Synthesis and Properties of 5,15-Dioxaporphyrin Bearing Various meso-Aryl Substituents.

Herein, a scope of meso-substituents for the synthesis of 5,15-dioxaporphyrins (DOPs), a novel antiaromatic porphyrinoid, was investigated. DOPs with various types of aryl substituents were synthesized by nucleophilic aromatic substitution reaction of nickel bis(α,α'-dibromodipyrrin) complexes bearing corresponding meso-aryl substituents and subsequent intramolecular annulation reaction of β-hydroxy-substituted intermediates. Using a copper dipyrrin complex instead of nickel complexes, a copper complex of DOP was synthesized for the first time.

Cyclo[4]pyrrole with - direct linkages.

A cyclo[4]pyrrole bearing pyrrole C()-C() direct linkages, a contracted porphyrin analogue with no -carbon bridge, was synthesized from an oligoketone-related precursor. X-ray crystallography and StrainViz analysis revealed a non-planar structure with a total strain of 20.8 kcal mol.

A novel BODIPY-based fluorescent probe for naked-eye detection of the highly alkaline pH.

A novel alkaline pH-responsive probe based on an asymmetric aza-BODIPY was synthesized in a one-pot Schiff base formation reaction. This pH-sensitive probe comprises an asymmetric aza-BODIPY as the luminescent core, with a benzothiazole moiety connected via an imine bond serving as the recognition site. The probe exhibits a turn-off fluorescence response upon exposure to alkaline pH (9.

Far-red fluorescence and chiroptical properties of pyrrolopyrrole aza-BODIPYs induced by the ,-chelation.

A titanium-mediated aza-BODIPY synthesis using diketopyrrolopyrrole bearing -anisyl substituents provided ,-chelated pyrrolopyrrole aza-BODIPYs in a one-pot manner ether bond cleavage and chelation of the resulting nucleophilic oxygen to the boron atom. The ,-chelation not only induces the redshifts of absorption and fluorescence but also endows chiroptical properties.

[22]Pentaphyrins(2.0.1.1.0) Displaying N-Fusion, Pyrrole-Rearrangement, and Dimerization Reactions Upon Oxidation and Metalation.

Exploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.

One-pot synthesis of azabora[6]helicene by a Schiff base forming reaction.

Azabora[6]helicene as a new heterohelicene analogue was synthesized by a one-pot reaction of commercially available 2,6-diaminopyridine and benzo[,]indole-2(1)-one and subsequent boron coordination. While the single-crystal X-ray diffraction analysis elucidated a helical structure in the solid state, a dynamic helicity inversion was observed in solution.

Facile Synthesis of Asymmetric aza-Boron Dipyrromethene Analogues Bearing Quinoxaline Moiety.

An asymmetric aza-BODIPY analogue bearing quinoxaline moiety was synthesized via a titanium tetrachloride-mediated Schiff-base-forming reaction of 6,7-dimethyl-1,4-dihydroquinoxaline-2,3-dione and benzo[]thiazol-2-amine. This novel aza-BODIPY analogue forms a complementary hydrogen-bonded dimer due to the quinoxaline moiety in the crystal structure. It also shows intense absorption and fluorescence, with fluorescence quantum yields close to unity.

Oxidation of 5,15-Dioxaporphyrin: Its Generality and Novelty as an Oxaporphyrin Analogue.

5,15-Dioxaporphyrin (DOP) is a novel meso-oxaporphyrin analogue and exhibits unique 20π-antiaromaticity, unlike its mother congener of 18π-aromatic 5-oxaporphyrin, commonly known as its cationic iron complex called verdohem, which is a key intermediate of heme catabolism. To reveal its reactivities and properties as an oxaporphyrin analogue, the oxidation of tetra-β-arylated DOP (DOP-Ar ) was explored in this study. Stepwise oxidation from the 20π-electron neutral state was achieved, and the corresponding 19π-electron radical cation and 18π-electron dication were characterized.

Post-Modification of Pyrrolopyrrole Aza-BODIPY toward High Near-Infrared Fluorescence Brightness.

Pyrrolopyrrole aza-BODIPYs (PPABs), dimeric aza-BODIPY analogues, exhibit intense absorption and fluorescence in the visible and near-infrared (NIR) regions. Here, we developed a facile postmodification by palladium-catalyzed coupling reactions to synthesize a series of donor-acceptor-donor (D-A-D) PPABs. Despite the possible fluorescence quenching dictated by the energy-gap low, D-A-D PPABs exhibit high-fluorescence brightness in the NIR region, implying their potential use as a bright NIR emitter.

The First Synthesis of Subporphyrins.

