Advanced Magnetic Resonance Studies of Tetraphenylporphyrinatoiron(III) Halides
- PDF / 2,271,981 Bytes
- 22 Pages / 439.37 x 666.142 pts Page_size
- 40 Downloads / 161 Views
Applied Magnetic Resonance
ORIGINAL PAPER
Advanced Magnetic Resonance Studies of Tetraphenylporphyrinatoiron(III) Halides Pagnareach Tin, et al. [full author details at the end of the article] Received: 9 June 2020 / Revised: 23 July 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract High-Frequency and -Field EPR (HFEPR) studies of Fe(TPP)X (X = F, Cl, Br; I, TPP2−= meso-tetraphenylporphyrinate dianion) and far-IR magnetic spectroscopic (FIRMS) studies of Fe(TPP)Br and Fe(TPP)I have been conducted to probe magnetic intra- and inter-Kramers doublet transitions in these S = 5/2 metalloporphyrin complexes, yielding zero-field splitting (ZFS) and g parameters for the complexes: Fe(TPP)F, D = +4.67(1) cm−1, E = 0.00(1) cm−1, g⊥ = 1.97(1), g|| = 2.000(5) by HFEPR; Fe(TPP)Cl, D = +6.458(2) cm−1, E = +0.015(5) cm−1, E/D = 0.002, g⊥ = 2.004(3), g|| = 2.02(1) by HFEPR; Fe(TPP)Br, D = +9.03(5) cm−1, E = +0.047(5) cm−1, E/D = 0.005, giso = 1.99(1) by HFEPR and D = +9.05 cm−1, giso = 2.0 by FIRMS; Fe(TPP)I, D = +13.84 cm−1, E = +0.07 cm−1, E/D = 0.005, giso = 2.0 by HFEPR and D = +13.95 cm−1, giso = 2.0 by FIRMS (the sign of E was in each case arbitrarily assigned as that of D). These results demonstrate the complementary nature of field- and frequency-domain magnetic resonance experiments in extracting with high accuracy and precision spin Hamiltonian parameters of metal complexes with S > 1/2. The spin Hamiltonian parameters obtained from these experiments have been compared with those obtained from other physical methods such as magnetic susceptibility, magnetic Mössbauer spectroscopy, inelastic neutron scattering (INS), and variable-temperature and -field magnetic circular dichroism (VT-VH MCD) experiments. INS, Mössbauer and MCD give good agreement with the results of HFEPR/FIRMS; the others not as much. The electronic structure of Fe(TPP)X (X = F, Cl, Br, I) was studied earlier by multi-reference ab initio methods to explore the origin of the large and positive D-values, reproducing the trends of D from the experiments. In the current work, a simpler model based on Ligand Field Theory (LFT) is used to explain qualitatively the trend of increasing ZFS from X = F to Cl to Br and to I as the axial ligand. Tetragonally elongated high-spin d5 systems Dedicated to Prof. Dante Gatteschi, Università degli Studi di Firenze, on the occasion of his birthday and in recognition of his contribution to the fields of molecular magnetism and magnetic resonance, and many years of service to the respective communities. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s0072 3-020-01236-8) contains supplementary material, which is available to authorized users.
13
Vol.:(0123456789)
P. Tin et al.
Scheme 1 Structures of Fe(TPP)X series of compounds
such as Fe(TPP)X exhibit D > 0, but X plays a key role. Spin delocalization onto X means that there is a spin–orbit coupling (SOC) contribution to D from X •, as − • opposed to none from closed-she
Data Loading...
