Silver Corrole Complexes: Unusual Oxidation States and Near-IR-Absorbing Dyes

• Published in: Chemistry : a European journal 2014-11, Vol.20 (48), p.15920-15932
• Main Authors: Sinha, Woormileela, Sommer, Michael G., Deibel , Naina, Ehret, Fabien, Sarkar, Biprajit, Kar, Sanjib
• Format: Article
• Language: English
• Subjects: Biology; Chemistry; Coordination Complexes - chemical synthesis; Coordination Complexes - chemistry; Coordination compounds; corroles; Crystallography, X-Ray; Dyes; dyes/pigments; electrochemistry; Ligands; Molecular Structure; Oxidation; Oxidation-Reduction; Photosynthesis; porphyrinoids; Porphyrins - chemical synthesis; Porphyrins - chemistry; Quantum Theory; Silver; Silver - chemistry; Spectrophotometry, Ultraviolet; Spectroscopy, Near-Infrared; Tasks; Valence
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201403609

Macrocycles such as porphyrins and corroles have important functions in chemistry and biology, including light absorption for photosynthesis. Generation of near‐IR (NIR)‐absorbing dyes based on metal complexes of these macrocycles for mimicking natural photosynthesis still remains a challenging task. Herein, the syntheses of four new AgIII corrolato complexes with differently substituted corrolato ligands are presented. A combination of structural, electrochemical, UV/Vis/NIR‐EPR spectroelectrochemical, and DFT studies was used to decipher the geometric and electronic properties of these complexes in their various redox states. This combined approach established the neutral compounds as stable AgIII complexes, and the one‐electron reduced species of all the compounds as unusual, stable AgII complexes. The one‐electron oxidized forms of two of the complexes display absorptions in the NIR region, and thus they are rare examples of mononuclear complexes of corroles that absorb in the NIR region. The appearance of this NIR band, which has mixed intraligand charge transfer/intraligand character, is strongly dependent on the substituents of the corrole rings. Hence, the present work revolves round the design principles for the generation of corrole‐based NIR‐absorbing dyes and shows the potential of corroles for stabilizing unusual metal oxidation states. These findings thus further contribute to the generation of functional metal complexes based on such macrocyclic ligands. A series of AgIII corrolato complexes was synthesized. They are capable of exhibiting an unusual oxidation state of the central silver atom on one‐electron reduction. Two of the oxidized complexes were found to absorb in the near‐IR (NIR) region (e.g., see figure), and thus are rare examples of monomeric corrole species that behave as NIR‐absorbing dyes.