Addressing Environmental Challenges of Porphyrin Mixtures Obtained from Statistical Syntheses

Abstract

Syntheses of complex molecular mixtures on the preparative scale are often challenging steps for chemists, which go hand in hand with expensive purification steps. Herein, the preparation and isolation of unsymmetrically substituted porphyrins, obtained from statistical reactions between two benzaldehydes, were investigated. Therefore, a semi-automated modular process was developed to lower the consumable costs, save time, and reduce waste production. We utilized a monomode microwave reactor equipped with an autosampler, and a medium pressure liquid chromatography (MPLC) flash purification device, equipped with a UV/Vis detector and a re-usable glass column packed with SiO 2. With this method, it was possible to synthesize and purify several statistical porphyrin mixtures, while simultaneously reducing the environmental factor (Efactor) significantly, compared to conventionally performed porphyrin syntheses. Our approach shows that a sustainable investigation of academically relevant low-symmetrical porphyrins can be carried out feasibly, without sacrificing invested time.

Electron beam-induced demetallation of Fe, Co, Ni, Cu, Zn, Pd, and Pt metalloporphyrins: insights in e-beam chemistry and metal cluster formations

“…Furthermore, the facile implementation of heteroatoms on the substrate, such as nitrogen, can be envisioned through additional molecular engineering of the porphyrin's periphery. [66][67][68][69][70] Incorporating heteroatom-rich substituents allows for precise modulation of material properties, potentially serving as dopants or anchor points within the substrate, thereby offering a means to fine-tune the materials as needed.…”

Main Strategies for the Synthesis of meso-Arylporphyrins

“…The statistical synthesis of unsymmetrical meso -tetraarylporphyrins always requires expensive and time-consuming methods for separation and purifica­tion of the products [ 218 ]. Therefore, to reduce con­sumable costs, save time, and minimize waste, a semi-automated modular process was developed that includes a monomode MW reactor equipped with an autosampler, an instant purification device by medium-pressure liquid chromatography with a UV/visible detector, and a reusable glass column filled with silica gel.…”

“…Hölzel et al [ 218 ] performed a two-stage mixed-aldehyde monopyrrole condensation in a microwave reactor following the Zerrouki methodology (Fig. 5 ).…”

“…For example, the lowest value of the E factor is typical for oil refining processes (<0.1), while pharmaceutical industry processes are character­ized by an E value of 25 to 100. The value of the environmental factor for the synthesis of unsymmet­rically substituted porphyrins using the proposed modular system is reduced to 530–624 [ 218 ].…”