Exploring Arylazo-3,5-Bis(trifluoromethyl)pyrazole Switches

Bogdan C Enache; Anamaria Hanganu; Cristina Tablet; Catalin C Anghel; Codruta C Popescu; Anca Paun; Niculina Daniela Hădade; Augustin M Mădălan; Mihaela Matache

doi:10.1021/acsomega.2c04984

Exploring Arylazo-3,5-Bis(trifluoromethyl)pyrazole Switches

ACS Omega. 2022 Oct 20;7(43):39122-39135. doi: 10.1021/acsomega.2c04984. eCollection 2022 Nov 1.

Authors

Bogdan C Enache^{1

2}, Anamaria Hanganu^{1

3}, Cristina Tablet^{4

5}, Catalin C Anghel^{1

6}, Codruta C Popescu¹, Anca Paun¹, Niculina Daniela Hădade⁶, Augustin M Mădălan⁷, Mihaela Matache¹

Affiliations

¹ Research Centre of Applied Organic Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, Faculty of Chemistry, University of Bucharest, 90 Panduri Street, 050663 Bucharest, Romania.
² Department of Research and Development, SC Microsin SRL, 51-63 Pericle Papahagi Street, 032364 Bucharest, Romania.
³ "C. D. Nenitzescu" Institute of Organic and Supramolecular Chemistry of the Romanian Academy, 202B Spl. Independentei, 060023 Bucharest, Romania.
⁴ Faculty of Pharmacy, Titu Maiorescu University, Gh. Sincai Bd. 16, 040317 Bucharest, Romania.
⁵ Department of Physical Chemistry, University of Bucharest, Regina Elisabeta Blvd. 4-12, 030018 Bucharest, Romania.
⁶ Supramolecular Organic and Organometallic Chemistry Centre, Faculty of Chemistry and Chemical Engineering, "Babes-Bolyai" University, 11 Arany Janos Str., 400028 Cluj-Napoca, Romania.
⁷ Inorganic Chemistry Department, Faculty of Chemistry, University of Bucharest, Regina Elisabeta Blvd. 4-12, 030018 Bucharest, Romania.

Abstract

Arylazopyrazoles stand out among the azoheteroarene photoswitches due to their excellent properties in terms of stability of the least stable isomer and conversion between isomers, leading to their use in several interesting applications. We report herein the synthesis of arylazo-trifluoromethyl-substituted pyrazoles and their switching behavior under light irradiation. UV-vis and NMR experiments showed that arylazo-1H-3,5-bis(trifluoromethyl)pyrazoles displayed very long half-lives in DMSO (days), along with reasonable values of other parameters that characterize a photoswitch. Inclusion of naphthyl moieties as aryl counterparts of the arylazopyrazoles is beneficial only in combination with trifluoromethyl groups, while extending the conjugation by grafting the pyrazole moiety with electron-donating or -withdrawing substituents positively affects the photoswitching behavior, in terms of isomerization yield and half-lives of the least stable isomer. The experimental values were correlated with theoretical calculations indicating the valuable influence of the trifluoromethyl groups onto the photoswitching behavior.