Ground- and excited-state properties of Re(I) carbonyl complexes - effect of triimine ligand core and appended heteroaromatic groups
| Autor: | Mariola Siwy, Karolina Sulowska, A. Świtlicka, Barbara Machura, Katarzyna Choroba, Sebastian Mackowski, Ewa Schab-Balcerzak, Sonia Kotowicz, Agata Szlapa-Kula, Justyna Grzelak, Anna Maroń |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Process Chemistry and Technology
General Chemical Engineering Quinoline Substituent Triimine ligands 02 engineering and technology Chromophore 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Acceptor 0104 chemical sciences chemistry.chemical_compound Crystallography Femtosecond transient absorption spectroscopy chemistry Electroluminescence Absorption band Excited state Pyridine Re(I) carbonyl complexes 0210 nano-technology HOMO/LUMO Photoluminescence |
| Popis: | In this work, a series of six rhenium(I) complexes bearing 2,2′:6′,2″-terpyridine (terpy), 2,6-di(thiazol-2-yl)pyridine (dtpy), and 2,6-di(pyrazin-2-yl)pyridine (dppy) with appended quinolin-2-yl and N-ethylcarbazol-3-yl groups were prepared and spectroscopically investigated to evaluate the photophysical consequences of both the trisheterocyclic core (terpy, dtpy and dppy) and the heterocyclic substituent. The [ReCl(CO)3(Ln-κ2N)] complexes are regarded as ideal candidates for getting structure–property relationships, while terpy-like framework represents an excellent structural backbone for structural modifications. The replacement of the peripheral pyridine rings of 2,2′:6′,2″-terpyridine by thiazoles and pyrazines resulted in a significant red-shift of the absorption and emission of [ReCl(CO)3(Ln-κ2N)] due to stabilization of the ligand-centred LUMO orbital. Both quinoline and N-ethylcarbazole are extended π-conjugation organic chromophores, but they differ in electron-donating abilities. The low-energy absorption band of Re(I) complexes with the triimine ligands bearing quinolin-2-yl group was contributed by the metal-to-ligand charge-transfer (MLCT) electronic transitions. The introduction of electron-donating N-ethylcarbazol-3-yl substituent into the triimine acceptor core resulted in the change of the character of the HOMO of Re(I) complexes and a significant increase of molar absorption coefficients of the long-wavelength absorption, which was assigned to a combination of 1MLCT and 1ILCT (intraligand charge-transfer) transitions. Regardless of the appended heteroaromatic group, the emitting excited state of Re(I) terpy-based complexes was demonstrated to have predominant 3MLCT character, as evidenced by comprehensive studies including static and time-resolved emission spectroscopy along with ultrafast transient absorption measurements. The diodes with Re(I) complexes dispersed molecularly in a PVK:PBD matrix were emissive and effects of the complex structure on colour of emitted light and its intensity was pronounced. |
| Databáze: | OpenAIRE |
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