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

Abstract 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 ( μ 4 ‐O) 2 ( μ 3 ‐OH) 2 (mdea) 6 (dnbz) 8 (N 3 ) 4 ]·MeCN· a H 2 O· b CH 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–4 f system, such a type of activity is determined for the first time. The magnetic studies indicate the antiferromagnetic (AF) interactions between the metal centers.

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