Singlet-Triplet Inversion in Triangular Boron Carbon Nitrides

03 June 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The discovery of singlet-triplet (ST) inversion in some π-conjugated triangle-shaped boron carbon nitrides is a remarkable breakthrough that defies Hund’s first rule. Deeply rooted in strong electron-electron interactions, ST inversion has garnered significant interest due to its potential to revolutionize triplet harvesting in organic LEDs. Using the well-established Pariser-Parr-Pople model for correlated electrons in π-conjugated systems, we employ a combination of CISDT and RASCI calculations to investigate the photophysics of several triangular boron carbon nitrides. Our findings reveal that ST inversion in these systems is primarily driven by a network of alternating electron- donor and electron-acceptor groups in the molecular rim, rather than by the triangular molecular structure itself.

Keywords

singlet triplet inversion
tadf
oled
triangulenes
borazine
pariser-parr-pople model
pi-conjugated systems

Supplementary materials

Title
Description
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Title
Electronic Supporting Information
Description
Electronic Supplementary Information (SI) available: Sec. S1 contains the PPP model in the Hartree-Fock approximation; Sec. S2 collects information on the basis set dimension and computation timings; Sec. S3 collects additional results obtained for different model parameters values as well as different molecular geometries (i.e., angles and bond lengths); Sec. S4 collects optical spectra calculated for the systems in Fig. 6.
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