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Detailed electronic, structural, photophysical, and redox studies of a series of meso-pentafluorophenyl-substituted hexaphyrins, namely amethyrin (1), rosarin (2), and rubyrin (3), are described. In prior work, it was found that the electronic states of the antiaromatic hexapyrrolic macrocycle, [24]rosarin 2, could be modified by exposure to several Brønsted acids (e.g., HCl, HBr and HI) to produce either one- and two-electron reduced species, or both. In an effort to gain further insights into the reactivity of hexaphyrins possessing different π-conjugation pathways, the β-dodecamethyl-substituted [24]amethyrin 1 was prepared and its electronic structure was analyzed along with that of the o-phenylene-bridged [26]rubyrin 3 and rosarin 2 The [4n] and [4n+2] π-conjugated formulations of 2 and 3, respectively, were inferred from steady-state, fs-transient absorption and two photon absorption measurements. Similar photophysical analyses lead to the conclusion that 1 is best considered as nonaromatic or weakly antiaromatic. Magnetic circular dichroism (MCD) spectroscopic analyses of hexaphyrins 1 and 3, as well as comparisons to 2, and theoretical perimeter MO diagram analyses provided support for the electronic assignments. In contrast to what was found for 2, simple protonation of 1 and 3 by halohydric acids did not induce an evident, redox-based change in the electronic structure of the macrocycle., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Effective delivery of therapeutic proteins is a formidable challenge. Herein, using a unique polymer family with a wide-ranging set of cationic and hydrophobic features, we developed a novel nanoparticle (NP) platform capable of installing protein ligands on the particle surface and simultaneously carrying therapeutic proteins inside by a self-assembly procedure. The loaded therapeutic proteins (e.g., insulin) within the NPs exhibited sustained and tunable release, while the surface-coated protein ligands (e.g., transferrin) were demonstrated to alter the NP cellular behaviors. In vivo results revealed that the transferrin-coated NPs can effectively be transported across the intestinal epithelium for oral insulin delivery, leading to a notable hypoglycemic response., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Unprecedented neutral perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) radicals and biradicals were synthesized by facile chemical oxidation of 4-hydroxyaryl-substituted PBIs. Subsequent characterization by optical and magnetic spectroscopic techniques, as well as quantum chemical calculations, revealed an open-shell singlet biradical ground state for the PBI biradical OS-2(..) (〈s(2)〉=1.2191) with a relatively small singlet-triplet energy gap of 0.041 eV and a large singlet biradical character of y=0.72., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Reductive metalation of [44]decaphyrin with [Pd2(dba)3] provided a Hückel aromatic [46]decaphyrin Pd(II) complex, which was readily oxidized upon treatment with DDQ to produce a Hückel antiaromatic [44]decaphyrin Pd(II) complex. In CH2Cl2 solution the latter complex underwent slow tautomerization to a Möbius aromatic [44]decaphyrin Pd(II) complex which exists as a mixture of conformers in dynamic equilibrium. To the best of our knowledge, these three Pd(II) complexes represent the largest Hückel aromatic, Hückel antiaromatic, and Möbius aromatic complexes to date., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A microfluidic approach to prepare photonic microparticles by repeated molding of photocurable colloidal suspension is reported. An elastomeric membrane with negative relieves which vertically separates two microfluidic channels is integrated; bottom channel is used for suspension flow, whereas water-filled top channel is used for pneumatic actuation of the membrane. Upon pressurization of the top channel, membrane is deformed to confine the suspension into its negative relieves, which is then polymerized by UV irradiation, making microparticles with mold shape. The microparticles are released from the mold by relieving the pneumatic pressure and flows through the bottom channel. This one cycle of molding, polymerization, and release can be repeatedly performed in microfluidic device of which pneumatic valves are actuated in a programmed manner. The microparticles exhibit structural colors when the suspension contains high concentration of silica nanoparticles; the nanoparticles form regular arrays and the microparticles reflect specific wavelength of light as a photonic crystals. The silica nanoparticles can be selectively removed to make pronounced structural colors. In addition, the microparticles can be further functionalized by embedding magnetic particles in the matrix of the microparticles, enabling the remote control of rotational motion of microparticles., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Direct β-to-β linked branched and cyclic porphyrin trimers and pentamers have been synthesized by the Suzuki-Miyaura coupling of β-borylporphyrins and β-bromoporphyrins. The cyclic porphyrin trimer, the smallest directly linked cyclic porphyrin wheel to date, and its twined pentamer, exhibit small electrochemical HOMO-LUMO gaps, broad nonsplit Soret bands, and red-shifted Q-bands, thus indicating large electronic