Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials

A series of four heterocyclic dimers has been synthesized, with twisted geometries imposed across the central linking bond by ortho‐alkoxy chains. These include two isomeric bicarbazoles, a bis(dibenzothiophene‐S,S‐dioxide) and a bis(thioxanthene‐S,S‐dioxide). Spectroscopic and electrochemical metho...

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Main Authors: Iain Wright, Andrew Danos, Stephanie Montanaro, Andrei S Batsanov, Andrew P Monkman, Martin R Bryce
Format: Default Article
Published: 2021
Subjects:
Heterocycles
Photophysics
OLED
Triplet
Dihedral angle
Online Access:https://hdl.handle.net/2134/14034803.v1
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author Iain Wright
Andrew Danos
Stephanie Montanaro
Andrei S Batsanov
Andrew P Monkman
Martin R Bryce
author_facet Iain Wright
Andrew Danos
Stephanie Montanaro
Andrei S Batsanov
Andrew P Monkman
Martin R Bryce
author_sort Iain Wright (3281406)
collection Figshare
description A series of four heterocyclic dimers has been synthesized, with twisted geometries imposed across the central linking bond by ortho‐alkoxy chains. These include two isomeric bicarbazoles, a bis(dibenzothiophene‐S,S‐dioxide) and a bis(thioxanthene‐S,S‐dioxide). Spectroscopic and electrochemical methods, supported by density functional theory, have given detailed insights into how para‐ vs. meta‐ vs. broken conjugation, and electron‐rich vs. electron‐poor heterocycles impact the HOMO‐LUMO gap and singlet and triplet energies. Crucially for applications as OLED hosts, the triplet energy (ET) of these molecules was found to vary significantly between dilute polymer films and neat films, related to conformational demands of the molecules in the solid state. One of the bicarbazole species shows a variation in ET of 0.24 eV in the different media – sufficiently large to “make‐or‐break” an OLED device – with similar discrepancies found between neat films and frozen solution measurements of other previously reported OLED hosts. From consolidated optical and optoelectronic investigations of different host/dopant combinations, we identify that only the lower ET values measured in neat films give a reliable indicator of host/guest compatibility. This work also provides new molecular design rules for obtaining very high ET materials and controlling their HOMO and LUMO energies.
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publishDate 2021
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spelling rr-article-140348032021-03-10T00:00:00Z Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials Iain Wright (3281406) Andrew Danos (1362450) Stephanie Montanaro (4235410) Andrei S Batsanov (10143587) Andrew P Monkman (10143590) Martin R Bryce (10143593) Heterocycles Photophysics OLED Triplet Dihedral angle A series of four heterocyclic dimers has been synthesized, with twisted geometries imposed across the central linking bond by ortho‐alkoxy chains. These include two isomeric bicarbazoles, a bis(dibenzothiophene‐S,S‐dioxide) and a bis(thioxanthene‐S,S‐dioxide). Spectroscopic and electrochemical methods, supported by density functional theory, have given detailed insights into how para‐ vs. meta‐ vs. broken conjugation, and electron‐rich vs. electron‐poor heterocycles impact the HOMO‐LUMO gap and singlet and triplet energies. Crucially for applications as OLED hosts, the triplet energy (ET) of these molecules was found to vary significantly between dilute polymer films and neat films, related to conformational demands of the molecules in the solid state. One of the bicarbazole species shows a variation in ET of 0.24 eV in the different media – sufficiently large to “make‐or‐break” an OLED device – with similar discrepancies found between neat films and frozen solution measurements of other previously reported OLED hosts. From consolidated optical and optoelectronic investigations of different host/dopant combinations, we identify that only the lower ET values measured in neat films give a reliable indicator of host/guest compatibility. This work also provides new molecular design rules for obtaining very high ET materials and controlling their HOMO and LUMO energies. 2021-03-10T00:00:00Z Text Journal contribution 2134/14034803.v1 https://figshare.com/articles/journal_contribution/Conformational_dependence_of_triplet_energies_in_rotationally_hindered_N_and_S_heterocyclic_dimers_new_design_and_measurement_rules_for_high_triplet_energy_OLED_host_materials/14034803 CC BY 4.0
spellingShingle Heterocycles
Photophysics
OLED
Triplet
Dihedral angle
Iain Wright
Andrew Danos
Stephanie Montanaro
Andrei S Batsanov
Andrew P Monkman
Martin R Bryce
Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials
title Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials
title_full Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials
title_fullStr Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials
title_full_unstemmed Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials
title_short Conformational dependence of triplet energies in rotationally‐hindered N‐ and S‐heterocyclic dimers: new design and measurement rules for high triplet energy OLED host materials
title_sort conformational dependence of triplet energies in rotationally‐hindered n‐ and s‐heterocyclic dimers: new design and measurement rules for high triplet energy oled host materials
topic Heterocycles
Photophysics
OLED
Triplet
Dihedral angle
url https://hdl.handle.net/2134/14034803.v1

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