MonoanionicN,N,O-Scorpionate Ligands and their Iron(II) and Zinc(II) Complexes: Models for Mononuclear Active Sites of Non-Heme Iron Oxidases and Zinc Enzymes

Abstract

The chemical behavior of two bis(3,5‐dialkylpyrazol‐1‐yl)acetic acids and their coordination properties towards ZnCl2 and FeCl2 was studied. Reaction of bis(3,5‐dimethylpyrazol‐1‐yl)acetic acid (bdmpza) (1) with ZnCl2 and FeCl2 gave the 2:1 complexes [(bdmpza)2Zn] (4) and [(bdmpza)2Fe] (5). Crystal structures of both complexes were obtained. In contrast, the sterically more hindered ligand bis(3,5‐di‐tert‐butylpyrazol‐1‐yl)acetic acid (bdtbpza) (3) coordinates only once to zinc(II) resulting in the complex [(bdtbpza)ZnCl] (6). This provides a structural model complex for the active sites of zinc enzymes such as thermolysin or carboxypeptidase. The good agreement with these active sites was demonstrated by a crystal structure of 6. To the best of our knowledge, this is the first report of zinc complexes with a monoanionic N,N,O‐tridentate ligand using a carboxylate O‐donor. Substitution of benzylthiolate for the chloride ligand 6 yielded [(bdtbpza)Zn(SCH2Ph)] (8) indicating that the bulky tert‐butyl groups do not prevent access to the zinc atom. Reaction of bdtbpza (3) with FeCl2 led to [(bdtbpza)FeCl] (7), which might serve as a structural model complex for the active sites of mononuclear non‐heme iron oxidases and oxygenases such as IPNS, DAOCS or CAS.

IR analysis of the carboxylate forms in structurally determined [CuII(κ3-L)2] species isolated from different acidic solutions

“…Hbdmpza and the metal compounds were prepared following previously reported procedures [11][12][13][14]. The single crystals for 2 and 3 were isolated by the same procedure.…”

Synthesis and Cytotoxic Activity Evaluation of New Cu(I) Complexes of Bis(pyrazol-1-yl) Acetate Ligands Functionalized with an NMDA Receptor Antagonist

“…Ligands L NMDA and L 2NMDA were prepared according to the procedure reported in Scheme 1. The acids LH and L 2 H [25,26] were activated with carbonyldiimidazole (CDI) and then treated with the amine NMDA-ANT. After separation and purification by column chromatography, L NMDA and L 2NMDA were obtained in a reasonable yield and purity [45].…”

“…In the search for copper-based anticancer agents [1], over the last few decades, our attention was focused on the design and synthesis of copper complexes of bis(azol-1-yl) carboxylate heteroscorpionate ligands [24][25][26] of general formula [HC(COOH)(az) 2 ], with az = pyrazole or 1,2,4-triazole [27][28][29][30]. Bis(azol-1-yl) carboxylic acids are convenient starting materials for the preparation of conjugated heteroscorpionate systems, due to the κ 3 -NNO coordination behavior of bis(azol-1-yl) methanes and to the presence of a carboxylic function suitable for the coupling with bioactive molecules [31][32][33][34][35][36].…”

Syntheses and Biological Studies of Cu(II) Complexes Bearing Bis(pyrazol-1-yl)- and Bis(triazol-1-yl)-acetato Heteroscorpionate Ligands

“…Among the well-known scorpionates [2,25,26], bis(azol-1-yl)acetate heteroscorpionate ligands of general formula [HC(COOH)(az) 2 ] (az = N -heterocyclic ring), first synthesized in 1999 by A. Otero and coworkers [27] and in 2001 by N. Burzlaff and coworkers [28,29], have recently attracted considerable attention, and their coordination chemistry towards main group and transition metals has been extensively studied [30,31,32].…”