Spectroscopic investigation of photophysics and tautomerism of amino- and nitroporphycenes. Issue 48 (1st December 2022)

• Record Type: Journal Article
• Authors: Mbakara, Idaresit; Gajewska, Agnieszka; Listkowski, Arkadiusz; Kijak, Michał; Nawara, Krzysztof; Kumpulainen, Tatu; Vauthey, Eric; Waluk, Jacek
• Is Part Of: Physical chemistry chemical physics. Volume 24:Issue 48(2022)
• Page Start: 29655
• Page End: 29666
• Publication Date: 2022-12-01
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d2cp04555a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Experiment and theory reveal similarities and differences between porphycenes substituted at the meso position with amino and nitro groups. Abstract : Parent, unsubstituted porphycene and its two derivatives: 2, 7, 12, 17-tetra- n -propylporphycene and 2, 7, 12, 17-tetra- t -butylporphycene were substituted at the meso position with amino and nitro groups. These two families of porphycenes were characterized in detail with respect to their spectral, photophysical, and tautomeric properties. Two trans tautomers of similar energies coexist in the ground electronic state, but only one form dominates in the lowest excited singlet state. Absorption, magnetic circular dichroism (MCD), and emission anisotropy combined with quantum-chemical calculations led to the assignment of S1 and S2 transitions in both tautomers. Compared with the parent porphycene, the S1 –S2 energy gap significantly increases; for one tautomeric form, the effect is twice as large as for the other. Both amino- and nitroporphycenes emit single fluorescence; previously reported dual emission of aminoporphycenes is attributed to a degradation product. Introduction of bulky t -butyl groups leads to a huge decrease in fluorescence intensity; this effect, arising from the interaction of the meso substituent with the adjacent t -butyl moiety, is particularly strong in the nitro derivative.