Synthesis and characterization of a 13-member macrocycle functionalized by tyramine arms: Complexation with Cu2+ and antioxidant capacity

A Practical Synthesis of Macrocyclic Schiff Base Bearing Hydroxyethyl Pendants Utilizing Solubility Discrepancies

Abstract:

Six macrocyclic Schiff bases bearing hydroxyethyl pendants have been synthesized in high yields via [2 + 2] condensation between the rigid dialdehydes and 2-[bis(2-aminoethyl)amino]ethanol or 1-[bis(2-aminoethyl)amino]-2-propanol at 0 oC for 12 hours in the CH3CN/H2O mixture. Solubility discrepancies between macrocyclic products and raw materials in selected solvents enable a facile separation and high yields, avoiding any intractable chromatographic purification. This straightforward synthetic protocol provides a relatively facile resolution with potential widespread applications for the synthesis of Schiff bases.

Comparative Studies of Structures and Peroxidase-like Activities of Copper(II) and Iron(III) Complexes with an EDTA-Based Phenylene-Macrocycle and Its Acyclic Analogue

With the objective of studying the conformational and macrocyclic effects of selected metal chelates on their peroxidase activities, Cu²⁺ and Fe³⁺ complexes were synthesized with a macrocyclic derivative of ethylenediaminetetraacetic acid and o-phenylenediamine (abbreviated as edtaodH₂) and its new open-chain analogue (edtabzH₂). The Fe³⁺ complex of edtaodH₂ has a peroxidase-like activity, whereas the complex of edtabzH₂ does not. The X-ray study of the former shows the formation of a dimeric molecule {[Fe(edtaod)]₂O} in which each metal with an octahedral coordination is overposed over the macrocyclic cavity, as a result of rigid macrocyclic frame, to form an Fe-O-Fe bridge; the exposure of the central metal to the environment facilitates the capture of oxygen to drive the biomimetic activity. The peroxidase-inactive Fe³⁺ complex consists of a mononuclear complex ion [Fe(edtabz)(H₂O)]⁺, the metal ion of which is suited in a distorted pentagonal bipyramid to be protected from environmental oxygen. The copper(II) complexes, which have mononuclear structures with high thermodynamic stability compared with the iron(III) complexes, show no peroxidase activity. The steric effects play a fundamental role in the biomimetic activity.

Copper(ii) complexes based on tripodal pyridyl amine derivatives as efficient anticancer agents

The in vitro cytotoxicity of a series of chlorido-Cu(ii) complexes based on tripod pyridyl N4-donor derivatives revealed significant-to-moderate cytotoxicity against human cancer cell lines with the best results obtained for [Cu(BQPA)Cl]ClO₄/PF₆ (5-ClO4/PF6) with IC₅₀ values of 4.7–10.8 μM.