carriers related to biological systems, Chem. Rev., 79 (1979) 139-179. https://doi.org/10.1021/cr60318a002.[5] Kuninobu Kasuga, Takeo Nagahara, Akira Tsuge, Kunihisa Sogabe, Yasuo Yamamoto, The preparation and some properties of cobalt(II) schiff base complexes and their molecular oxygen adducts, Bull. Chem. Soc. Jpn., 56 (1983) 95-98. https://doi.org/10.1246/bcsj.56.95.[6] H. Pellissier, H. Clavier, Enantioselective cobalt-catalyzed transformations, Chem. Rev., 114 (2014) 2775-2823. https://doi.org/10.1021/ cr4004055.[7] R. H. Crabtree, Energy Production and Storage: Inorganic Chemical Strategies for a Warming World, first ed., John Wiley & Sons, West Sussex, 2010.[8] P. Sravanthi, C. Chandrakala, KS. Nagaraja, B. Jeyaraj, Development of cobalt Schiff base precursors for nanocrystalline cobalt oxide thin film by thermal CVD method, International journal of pharmaceutical, chemical and biological sciences, 5(1) (2015) 112-125. http:/ /www.ijpcbs.com/files/volume5-1-2015/12.pdf.[9] B. O. West, Complexes of tervalent cobalt with N-substituted salicylideneimines, J. Chem. Soc., 0 (1960) 4944-4947. https://doi.org/10. 1039/JR9600004944.[10] A. Ourari, Y. Ouennoughi, S. Bouacida, Tris(2-{[2-(4-meth¬oxy¬phen¬yl)eth¬yl]imino-meth¬yl}phenolato-κ2N,O1)cobalt(III), Acta Cryst., E68 (2012) m803-m804. https://doi.org/10.1107/ S1600536812023033.[11] A. Chakravorty , R. H. Holm, Identification of the geometrical isomers of some tris-chelate cobalt(III) complexes by nuclear resonance, Inorg. Chem., 3 (1964) 1521-1524. https://doi. org/10.1021/ic50021a010.[12] S. Li, S.-B. Wang, K. Tang, Y.-F. Ma, Tris [2-(propyliminomethyl)phenolato-κ2 N,O]cobalt(III), Acta Cryst., E64 (2008) m823. https://doi.org/ 10.1107/S1600536808014074.

A facile and metal-free method for the preparation of free base meso-aminodiarylporphyrins from readily available meso-bromodiarylporphyrins is described. Simple treatment of meso-bromoporphyrins with sodium azide and sodium ascorbate in DMF affords the corresponding meso-aminoporphyrins in very good yields. This method involves the aromatic nucleophilic substitution (SNAr) of a bromo group with an azido group and the subsequent in situ reduction of the introduced azido group by sodium ascorbate. This amination reaction can be scaled up to gram scale without any decrease of the product yield. The amination reaction of free base meso-dibromoporphyrin affords a monoaminated product selectively, whereas that of the Ni(II) complex furnishes a diaminated product that is oxidized by air under ambient conditions but isolable as a trifluoroacetyl ester. Metal-insertion reactions of the obtained free base aminoporphyrins afford the corresponding metal complexes (Ni(II), Cu(II), Zn(II), and Pd(II)) all in good yiel...

Based on our recent reinvestigation of the disproportionation reaction of 3,3′,5,5′-tetraphenyl-4,4′-biphenoquinone, which exhibited drastic color change, we performed the synthesis and characterization of 3,3′′,5,5′′-tetraphenyl-4,4′′-terphenoquinone with the aim of obtaining enhanced physical properties, such as lower reduction potentials and bathochromic shift in light absorption, and realizing a disproportionation reaction at a lower temperature. To construct the terphenyl and/or terphenoquinone skeletons, the Suzuki-Miyaura coupling, which involves coupling between 1,4-diiodobenzene and the boronic acid ester with phenyl and oxygen moieties attached was carried out. The subsequent hydroquinone formation reaction and oxidation reaction yielded a brilliant ultramarine-blue terphenoquinone. The quinone showed properties typical of π-expanded quinones, namely, positively shifted reduction potential, small on-site Coulomb repulsion, and lower excitation energy. DSC measurement of this product showed an exothermic process at 212.5 °C and this temperature was much lower than that of the corresponding biphenoquinone, 289.5 °C. The products of this reaction were similar to those of the biphenoquinone reaction, i. e., two benzofurans and the corresponding hydroquinone.