Because of the rich coordination chemistry and unique optical and electrochemical properties, porphyrin analogues have been intensively investigated. Among them, subporphyrins have been long-awaited molecules, with only their boron complexes known to date because of the crucial role of the central boron atom as a template in synthesis. The challenges related to the synthesis of a genuine subporphyrin (boron-free) have finally been met and reported in a recent article from Kim, Osuka, and Song.

Spontaneous Assembly and Three-Dimensional Stacking of Antiaromatic 5,15-Dioxaporphyrin on HOPG.

Antiaromatic compounds have recently received considerable attention because of their novel properties such as narrow HOMO-LUMO gaps and facile formation of mutual stacking. Here, the spontaneous assembly of antiaromatic meso-2-thienyl-substituted 5,15-dioxaporphyrin (DOP-1) is scrutinized at the liquid-solid interface by scanning tunneling microscopy (STM). Polymorphism in monolayers characterized by the orthogonal and parallel assemblies is found at the low concentration of 0.

Janus Pyrrolopyrrole Aza-dipyrrin: Hydrogen-Bonded Assemblies and Slow Magnetic Relaxation of the Cobalt(II) Complex in the Solid State.

A novel pyrrolopyrrole azadipyrrin (Janus-PPAD) with Janus duality was synthesized by a Schiff base-forming reaction of diketopyrrolopyrrole. The orthogonal interactions of the hydrogen-bonding ketopyrrole and metal-coordinating azadipyrrin moieties in Janus-PPAD enabled the metal ions to be arranged at regular intervals: zinc(II) and cobalt(II) coordination provided metal-coordinated Janus-PPAD dimers, which can subsequently form hydrogen-bonded one-dimensional arrays both in solution and in the solid state. The supramolecular assembly of the zinc(II) complex in solution was investigated by H NMR spectroscopy based on the isodesmic model, in which a binding constant for the elongation of assemblies is constant.

Periphery-Fused Chiral AB-Type Subporphyrin.

Despite significant interest, the chiroptical properties of subporphyrins have rarely been investigated because chiral subporphyrins are elusive. Here, inherently chiral subporphyrins are elaborated by forming a fused pyran ring at the periphery of an AB-type -aryl-substituted subporphyrin. Their circular dichroism (CD) properties are largely affected by the peripheral substituents and the dihedral angles between the -aryl substituents and the subporphyrin core: the β-perbromo subporphyrin with an orthogonal arrangement of the -phenyl substituents to the subporphyrin core exhibits weak CD signals corresponding to the Q bands, whereas the unsubstituted species with smaller dihedral angles shows relatively intense CD signals.

An Electron-Accepting aza-BODIPY-Based Donor-Acceptor-Donor Architecture for Bright NIR Emission.

A bright near-infrared (NIR) fluorescent molecule was developed based on the donor-acceptor-donor (D-A-D) approach using an aza-BODIPY analog called pyrrolopyrrole aza-BODIPY (PPAB) as an electron-accepting chromophore. Directly introducing electron-donating triphenylamine (TPA) to develop a D-A-D structure caused redshifts of absorption and emission of PPAB into the NIR region with an enhanced fluorescence brightness of up to 5.2×10  m  cm , whereas inserting a phenylene linker between the TPA donor and the PPAB acceptor induced solvatochromic behavior in emission.

TTF-Annulated Silicon Phthalocyanine Oligomers and Their External-Stimuli-Responsive Orientational Ordering.

Orientational control of functional molecules is essential to create complex functionalities as seen in nature; however, such artificial systems have remained challenge. Herein, we have succeeded in controlling rotational isomerism of μ-oxo silicon phthalocyanine (SiPc) oligomers to achieve an external-stimuli-responsive orientational ordering using intermolecular interactions of tetrathiafulvalene (TTF). In this system, three modes of orientations, free rotation, eclipsed conformation, and staggered conformation, were interconverted in response to the oxidation states of TTF, which varied interactions from association due to formation of mixed-valence TTF dimer to dissociation due to electrostatic repulsion between TTF dications.

Copper 1,19-Diaza-21,24-dicarbacorrole: A Corrole Analogue with an N-N Linkage Stabilizes a Ground-State Singlet Organocopper Species.

A copper complex of a heterocorrole analogue with an N-N linkage, 1,19-diaza-21,24-dicarbadibenzocorrole (Cu-5), was successfully synthesized via oxidative metalation-cyclization of a tetrapyrrolic precursor. The N-N linkage in the skeleton of Cu-5, which serves as a mediator of π-electron delocalization, features an 18π aromatic system. The electronic structure of Cu-5 is best described as a ground-state singlet species stabilized by the distinct NNCC coordination core.

Rational design of pyrrolopyrrole-aza-BODIPY-based acceptor-donor-acceptor triads for organic photovoltaics application.

