Varying Electronic Structures of Diosmium Complexes from Noninnocently Behaving Anthraquinone-Derived Bis-chelate Ligands
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- 作者：Abhishek Mandal ; Anita Grupp ; Brigitte Schwederski ; Wolfgang Kaim ; Goutam Kumar Lahiri
- 刊名：Inorganic Chemistry
- 出版年：2015
- 出版时间：August 17, 2015
- 年：2015
- 卷：54
- 期：16
- 页码：7936-7944
- 全文大小：638K
- ISSN：1520-510X
文摘
The new compounds [(bpy)2OsII(渭-L12鈥?/sup>)OsII(bpy)2](ClO4)2 ([1](ClO4)2) and [(pap)2OsII(渭-L12鈥?/sup>)OsII(pap)2](ClO4)2 ([2](ClO4)2) (H2L1 = 1,4-dihydroxy-9,10-anthraquinone, bpy = 2,2/-bipyridine, and pap = 2-phenylazopyridine) and [(bpy)2OsII(渭-L2鈥⑩€?/sup>)OsII(bpy)2](ClO4)3 ([3](ClO4)3) and [(pap)2OsII(渭-L22鈥?/sup>)OsII(pap)2](ClO4)2 ([4](ClO4)2) (H2L2 = 1,4-diamino-9,10-anthraquinone) have been analytically identified as the meso and rac diastereoisomers, respectively. The paramagnetic [3](ClO4)3 was also characterized by crystal structure determination. In CD3CN solution, [3](ClO4)3 displays rather narrow but widely split (13 > 未 > 鈭? ppm) resonances in the 1H NMR spectrum, yet no EPR signal was observed down to 120 K. Cyclic voltammetry and differential pulse voltammetry reveal several accessible redox states on oxidation and reduction, showing that the replacement of 1,4-oxido by imido donors causes cathodic shifts and that the substitution of bpy by the stronger 蟺-accepting pap ligands leads to a strong increase of redox potentials. Accordingly, system 3n with the lowest (2+/3+) potential was synthetically obtained in the mono-oxidized (3+) form. The (3+) intermediates display small comproportionation constants Kc of about 103 and long-wavelength near-infrared absorptions; an EPR signal with appreciable g splitting (1.84, 1.96, and 2.03) was only observed for 43+, which exhibits the smallest spin density on the osmium centers. An oxidation state formulation [OsIII(渭-L鈥?鈥?/sup>)OsIII]3+ with some [OsII(渭-L2鈥?/sup>)OsIII]3+ contribution was found to best describe the electronic structures. UV鈥搗is鈥揘IR absorption spectra were recorded for all accessible states by OTTLE spectroelectrochemistry and assigned on the basis of TD-DFT calculations. These results and additional EPR measurements suggest rather variegated oxidation state situations, e.g., the pap ligands competing with the bridge L for electrons, while the oxidation produces mixed spin systems with variable metal/ligand contributions.