[18]/[20]π Hemiporphyrazine: A Redox-Switchable Near-Infrared Dye

An aromatic hemiporphyrazine with an 18π-electron structure has been synthesized by oxidizing 20π-electron 8,10,21,23-tetrahydroxy-28,30-dicarba-27<i>H</i>,29<i>H</i>-hemiporphyrazine with bulky aryl ether substituents. The aromatic nature of the oxidized form was characterized by means of various spectroscopic methods and single-crystal X-ray analysis, with the help of quantum-chemical calculations. The oxidized hemiporphyrazine exhibited an intense absorption at ∼850 nm. The redox process was found to be reversible

[18]/[20]π Hemiporphyrazine: A Redox-Switchable Near-Infrared Dye

An aromatic hemiporphyrazine with an 18π-electron structure has been synthesized by oxidizing 20π-electron 8,10,21,23-tetrahydroxy-28,30-dicarba-27<i>H</i>,29<i>H</i>-hemiporphyrazine with bulky aryl ether substituents. The aromatic nature of the oxidized form was characterized by means of various spectroscopic methods and single-crystal X-ray analysis, with the help of quantum-chemical calculations. The oxidized hemiporphyrazine exhibited an intense absorption at ∼850 nm. The redox process was found to be reversible

Unraveling the Electronic Structure of Azolehemiporphyrazines: Direct Spectroscopic Observation of Magnetic Dipole Allowed Nature of the Lowest π–π* Transition of 20π-Electron Porphyrinoids

Hemiporphyrazines are a large family of phthalocyanine analogues in which two isoindoline units are replaced by other rings. Here we report unambiguous identification of 20π-electron structure of triazolehemiporphyrazines (<b>1</b>, <b>2</b>) and thiazolehemiporphyrazine (<b>3</b>) by means of X-ray analysis, various spectroscopic methods, and density functional theory (DFT) calculations. The hemiporphyrazines were compared in detail with dibenzotetraazaporphyrin (<b>4</b>), a structurally related 18π-electron molecule. X-ray analysis revealed that tetrakis­(2,6-dimethylphenyloxy)­triazolehemiporphyrazine (<b>1b</b>) adopted planar geometry in the solid state. A weak absorption band with a pronounced vibronic progression, observed for all the hemiporphyrazines, was attributed to the lowest π–π* transition with the electric-dipole-forbidden nature. In the case of intrinsically chiral vanadyl triazolehemiporphyrazine (<b>2</b>), a large dissymmetry (<i>g</i>) factor was detected for the CD signal corresponding to the lowest π–π* transition with the magnetic-dipole-allowed nature. Molecular orbital analysis and NICS calculations showed that the azolehemiporphyrazines have a 20π-electron system with a weak paratropic ring current