Near-Infrared-II Absorbing Doubly N-Confused Dioxo-Heptaphyrins as Robust Photothermal Conversion Agents.

We present the synthesis of a novel meso-aryl-substituted [32]heptaphyrin 1 composed of two confused pyrrole units with a cisoid configuration. Under specific oxidative conditions, the α-carbons of the confused pyrrole units in the precursor were directly linked to yield a hybrid bicyclic compound 2, which integrates distorted corrorin and sapphyrin moieties. Compound 2 possesses a pseudo-annulenoannulene structure along with an emissive character in the near-infrared region.

Anion-Mediated Synthesis of Diethynyl-Substituted Doubly N-Confused Dioxohexaphyrin Dyes That Exhibit Enhanced Photoacoustic Signals in the NIR-II Region.

We herein report the anion-mediated synthesis of diethynyl-substituted doubly N-confused dioxohexaphyrins with hydrogen sulfate anions in an acid condensation of the tripyrrane and silyl-protected propiolaldehyde and subsequent oxidation in a one-pot fashion. Further, functionalization through silyl deprotection and Sonogashira cross-coupling reaction yielded the anisotropically π-extended derivative along a longer molecular axis. The modified hexaphyrin dye exhibited an intense S → S transition at around 1100 nm in the near-infrared-II region and enhanced photoacoustic signal intensity suitable for high-resolution imaging applications.

Open-Chain Tetrapyrroles Meet Metal Ions in the Functional Molecular Material Science.

Open-chain tetrapyrroles and their analogues, consisting of four pyrrole rings linked by methylene or methine carbons, originate from natural and synthetic pathways. These compounds exhibit unique structural flexibility due to their extended π-conjugation and tunable coordination with metal ions, enabling precise control over electronic and geometric properties. Such structural versatility makes them promising candidates for chiroptical, optoelectronic, and biorelated applications.

Dimerization of Hexaphyrin with an Appendant Pyrrole Possessing a Reactive Site to Alleviate the Steric Hindrance.

Oxidative dimerization of π-conjugated molecules is a straightforward approach for effectively extending π-conjugation and absorption features. However, it is challenging to construct dimeric species of bulky π-conjugated frameworks because of the steric hindrances and/or poor regioselectivity. To address these issues, a pyrrole unit has been regioselectively appended to the α position of N-confused hexaphyrin (1.

Metal-Bridging Cyclic Bilatriene Analogue Affords Stable π-Radicaloid Dyes with Near-Infrared II Absorption.

Stable neutral metal radicaloid complexes have been synthesized from a modified tetrapyrrolic pigment, bilatriene, with iridium(I) and rhodium(I) cyclooctadiene (COD) synthons. The bilatriene skeleton contains α-linked conjugated pyrrole units, whereas an N-confused analogue used in this work possesses β-linked pyrrole moieties at the terminal, demonstrating a unique metal binding capability. Unprecedentedly, the metal-COD cations are accommodated at the outer nitrogen sites, which induced the formation of open-shell metal-radicaloid species.

Bowl-Shaped Anthracene-Fused Antiaromatic Ni(II) Norcorrole: Synthesis, Structure, Assembly with C, and Photothermal Conversion.

The synthesis of bowl-shaped antiaromatic molecules is challenging because the molecular distortion further destabilizes these already inherently reactive molecules. Here, we report the synthesis and properties of bowl-shaped fused anthrylnorcorroles that exhibit near-infrared (NIR) absorption reaching 1900 nm. The oxidation of meso-anthryldibromodipyrrin provides fused anthryldibromodipyrrin, which was converted to the fused mono- and bisanthrylnorcorroles through Ni(0)-mediated intramolecular coupling with a bis(dibromodipyrrin) Ni(II) complex.

Metalla-Carbaporphyrinoids Consisting of an Acyclic N-Confused Tetrapyrrole Analogue Served as Stable Near-Infrared-II Dyes.

