| Autor: |
Schnaubelt, Linda, Petzold, Holm, Hörner, Gerald, Rüffer, Tobias, Klein, Niels, Lang, Heinrich |
| Předmět: |
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| Zdroj: |
European Journal of Inorganic Chemistry; 2/21/2019, Vol. 2019 Issue 7, p988-1001, 14p |
| Abstrakt: |
Tara‐decorated terpyridines 1–3 and their 1:2 Co2+ [Co(L)2](ClO4)2 (L = 1–3) and Co3+ complexes [Co(L)2](ClO4)2(SbCl6) (L = 1,3) are reported. The solid‐state complex metrics of [Co(3)2]2+ and [Co(1)2]3+ indicate an assignment as spin‐quartet Co2+ or spin‐singlet Co3+, which is in accord with DFT and 1H NMR studies. Vis‐NIR spectra of 1[Co3+(L)2]3+ show characteristic Tara→Co3+ charge‐transfer bands, giving no direct indication of L‐based oxidation events, irrespective of the solvent. Theoretical studies reveal no charge transfer induced spin transition in [Co3+(L)2]3+, although a substantial decrease of the HOMO‐LUMO gap prevails in [Co3+(1)2]3+ as compared with [Co(tpy)2]3+. The destabilisation of the HOMO is not sufficient to allow an equilibration among closed‐ and open‐shell formulations. The computed singlet‐triplet and singlet‐quintet splitting in [Co(1)2]3+ renders these open‐shell formulations to reside only moderately above the ground state. Design criteria are derived from this analysis aiming at a further stabilisation of the open‐shell species through implementation of more strongly electron releasing Tara substituents. Co3+ complexes containing triarylamine‐substituted polypyridyl ligands evince smaller HOMO‐LUMO gaps than the parent 2,2′:6′,2′′‐terpyridine congener. Extended DFT calculations revealed high‐lying triarylamine‐borne donor levels within the examined complexes. The energies of the LUMOs are unaffiliated to the ligand topology. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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