Photoremovable protecting groups (PPGs) represent one of the main contemporary implementations of photochemistry in diverse fields of research and practical applications. For the past half century, organic and metal-complex PPGs were considered mutually exclusive classes, each of which provided unique sets of physical and chemical properties thanks to their distinctive structures. Here, we introduce the meso-methylporphyrin group as a prototype hybrid-class PPG that unites traditionally exclusive elements of organic and metal-complex PPGs within a single structure. We show that the porphyrin scaffold allows extensive modularity by functional separation of the metal-binding chromophore and up to four sites of leaving group release. The insertion of metal ions can be used to tune their spectroscopic, photochemical, and biological properties. We provide a detailed description of the photoreaction mechanism studied by steady-state and transient absorption spectroscopies and quantum-chemical calculations. Our approach applied herein could facilitate access to a hitherto untapped chemical space of potential PPG scaffolds.

Basic Chemistry Program Graduate School of Advanced Science and Engineering Hiroshima University Higashi Hiroshima 739 8526 Japan

Department of Chemistry Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic

Department of Physical Chemistry University of Chemistry and Technology Prague Technická 5 16628 Prague 6 Czech Republic

Department of Physiology and Pharmacology Sackler School of Medicine Tel Aviv University 6997801 Tel Aviv Israel

RECETOX Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic

School of Plant Sciences and Food Security Faculty of Life Sciences Tel Aviv University Tel Aviv 6997801 Israel

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