interactions between the constituent porphyrin units., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Incorporation of Si(IV) into an expanded porphyrin has been achieved for the first time. Treatment of [28]hexaphyrin 1 with CH(3)SiCl(3) and N,N-diisopropylethylamine gave Si(IV) complex 2 and its N-fused product 4 that both have Möbius aromatic nature. In both complexes, the coordinated Si atom is satisfied in a typical trigonal bipyramidal coordination. Si(IV) incorporation induces conformational rigidification and redshifted absorption profiles due to σ-π conjugation between the Si atom and hexaphyrin macrocycle. Tamao-Fleming oxidation of 2 with H(2)O(2) gave β-hydroxy [28]hexaphyrin 5, which exists as a ruffled rectangular shape in the solid state, yet it has been revealed to exist predominantly as a twisted Möbius aromatic conformer in CH(2)Cl(2)., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A cross-conjugated hexaphyrin that carries two meso-oxacyclohexadienylidenyl (OCH) groups 9 was synthesized from the condensation of 5,10-bis(pentafluorophenyl)tripyrrane with 3,5-di-tert-butyl-4-hydroxybenzaldehyde. The reduction of 9 with NaBH4 afforded the Möbius aromatic [28]hexaphyrin 10. Bis-rhodium complex 11, prepared from the reaction of 10 with [{RhCl(CO)2}2], displays strong Hückel antiaromatic character because of the 28 π electrons that occupy the conjugated circuit on the enforced planar structure. The oxidation of 11 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yielded complexes 12 and 13 depending upon the reaction conditions. Both 12 and 13 are planar owing to bis-rhodium metalation. Although complex 12 bears two meso-OCH groups at the long sides and is quinonoidal and nonaromatic in nature, complex 13 bears 3,5-di-tert-butyl-4-hydroxyphenyl and OCH groups and exhibits a moderate diatropic ring current despite its cross-conjugated electronic circuit. The diatropic ring current increases upon increasing the solvent polarity, most likely due to an increased contribution of an aromatic zwitterionic resonance hybrid., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Perylene bisimide (PBI) derivatives with various alkynyl-phenyl substituents at a single bay position have been synthesised by Sonogashira coupling. NMR spectroscopic studies reveal the unsymmetric nature of the dyads. All of the dyads undergo two reversible reductions, which demonstrates their structural and electrochemical rigidity. The synthesised dyads show a remarkable redshift in their absorption maxima and sharp vibronic progression. Electron-rich substituents facilitate efficient charge transfer from the substituent HOMO to the electron-deficient PBI core. The most interesting spectral signatures were exhibited by a PBI with a strongly electron-donating ethynyl(dimethylaminophenyl) substituent. The steady-state features of this PBI showed a broad absorption that covered almost the whole visible region with no emission. A twisted intramolecular charge-transfer (TICT) process, related to the rotational motion of ethynyl(dimethylaminophenyl) PBI, was also demonstrated. Computational investigations shed light on the coplanarity of the various substituents with respect to the PBI core; the PBI core itself remains flat without any noticeable deformation even after mono-functionalisation. This illustrates that mono-functionalisation exerts meagre steric hindrance on the bay positions relative to disubstituted analogues. Despite several previous reports on the structural characterisation of 1,7-disubstituted PBI derivatives, we present the first structural characterisation of a mono-bay ethynyl-phenyl substituted PBI. The solid-state structure of the phenyl derivative has a flat PBI core without any noticeable steric constraints from the substituents, as predicted. In contrast, single-crystal X-ray analysis for the mono-bromo bay-substituted PBI shows that the bromine substituent is not in the plane of the PBI core., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

7,8-Dehydropurpurin has attracted much attention owing to the dual 18π- and 20π-electron circuits in its macrocyclic conjugation. The two-fold Pd-catalyzed [3+2] annulation of meso-bromoporphyrin with 1,4-diphenylbutadiyne furnished 7,8-dehydropurpurin dimers. The 8(a) ,8(a) -linked dimer displays a red-shifted and enhanced absorption band in the NIR region and a small electrochemical HOMO-LUMO band gap as a consequence of efficient conjugation between the two coplanar 7,8-dehydropurpurin units. Treatment of this dimer with N-bromosuccinimide in chloroform and ethanol gave β-to-β vinylene-bridged porphyrin dimers. Owing to the highly constrained conformations, these dimers exhibit perturbed absorption spectra, small Stokes shifts, and high fluorescence quantum yields., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A set of hybrids having gradual variation in distances between hexaphyrin and bodipy moieties, given by uses of phenylene, biphenylene, and triphenyelene bridges was prepared. Efficient PET processes from bodipy (donor) to [26]- or [28]hexaphyrin (acceptor) were successfully observed, where the PET speed was controlled by intramolecular distances between the donor and the acceptor. UV irradiation at 515 nm raised a band corresponding to the bodipy absorption. As the time delayed, the bodipy bands decreased and new absorption bands at 615 and 580 nm