Preprint Article Version 1 This version is not peer-reviewed

Excited-State Dynamics of Room-Temperature Phosphorescent Organic Materials Based on Monobenzil and Bisbenzil Frameworks

Version 1 : Received: 25 July 2020 / Approved: 26 July 2020 / Online: 26 July 2020 (02:44:23 CEST)

How to cite: Maduwantha, K.; Yamada, S.; Koswattage, K.R.; Konno, T.; Hosokai, T. Excited-State Dynamics of Room-Temperature Phosphorescent Organic Materials Based on Monobenzil and Bisbenzil Frameworks. Preprints 2020, 2020070631 (doi: 10.20944/preprints202007.0631.v1). Maduwantha, K.; Yamada, S.; Koswattage, K.R.; Konno, T.; Hosokai, T. Excited-State Dynamics of Room-Temperature Phosphorescent Organic Materials Based on Monobenzil and Bisbenzil Frameworks. Preprints 2020, 2020070631 (doi: 10.20944/preprints202007.0631.v1).

Abstract

Room-temperature phosphorescent (RTP) materials have been attracted tremendous interest owing to their unique material characteristics and potential applications for state-of-the-art optoelectronic devices. Recently, we have reported a synthesis and fundamental photophysical properties of new RTP materials based on benzil, i.e., fluorinated monobenzil derivative and fluorinated and non-fluorinated bisbenzil derivative analogues [Yamada, S. et al, Beilstein J. Org. Chem. 2020, 16, 1154–1162.]. To further understand their RTP properties, here we investigated the excited-state dynamics and photostability of the derivatives by means of time-resolved and steady-state photoluminescence spectroscopies. For these derivatives, clear RTP emissions with lifetimes on the microsecond timescale were identified. Among them, the monobenzil derivative was found to be the most efficient RTP material, showing both the longest lifetime and highest amplitude RTP emission. Time-resolved photoluminescence spectra measured at 77 K and density functional theory calculations revealed the existence of a second excited triplet state in the vicinity of the first excited singlet state for the monobenzil derivative, indicative of the presence of a fast intersystem crossing pathway. A discussion of the correlation between the excited state dynamics, emission properties, and conformational flexibility of the three derivatives is presented.

Subject Areas

room temperature phosphorescence; organic molecule; excited state dynamics; time-resolved photoluminescence spectroscopy; photostability

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