The tendency of the charge transfer system, derived from chloranilic acid and 2-amino-2-(hydroxymethyl)-1,3-propanediol towards copper(II) complex-formation: characterization, anion impact, and biological studies

Synthesis, characterization, DNA binding interactions, DFT calculations, and Covid-19 molecular docking of novel bioactive copper(I) complexes developed via unexpected reduction of azo-hydrazo ligands

In this work, we focused on the 3rd goal of the sustainable development plan: achieving good health and supporting well-being. Two redox-active hydrazo ligands namely, phenylcarbonohydrazonoyldicyanide (PCHD) and pyridin-4-ylcarbonohydrazonoyl-dicyanide (PyCHD), and their copper(I) complexes have been synthesized and characterized. The analytical data indicates the formation of copper(I) complexes despite starting with copper(II) perchlorate salt. The 1H-NMR and UV-visible spectral studies in DMSO revealed that PyCHD mainly exists in its azo-form, while PCHD exists in azo ↔ hydrazo equilibrium form, and confirmed the copper(I) oxidation state. XPS, spectral and electrochemistry data indicated the existence of copper(I) valence of both complexes. Cyclic voltammetry of PCHD and its copper(I) complex supported the reduction power of the ligand. The antimicrobial activity, cytotoxicity against the mammalian breast carcinoma cell line (MCF7), and DNA interaction of the compounds are investigated. All compounds showed high antimicrobial, and cytotoxic activities, relative to the standard drugs. Upon studying the wheat DNA binding, PCHD and PyCHD were found to bind through external contacts, while both [Cu(PCHD)2]ClO4.H2O and [Cu(PyCHD)2]ClO4.H2O were intercalated binding. In-silico molecular docking simulations against Estrogen Receptor Alpha Ligand Binding Domain (ID: 6CBZ) were performed on all produced compounds and confirmed the invitro experimentally best anticancer activity of [Cu(PyCHD)2]ClO4.H2O. The molecular docking tests against SARS-CoV-2 main protease (ID: 6 WTT) showed promising activity in the order of total binding energy values: [Cu(PCHD)2]ClO4.H2O > [Cu(PyCHD)2]ClO4.H2O > PCHD > PyCHD.

Thermally induced charge transfer in a quinoid-bridged linear Cu3 compound

Charge transfer always occurs in molecular valence tautomers, leading to the redistribution of electron density and exhibiting electrical, optical, and magnetic properties, and can be further controlled by multiple external stimuli such as temperature, light and electric field. The design of molecule-based materials capable of charge transfer remains a challenge. Herein, a linear Cu₃ compound [(CH₃)₃NCH₂CH₂Br]₂[Cu₃L₄(H₂O)₂] (H₂L = chloranilic acid) (1) with a multi-center donor-acceptor architecture was constructed using the redox-active chloranilic acid quinoid ligand. Temperature-dependent dielectric measurement was performed to capture the charge transfer valence tautomer transition because it is difficult to detect this transition by crystal structure and magnetism analysis. Temperature-dependent XPS and EPR further confirmed that the charge transfer valence tautomer transition is based on the Cu^II-L^2- to Cu^I-L^-˙ multi-center charge transfer. Thus, the present work builds a charge transfer compound with a multi-center donor-acceptor architecture and proves that dielectric measurement is a very effective means to detect charge transfer.