Metal‐Assisted One‐Pot Synthesis of Isoporphyrin Complexes

Abstract

Zinc and cadmium complexes of meso-arylisoporphyrins carrying a pyrrolyl or dipyrrinyl substituent at the sp(3) carbon atom were obtained through a simple one-pot variation of the Alder-Longo porphyrin synthesis. Key to the formation and stabilization of isoporphyrins is the presence of metal acetates during the oxidative macrocyclization step. The characteristic Q-bands of isoporphyrins are found in the NIR region between 750 nm and 880 nm. All of the isolated pyrrolyl- and dipyrrinyl-appended isoporphyrins are stable under typical laboratory conditions and allow chemical transformations like BF2 coordination, transmetalation, and ligand exchange.

Zinc‐ and Cadmium meso‐Aryl‐Isoporphyrins: Non‐Aromatic NIR Dyes with Distinct Conformational Features

“…From the above investigations, it appears that the conditions mentioned in the preliminary study [10] are already very well adapted to the preferential formation of isoporphyrins from typical benzaldehydes. Further optimization for different aryl aldehydes may be achieved mainly by varying the solvent polarity in the condensation step (e. g. for 9, 10 and 15), and by limiting the formation of the undesired pyrrolyl or dipyrrinyl derivatives through the same measure.…”

“…This may be related to the increased effective conjugation in these compounds, to their larger saddling mode amplitude, or both. For the less saddled dipyrrinyl derivatives 12-14 and 17, [10] however, similar shifts of the β-CH signals are observed, so that an influence of the saddling mode on the 1 H NMR chemical shift is rather negligible.…”

“…The ruffling mode is Table 1. Selected bond lengths /Å and angles /°from the molecular structures of 1, 16 [10] and 14. [a] Displacement of the Zn atom from the N 4 mean squares plane.…”

“…[23] DFT and TD-DFT calculations for isoporphyrins 1 and 8: For isoporphyrins chlorozinc-tetraphenyl-pyrrolylisoporphyrin 1 and chlorozinc-tetrathienylpyrrolyl-isoporphyrin 8 a geometry optimization with subsequent normal mode analysis was performed, starting from a structure based on geometric data obtained from Xray diffraction analysis of the methoxy derivative 16. [10] For all calculations ORCA in Version 4.1.1 has been used. [24] Geometry optimization was performed using GGA functional BP86 [25] with triple zeta def2-TZVP basis [26] using D3BJ dispersion correction.…”

“…[9] Recently, we reported a simpler synthetic pathway to stabilized isoporphyrins II by a one-pot approach. [10] This type of isoporphyrin formation was serendipitously unraveled during a study of a variation of the Adler-Longo porphyrin synthesis, [11] using the Gryko conditions for corrole formation [12] and zinc-or cadmium acetate as additional template reagents. In some cases, the isoporphyrins emerged even as major products, despite the known sensitivity of this substance class.…”