Silver(I) and mercury(II) complexes with N,N′-bis(acetylacetone)-1R,2R-diaminocyclohexane ligands exhibiting three different coordination modes

Binding Selectivity of Methanobactin from Methylosinus trichosporium OB3b for Copper(I), Silver(I), Zinc(II), Nickel(II), Cobalt(II), Manganese(II), Lead(II), and Iron(II)

Methanobactin (Mb) from Methylosinus trichosporium OB3b is a member of a class of metal binding peptides identified in methanotrophic bacteria. Mb will selectively bind and reduce Cu(II) to Cu(I), and is thought to mediate the acquisition of the copper cofactor for the enzyme methane monooxygenase. These copper chelating properties of Mb make it potentially useful as a chelating agent for treatment of diseases where copper plays a role including Wilson's disease, cancers, and neurodegenerative diseases. Utilizing traveling wave ion mobility-mass spectrometry (TWIMS), the competition for the Mb copper binding site from Ag(I), Pb(II), Co(II), Fe(II), Mn(II), Ni(II), and Zn(II) has been determined by a series of metal ion titrations, pH titrations, and metal ion displacement titrations. The TWIMS analyses allowed for the explicit identification and quantification of all the individual Mb species present during the titrations and measured their collision cross-sections and collision-induced dissociation patterns. The results showed Ag(I) and Ni(II) could irreversibly bind to Mb and not be effectively displaced by Cu(I), whereas Ag(I) could also partially displace Cu(I) from the Mb complex. At pH ≈ 6.5, the Mb binding selectivity follows the order Ag(I)≈Cu(I)>Ni(II)≈Zn(II)>Co(II)>>Mn(II)≈Pb(II)>Fe(II), and at pH 7.5 to 10.4 the order is Ag(I)>Cu(I)>Ni(II)>Co(II)>Zn(II)>Mn(II)≈Pb(II)>Fe(II). Breakdown curves of the disulfide reduced Cu(I) and Ag(I) complexes showed a correlation existed between their relative stability and their compact folded structure indicated by their CCS. Fluorescence spectroscopy, which allowed the determination of the binding constant, compared well with the TWIMS analyses, with the exception of the Ni(II) complex. Graphical abstract ᅟ.

A one-dimensional coordination polymer formed from the reaction of 1,1-diphenyl-3,3'-[(1R,2R)-cyclohexane-1,2-diylbis(azanediyl)]dibut-2-en-1-one with MnCl2·4H2O

In the title coordination polymer, catena-poly[[dichloridomanganese(II)]-μ-1,1-diphenyl-3,3'-[(1R,2R)-cyclohexane-1,2-diylbis(azaniumylylidene)]dibut-1-en-1-olate-κ(2)O:O'], [MnCl2(C26H30N2)]n, synthesized by the reaction of the chiral Schiff base ligand 1,1-diphenyl-3,3'-[(1R,2R)-cyclohexane-1,2-diylbis(azanediyl)]dibut-2-en-1-one (L) with MnCl2·4H2O, the asymmetric unit contains one crystallographically unique Mn(II) ion, one unique spacer ligand, L, and two chloride ions. Each Mn(II) ion is four-coordinated in a distorted tetrahedral coordination environment by two O atoms from two L ligands and by two chloride ligands. The Mn(II) ions are bridged by L ligands to form a one-dimensional chain structure along the a axis. The chloride ligands are monodentate (terminal). The ligand is in the zwitterionic enol form and displays intramolecular ionic N(+)-H...O(-) hydrogen bonding and π-π interactions between pairs of phenyl rings which strengthen the chains.