Semi-Rigid (Aminomethyl) Piperidine-Based Pentadentate Ligands for Mn(II) Complexation

Two pentadentate ligands built on the 2-aminomethylpiperidine structure and bearing two tertiary amino and three oxygen donors (three carboxylates in the case of AMPTA and two carboxylates and one phenolate for AMPDA-HB) were developed for Mn(II) complexation. Equilibrium studies on the ligands and the Mn(II) complexes were carried out using pH potentiometry, 1H-NMR spectroscopy and UV-vis spectrophotometry. The Mn complexes that were formed by the two ligands were more stable than the Mn complexes of other pentadentate ligands but with a lower pMn than Mn(EDTA) and Mn(CDTA) (pMn for Mn(AMPTA) = 7.89 and for Mn(AMPDA-HB) = 7.07). 1H and 17O-NMR relaxometric studies showed that the two Mn-complexes were q = 1 with a relaxivity value of 3.3 mM−1 s−1 for Mn(AMPTA) and 3.4 mM−1 s−1 for Mn(AMPDA-HB) at 20 MHz and 298 K. Finally, the geometries of the two complexes were optimized at the DFT level, finding an octahedral coordination environment around the Mn2+ ion, and MD simulations were performed to monitor the distance between the Mn2+ ion and the oxygen of the coordinated water molecule to estimate its residence time, which was in good agreement with that determined using the 17O NMR data.

Regulation of the self-assembly morphology of azobenzene-bearing double hydrophobic block copolymers in aqueous solution by shifting the dynamic host–guest complexation

The complexation equilibrium between azo and β-CD can be shifted by various methods, thus the micellar morphology of azo-bearing block copolymers is altered.

Generation of spatiotemporal calcium patterns by coupling a pH-oscillator to a complexation equilibrium

Calcium waves and patterns have been observed in the bromate–sulfite–ferrocyanide–CaEDTA reaction–diffusion system, where pH-oscillations drive binding and release of calcium ions.

Heavy-metal extraction capability of chalcogenoic aminophosphines derived from 1-amino-4-methylpiperazine

Aminophosphine of the type (Ph2PNHR) derived from 1-amino-4-methylpiperazine and its chalcogen derivatives (Ph2P(X)NHR X = S, Se) were used as ligands in solvent extraction of metal picrates such as Cu2+, Ni2+, and Pb2+ from the aqueous to the organic phase. Influence of parameters such as pH of the aqueous phase, ligand concentration in the organic phase, and concentration of the extractant extracted from the aqueous to the organic phase was investigated to determine the ligands’ ability to extract metal ions. Metal picrate extraction was investigated at 25°C using UV-VIS spectrophotometry in dichloromethane in the absence and in the presence of Ph2PNHR and chalcogenides. The extraction results revealed that the extraction percentage of Cu2+, Ni2+, and Pb2+ metals was much higher at lower pH values, indicating an acidity dependent complexation equilibrium.