New Dinuclear Cobalt(II) and Zinc(II) Complexes of a Carboxylate-Rich Dinucleating Ligand: Synthesis, Structure, Spectroscopic Characterization, and Their Interactions with Sugars

Abstract

Sugar-metal ion interactions in aqueous medium are involved in many biochemical processes such as the transport and storage of metals, the function and regulation of sugar-metabolizing metalloenzymes, the mechanism of action of metal-containing pharmaceuticals, and toxic metal metabolism. To understand such interactions we synthesized and fully characterized two new dinuclear cobalt(II) and zinc(II) complexes as carbohydrate binding models for xylose/glucose isomerases (XGI). Synthesis of the dicobalt complex, Na3[Co2(ccdp)(μ-HCO2)]BF4·9H2O·2CH3OH (1), was performed in methanol with stoichiometric amounts of Co(BF4)2·6H2O and the dinucleating ligand, H5ccdp (H5ccdp = N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[carboxymethyl]-1,3-diaminopropan-2-ol), in the presence of NaOH at ambient temperature in an argon glovebox. Similarly, the dizinc complex, [NMe4]2[Zn2(ccdp)(μ-OAc)]·CH3OH (2), was synthesized from Zn(OAc)2·2H2O and H5ccdp in the presence of NMe4OH at ambient temperature in methanol. Binding of the complexes with carbohydrates was investigated under different reaction conditions. In aqueous alkaline media, complexes 1 and 2 showed chelating ability towards the biologically important sugars, d-glucose and d-xylose, and a polyalcohol enzyme inhibitor (xylitol). In solution, each complex forms a 1:1 complex-substrate bound product with specific binding constant values. Synthesis, characterization details, and substrate binding using spectroscopic techniques and single-crystal X-ray diffraction are reported.

Synthesis, crystal structure and investigation of mononuclear copper(II) and zinc(II) complexes of a new carboxylate rich tripodal ligand and their interaction with carbohydrates in alkaline aqueous solution

“…Secondly, H 3 camb as a mono -nucleating ligand gives a structural complementarity to our reported di -nucleating ligand, H 5 ccdp; and thus, it presents an opportunity to study and contrast the effect of metal nuclearity on the complex–carbohydrate interaction without significantly altering the molecular structure of the ligands [33,34]. For comparison reasons, the molecular structures of H 5 ccdp and H 3 camb ligands are depicted in Fig.…”

“…Furthermore, the biologically relevant aspects of carbohydrate complexes of Fe 3+ , Cr 3+ , VO 2+ , and Zn 2+ , have also been reported [32–35,37–43]. It has also been elucidated that carboxylato-bridged dinuclear complexes of Mg 2+ , Mn 2+ , Co 2+ , Ni 2+ , and Zn 2+ , are involved in non-redox active enzymatic processes [33,44–51]. …”

Synthesis, structure, spectral characterization and DNA binding affinity of new water soluble trinuclear copper(II) complexes with partial cubane Cu3O4 cores

“…Calcd. for C 11 A methanol (10 ml) solution of Cu(ClO 4 ) 2 Á6H 2 O (0.415 g, 1.12 mmol) was added to a solution of H 2 cbal (0.250 g, 1.12 mmol) and NaOH (0.089 g, 2.24 mmol) in methanol (10 ml) with magnetic stirring during a period of 15 min. The reaction mixture was stirred for 1 h resulting in a blue solution.…”

“…The carboxylate-rich ligands have been used by us [9][10][11][12] as a way to bind the divalent Co(II), Cu(II) and Zn(II) metal ions to produce mono-, di-, tetra-, hexa-, and heptanuclear complexes under various reaction conditions. Several tridentate [O 2 N] or [ON 2 ] donor set ligands have readily afforded trinuclear copper(II) complexes with [Cu 3 O] core [13][14][15][16].…”

“…However, the systematic and detailed study of such binding and cleavage of biological macromolecules has been sporadic, probably due to the unavailability of structurally characterized highly water soluble trinuclear copper(II) complexes [25,26]. Very recently, we reported di-, tetraand hexanuclear copper(II), zinc(II) and cobalt(II) complexes built upon dinucleating ligands and their binding interactions with various biological micro-and macromolecules in aqueous medium [11,12,22]. While the study has established a strong interaction between the complexes and the biomolecules, none of the complexes had direct structural resemblance to any known metalloprotein.…”