The Glaser–Hay coupling reaction of a tetraphenylporphyrin derivative having two acetylenes in the quasi-trans positions was carried out. Although this oxidative coupling reaction has high reactivity and produces various butadiynylene oligomers, the degree of oligo­merization was low. A large substrate and/or product might decrease the frequency factor of the Arrhenius equation and the resultant rate constant. This finding is in agreement with that of the one-pot synthesis of structurally well-defined porphyrin oligomers, such as trimers and tetramers, which are used frequently in the field of advanced materials.

Oxo(porphyrinato)vanadium(IV), the oxovanadium [V IV O] 2+ complex of unsubstituted porphyrin, was prepared and structurally characterized. Our synthetic method enabled us to obtain 1 in sufficient quantity. The paramagnetic complex was characterized by IR and mass spectroscopic measurements. The IR spectrum contained a strong absorption at 994 cm −1 (in KBr matrix) attributable to the V O stretching mode. Single-crystal diffraction study revealed that 1 was a pot lid shaped molecule, i.e. , 1 exhibited a five-coordinate pseudo -square pyramidal geometry at the vanadium center. Vanadium was located above the porphyrin mean plane with a distance of 0.537(1) A, and an oxygen atom was coordinated perpendicularly with a bond distance of 1.599(2) A. The ligation of electropositive [V IV O] 2+ induced a partial negative charge on N and a positive charge on vanadium. The resultant polarization induced an electrostatic attractive interaction, affording a dimer in the solid state with a very short interplanar distance of 3.269(2) A. This dimer unit was packed in a herringbone manner.

A palladium(II) complex of our π-expanded ligand, i.e., a salicylaldimine-style ligand based on pyrene, was synthesized and characterized. A treatment of this ligand (L) with palladium(II) acetate afforded the desired metal complex, Pd(II)L2, 3(Pd). Single crystal diffraction study revealed that this complex is a square planar four-coordinate palladium(II) complex. The structure of 3(Pd), i.e., shapes of the complexes, bond distances and angles, packing motif, is nearly identical with those of the previously reported the platinum(II) complexes, 2(Pt), as well as in the range of the values reported for structurally similar salicylaldiminato palladium(II) complexes. Although the IR spectrum of 3(Pd) is similar to that of 2(Pt), 1H NMR of 3(Pd) reflects the electronegative character of palladium, i.e., higher field shift was observed comparing with the spectrum of 2(Pt). The incorporated palladium induces the stabilization of the Kohn–Sham orbitals containing d-orbital coefficients of the metal. The significant difference is the following: the LUMO of 2(Pt) is the π-orbitals of the ligand, contrary, that of 3(Pd) is the vacant 4 d x 2 - y 2 of Pd. Therefore, excitations from occupied π-orbitals to this LUMO are mostly forbidden and the allowed transition to LUMO+1 and the higher π-orbitals were shifted to blue region. The lowest excitation energy of 3(Pd) was found at 497 nm.

A pyrene-based new ligand (1) attaching hydroxyl and imine group, i.e., a salicylaldimine-style ligand based on pyrene, was designed and synthesized. The ligand was prepared from the commercially available pyrene in five steps. A treatment of this ligand 1 (L) with Pt(II)Cl2(PhCN)2 in the presence of AcONa in PhCl afforded the corresponding metal complex, Pt(II)L2 (2) (80%). Single crystal diffraction study revealed that the complex is a square planar four-coordinated platinum(II) complex. The ligands bind to the metal in trans-manner. The coordination geometry, i.e., bond distances and angles for the coordination site, is the typical of the reported platinum(II) salicylaldiminatos, e.g., the mean Pt–N distance (d(Pt–N)): 2.011 and d(Pt–O): 1.994 A, respectively. The expansion of the π-system of the ligand induces the bathochromic shift in absorption spectra. The lowest excitation energy of 2 was found at 520 nm. Theoretical studies suggest that this phenomenon is attributable to the narrowing intramolecular HOMO–LUMO gap of 2.

A push–pull porphyrin dimer with multiple electron-donating groups has been synthesized as a sensitizer with an excellent light-harvesting ability in the near-infrared region for dye-sensitized solar cells (DSSCs). The DSSC based on the sensitizer exhibited the photocurrent generation exceeding a wavelength of 900 nm, together with a power conversion efficiency of 6.21% under AM 1.5 condition.

We studied the conductance of Au/1,4-benzenedicarbothioamide (BDTA)/Au junctions at room temperature and measured a single-molecule conductance of BDTA. A carbothioamide (thioamide, – CSNH 2 ) group of this molecule consists of two potential linkers, thioketone and amine groups, and would thus be expected to show high conductance. The experimental single-molecule conductance of BDTA is ( 0.8 – 1.0 ) × 10 - 3 G 0 which roughly compares with that of π -conjugated molecules. We consider that this relatively high conductance of Au/BDTA/Au is due to the homoconjugation of π -orbitals of benzene and sulfur while the amine group is likely to remain as a side group. We also observed that Au/BDTA/Au junctions can exist in multiple configurations of different conductances.

