Light-induced substrate transformations in artificial photosynthetic devices and functional enzyme model systems strongly depend on the feasibility of multielectron transfer catalysis [1,2]. The crucial advantage of coupling multiple redox equivalents and proton transfer steps in photocatalysis is to avoid free radical reaction pathways and energetic constraints due to charge accumulation, as these processes can decrease both the long-term stability and the efficiency of the corresponding systems. In this context, certain coordination compounds including tetrapyrrole-based derivatives such as porphyrin, corrole and phthalocyanine complexes have been shown to achieve an efficient fusion of the complementary functions of a light-harvester, a photoredox interface, a substrate recognition site and a mediator for chemical reactions [3-6]. To further improve the performance of such systems, the design of long-term stable processes for artificial photosynthetic energy storage and green synthetic chemistry using artificial (photo)enzymes has to be achieved with sustainable, environmentally benign and earth-abundant bulding blocks. Another crucial aspect in the context of solar chemistry and catalysis is not only the requirement for using visible light, but also to shift the threshold wavelength of the photosensitizers as far as possible to the red and NIR-spectral regions. Some of our recent developments in this direction will be presented in this contribution.

[1] G. Knör, Chem. Eur. J. 2009, 15, 568

[2] G. Knör, Coord. Chem. Rev. 2015, 304-305, 102

[3] M. Hajimohammadi, C. Schwarzinger, G. Knör, RSC Advances 2012, 2, 3257

[4] C. Uslan, K. T. Oppelt, L. M. Reith, B. Ş. Sesalan, G. Knör, Chem. Commun. 2013, 49, 8108

[5] K. T. Oppelt, E. Wöß, M. Stiftinger, W. Schöfberger, W. Buchberger, G. Knör, Inorg. Chem. 2013, 52, 11910

[6] M. Ertl, E. Wöß, G. Knör, Photochem. Photobiol. Sci. 2015, 14, 1826