Nonlinear Optical Properties as a Guide to Aromaticity in Congeneric Pentapyrrolic Expanded Porphyrins: Pentaphyrin, Sapphyrin, Isosmaragdyrin, and Orangarin

Abstract

On the basis of two-photon absorption and time-resolved spectroscopic measurements, as supported by theoretical calculations of quantitative aromaticity, a relationship between the nonlinear optical properties and aromaticity index has been established for a series of four fully conjugated pentapyrrolic expanded porphyrins, namely pentaphyrin (1.1.1.1.1), sapphyrin (1.1.1.1.0), isosmaragdyrin (1.1.1.0.0), and orangarin (1.0.1.0.0), all of which proved amenable to study in dichloromethane.

Figure Eights, Möbius Bands, and More: Conformation and Aromaticity of Porphyrinoids

“…[39,47,100] Two-photon absorption crosssections have been recently found to correlate with NICS values of some porphyrinoids, and have therefore been advocated as a useful aromaticity criterion. [101][102][103] Magnetic Criteria. The importance of proton chemical shifts as an aromaticity measure was recognized in the very first NMR spectroscopic study of porphyrin derivatives.…”

“…Orangarin, a [20]annulenoid antiaromatic macrocycle, [55] is markedly paratropic, as evidenced by its center NICS value of 43 ppm. [102] In spite of their aromatic character, smaragdyrins and their oxa analogues are unstable towards acids and light, [56,182] but they can be made more robust by appropriate peripheral substitution. [183][184][185][186][187][188] Interestingly, no pentaphyrins containing less than two meso carbons have yet been reported.…”

Figure‐Eight‐Strukturen, Möbius‐Bänder und mehr: Konformation und Aromatizität von Porphyrinoiden

“…Der antiaromatische [20]Annulen-Makrocyclus von Orangarin [55] ist merklich paratrop mit einem NICS-Wert von 43 ppm. [102] Trotz ihres aromatischen Charakters sind Smaragdyrin und seine Oxa-Analoga gegenüber Säure und Licht instabil, [56,182] können jedoch durch geeignete periphere Substitution robuster gemacht werden. [183][184][185][186][187][188] Interessanterweise wurden bis jetzt noch keine Pentaphyrine beschrieben, die weniger als zwei Mesokohlenstoffatome …”

Synthesis and Properties of AABAAB-Type Macroheterocyclic Compounds with Fragments of 1,2,4- and 1,3,4-Thiadiazole

“…A white residue was filtrated and dried. Yield: 0.57 g (59 % (3,7,11,15,19,23)hexaazacyclotetracosene (8). A mixture of 4 (0.16 g, 0.62 mmol) and 1 (0.05 g, 0.31 mmol) was dissolved in phenol at 100-110 o C and reacted for 50 hours.…”

“…[3,4] Macroheterocyclic compounds (Mc) with expanded coordination cavities comprised of 6 smaller heterocyclic moieties that are linked to each other via aza-bridges are fundamentally interesting. [5][6][7][8] However, purification of similar compounds is difficult what can negatively affect their basic research and application.…”