INFLUENCE OF SOLVENT AND PERIPHERAL SUBSTITUTION ON THE SPECTRALLUMINSESCENT CHARACTERISTICS OF THE FREE BASE CORROLES AND THEIR PROTONATED FORMS

UDC 535.37+541.65+543.4

  • Shakel Anton Yur’evich − student. Belarusian State Technological University (13a, Sverdlova str., 220006, Minsk, Republic of Belarus). E-mail: a.shakel@mail.ru

  • Sokhibova Anarkhan Muhfizullokyzy − student. Belarusian State Technological University (13a, Sverdlova str., 220006, Minsk, Republic of Belarus). E-mail: anarxan.soxibova@bk.ru

  • Petrova Darya Vadimovna − PhD (Chemistry), researcher. Institute of Physics of Microstructures of RAS (7, Akademicheskaya Str., Nizhny Novgorod, 603087, Russian Federation); Ivanovo State University of Chemistry and Technology (7, Ave. Sheremetevsky, 153000, Ivanovo, Russian Federation). E-mail: dar.isuct@yandex.ru

  • Semeikin Aleksandr Stanislavovich − Professor, Ivanovo State University of Chemistry and Technology (7, Ave. Sheremetevsky, 153000, Ivanovo, Russian Federation). E-mail: semeikin@isuct.ru

  • Kruk Mikalai Mikalaevich − DSc (Physics and Mathematics), Associate Professor, Head of the Department of Physics. Belarusian State Technological University (13a, Sverdlova str., 220006, Minsk, Republic of Belarus). E-mail: m.kruk@belstu.by

DOI: https://doi.org/10.52065/2520-6141-2022-260-2-36-42

Key words: corrole, peripheral substitution, protonation, fluorescence.

For citation: Shakel A. Yu., Sokhibova A. M., Petrova D. V., Semeikin A. S., Kruk M. M. Influence of solvent and peripheral substitution on the spectral-luminescent characteristics of the free base corroles and their protonated forms. Proceedings of BSTU, issue 3, Physics and Mathematics. Informatics, 2022, no. 2 (260), pp. 36–42 (In Russian). DOI: https://doi.org/10.52065/2520-6141-2022-260-2-36-42.

Abstract

Absorption and fluorescence spectroscopies were used to study the spectral and luminescent characteristics of free bases and protonated forms of two corroles substituted in the  Сb-positions of the macrocycle by alkyl groups. The studied compounds differ in the architecture of peripheral substitution, which allows to control the size of the macrocycle core by changing the  С1–С19 bond length in the dipyrrole fragment. The role of the nature of the solvent in the formation of spectral-luminescent characteristics has been studied. It has been established that the free bases of corroles exhibit weak solvatochromic dependence due to universal interactions during solvation. It was found that the quantum yield of fluorescence in aprotic solvents is higher than in the protic solvent ethanol. In this case the value of the Stokes shift does not change, which indicates the absence of significant differences in the conformational relaxation of the macrocycle upon the  S1 state population. The phenomenon is explained by a shift in the NH-tautomeric equilibrium. When the protonated form is formed in the solution, a hypsochromic shift of the absorption bands in the visible region of the spectrum and a bathochromic shift of the Soret band are observed, in contrast to the corroles substituted by aryl groups in the Сm-positions of the macrocycle, which are characterized by significant bathochromic shifts of all the absorption bands upon protonation. It is shown that the fluorescence quantum yield of the protonated form decreases, and the magnitude of the change depend on the substitution architecture. A corrole with a longer  С1–С19 bond has a 4–5-fold decrease, while a corrole with a shorter  С1–С19 bond has only a twofold decrease. It is proposed to explain the difference by the fact that the relative increase in the probabilities of nonradiative channels of deactivation of the  S1 state, caused by the growth of out-of-plane distortions during protonation, is smaller in the latter case.

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13.05.2022