Synthesis, crystal structure and magnetic properties of the new Cu(II)/Mn(II) coordination polymer [{Cu(cyclam)MnCl3(H2O)2}Cl]

Herein, we report a comprehensive coordination study of the previously reported ligands cyclam, CB-cyclam TMC, DMC, CB-DMC, and of their C-functional analogues, cyclam-E, CB-cyclam-E, TMC-E, DMC-E and CB-DMC-E. This group of ligands includes cyclam, cross-bridged cyclams, their di-or tetramethylated derivatives and the analogues bearing an additional hydroxyethyl group on one β-N position of the ring. These Cu(II) and Zn(II) complexes of these macrocycles have been highlighted previously for the biological interest, but the details of their structures in the solid state and in solution remained largely unexplored. In particular, we analyzed the impact that adding non-coordinating Nmethyl and C-hydroxyethyl functionalities has in the structures of the complexes. All the Cu(II) and Zn(II) complexes were synthetized and investigated using single crystal X-ray diffraction and NMR, electronic absorption and EPR spectroscopies, along with DFT studies. Dissociation kinetics experiments in acidic conditions and an electrochemical study were also performed. A special attention was paid to analyze the different configurations present in solution and in the solid state, as well as the impact of the Cappended hydroxyethyl group on the coordination behavior. Various ratios of the trans-I, trans-III, and cis-V configurations have been observed depending on the degree of N-methylation and the presence of the ethylene cross-bridge.

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Crown-hydroxylamines are pH-dependent chelating N,O-ligands with a potential for aerobic oxidation catalysis

Lesnikov,

Golovanov,

Nelyubina

et al. 2023

Nat Commun

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Despite the rich coordination chemistry, hydroxylamines are rarely used as ligands for transition metal coordination compounds. This is partially because of the instability of these complexes that undergo decomposition, disproportionation and oxidation processes involving the hydroxylamine motif. Here, we design macrocyclic poly-N-hydroxylamines (crown-hydroxylamines) that form complexes containing a d-metal ion (Cu(II), Ni(II), Mn(II), and Zn(II)) coordinated by multiple (up to six) hydroxylamine fragments. The stability of these complexes is likely to be due to a macrocycle effect and strong intramolecular H-bonding interactions between the N−OH groups. Crown-hydroxylamine complexes exhibit interesting pH-dependent behavior where the efficiency of metal binding increases upon deprotonation of the hydroxylamine groups. Copper complexes exhibit catalytic activity in aerobic oxidation reactions under ambient conditions, whereas the corresponding complexes with macrocyclic polyamines show poor or no activity. Our results show that crown-hydroxylamines display anomalous structural features and chemical behavior with respect to both organic hydroxylamines and polyaza-crowns.

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Synthesis, crystal structure and magnetic properties of the new Cu(II)/Mn(II) coordination polymer [{Cu(cyclam)MnCl3(H2O)2}Cl]

Cited by 5 publications

References 28 publications

Copper and copper-manganese 1D coordination polymers: Synthesis optimization, crystal structure and preliminary studies as catalysts for Baylis–Hillman reactions

Copper and copper-manganese 1D coordination polymers: Synthesis optimization, crystal structure and preliminary studies as catalysts for Baylis–Hillman reactions

Complexation of C-Functionalized Cyclams with Copper(II) and Zinc(II): Similarities and Changes When Compared to Parent Cyclam Analogues

Crown-hydroxylamines are pH-dependent chelating N,O-ligands with a potential for aerobic oxidation catalysis

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