We present herein the synthesis of novel pseudo-metalla-carbaporphyrinoid species (1M: M=Pd and Pt) achieved through the inner coordination of palladium(II) and platinum(II) with an acyclic N-confused tetrapyrrin analogue. Despite their tetrapyrrole frameworks being small, akin to well-known porphyrins, these species exhibit an unusually narrow HOMO-LUMO gap, resulting in an unprecedentedly low-energy absorption in the second near-infrared (NIR-II) region. Density functional theory (DFT) calculations revealed unique d-p-conjugated electronic structures involving the metal d-ligand p hybridized molecular orbitals of 1M.

Reversible open-closed conformational switching of nano-size metalloporphyrin dimers triggered by light and temperature.

The current work demonstrates the reversible control of substantial molecular motion in 'nano-sized' molecules, where two structural isomers can 'open' and 'close' their cavities in response to light or heat. The isomers differ widely in their photophysical properties, including colour, polarity, two-photon absorption and π-conjugation, and can easily be separated through column chromatography and thus have wide applicability.

Stable Dication Diradicals of Triply Fused Metallo Chlorin-Porphyrin Heterodimers: Impact of the Bridge on the Control of Spin Coupling to Reactivity.

We report an unexpected rearrangement, controlled by the nature of the bridge, leading to the formation of novel, remarkably stable triply fused dinickel(II)/dicopper(II) chlorin-porphyrin dication diradical heterodimers in excellent yields. Here, a dipyrromethene bridge gets completely fused between two porphyrin macrocycles with two new C-C and one C-N bonds. The two macrocycles exhibit extensive π-conjugation through the bridge, which results in an antiferromagnetic coupling between the two π-cation radicals.

Supramolecular Recognition within a Nanosized "Buckytrap" That Exhibits Substantial Photoconductivity.

We report here a nanosized "buckytrap", , constructed from two bis-zinc(II) expanded-TTF (exTTF) porphyrin subunits. Two forms, and , differing in the axial ligands, HO vs tetrahydrofuran (THF), were isolated and characterized. Discrete host-guest inclusion complexes are formed upon treatment with fullerenes as inferred from a single-crystal X-ray structural analyses of with C.

Ruthenium(iv) N-confused porphyrin μ-oxo-bridged dimers: acid-responsive molecular rotors.

Ruthenium(iv) N-confused porphyrin μ-oxo-bridged complexes were synthesized oxidative dimerization of a ruthenium(ii) N-confused porphyrin complex using 2,2,6,6-tetramethylpiperidine 1-oxyl. The deformed core planes in the dimers conferred a relatively high ring rotational barrier of 16 kcal mol. Rotation of the complexes was controlled by protonating the peripheral nitrogen.

Exercise training using hybrid assistive limb (HAL) lumbar type for locomotive syndrome: a pilot study.

Background: With a rapidly aging population in Japan, locomotive syndrome is becoming an increasingly serious social problem. Exercise therapy using the lumbar type HAL, which is a wearable robot suit that can assist voluntary hip joint motion, would be expected to cause some beneficial effects for people with locomotive syndrome. The purpose of this study was to assess whether the deterioration of low back pain and any other adverse events would occur following HAL exercise therapy.

Iridium Complex of N-Fused Bilatrienone: Oxidative Cleavage of N-Fused Porphyrin Induced by Iridium-Cyclooctadiene Complexation.

N-fused porphyrin (NFP) is a unique class of photostable near-infrared dyes with an 18π aromatic tetrapyrrole macrocyclic skeleton containing a tri-fused pentacyclic moiety. Here, the synthesis of an iridium complex of N-fused bilatrienone is reported as the degradation product of Ir-cyclooctadiene (cod)-induced oxidative cleavage of NFP under aerobic conditions. Similar to the native bilin chromophores, the ring-opened complex featured a broken π-conjugation circuit and exhibited a broad visible absorption band.

Solvent-Controlled Self-Assembled Oligopyrrolic Receptor.

We report a fully organic pyridine-tetrapyrrolic U-shaped acyclic receptor , which prefers a supramolecular pseudo-macrocyclic dimeric structure () in a less polar, non-coordinating solvent (e.g., CHCl).

Chiral Interlocked Corrole Dimers Directly Linked at Inner Carbon Atoms of Confused Pyrrole Rings.

