Potassium Poly(Heptazine Imide): Transition Metal‐Free Solid‐State Triplet Sensitizer in Cascade Energy Transfer and [3+2]‐cycloadditions. Issue 35 (9th June 2020)

• Record Type: Journal Article
• Authors: Savateev, Aleksandr; Tarakina, Nadezda V.; Strauss, Volker; Hussain, Tanveer; ten Brummelhuis, Katharina; Sánchez Vadillo, José Manuel; Markushyna, Yevheniia; Mazzanti, Stefano; Tyutyunnik, Alexander P.; Walczak, Ralf; Oschatz, Martin; Guldi, Dirk M.; Karton, Amir; Antonietti, Markus
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 35(2020)
• Page Start: 15061
• Page End: 15068
• Publication Date: 2020-06-09
• Subjects: carbon nitrides -- organic photocatalysis -- potassium poly(heptazine imide) -- singlet oxygen -- solid-state sensitizer; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202004747
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Polymeric carbon nitride materials have been used in numerous light‐to‐energy conversion applications ranging from photocatalysis to optoelectronics. For a new application and modelling, we first refined the crystal structure of potassium poly(heptazine imide) (K‐PHI)—a benchmark carbon nitride material in photocatalysis—by means of X‐ray powder diffraction and transmission electron microscopy. Using the crystal structure of K‐PHI, periodic DFT calculations were performed to calculate the density‐of‐states (DOS) and localize intra band states (IBS). IBS were found to be responsible for the enhanced K‐PHI absorption in the near IR region, to serve as electron traps, and to be useful in energy transfer reactions. Once excited with visible light, carbon nitrides, in addition to the direct recombination, can also undergo singlet–triplet intersystem crossing. We utilized the K‐PHI centered triplet excited states to trigger a cascade of energy transfer reactions and, in turn, to sensitize, for example, singlet oxygen ( 1 O2 ) as a starting point to synthesis up to 25 different N‐rich heterocycles. Abstract : The triplet excited states of the new heterogeneous triplet sensitizer, potassium poly(heptazine imide), can be used to trigger a cascade of energy‐transfer reactions and, in turn, to sensitize, for example, singlet oxygen ( 1 O2 ), as a starting point to synthesize N‐rich heterocycles. In this way aldoximes can be converted into 1, 2, 4‐oxadiazoles under visible light irradiation.