Synthesis and characterization of ML and ML₂ metal complexes with amino acid substituted bis(2-picolyl)amine ligands

Abstract

Metal complexes with ML or ML2 stoichiometry have been isolated in the reaction of Zn(NO3)2, ZnBr2 or M(NO3)2/NaBF4, M = Zn(ii), Co(ii) or Ni(ii), with either amino acid or amine substituted tridentate nitrogen ligands based on bis(2-picolyl)amine (bpa) or bis(2-quinaldyl)amine (bqa). The stoichiometry (M : L = 1 : 1 or 1 : 2) and stereochemistry (mer, trans-fac or cis-fac) of the products have been studied by NMR and IR spectroscopy, X-ray single crystal analysis and quantum-chemical calculations with an implicit SMD solvation model.

Stereochemistry of Hexacoordinated Zn(II), Cu(II), Ni(II), and Co(II) Complexes with Iminodiacetamide Ligands

“…The addition of KI converts the chloroacetamides to more reactive iodoacetamides, accelerating the reaction. 20 The second synthetic step was initially attempted according to a previously reported procedure, 15,16 by nucleophilic substitution in acetonitrile using potassium carbonate as a base, resulting in a mixture of mono-and disubstituted amine. Ligand L1 was obtained in moderate yield (41%) due to low solubility of the intermediate, monosubstituted amine in acetonitrile, which precipitates from the reaction mixture and is not available for further substitution.…”

“…, indicate a strong Zn─N bond, while broad signals of the corresponding ML2 complexes show a weaker bond and a Zn─N cleavage/coordination kinetics faster than the NMR timescale. 15,30 As the Zn─N bond weakens, nitrogen inversion is enabled and α-CH2 protons are magnetically equivalent. To further study this assumption, variable temperature (VT) NMR was recorded for ML and ML2 complexes of L1 and Zn 2+ .…”

“…13,14 For octahedral ML2 complexes, different geometrical isomers are known: mer, trans-fac, Δ-and Λ-cis-fac (see Figure S2). 15 This potential coordination variety of imda complexes is in opposition to hexacoordiated EDTA complexes that can only form a cisfac isomer, because of the ethylene bridge linking the amine nitrogen atoms. By analyzing structures of ML2 complexes with imda ligands in the Cambridge Structural Database (CSD), it is apparent that they preferentially form trans-fac isomers.…”

The Metal Effect on Self-Assembling of Oxalamide Gelators Explored by Mass Spectrometry and DFT Calculations

“…In this way all of the reported computational data correspond to the gas-phase Gibbs free energies at a temperature of 298.15 K and a pressure of 1 atm. The choice of such a computational setup was prompted by our recent success in modeling the properties of gelator molecules [23] and metal binding affinities [24], as well as correctly reproducing thermodynamic and kinetic parameters of organic [25,26] and enzymatic [27] reactions. In order to circumvent problems with the flexibility of the investigated systems, we tried many different conformations in each studied case and report here the results corresponding to the most stable structures.…”

Bispicolyamine-Based Supramolecular Polymeric Gels Induced by Distinct Different Driving Forces with and Without Zn2+

“…The idea was to induce metal-binding to modify the gel behavior. Thus far, the available research on coordination geometries between BPA and Zn 2+ have reported mainly tetrahedral, square pyramidal, trigonal bipyramidal, and octahedral structures [ 48 , 49 , 50 , 51 , 52 ]. Having those varieties indicates that the coordination number of the complex and the ligand-to-metal ratio could significantly influence the self-assemblage orientation of the molecules.…”