corresponding to respective absorption bands of [28]- and [26]-hybrids gradually appeared. Whereas the femtosecond transient absorption spectra of [28]/[26]-hybrids having terphenylene bridges completely showed energy transfers from bodipy to hexaphyrin, irradiation of the hybrids using 615 and 580 nm pulses did not induce opposite ways of the PET process. On the basis of enlarged center-to-center-distances of [26]-hybrids than those of [28]-hybrids, the set of [26]-hybrids resulted in slow decay/rise processes. PET parameters obtained with the experiments were fairly consistent with the PET parameters calculated., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Protonation of meso-aryl [28]hexaphyrins(1.1.1.1.1.1) triggered conformational changes. Whereas protonation with trifluoroacetic acid led to the formation of monoprotonated Möbius aromatic species, protonation with methanesulfonic acid led to the formation of diprotonated triangular antiaromatic species. A peripherally hexaphenylated [28]hexaphyrin was rationally designed and prepared to undergo diprotonation to favorably afford a triangular-shaped antiaromatic species., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The treatment of an antiaromatic norcorrole Ni(II) complex with a kinetically stabilized silylene provided ring-expansion products in excellent yields through the highly regio- and stereoselective insertion into the β-β pyrrolic CC bonds. The resultant Ni(II) porphyrinoid monoinsertion product exhibited relatively strong near-IR absorption bands due to the small HOMO-LUMO gap in spite of the disrupted cyclic π-conjugation by the silicon atom., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two examples of core-modified 36π doubly fused octaphyrins that undergo a conformational change from a twisted figure-eight to an open-extended structure induced by protonation are reported. Syntheses of the two octaphyrins (in which Ar=mesityl or tolyl) were achieved by a simple acid-catalyzed condensation of dipyrrane unit containing an electron-rich, rigid dithienothiophene (DTT) core with pentafluorobenzaldehyde followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The single-crystal X-ray structure of the octaphyrin (in which Ar=mesityl) shows a figure-eight twisted conformation of the expanded porphyrin skeleton with two DTT moieties oriented in a staggered conformation with a π-cloud distance of 3.7 Å. Spectroscopic and quantum mechanical calculations reveal that both octaphyrins conform to a [4n]π nonaromatic electronic structure. Protonation of the pyrrole nitrogen atoms of the octaphyrins results in dramatic structural change, which led to 1) a large redshift and sharpening of absorption bands in electronic absorption spectrum, 2) a large change in chemical shift of pyrrole β-CH and -NH protons in the (1)H NMR spectrum, 3) a small increase in singlet lifetimes, and 4) a moderate increase in two-photon absorption cross-section values. Furthermore, nucleus-independent chemical shift (NICS) values calculated at various geometrical positions show positive values and anisotropy-induced current density (AICD) plots indicate paratropic ring-currents for the diprotonated form of the octaphyrin (in which Ar=tolyl); the single-crystal X-ray structure of the diprotonated form of the octaphyrin shows an extended structure in which one of the pyrrole ring of each dipyrrin subunit undergoes a 180° ring-flip. Four trifluoroacetic acid (TFA) molecules are bound above and below the molecular plane defined by meso-carbon atoms and are held by N-H···O, N-H···F, and C-H···F intermolecular hydrogen-bonding interactions. The extended-open structure upon protonation allows π-delocalization and the electronic structure conforms to a [4n]π Hückel antiaromatic in the diprotonated state., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Internal bridges: [26]Hexaphyrins with an aromatic strap in 5,20 position have two potentially cyclic conjugated networks, that is, [18]porphyrin and [26]hexaphyrin, and show a formal analogy with [18]annuleno[18]annulens. 1,3-Phenylene-, 2,5-thienylene-, and 2,5-pyrrylene-bridged [26]hexaphyrins have been synthesized and characterized., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Take the shortcut: The synthesis of core-modified meso aryl hexaphyrins with an internal thiophene bridge is reported. Introduction of the thiophene bridge alters the electronic structure as well as the π-electron circuit, resulting in increases in singlet lifetime (τ(s)) and the two-photon absorption (TPA) cross-section. Furthermore, for the sulfur derivative, the internal bridging thiophene participates in a π-electron conjugation pathway., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Singly twisted Möbius antiaromatic [34]heptaphyrin A and doubly twisted Hückel aromatic [34]heptaphyrin B were formed by a phosphorus insertion reaction. A rearranges thermally to give the more stable B with P=O migration from NNN to NNC, and thus A is a rare case of a kinetically controlled Möbius antiaromatic molecule., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

