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Luminescent halogen-substituted 2-(N-arylimino)pyrrolyl boron complexes: the internal heavy-atom effect

Rodrigues, Ana I.; Krishnamoorthy, Paramasivam; Gomes, Clara S.B.; Carmona, Nicolas; Di Paolo, Roberto E.; Pander, Piotr; Pina, João; Sérgio Seixas de Melo, J.; Dias, Fernando B.; Calhorda, Maria José; Maçanita, António L.; Morgado, Jorge; Gomes, Pedro T.

Luminescent halogen-substituted 2-(N-arylimino)pyrrolyl boron complexes: the internal heavy-atom effect Thumbnail


Authors

Ana I. Rodrigues

Paramasivam Krishnamoorthy

Clara S.B. Gomes

Nicolas Carmona

Roberto E. Di Paolo

João Pina

J. Sérgio Seixas de Melo

Maria José Calhorda

António L. Maçanita

Jorge Morgado

Pedro T. Gomes



Abstract

A group of new boron complexes [BPh2{2N,N’-NC4H3-2-C(H)=N-C6H4X}] (X= 4-Cl 4c, 4-Br 4d, 4-I 4e, 3-Br 4f, 2-Br 4g, 2-I 4h) containing different halogens as substituents in the N-aryl ring have been synthesized and characterized in terms of their molecular properties. Their photophysical characteristics have been thoroughly studied in order to understand whether these compounds exhibit internal heavy atom effect. Phosphorescence emission was found for some of the synthesized halogen-substituted boron molecules, in particular for 4g and 4h. DFT and TDDFT calculations showed that the lower energy absorption band resulted from the HOMO to LUMO (-*) transition, except for 2-I 4h, where the HOMO-1 to LUMO transition was also involved. The strong participation of iodine orbitals in HOMO-1 is reflected on the calculated absorption spectra of the iodine derivatives, especially 2-I 4h, when spin-orbit coupling (SOC) was included. Organic light-emitting diodes (OLEDs) based on these compounds, in the neat form or dispersed in a matrix, were also fabricated and tested. The devices based on films prepared by thermal vacuum deposition showed the best performance. When neat compounds were used, a maximum luminance (Lmax) of 1812 cd m-2 was obtained, with maximum external quantum efficiency (EQEmax) of 0.15%. An EQEmax of ca. 1% along with a maximum luminance of 494 cd m-2 were obtained for a device fabricated by co-deposition of the boron complex and a host compound (1,3-bis(N-carbazolyl)benzene, mCP).

Citation

Rodrigues, A. I., Krishnamoorthy, P., Gomes, C. S., Carmona, N., Di Paolo, R. E., Pander, P., …Gomes, P. T. (2020). Luminescent halogen-substituted 2-(N-arylimino)pyrrolyl boron complexes: the internal heavy-atom effect. Dalton Transactions, 49(29), 10185-10202. https://doi.org/10.1039/d0dt01845g

Journal Article Type Article
Acceptance Date Jun 29, 2020
Online Publication Date Jun 29, 2020
Publication Date 2020-08
Deposit Date Aug 16, 2020
Publicly Available Date Jun 29, 2021
Journal Dalton Transactions
Print ISSN 1477-9226
Electronic ISSN 1477-9234
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 49
Issue 29
Pages 10185-10202
DOI https://doi.org/10.1039/d0dt01845g

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