Coordination chemistry of mixed pyridine-phenol ligands; mononuclear palladium(II) and dinuclear copper(II) complexes of derivatives of bidentate N,O-chelating ligands based on 2-(2-hydroxyphenyl)pyridine

Organometallic Ru(II), Rh(III) and Re(I) complexes of sterane-based bidentate ligands: synthesis, solution speciation, interaction with biomolecules and anticancer activity

In this study, we present the synthesis, characterization and in vitro cytotoxicity of six organometallic [Ru(II)(η6-p-cymene)(N,N)Cl]Cl, [Rh(III)(η5-C5Me5)(N,N)Cl]Cl and [Re(I)(CO)3(N,N)Cl] complexes, in which the (N,N) ligands are sterane-based 2,2'-bipyridine derivatives (4-Me-bpy-St-OH, 4-Ph-bpy-St-OH). The solution chemical behavior of the ligands and the complexes was explored by UV-visible spectrophotometry and 1H NMR spectroscopy. The ligands and their Re(I) complexes are neutral at pH = 7.40; this contributes to their highly lipophilic character (log D7.40 > +3). The Ru(II) and Rh(III) half-sandwich complexes are much more hydrophilic, and this property is greatly affected by the actual chloride ion content of the medium. The half-sandwich Ru and Rh complexes are highly stable in 30% (v/v) DMSO/water (<5% dissociation at pH = 7.40); this is further increased in water. The Rh(III)(η5-C5Me5) complexes were characterized by higher water/chloride exchange and pKa constants compared to their Ru(II)(η6-p-cymene) counterparts. The Re(I)(CO)3 complexes are also stable in solution over a wide pH range (2-12) without the release of the bidentate ligand; only the chlorido co-ligand can be replaced with OH- at higher pH values. A comprehensive discussion of the binding affinity of the half-sandwich Ru(II) and Rh(III) complexes toward human serum albumin and calf-thymus DNA is also provided. The Ru(II)(η6-p-cymene) complexes interact with human serum albumin via intermolecular forces, while for the Rh(III)(η5-C5Me5) complexes the coordinative binding mode is suggested as well. They are also able to interact with calf-thymus DNA, most likely via the coordination of the guanine nitrogen. The Ru(II)(η6-p-cymene) complexes were found to be the most promising among the tested compounds as they exhibited moderate-to-strong cytotoxic activity (IC50 = 3-11 μM) in LNCaP as well as in PC3 prostate cells in an androgen receptor-independent manner. They were also significantly cytotoxic in breast and colon adenocarcinoma cancer cell lines and showed good selectivity for cancer cells.

Investigation of Taniaphos as a chiral selector in chiral extraction of amino acid enantiomers

Finding chiral selector with high stereoselectivity to a variety of amino acid enantiomers remains a challenge and warrants further research. In this work, Taniaphos, a chiral ligand with rotatable spatial configuration, was employed as a chiral extractant to enantioseparate various amino acid enantiomers. Phenylalanine (Phe), homophenylalanine (Hphe), 4-nitrophenylalanine (Nphe), and 3-chloro-phenylglycine (Cpheg) were used as substrates to evaluate the extraction efficiency. The results revealed that Taniaphos-Cu exhibited good abilities to enantioseparate Phe, Hphe, Nphe, and Cpheg with the highest separation factors (α) of 3.13, 2.10, 2.32, and 2.14, respectively. Taniaphos-Cu is more conducive to combine with D-amino acid in extraction. The influences of pH, Taniaphos-Cu, and concentration and extraction temperature on extraction were comprehensively evaluated. The highest performance factors (pf) for Phe, Hphe, Nphe, and Cpheg at optimal extraction conditions were 0.08892, 0.1250, 0.09621, and 0.08021, respectively. The recognition mechanism between Taniaphos-Cu and amino acid enantiomers was discussed. The coordination interaction between Taniaphos-Cu and COO^- , π-π interaction between Taniaphos-Cu and amino acid enantiomers are important acting forces in chiral extraction. The steric-hindrance between NH₂ and OH lead to Taniaphos-Cu-D-Phe is more stable than Taniaphos-Cu-L-Phe. This work provided a chiral extractant that has good abilities to enantioseparate various amino acid enantiomers.

The synthesis and structure of terpyridine-N-oxide complexes of copper(II) perchlorate

The co-ordination of a series of terpyridine-N-oxide ligands to the Cu(ii) ion is reported. Addition of two equivalents of ligand results in the formation of the expected 2 : 1 six co-ordinate product, while the addition of one equivalent of ligand allows the isolation of 1 : 1 species if the ligand has a meridonal binding mode. The five complexes isolated were characterised in the solid state by X-ray crystallography while they are studied in solution using EPR, UV-vis spectroscopy and IR spectroscopy.

1H NMR determination of absolute configuration of 1- or 2-aryl-substituted alcohols and amines by means of their diastereomers: novel separation technique of diastereomeric derivatives of pyridyl alcohols by extraction

A convenient method to determine the absolute configuration of trans-2-aryl cyclohexanols, 1-aryl alcohols and amines was achieved. This method takes advantage of the 1H NMR spectroscopic observations of the remarkable high-field shift of C18-CH3 protons caused by the aromatic shielding effect. It is based on a discrimination of the difference of the environments in two diastereomers derived from 3 beta-acetoxy-5-etienic acid. Furthermore, it was observed that the corresponding diastereomeric derivatives of the pyridyl alcohols were simply separated by extraction based on the difference in their basicity.

Synthesis and crystal structure of 2,3-bis[3-(2-pyridyl)pyrazol-1-yl]hydroquinone dihydrate at 158 K

2,3-Bis[3-(2-pyridyl)pyrazol-1-yl]hydroquinone dihydrate crystallises in the space group C2/c with half a molecule of the title compound and a water molecule in the asymmetric unit. A two-fold rotation axis relates the two 3-(2-pyridyl)pyrazol-1-yl substituents. The pyridine and pyrazole rings are approximately coplanar while the pyrazole ring is orthogonal to the benzene ring. Each water molecule is hydrogen bonded to the hydroxyl group and also to nitrogen atoms of two adjacent molecules; these hydrogen bonding interactions give rise to a two-dimensional network architecture.