meso-Hexakis(pentafluorophenyl)-substituted neutral hexaphyrin with a 26π-electronic circuit can be regarded as a real homolog of porphyrin with an 18π-electronic circuit with respect to a quite flat molecular structure and strong aromaticity. We have investigated additional aromaticity enhancement of meso-hexakis(pentafluorophenyl)[26]hexaphyrin(1.1.1.1.1.1) by deprotonation of the inner N-H groups in the macrocyclic molecular cavity to try to induce further structural planarization. Deprotonated mono- and dianions of [26]hexaphyrin display sharp B-like bands, remarkably strong fluorescence, and long-lived singlet and triplet excited-states, which indicate enhanced aromaticity. Structural, spectroscopic, and computational studies have revealed that deprotonation induces structural deformations, which lead to a change in the main conjugated π-electronic circuit and cause enhanced aromaticity., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthesis, characterization, photophysical properties, and theoretical analysis of a series of tetraaza porphyrin analogues (H-Pn: n=1-4) containing a dipyrrin subunit and an embedded 1,10-phenanthroline subunit are described. The meso-phenyl-substituted derivative (H-P1) interacts with a Mg(2+) salt (e.g., MgCl(2), MgBr(2), MgI(2), Mg(ClO(4))(2), and Mg(OAc)(2)) in MeCN solution, thereby giving rise to a cation-dependent red-shift in both the absorbance- and emission maxima. In this system, as well as in the other H-Pn porphyrin analogues used in this study, the four nitrogen atoms of the ligand interact with the bound magnesium cation to form Mg(2+)-dipyrrin-phenanthroline complexes of the general structure MgX-Pn (X=counteranion). Both single-crystal X-ray diffraction analysis of the corresponding zinc-chloride derivative (ZnCl-P1) and fluorescence spectroscopy of the Mg-adducts that are formed from various metal salts provide support for the conclusion that, in complexes such as MgCl-P1, a distorted square-pyramidal geometry persists about the metal cation wherein a chloride anion acts as an axial counteranion. Several analogues (HPn) that contain electron-donating and/or electron-withdrawing dipyrrin moieties were prepared in an effort to understand the structure-property relationships and the photophysical attributes of these Mg-dipyrrin complexes. Analysis of various MgX-Pn (X=anion) systems revealed significant substitution effects on their chemical, electrochemical, and photophysical properties, as well as on the Mg(2+)-cation affinities. The fluorescence properties of MgCl-Pn reflected the effect of donor-excited photoinduced electron transfer (d-PET) processes from the dipyrrin subunit (as a donor site) to the 1,10-phenanthroline acceptor subunit. The proposed d-PET process was analyzed by electron paramagnetic resonance (EPR) spectroscopy and by femtosecond transient absorption (TA) spectroscopy, as well as by theoretical DFT calculations. Taken together, these studies provide support for the suggestion that a radical species is produced as the result of an intramolecular charge-transfer process, following photoexcitation. These photophysical effects, combined with a mixed dipyrrin-phenanthroline structure that is capable of effective Mg(2+)-cation complexation, lead us to suggest that porphyrin-inspired systems, such as HPn, have a role to play as magnesium-cation sensors., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new member of the cyclo[n]pyrrole class of expanded porphyrins could be prepared from the corresponding thiophene-containing terpyrrole precursor through use of a mild electrochemical oxidative procedure. The isolated macrocycle, featuring nine heterocyclic subunits directly connected through their α,α'-positions, is the largest cyclo[n]pyrrole derivative reported to date (see figure)., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We have investigated conformational switching dynamics of meso-heptakis(pentafluorophenyl) [32]heptaphyrin(1.1.1.1.1.1.1) in various solvents using steady-state, time-resolved, and temperature-dependent spectroscopy. Absorption and fluorescence spectra of [32]heptaphyrin are quite sensitive to solvent environments. In nonpolar toluene, the antiaromatic figure-of-eight conformation is dominant, as seen in the X-ray crystallography, based on broad and weak absorption bands without any fluorescence and moderate paratropic ring current. On the other hand, a well-resolved sharp absorption spectrum, strong fluorescence, and diatropic ring current in the 1H NMR spectrum in slightly polar THF indicate that most of [32]heptaphyrin molecules take significantly distorted Möbius conformation with aromatic character. By using transient absorption (TA) spectroscopy, the lowest singlet excited-state lifetimes have been revealed to decay biexponentially with the time constants of 5 and 65 ps for figure-of-eight and Möbius conformations, respectively. Based on these results along with vertical excitation energy calculations, we are able to assign two conformers as Hückel antiaromatic and Möbius aromatic species, respectively; it shoulf be noted that the aromaticity/antiaromaticity does not change with temperature variation. Interestingly, in moderately polar solvent, ethyl ether, we find out that these two conformational isomers coexist with a dynamic equilibrium, as revealed by excitation-wavelength-dependent TA, temperature-dependent absorption and 1H NMR spectra. Through our findings, we have demonstrated that the conformational switching dynamics between Hckel antiaromatic and Möbius aromatic conformers in [32]heptaphyrin(1.1.1.1.1.1.1) are strongly affected by solvent medium as well as temperature.

