Heterometallic decanuclear [Fe6-Ln4] coordination clusters with enzymatic mimic activity: Synthesis, structures, magnetic properties, and evaluation of catecholase activity

Three [Fe-6-Ln(4)] clusters are isolated through N-methyldiethanolamine (H(2)mdea) and 3,5-dinitrobenzoic acid (Hdnbz) acting as ligands together with sodium azide. The X-ray study demonstrates that these compounds are isostructural formulated as [Fe(6)Ln(4)(mu(4)-O)(2)(mu(3)-OH)(2)(mdea)(6)(dnbz)(8)(N-3)(4)]center dot MeCN center dot aH(2)O center dot bCH(2)Cl(2) (where Ln = Tb (1), a = 2, b = 3; Ho (2), a = 2, b = 2; Er (3), a = 1, b = 1). All these compounds are centrosymmetric in structure. The catecholase activity for the clusters (1-3) was also studied in methanol by ultraviolet-visible spectrophotometry via 3,5-di-tertiarybutyl catechol (3,5-DTBC) employed as a model substrate for the identification of the compounds as a functional model for metalloenzymes. During this study, the parameters for catecholase activity are estimated as K-cat = 1022.12 (1), 827.76 (2), 562.36 (3) h(-1); KM = 0.6858 (1), 0.6467 (2), 0.4872 (3) M; and V-max = 0.2840 (1), 0.2291 (2), 0.1556 (3) M min(-1). In the Fe-4f system, such a type of activity is determined for the first time. The magnetic studies indicate the antiferromagnetic (AF) interactions between the metal centers.

Automated summary

Three [Fe-6-Ln(4)] clusters were obtained using N-methyldiethanolamine and 3,5-dinitrobenzoic acid as ligands with sodium azide. X-ray study revealed that these compounds have the same structure and are centrosymmetric. These clusters also exhibit catecholase activity and serve as functional models for metalloenzymes.