A facile synthetic strategy towards conformationally stable chiral chromophores based on dimeric porphyrinoids has been established. A peculiar class of face-to-face intramolecularly interlocked corrole dimers were formed by the oxidative C-C coupling linked at the inner carbon sites upon simple treatment of copper(II) ions. Their intrinsic electronic structures were modulated by the peripheral corrole ring annulations, which lead to distinct optical properties and redox profiles.

Benzo-Tetrathiafulvalene- (BTTF-) Annulated Expanded Porphyrins: Potential Next-Generation Multielectron Reservoirs.

Two sterically crowded benzo-tetrathiafulvalene (BTTF)-annulated expanded porphyrins (BTTF7-F and BTTF8) are synthesized. Detailed photophysical investigations reveal their intrinsic intramolecular charge transfer (CT) character, originated from partial electron transfer from electron-rich TTF units to the relatively electron-deficient macrocyclic core. This finding stands in contrast to what was observed in the previously reported Figure-of-eight conformer of BTTF-annulated [28]hexaphyrin (BTTF6), in which a typical π-π* electronic transition from HOMO to LUMO was observed.

Expanded N-Confused Phlorin: A Platform for a Multiply Fused Polycyclic Ring System via Oxidation within the Macrocycle.

Novel interrupted π-conjugated macrocycles derived from expanded porphyrinoids were synthesized, and their unique reactivity was investigated in this work. The specific porphyrin analogs, so-called phlorins and isoporphyrins, possess a -sp methylene moiety, showing inner 3NH and 1NH pyrrolic cores, respectively, and extended near-infrared (NIR) absorption. Expanded N-confused pentapyrrolic phlorin analog bears an interrupted cyclic π-conjugated system that is featured by a distinct higher HOMO and a lower LUMO.

NH Tautomerism of N-Confused Porphyrin: Solvent/Substituent Effects and Isomerization Mechanism.

The effects of substituents and solvents on the NH tautomerism of N-confused porphyrin () were investigated. The structures, electronic states, and aromaticity of NH tautomers ( and ) were studied by absorption and nuclear magnetic resonance (H, C, and N) spectroscopies, single-crystal X-ray diffraction analysis, and theoretical calculations. The relative stability of the tautomers is highly affected by solvents, with the -type tautomer being more stable in nonpolar solvents, while the -type tautomer being highly stabilized in polar solvents with high donor numbers such as ,-dimethylformamide (DMF), pyridine, and acetone.

Synthesis of Helically π-Extended N-Confused Porphyrin Dimer via meso-Bipyrrole-Bridge with Near-Infrared-II Absorption Capability.

Quinoidal dimeric porphyrin dye synthesis exhibiting second near-infrared (NIR-II) absorbability is described herein. A precisely designed meso-pyrrolyl-substituted N-confused porphyrin possesses a distinct metal coordination site at the periphery. Nickel metalation of this compound led to the oxidative C-H coupling between adjacent α-pyrrole rings, affording two dimeric complexes, which exhibited intense NIR-II absorptions ranging from 1000 to 1400 nm.

Near-Infrared-III-Absorbing and -Emitting Dyes: Energy-Gap Engineering of Expanded Porphyrinoids via Metallation.

The synthesis of organometallic complexes of modified 26π-conjugated hexaphyrins with absorption and emission capabilities in the third near-infrared region (NIR-III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis-Pd and bis-Pt complexes of hexaphyrin via N-confusion modification led to substantial metal d -p interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO-LUMO energy gap.

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.

Semiconducting Supramolecular Organic Frameworks Assembled from a Near-Infrared Fluorescent Macrocyclic Probe and Fullerenes.

We report here a new extended tetrathiafulvalene (exTTF)-porphyrin scaffold, , that acts as a ball-and-socket receptor for C and C. Supramolecular interactions between and these fullerenes serve to stabilize 3D supramolecular organic frameworks (SOFs) in the solid state formally comprising peapod-like linear assemblies. The SOFs prepared via self-assembly in this way act as "tunable functional materials", wherein the complementary geometry of the components and the choice of fullerene play crucial roles in defining the conductance properties.