التفاصيل البيبلوغرافية
| العنوان: |
Tetranuclear NiII-Mannich base complex with oxygenase, water splitting and ferromagnetic and antiferromagnetic coupling properties. |
| المؤلفون: |
Patra, Arka, Das, Avijit, Sarkar, Abhimanyu, Gómez-García, Carlos J., Sinha, Chittaranjan |
| المصدر: |
Dalton Transactions: An International Journal of Inorganic Chemistry; 8/28/2024, Vol. 53 Issue 32, p13515-13528, 14p |
| مصطلحات موضوعية: |
OXYGEN evolution reactions, ELECTRON paramagnetic resonance spectroscopy, X-ray diffraction measurement, TURNOVER frequency (Catalysis), PHENOXIDES |
| مستخلص: |
A new Mannich base (2-(4-(2-hydroxy-3-methoxy-5-methylbenzyl)-piperazin-1-yl)methyl)-6-methoxy-4-ethylphenol (H2L) and its tetranuclear NiII complex [Ni4L2(μ1,1-Cl)2(H2O)4]Cl2 (compound 1) are characterised using single-crystal X-ray diffraction measurements. Compound 1 contains four different NiII centres in a rhombus-like structure. Two Ni atoms (Ni1 and Ni2) have a NiN2O4 coordination sphere, while the other two (Ni3 and Ni4) have a NiO4Cl2 coordination environment and Ni–Cl–Ni bridges connect them. Ni1 and Ni2 are linked to Ni3 and Ni4 by phenoxide bridges. Variable temperature magnetic susceptibility measurements of 1 indicate the presence of alternating antiferromagnetic coupling (J1 = −6.6(1) cm−1) through the phenoxide bridge along the sides of the rhombus and ferromagnetic coupling (J2 = 8.4(1) cm−1) through the double Cl bridge along the short diagonal of the rhombus with a zero-field splitting of ‖D‖ = 2.7(1) cm−1. Compound 1 shows oxidase (catecholase-like and phenoxazinone synthase-like) activity. The oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) gives 3,5-di-tert-butylquinone (3,5-DTBQ) and H2O2 and the oxidation of o-aminophenol (OAP) produces 2-aminophenoxazin-3-one (APX) and H2O with turnover numbers of 28.32 and 17.52 h−1, respectively, under aerobic conditions. A mechanism for the oxidase activity catalysed by compound 1 is proposed in line with ESI-mass spectrometry, EPR spectroscopy, and electrochemical data. The reaction involves the cleavage of the tetranuclear Ni4-core to form a mononuclear NiII complex in the presence of the substrate (3,5-DTBC/OAP). This NiII complex is reduced to NiI with the concomitant oxidation of the substrate (3,5-DTBQ/APX). Formation of a radical intermediate is confirmed using EPR. In the catecholase-like activity, O2 is reduced to H2O2 while in the phenoxazinone synthase-like activity O2 produces H2O. Compound 1 participated in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in a strongly basic medium with an onset potential of 418 mV and a Tafel slope of 121 mV dec−1 for OER and an onset potential of 477 mV and Tafel slope of 146 mV dec−1 for HER. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
Complementary Index |