Studies of the molecular structure and the basic spectroscopic properties of 3-selenocyanatoindole, an important reference compound in organoselenium chemistry, were carried out. Single-crystal diffraction analysis revealed that the selenocyanation of indole occurred at 3-position. The characteristic feature of its molecular structure is the perpendicularly connected SeCN group. Theoretical studies indicated that the SeCN group attached to arene rotates freely at room temperature and takes any conformation in the solid state depending on the packing effect. A hitherto unreported 77Se NMR spectrum of the title compound showed a large upfield shift that suggests the strong electron-donating nature of indole-3-yl.

Visible light irradiation of anthracene in the presence of platinum(II) porphyrin (PtPor) and dioxygen affords anthraquinone as the main product. This reaction involves two steps: the [4+2]cycloaddition of anthracene with singlet oxygen to afford anthracene-9,10-endoperoxide and the degradation of endoperoxide. PtPor catalyzes both reactions.

Axially chiral biaryls based on pyrene, 1,1′-bipyrene-2,2′-diol derivatives 2, were designed and synthesized from 2-hydroxypyrene. Simple optical resolution was carried out and the absolute configu...

A series of structurally well-defined molecular wires were designed and synthesized. The wires consisted of metalloporphyrins connected by platinum acetylides. Stepwise synthesis afforded stable wi...

An intramolecular oxidative C–C bond formation reaction of a 1,2-bis(pyren-2-yl)benzene derivative gave benzodinaphthopentaphene, a new polycyclic aromatic hydrocarbon. Its expanded π-system induce...

A facile and mild method for the preparation of platinum(II) porphyrin complexes is reported. A simple treatment of free-base porphyrins with 1.5 equiv of [PtCl2(PhCN)2] in the presence of sodium p...

LEC-1 is a major galectin in Caenorhabditis elegans and contains two carbohydrate recognition domains (CRDs), N-CRD and C-CRD. To determine the role of LEC-1, we examined the phenotypes of a mutant C. elegans strain lacking lec-1. We observed negligible differences in embryogenesis, morphogenesis and egg laying at 20 °C between the mutant and the wild-type. Furthermore, the life spans of the mutant and the wild-type were equivalent at either 20 °C or 25 °C. However, the lec-1 mutant showed a greater susceptibility to H2O2 and paraquat than the wild-type. This result suggests an increased susceptibility to oxidative stress, with the phenotypes being similar to those of lec-10 deletion mutants as previously described. To understand the molecular mechanism underlying this phenotype, C. elegans proteins bound by either the LEC-1 N-CRD or C-CRD were isolated and identified using a nano liquid chromatography-tandem mass spectrometry technique. MIG-6 was identified as a major binding partner of LEC-1 with both N- and C-CRD. From these results and previous reports, we speculate that interaction of LEC-1 and MIG-6 in the pharynx may affect susceptibility to paraquat and that LEC-10 has different functions from LEC-1 in regulating H2O2 and paraquat resistance in the intestine.

meso-Mono- or diazidoporphyrins were readily obtained in high yields by the catalyst-free aromatic nucleophilic reaction of the corresponding bromoporphyrins with azide anions under mild conditions. The molecular structures of the obtained azides were unambiguously determined by X-ray crystallographic analysis.

In this communication, we report the superior role of 1,3-dimethyl-2-imidazolidinone (DMI) as a solvent for aromatic Finkelstein iodination (AFI), the conversion of aryl bromides to aryl iodides. DMI accelerates the reaction rate and affords product(s) that could not be prepared using previous methods. Our findings for AFI avoid the use of toxic solvents such as N,N-dimethylformamide and hexamethylphosphoramide.

Free-base meso-propanoyloxylated (–OCOEt) porphyrins and dioxoporphodimethenes (quinoid forms of dihydroxyporphyrins) were efficiently synthesized by the treatment of the corresponding meso-diarylp...

The authors propose 4-alkoxy-3,5-diisopropyl-phenyl (DIPP) group as the most suitable substituent to realize porphyrin based advanced materials (PAMs). Our experiments reveal that DIPP achieved the introduction of the following properties on porphine and/or PAMs: (1) easy synthesis, (2) high solubility, (3) good crystallinity natures, and (4) single molecule visualization by scanning tunneling microscopy.