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Two copper(ii) complexes were investigated as catalysts for selective oxidation of styrene to benzaldehyde and of cyclohexane to KA oil.

Cage metal complexes iron(II) clathrochelates, which are inherently CD silent, were discovered to demonstrate intensive output in induced circular dichroism (ICD) spectra upon their assembly to albumins. With the aim to design clathrochelates as protein-sensitive CD reporters, the approach for the functionalization of one chelate a-dioximate fragment of the clathrochelate framework with two nonequivalent substituents was developed, and constitutional isomers of clathrochelate with two nonequivalent carboxyphenylsulfide groups were synthesized. The interaction of designed iron(II) clathrochelates and their symmetric homologues with globular proteins (serum albumins, lysozyme, blactoglobulin (BLG), trypsin, insulin) was studied by protein fluorescence quenching and CD techniques. A highly-intensive ICD output of the clathrochelates was observed upon their association with albumins and BLG. It was shown that in the presence of BLG, different clathrochelate isomers gave spectra of inverted signs, indicating the stabilization of opposite configurations (L or D) of the clathrochelate framework in the assembly with this protein. So, we suggest that the isomerism of the terminal carboxy group determined preferable configurations of the clathrochelate framework for the fixation in the protein binding site. MALDI TOF results show the formation of BLG-clathrochelate complex with ratio 1 : 1. Based on the docking simulations, the binding of the clathrochelate molecule (all isomers) to the main BLG binding site (calyx) in its open conformation is suggested. The above results point that the variation of the ribbed substituents at the clathrochelate framework is an effective tool to achieve the specificity of clathrochelate ICD reporting properties to the target protein. Scheme 1 Chemical drawings of the isomeric dicarboxyl-terminated iron(II) cage complexes and their dichloroclathrochelate precursor. 24220 | RSC Adv., 2019, 9, 24218-24230 This journal is View Article Online 2.6. Study of the BLG-clathrochelate 3 assembly by MALDI-TOF mass-spectrometry The corresponding spectra were obtained on a Bruker Daltonics MALDI-TOF mass spectrometer. The sample was prepared by mixing 50 ml of BLG solution (2 mg ml À1 in 0.1 M aqueous 24222 | RSC Adv., 2019, 9, 24218-24230 This journal is Scheme 2 Synthesis of the dicarboxyphenylsulfide iron(II) clathrochelates with equivalent (on top) and non-equivalent (on bottom) ribbed substituents. R 1 s R 2 .This journal is

Increasing attention has been recently devoted to 89 Zr(IV) and 68 Ga(III) radionuclides, due to their favorable decay characteristics for positron emission tomography (PET). In the present paper, a deep investigation is presented on Ga(III) and Zr(IV) complexes with a series of tri-( H 3 L1 , H 3 L3 , H 3 L4 and desferrioxamine E, DFOE ) and tetrahydroxamate ( H 4 L2 ) ligands. Herein, we describe the rational design and synthesis of two cyclic complexing agents ( H 3 L1 and H 4 L2 ) bearing three and four hydroxamate chelating groups, respectively. The ligand structures allow us to take advantage of the macrocyclic effect; the H 4 L2 chelator contains an additional side amino group available for a possible further conjugation with a biomolecule. The thermodynamic stability of Ga(III) and Zr(IV) complexes in solution has been measured using a combination of potentiometric and pH-dependent UV–vis titrations, on the basis of metal–metal competition. The Zr(IV)- H 4 L2 complex is characterized by one of the highest formation constants reported to date for a tetrahydroxamate zirconium chelate (log β = 45.9, pZr = 37.0), although the complex-stability increase derived from the introduction of the fourth hydroxamate binding unit is lower than that predicted by theoretical calculations. Solution studies on Ga(III) complexes revealed that H 3 L1 and H 4 L2 are stronger chelators in comparison to DFOB. The complex stability obtained with the new ligands is also compared with that previously reported for other hydroxamate ligands. In addition to increasing the library of the thermodynamic stability data of Ga(III) and Zr(IV) complexes, the present work allows new insights into Ga(III) and Zr(IV) coordination chemistry and thermodynamics and broadens the selection of available chelators for 68 Ga(III) and 89 Zr(IV).

Four different crystal structures for quinolinehydroxamic acid (QuinHA) and picolinehydroxamic acid (PicHA) MCs with Cu­(II) and Ni­(II), and solution studies on the formation of Cu­(II), Ni­(II), and Zn­(II) MC complexes with QuinHA, PicHA, and pyrazylohydroxamic acid (PyzHA) are described. In polynuclear complex 1, [Cu5(QuinHA-2H)4(NO3)­(DMSO)4]­(NO3), the metallamacrocyclic cavity is formed by four Cu­(II) ions and four doubly deprotonated hydroximate ligands, and the center of the cavity is occupied by the fifth Cu­(II) ion coordinated by four hydroximate oxygen atoms. The complex 2, [Cu10(PicHA-2H)8(H2O)4(ClO4)3]­(ClO4)·4H2O, exhibits a dimeric structure based on two pentanuclear collapsed 12-MC-4 Cu4(PicHA-2H)4 fragments united by two chiral capping Cu­(II) ions exo-coordinated to the peripheral vacant (O,O′) chelating units of each tetranuclear collapsed MC moiety. 3, [CaNi5(QuinHA-2H)5(H2O)2(Py)10]­(NO3)2, and 4, [CaNi5(PicHA-2H)5(DMF)2(Py)8]­(NO3)2, are planar 15-membered rings consisting of a PicHA or QuinHA ligand, respectively. To understand fully the correlation between species isolated in the solid state and those presented in solution, the solution equilibria were investigated, showing the dependence of the MCs topologies and stability constants (log β) on the ligand structure and metal ion.