All-aza smaragdyrin, a historic but elusive pentapyrrolic macrocycle, was successfully synthesized and characterized for the first time. [22]­Smaragdyrin BF2-complex 3 was smoothly synthesized by 2-fold SNAr reaction of 1,9-dibromo-5-mesityldipyrrin with 5,10-dimesityltripyrrane. Treatment of 3 with methanesulfonic acid gave [20]­smaragdyrin 5 as a stable antiaromatic compound. Reduction of 5 with NaBH4 under inert conditions gave [22]­smaragdyrin 6 as an aromatic congener, which was easily oxidized back to 5 in the air. Complex 3 was interconvertible with its 20π-congener 4 via oxidation with MnO2 and reduction with NaBH4. Treatment of 3 or 4 with CuCl2 in the presence of NaOAc gave hetero bimetal complex 8.

Proton-coupled electron transfer (PCET) is an important chemical and biological phenomenon. It is attractive as an on-off switching mechanism for redox-active synthetic systems but has not been extensively exploited for this purpose. Here we report a core-modified planar weakly antiaromatic/nonaromatic octaphyrin, namely, a [32]octaphyrin(1.0.1.0.1.0.1.0) (1) derived from rigid naphthobipyrrole and dithienothiophene (DTT) precursors, that undergoes proton-coupled two-electron reduction to produce its aromatic congener in the presence of HCl and other hydrogen halides. Evidence for the production of a [4 n + 1] π-electron intermediate radical state is seen in the presence of trifluoroacetic acid. Electrochemical analyses provide support for the notion that protonation causes a dramatic anodic shift in the reduction potentials of octaphyrin 1, thereby facilitating electron transfer from halide anions (viz. I, Br, and, Cl). Electron-rich molecules, such as tetrathiafulvene (TTF), phenothiazine (PTZ), and catechol, were also found to induce PCET in the case of 1. Both the oxidized and two-electron reduced forms of 1 were characterized by X-ray diffraction analyses in the solid state and in solution via spectroscopic means.

An expanded metalloporphyrin-based "black dye" Au−Pd oxohexaphyrin (AuPd-1) with absorption capabilities across the visible-to-near-infrared (NIR) range was synthesized. This black dye, AuPd-1, possessed efficient light-harvesting and photostable capabilities, which were indicative of superior photothermal (PT) conversion abilities. Encapsulation of AuPd-1 with a micellar nanocapsule resulted in a compound that demonstrated intense photoacoustic (PA) properties in the NIR region in water. This finding indicated how metal (d)−ligand (π) molecular orbital interactions in metalloporphyrins could aid in the design of visible-to-NIR lightharvesting black dyes for PT and PA applications.

The first Si 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 complexes. The Si 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 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 state. These intriguing optical properties have been comprehensively studied by magnetic circular dichroism (MCD) spectroscopy, femtosecond transient absorption (fs-TA) measurements, and theoretical calculations.

p-p Stackingi so mnipresent not only in nature but in aw ide variety of practical fields appliedt oo ur lives. Becauseo fi ts importance in ap erformance of natural and artificial systems, such as light harvesting system and working layer in device, many researchers have put intensive effort into identifying its underlying nature. However,f or the case of p-p stacked systemsc omposed of antiaromatic units, the understanding of the fundamentalm echanisms is still unclear.H erein, we synthesized an ew type of planar b,b'-phenylene-bridgedh exaphyrin (1.0.1.0.1.0),r eferred as naphthorosarin whichp ossesses the 24p-electronc onjugated pathway.E specially,t he corresponding antiaromaticp orphyrinoid shows the unique property to form dimeric species adopting the face-to-face geometry which is unprecedentedi nc ases of known annulated naphthorosarins. In order to elucidate the intriguing properties derived from the stacked dimer,t he current study focuses on the experimental support to rationalizet he observed p-p interactions betweent he two subunits.