Synthesis, Photophysical and Electrochemical Studies of Β-Disubstituted Silver Corroles

Abstract

β-Substituted corroles have been widely used in variety of applications and exhibit unique electronic and photophysical properties [1]. π-Extension at the β-position using functional groups such as phenylethynyl or pyrrolopyrazino induces intriguing stability and planarity of the macrocyclic core [2]. Keeping this in mind, a series of β-disubstituted silver tritolylcorroles (R2[TTC]Ag) have been synthesized via Pd-catalyzed reactions in good to excellent yields (Fig. 1a). Herein we are trying to investigate the effect of the various β-substituents such as methyl (Me), phenyl (Ph), methyl acrylate (MA) and phenylethynyl (PE) on photophysical and electrochemical properties. In cyclic voltammetric studies, the first oxidation potential of Me2[TTC]Ag 2 decreases (cathodic shift) by 70 mV compared to [TTC]Ag due the inductive effect of two methyl groups while in case of (MA)2[TTC]Ag 4, there is large anodic shift (170 mV) in the first oxidation potential probably due to strong electron withdrawing effect of two methyl acrylate group compared to 2 (Fig. 1b). Complex 4 depicted very high dipole moment (10.31 D), which could be utilized in NLO studies (Fig. 1c). We have investigated the effect of both electron-accepting and -donating substituents through single, double and triple bond on the macrocyclic ring using photophysical, theoretical and electrochemical studies. Complexes (2-5) exhibited remarkable broadening and increase in the intensity of red shifts of soret and Q bands of absorption spectra. Here, we have synthesized corroles with side extension of π-arm which helps in shifting of Q bands towards NIR region which could be helpful in PDT or optoelectronic applications. Figure 1. (a) Molecular structures of R2[TTC]Ag; (b) Comparative Cyclic voltammograms (CVs) of [TPC]Ag, Me2[TTC]Ag and MA2[TTC]Ag complexes in CH2Cl2 at 298 K under argon atmosphere; (c) The directions of calculated dipole moment of MA2[TTC]Ag. References (a) R. Mishra, B. Basumatary, R. Singhal, G. D. Sharma and J. Sankar, ACS Appl. Mater. Interfaces 2018, 10, 31462–31471; (b) S. Gonglach, S. Paul, M. Haas, F. Pillwein, S. S. Sreejith, S. Barman, R. De, S. Müllegger, P. Gerschel, U. P. Apfel, H. Coskun, A. Aljabour, P. Stadler, W. Schöfberger and S. Roy, Commun. 2019, 10, 1–10; (c) W. Sinha, A. Mahammed, N. Fridman, Z. Gross, ACS Catal., 2020, 10, 3764–3772; (d) R. F. Einrem, A. B. Alemayehu, S. M. Borisov, A. Ghosh, O. A. Gederaas, ACS Omega 2020, 5, 10596–10601.(a) P. Yadav, M. Sankar, X. Ke, L. Cong, K. M. Kadish, Dalton Trans. 2017, 46, 10014–10022; (b) M. Stefanelli, M. L. Naitana, M. Chiarini, S. Nardis, A. Ricci, F. R. Fronczek, C. Lo Sterzo, K. M. Smith, R. Paolesse, J. Org. Chem. 2015, 2015, 6811–6816; (c) B. Berionni Berna, S. Nardis, P. Galloni, A. Savoldelli, M. Stefanelli, F. R. Fronczek, K. M. Smith, R. Paolesse, Org. Lett. 2016, 18, 3318–3321. Figure 1