Electronic Perturbations of Iron Dipyrrinato Complexes via Ligand [beta]-Halogenation and meso-Fluoroarylation
- Harvard
Systematic electronic variations were introduced into the monoanionic dipyrrinato ligand scaffold via halogenation of the pyrrolic {beta}-positions and/or via the use of fluorinated aryl substituents in the ligand bridgehead position in order to synthesize proligands of the type 1,9-dimesityl-{beta}-R{sub 4}-5-Ar-dipyrrin [R = H, Cl, Br, I; Ar = mesityl, 3,5-(F{sub 3}C){sub 2}C{sub 6}H{sub 3}, C{sub 6}F{sub 5} in ligand 5-position; {beta} = 2,3,7,8 ligand substitution; abbreviated ({sup {beta},Ar}L)H]. The electronic perturbations were probed using standard electronic absorption and electrochemical techniques on the different ligand variations and their divalent iron complexes. The free-ligand variations cause modest shifts in the electronic absorption maxima ({lambda}{sub max}: 464-499 nm) and more pronounced shifts in the electrochemical redox potentials for one-electron proligand reductions (E{sub 1/2}: -1.25 to -1.99 V) and oxidations (E{sub 1/2}: +0.52 to +1.14 V vs [Cp{sub 2}Fe]{sup +/0}). Installation of iron into the dipyrrinato scaffolds was effected via deprotonation of the proligands followed by treatment with FeCl{sub 2} and excess pyridine in tetrahydrofuran to afford complexes of the type ({sup {beta},Ar}L)FeCl(py) (py = pyridine). The electrochemical and spectroscopic behavior of these complexes varies significantly across the series: the redox potential of the fully reversible Fe{sup III/II} couple spans more than 400 mV (E{sub 1/2}: -0.34 to +0.50 V vs [Cp{sub 2}Fe]{sup +/0}); {lambda}{sub max} spans more than 40 nm (506-548 nm); and the {sup 57}Fe Moessbauer quadrupole splitting (|{Delta}E{sub Q}|) spans nearly 2.0 mm/s while the isomer shift ({delta}) remains essentially constant (0.86-0.89 mm/s) across the series. These effects demonstrate how peripheral variation of the dipyrrinato ligand scaffold can allow systematic variation of the chemical and physical properties of iron dipyrrinato complexes.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- NSFUNIVERSITY
- OSTI ID:
- 1049577
- Journal Information:
- Inorg. Chem., Vol. 50, Issue (14) ; 07, 2011; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- ENGLISH
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