Modulating the M−M Distance in Dinuclear Complexes. New Ligand with a 2,2‘-Biphenol Fragment as Key Unit:  Synthesis, Coordination Behavior, and Crystal Structures of Cu(II) and Zn(II) Dinuclear Complexes

Abstract

The synthesis and characterization of the new polyamino-phenolic ligand 3,3'-bis[N,N-bis(2-aminoethyl)aminomethyl]-2,2'-dihydroxybiphenyl (L) are reported. L contains two diethylenetriamine units linked by a 1,1'-bis(2-phenol) group (BPH) on the central nitrogen atom which allows two separate binding amino subunits in a noncyclic ligand. The basicity and binding properties of L toward Cu(II) and Zn(II) were determined by means of potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, I = 0.15 mol dm-3). L behaves as a pentaprotic base and as a monoprotic acid under the experimental conditions used, yielding the H5L5+ or H-1L- species, respectively. L forms both mono- and dinuclear species with both metal ions investigated; the dinuclear species are largely prevalent in aqueous solution with a L/M(II) molar ratio of 1:2 at pH higher than 7. L shows different behavior in Cu(II) and Zn(II) binding, affecting the dinuclear species formed and the distance between the two coordinated metal ions, which is greater in the Zn(II) than in the Cu(II) dinuclear species. This difference can be attributed to the different degree of protonation of BPH which influences the angle between the phenyl rings in the two systems. In this way, it is possible to modulate the M(II)-M(II) distance by the choice M(II) and to space the two M(II) farther away than was possible with the previously synthesized ligands. L does not saturate the coordination sphere of the coordinated M(II) ions in the dinuclear species, and thus, these latter species are prone to add guests. 1H and 13C NMR experiments carried out in aqueous solution, as well as the crystal structures of the dinuclear Cu(II) and Zn(II) species formed in aqueous solution, aided in elucidating the involvement of L and BPH in Zn(II) and Cu(II) stabilization.

Unsymmetric Compartmental Ligands for Metallobiosite Modelling: A Mini Review

“…56 Cooperative interactions between the two adjacent metal centers are important in bioinorganic model studies, organic synthesis and catalysis and give rise to interesting physicochemical properties. [49][50][51][56][57][58][59][60][61][62][63][64][65][66][67] It is evident that the use of small-molecule model compounds can provide useful information in understanding biological functions and the mechanistic pathway of the bimetallic cores. This is a budding area of coordination chemistry with respect to ligand design and synthesis as well as in the application of the formed dinuclear complexes, as speculative, and to an extent corroborative, a model for binuclear metal centers.…”

Crystal structure of bis{μ2-2,2′-[(4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(methylene)]bis(4-oxo-4H-pyran-3-olato)}dicobaltcalcium bis(perchlorate) 1.36-hydrate

“…Polynuclear metal complexes have long been studied due to their versatility. They find applications in many fields, ranging from molecular recognition to transport and catalysis (Gokel & Barbour, 2017;Weber & Gokel, 2012;Ambrosi et al, 2007aAmbrosi et al, ,b, 2008Ambrosi et al, , 2009aMartell & Hancock, 1996;Voegtle, 1996;Zelewsky, 1996;Lehn, 1988), to name just a few. Moreover, they find applications in the field of bioinorganic chemistry (Fanelli et al, 2016;Marchetti et al, 2015;Patra et al, 2014), for instance as anticancer agents (Bruijnincx & Sadler, 2008) and artificial metalloproteases (Suh & Chei, 2008).…”

Synthesis and Characterization of Octaazatricyclotetracosane (Octc) Macrocyclic Complexes of Ni (Ii), Cu (Ii) Transition Metal Ions Derived From 1, 3-Diaminopropane Containing Aza Ligands

“…Whereas the complexes of copper (II) are Violet (brown liquid).All the complexes are highly soluble in water due to their ionic nature [11].Most of them are soluble in many other polar solvents, like methanol, ethanol, DMF, DMSO etc [12]. Similarly, the molar conductance (ohm - [13].…”