Experimental and Theoretical Investigations of Magnetic Exchange Pathways in Structurally Diverse Iron(III) Schiff-Base Complexes

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• 作者：Radovan Herchel ; Ivan Nemec ; Marek Machata ; Zden臎k Tr谩vn铆膷ek
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：September 8, 2015
• 年：2015
• 卷：54
• 期：17
• 页码：8625-8638
• 全文大小：888K
• ISSN：1520-510X

文摘

The synthesis, and the structural and magnetic properties, of the following new iron(III) Schiff base complexes with the {O鈥?N,O鈥硙-chelating ligand H₂L (2-hydroxyphenylsalicylaldimine) are reported: K[FeL₂]路H₂O (1), (Pr₃NH)[FeL₂]路2CH₃OH (2), [FeL(bpyO₂) (CH₃OH)][FeL₂]路CH₃OH (3), [Fe₂L₃(CH₃OH)]路2CH₃OH路H₂O (4), and [{Fe₂L₂}(渭鈥揙H)₂{FeL(bpyO₂)}₂][BPh₄]₂路2H₂O (5), where Pr₃NH⁺ represents the tripropylammonium cation and bpyO₂ stands for 2,2鈥?bipyridine-N-dioxide. A thorough density functional theory (DFT) study of magnetic interactions (the isotropic exchange) at the B3LYP/def-TZVP level of theory was employed, and calculations have revealed superexchange pathways through intramolecular/intermolecular noncovalent contacts (蟺鈥撓€ stacking, C鈥揌路路路O and O鈥揌路路路O hydrogen bonds, diamagnetic metal cations) and/or covalent bonds ((渭-O_Ph, 渭-OH) or bis(渭-O_Ph) bridging modes), which helped us to postulate trustworthy spin Hamiltonians for magnetic analysis of experimental data. Within the reported family of compounds 1鈥?b>5, the mediators of the antiferromagnetic exchange can be sorted by their increasing strength as follows: 蟺鈥撓€ stacking (J^DFT = 鈭?.022 cm^鈥?/J^mag = 鈭?.025(4) cm^鈥? in 2) < C鈥揌路路路O contacts and 蟺鈥撓€ stacking (J^DFT = 鈭?.19 cm^鈥?/J^mag = 鈭?.347(9)cm^鈥? in 1) < O鈥揌路路路O hydrogen bonds (J^DFT = 鈭?.53 cm^鈥?/J^mag = 鈭?.41(1) cm^鈥? in 3) < bis(渭-O_Ph) bridge (J^DFT = 鈭?3.8 cm^鈥?/J^mag = 鈭?2.3(9) cm^鈥? in 4) < (渭-O_Ph, 渭-OH) bridge (J^DFT = 鈭?8.0 cm^鈥?/J^mag = 鈭?7.1(2) cm^鈥? in 5), where J^DFT and J^mag are the isotropic exchange parameters derived from DFT calculations, and analysis of the experimental magnetic data, respectively. The good agreement between theoretically calculated and experimentally derived isotropic exchange parameters suggests that this procedure is applicable also for other chemical and structural systems to interpret magnetic data properly.