Evaluation of Zn²⁺ Coordination Structures in Chiral Zn²⁺ Complexes Based on Shape Measurement Factors: Relationships between Activity and the Coordination Structure

Abstract

We previously reported on enantioselective aldol reactions of acetone and cyclic ketones with benzaldehyde derivatives catalyzed by chiral Zn 2+ complexes that mimic class II aldolases. The results and mechanistic studies indicated that the catalytic activity of Zn 2+ complexes is dependent not only on the coordination numbers of Zn 2+ but also on its coordination structure. In this study, we report on shape measures (abbreviated as S values in this manuscript) of such Zn 2+ complexes with respect to the 5-coordination structure based on calculations with continuous shape measures (CShM) using their crystal structures. The S values of Zn 2+ ions in Zn 2+ complexes for trigonal bipyramidal (D 3h ) or square pyramidal (C 4v ) [a]

Design, Synthesis, and Biological Evaluation of Boron-Containing Macrocyclic Polyamines and Their Zinc(II) Complexes for Boron Neutron Capture Therapy

“…An interesting finding was that the T m value was raised by 20a (Δ T m = +6 °C at r = 1.0), suggesting that 19b and 20a interact with ctDNA in different modes. It should be noted that coordination sites of Zn 2+ , whose general coordination number is 4–6 (or 7), ,, would be almost occupied by the coordination of five nitrogens from its [15]­aneN 5 ring unit of 20a and hence Lewis acidity of the Zn 2+ ion would be considerably reduced. Therefore, it is considered that these factors would hamper the coordination of 20a with dT – sites in DNA and that 20a interacts with ctDNA mainly by the electrostatic interaction to stabilize the DNA double-strand, as shown in 37 of Scheme . , These data support the efficient DNA damage induced by 10 B-16b , 10 B-19b , 10 B-17a , and 10 B-20a at the close position upon neutron irradiation, as proposed in Scheme .…”