Isolation and Characterization of a Monoprotonated Hydroporphyrin. Issue 48 (6th December 2018)

• Record Type: Journal Article
• Authors: Arkhypchuk, Anna I.; Orthaber, Andreas; Kovacs, Daniel; Borbas, K. Eszter
• Is Part Of: European journal of organic chemistry. Issue 48(2018)
• Page Start: 7051
• Page End: 7056
• Publication Date: 2018-12-06
• Subjects: Functional organic materials -- Chlorin -- Tetrapyrrole -- Protonation -- Absorption -- Fluorescence; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201801472
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : A simple protocol for the controlled preparation of mono‐ and diprotonated hydroporphyrins (chlorins) is presented. The chlorins carried 10‐aryl groups with electron‐neutral (phenyl), electron‐donating ( p ‐OMe‐C6 H4 ) or electron‐withdrawing (pentafluorophenyl) substituents. The protonation reactions were readily followed by UV/Vis absorption spectroscopy, enabling the determination of the first (4.8–5.3) and second p K a 's (1.7–0.5). Both mono‐ and diprotonated species were fully characterized by 1 H NMR spectroscopy, which, in combination with theoretical studies, showed that these macrocycles were significantly distorted in solution. A 10‐phenyl‐substituted monoprotonated chlorin was characterized by X‐ray crystallography. This is the first structurally characterized hydroporphyrin monocation, and the first crystal structure of a sterically unencumbered singly protonated tetrapyrrole. The photostabilities of the mono‐ and diprotonated 10‐phenylchlorins were measured upon irradiation into their Soret bands; protonation yielded increased photostabilities. Abstract : The controlled stepwise mono‐ and diprotonation of synthetic hydroporphyrins carrying is reported. Protonations were readily followed by UV/Vis absorption spectroscopy, enabling the determination of the first and second p K a 's. Both mono‐ and diprotonated species were significantly distorted in solution. A monoprotonated chlorin was characterized by X‐ray crystallography.