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Spin state variability in Fe(²⁺) complexes of substituted (2-(pyridin-2-yl)-1,10-phenanthroline) ligands as versatile terpyridine analogues

Title data

Petzold, Holm ; Djomgoue, Paul ; Hörner, Gerald ; Heider, Silvio ; Lochenie, Charles ; Weber, Birgit ; Rüffer, Tobias ; Schaarschmidt, Dieter:
Spin state variability in Fe(²⁺) complexes of substituted (2-(pyridin-2-yl)-1,10-phenanthroline) ligands as versatile terpyridine analogues.
In: Dalton Transactions. Vol. 46 (2017) Issue 19 . - pp. 6218-6229.
ISSN 1477-9234
DOI: https://doi.org/10.1039/C7DT00422B

Abstract in another language

Fe(2+) spin crossover complexes [Fe(L)2](2+) (L = 2-(6-R(1)-pyridin-2-yl)-1,10-phenanthroline with R(1) = H, methoxy, bromo, -(1H-pyrazol-1-yl) or L = 2-(3-methoxy-pyridin-2-yl)-1,10-phenanthroline) were prepared. These air stable and durable complexes show SCO behaviour with very different transition temperatures T1/2 ranging from 130 K to 600 K depending on the substitution pattern. The use of (1)H NMR spectroscopy to elucidate the thermodynamics and kinetics of SCO in a solution of this series is described in detail. By introduction of an additional pyrazole donor (R(1)) in the ortho-position to the pyridine, the N6 octahedral coordination sphere is expanded to N8 coordination with a trigonal dodecahedral structure. This leads to a strong stabilization of the high spin state and an increased longitudinal relaxation R1 of the proton spins. The larger R1 values were ascribed to different electronic structures with non-orbital degenerate quintet ground states and a larger energetic separation from the first excited state. These results are also supported by Mössbauer spectroscopy. The N8 coordination sphere stabilizes the complex in the high spin state and no indication for SCO was found. DFT calculations confirmed the experimentally obtained order of T1/2 and allowed the calculation of the complex structure in experimentally non-accessible spin states. Complexes of this series can be oxidized to the Fe(3+) complexes in a chemically reversible fashion. Interestingly, the lowest oxidation potential was observed for the N8 coordinated complex.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry IV > Chair Anorganic Chemistry IV - Univ.-Prof. Dr. Birgit Weber
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry IV
Result of work at the UBT: No
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 25 Jul 2017 11:14
Last Modified: 25 Jul 2017 11:14
URI: https://eref.uni-bayreuth.de/id/eprint/38799