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Predictable Electronic Tuning By Choice of Azine Substituent in Five Iron(II) Triazoles: Redox Properties and DFT Calculations
Author(s) -
RodríguezJiménez Santiago,
Bondì Luca,
Yang Mingrui,
Garden Anna L.,
Brooker Sally
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201801537
Subject(s) - azine , pyridazine , chemistry , pyrazine , pyridine , redox , cyclic voltammetry , crystallography , ligand (biochemistry) , substituent , medicinal chemistry , pyrimidine , stereochemistry , inorganic chemistry , electrochemistry , biochemistry , receptor , electrode
Five new mononuclear iron(II) tris ‐ligand complexes, and four solvatomorphs, have been made from the azine‐substituted 1,2,4‐triazole ligands ( L azine ): [Fe II ( L pyridazine ) 3 ](BF 4 ) 2 ( 1 ), [Fe II ( L pyrazine ) 3 ](BF 4 ) 2 ( 2 ), [Fe II ( L pyridine ) 3 ](BF 4 ) 2 ( 3 ), [Fe II ( L 2pyrimidine ) 3 ](BF 4 ) 2 ( 4 ), and [Fe II ( L 4pyrimidine ) 3 ](BF 4 ) 2 ( 5 ). Single‐crystal XRD and solid‐state magnetometry reveal that all of them are low‐spin (LS) iron(II), except for solvatomorph 5 ⋅4 H 2 O. Evans method NMR studies in CD 2 Cl 2 , (CD 3 ) 2 CO and CD 3 CN show that all are LS in these solvents, except 5 in CD 2 Cl 2 (consistent with L 4pyrimidine imposing the weakest field). Cyclic voltammetry in CH 3 CN vs. Ag/0.01 m AgNO 3 reveals an, at best quasi‐reversible, Fe III/II redox process, with E pa increasing from 0.69 to 0.99 V as the azine changes: pyridine< pyridazine<2‐pyrimidine<4‐pyrimidine< pyrazine. The observed E pa values correlate linearly with the DFT calculated HOMO energies for the LS complexes.