Copper(II) complexes with meclofenamate ligands: Structure, interaction with DNA and albumins, antioxidant and anticholinergic activity

The interaction of copper(II) with the non-steroidal anti-inflammatory drug sodium meclofenamate (Na-mclf) in the presence or absence of the nitrogen-donor co-ligands pyridine (py) or 2,2'-bipyridylamine (bipyam), yielded the novel Cu(II) complexes [Cu₂(mclf-O,O')₄(MeOH)₂]·2MeOH (1·2MeOH), [Cu(mclf-O)₂(py)₃]·H₂O·0.5MeOH (2·H₂O·0.5MeOH) and [Cu(mclf-O,O')₂(bipyam)] (3). The characterization of the complexes was achieved by various techniques, including single-crystal X-ray crystallography. In order to study the binding mode and strength of the complexes to calf-thymus (CT) DNA, various techniques were employed which suggested intercalation between the DNA-bases as the most possible interaction mode. Competitive studies with ethidium bromide (EB) revealed the ability of the complexes to displace the EB from the EB-DNA adduct, verifying the intercalative binding mode. The affinity of the complexes to bovine and human serum albumin proteins (SAs) was investigated by fluorescence emission spectroscopy and the corresponding binding constants bear relatively high values, showing that the complexes bind tightly and possibly reversibly to SAs. The antioxidant activity of the complexes against 1,1-diphenyl-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals and the ability to reduce H₂O₂ proved to be of significant magnitude. The in vitro inhibitory activity against the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) was evaluated, in order to assess the anticholinergic ability of the complexes, which appeared promising.

Highly enantioselective Friedel–Crafts alkylation of N,N-dialkylanilines with trans-β-nitrostyrene catalyzed by a homochiral metal–organic framework

The first enantioselective Friedel–Crafts alkylation of N,N-dialkylanilines with trans-β-nitrostyrene catalyzed by a homochiral MOF afforded the addition products in high yields (∼96%) with excellent ee (∼98%).

Efficient HPLC enantiomer separation using a pillared homochiral metal–organic framework as a novel chiral stationary phase

HPLC enantioseparation of various racemates using novel pillared homochiral MOF–silica composite as chiral stationary phase has been successfully demonstrated.

Enantioselective Diels–Alder reaction in the confined space of homochiral metal–organic frameworks

A novel homochiral porous MOF synthesized using (R)-2,2′-dihydroxy-1,1′-binaphthyl-4,4′-dibenzoic acid was shown to be an effective heterogeneous catalyst for asymmetric Diels–Alder reaction between isoprene and N-ethyl maleimide.

Chirality control of self-assembled achiral nanofibers using amines in their solid state

Although there are numerous examples of helical and spiral conformations in nature, including plant tendrils, snail shells, and even collagen, the occurrence of supramolecular systems that are able to reversibly undergo solid-to-solid helical transformation based on environmental chiral triggers is rare. In this work, we present a supramolecular, non-helical nanofiber which shows a distinct helical rearrangement in the presence of specific diamines and monoamines, such as cyclohexanediamines, alanine, lysine, and phenylalanine, depending on the molecular chirality of the surrounding analytes. A detailed investigation on the structural organization of the nanofibers using SEM and CD spectra analysis confirmed the repeatable and reversible nature of this amplification of chiral information. Further preparation of an electrospun nanofiber film was demonstrated for distinguishing chiral diamines and monoamines in solution by film immersion and CD analysis, which is the first example of amplification of chiral information in the solid-state using electrospun nanofiber films. With this system, we could demonstrate a reusable means for detecting the molecular chirality, which also provided a unique example of reversible control of solid state rearrangement in supramolecular helicity.

Emerging enantiomeric resolution materials with homochiral nano-fabrications

The major scientific challenge of enantiomeric separation is to develop simple, rapid, and sensitive routine analytical methods. Generally, enantio-resolution is still based on "three-point interaction" theory, which indicates that homochiral sites are needed for enantio-selective interaction. However, in recent years, advanced materials with precise homochiral fabrication at the nanoscale have been synthesized, and have shown great potential in development of high-throughput enantio-resolution methods. This tutorial review summarizes fabrication and applications of homochiral materials for enantio-selective recognition and separation. These materials, which include intrinsic and restructured chiral metal surfaces, plasmonic nanostructures, coordination polymers, organic polymer sensors, and molecularly imprinted polymers, have been applied as sensors or chiral stationary phases (CSPs) for efficient enantio-resolution.