Bidipyrrin-bridged macrocycles, prepared from Ni(II)-bridged dipyrrin-based nanorings by intramolecular oxidative biaryl coupling reactions, yielded [2+4]-type Zn(II)-assisted stable twisted-ring dimers comprising two double helices. These [2+4]-type metal complexes can be optically resolved by chiral HPLC and exhibit tunable electronic and optical properties as a result of spring-like motions. The double helices behave as glue to connect two macrocycles and as the screws of hinges to form thermally responsive synchronized spring systems., (Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

meso-Triazolyl-appended Zn(II)-porphyrins were readily prepared by Cu(I)-catalyzed 1,3-dipolar cycloaddition of benzyl azide to meso-ethynylated Zn(II)-porphyrin (click chemistry). In noncoordinating CHCl(3) solvent, spontaneous assembly occurred to form tetrameric array (3)(2) from meso-meso-linked diporphyrins 3, and dodecameric porphyrin squares (4)(4) and (5)(4) from the L-shaped meso-meso-linked triporphyrins 4 and 5. The structures of these assemblies were examined by (1)H NMR spectra, absorption spectra, and their gel permeation chromatography (GPC) retention time. Furthermore, the structures of the dodecameric porphyrin squares (4)(4) and (5)(4) were probed by small- and wide-angle X-ray scattering (SAXS/WAXS) measurements in solution using a synchrotron source. Excitation-energy migration processes in these assemblies were also investigated in detail by using both steady-state and time-resolved spectroscopic methods, which revealed efficient excited-energy transfer (EET) between the meso-meso-linked Zn(II)-porphyrin units that occurred with time constants of 1.5 ps(-1) for (3)(2) and 8.8 ps(-1) for (5)(4).

Effective peripheral fabrication methods of meso-aryl-substituted subporphyrins were explored for the first time. Hexabrominated subporphyrins 2 were prepared quantitatively from the bromination of subporphyrins 1 with bromine. Hexaphenylated subporphyrins 3 and hexaethynylated subporphyrins 4 and 5 were synthesized by Suzuki-Miyaura coupling and Stille coupling, respectively, in good yields. X-ray crystal structures of 2 b, 3 b, 4 b, and 5 a revealed preservation of the bowl-shaped bent structures with bowl depths similar to that of 1. Hexaethynylated subporphyrins exhibit large two-photon-absorption cross-sections due to effective delocalization of the conjugated network to the ethynyl substituents.

We report the synthesis and characterization of L- and T-shaped porphyrin tapes as extensible structural motifs of two-dimensionally extended porphyrin tapes. The two-photon absorption (TPA) cross-section values (sigma((2))) for L- and T-shaped porphyrin tapes as well as those for linear trimeric and tetrameric porphyrin tapes were measured by an open-aperture Z-scan method at 2300 nm, a wavelength at which the one-photon absorption contribution is either zero or almost negligible. Under these conditions, the sigma((2)) values for the linear porphyrin tape trimer and tetramer were determined to be 18 500 and 41 200 GM, respectively. The sigma((2)) value for the L-shaped trimer was determined to be 8700 GM, which is only half that of the linear trimer, whereas the sigma((2)) value for the T-shaped tetramer was measured to be 35 700 GM. These results clearly indicate the dependence of the TPA cross-section on the molecular shape, which underscores the importance of directionality in the pi-conjugation pathway for the enhancement of TPA cross- section.