Assessment of the intramolecular magnetic interactions in the highly saddled iron(iii) porphyrin π-radical cations: the change from planar to saddle conformations. Issue 36 (4th September 2019)

• Record Type: Journal Article
• Authors: Chen, Ching-Chin; Wu, Yi-Wen; Nakamura, Mikio; Cheng, Ru-Jen; Tseng, Tzu-Hsien; Chen, Peter P.-Y.
• Is Part Of: Dalton transactions. Volume 48:Issue 36(2019)
• Page Start: 13820
• Page End: 13833
• Publication Date: 2019-09-04
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt02714a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The intramolecular magnetic interactions in one-electron oxidized iron(iii ) porphyrin π-radical cations with planar and saddle conformations have been compared by means of a variety of spectroscopic, physical methods and unrestricted DFT calculations. Abstract : The intramolecular magnetic interactions in one-electron oxidized iron(iii ) porphyrin π-radical cations, [Fe(OETPP˙)Cl][SbCl6 ] (1 ), [Fe(OMTPP˙)Cl][SbCl6 ] (2 ) and [Fe(TPP˙)Cl][SbCl6 ] (3 ), have been compared by means of X-ray crystallography, SQUID magnetometry, cyclic voltammetry, UV-Vis spectroelectrochemical analysis, NMR spectroscopy analysis and unrestricted DFT calculations. Unlike a generally recognized antiferromagnetic coupling d xy ↑ d xz ↑ d yz ↑ d z 2 ↑ d x 2 − y 2 ↑ P˙ + (a2u ) ↓ ( S = 2) state via a weak bonding interaction as in (3 ), we have disclosed that a strong bonding interaction among iron d x 2 − y 2 and porphyrin a2u orbitals forms in (1 ) into a highly delocalized Ψπ = [P˙ + (a2u ) + Fe III (d x 2 − y 2, d z 2 )] orbital that is able to accommodate two spin-paired electrons to form the Ψπ 2 d xy 1 d xz 1 d yz 1, d z 2 1 ( S = 2) ground state. Concurrently, the spin polarization effect is exerted on the paired spins in the Ψπ orbital by magnetic induction from the remaining unpaired electrons in the iron d orbitals. The interpretation mentioned above is further verified by the diamagnetic nature of the saddled copper(ii ) porphyrin π-cation radical, Cu II (OETPP˙)(ClO4 ) ( S = 0), where the strong bonding interaction leads to the Ψπ 2 d xy 2 d xz 2 d yz 2 d z 2 2 ( S = 0) ground state but no spin polarization exists. Thus, the magnetic nature of the iron(iii ) porphyrin π-radical cation is tuneable by saddling the ring planarity.