Acceptor-donor-acceptor triads consisting of diketopyrrolopyrrole (DPP) or pyrrolopyrrole aza-BODIPY (PPAB) or both as acceptors and cyclopentadithiophene as a donor were rationally designed for near infrared (NIR) photovoltaics application. Among them, the PPAB-based triad exhibited the highest power conversion efficiency of 3.88% owing to the panchromatic absorption in the UV/vis/NIR regions.

Tungsten(VI) Complex of N-Fused Porphyrin Absorbing Near-Infrared Light beyond 1000 nm.

Incorporating tungsten into the N3 core of a N-fused porphyrin (NFP; 1) affords high-valent tungsten(VI)-NFP complexes, WClO -1 and 21-chlorinated WClO -3. The X-ray structure of WClO -1 reveals a distorted octahedral geometry with sitting atop metal coordination. The absorption spectrum of WClO -1 displays bathochromically shifted Q-like bands beyond 1000 nm, indicating an inherently narrow HOMO-LUMO energy gap.

Pyrrolopyrrole Aza-BODIPY Analogues as Near-Infrared Chromophores and Fluorophores: Red-Shift Effects of Substituents on Absorption and Emission Spectra.

Pyrrolopyrrole aza-BODIPY analogues (PPABs) are a new class of UV/vis and near-infrared chromophores. Varying the substituents results in red-shifts of both the absorption and emission spectra. Extension of the lengths of the oligothiophene substituents from thiophene to quaterthiophene caused red-shifts of the absorption and emission from 699 and 712 nm to 809 and 853 nm, respectively.

Subphthalocyanine-Stoppered [2]Rotaxanes: Synthesis and Size/Energy Threshold of Slippage.

Subphthalocyanine (SubPc)-stoppered [2]rotaxanes were synthesized for the first time. The rotaxane bearing unsubstituted SubPc as a stopper exhibited an equilibrium of slipping-on and slipping-off, whereas a perfluorinated SubPc stopper completely blocked slippage of the ring due to its slightly larger size. Kinetic studies revealed the Gibbs free energy of activation for the slipping-on and slipping-off processes.

Three-dimensional aromaticity in an antiaromatic cyclophane.

Understanding of interactions among molecules is essential to elucidate the binding of pharmaceuticals on receptors, the mechanism of protein folding and self-assembling of organic molecules. While interactions between two aromatic molecules have been examined extensively, little is known about the interactions between two antiaromatic molecules. Theoretical investigations have predicted that antiaromatic molecules should be stabilized when they stack with each other by attractive intermolecular interactions.

Efficient Electrogenerated Chemiluminescence of Pyrrolopyrrole Aza-BODIPYs in the Near-Infrared Region with Tripropylamine: Involving Formation of S and T States.

Efficient electrogenerated chemiluminescences (ECLs) of three pyrrolopyrrole aza-BODIPYs in the near-infrared region by using tripropylamine as a coreactant are reported. Kinetic analysis based on Marcus theory indicates the direct formation of S and T states through the electron transfer reaction, which affects the ECL efficiencies.

aza-BODIPY synthesis towards vis/NIR functional chromophores based on a Schiff base forming reaction protocol using lactams and heteroaromatic amines.

aza-BODIPY is a class of heteroatom-containing BODIPY analogues targeting near infrared (NIR) chromophores and fluorophores. As a synthetic strategy towards aza-BODIPY structures, we have, recently, developed a Schiff base forming reaction using readily available lactams and heteroaromatic amines. Absorption and fluorescence of a series of compounds cover the whole range of the ultraviolet (UV)/visible (vis)/NIR regions.

Bis(1,3-dithiol-2-ylidene)-Substituted Subtriazachlorin: A Subphthalocyanine Analogue with Redox Properties.

Bis(1,3-dithiol-2-ylidene)-substituted subtriazachlorin was formed because of an unusual reaction of a 1,3-dithiole-2-one-fused subphthalocyanine in a triethylphosphite-mediated tetrathiafulvalene synthesis. In this novel molecule, the bis(1,3-dithiol-2-ylidene)ethane moiety and subtriazachlorin structure are fused, resulting in an electron-donating ability and broad absorption in the near-infrared region.

1,3-Dithiole-2-one-Fused Subphthalocyanine and Subporphyrazine: Synthesis and Properties Arising from the 1,3-Dithiole-2-one Units.

Subphthalocyanine (SubPc) and its benzo ring-removed analogue, subporphyrazine (SubPz), bearing 1,3-dithiole-2-one (SCO) groups as a new class of substituents were synthesized. In addition to the perturbed optical properties due to the presence of electron-withdrawing SCO units, the deep bowl-shaped structure of the SubPz derivative allowed concave-convex interaction to form a unique co-crystal structure with C. Finally, using the reactivity of the peripheral SCO units, SCO-fused SubPc was successfully converted into tetrathiafulvalene (TTF)-annulated SubPc in a yield higher than that of the direct synthesis from a TTF-fused phthalonitrile.