Anion-Directed Metallocages: A Study on the Tendency of Anion Templation

Self-assembly of Cu(NO₃ )₂ ⋅3 H₂ O and di(3-pyridylmethyl)amine (dpma) with addition of different acids (HNO₃ , HOAc, HCl, HClO₄ , HOTf, HPF₆ , HBF₄ , and H₂ SO₄ ) afforded a family of anion-templated tetragonal metallocages with a cationic prismatic structure of [(G^n- )⊂{Cu₂ (Hdpma)₄ }]^(8-n)+ (G^n- =NO₃^- , PF₆^- , SiF₆^2- ) with different ligating anions/solvents (NO₃^- , Cl^- , ClO₄^- , OTf^- , H₂ O) outside the cage. Systematic competitive experiments have rationalized the tendency of anion templation towards the formation of metallocages [(G^n- )⊂{Cu₂ (Hdpma)₄ }]^(8-n)+ as occurring in the order SiF₆^2- ≈PF₆^- >NO₃^- >SO₄^2- ≈ClO₄^- ≈BF₄^- . This sequence is mostly elucidated by shape control over size selectivity and electrostatic attraction between the cationic {Cu₂ (Hdpma)₄ }⁸⁺ host and the anionic guests. In addition, these results have also roughly ranked the anion coordination ability in the order Cl^- , ClO₄^- , OTf^- >NO₃^- >BF₄^- , CH₃ SO₄^- . Magnetic studies of metallocages 1 t and 2-4 suggest that the fitted magnetic interaction, being weakly magnetically coupled overall, is interpreted as a result of the combination of intracage ferromagnetic coupling integrals and intercage antiferromagnetic exchange; both contributions are very weak and comparable in strength.

Controllable assembly of Cu(ii) coordination compounds based on a flexible zwitterionic benzimidazole–dicarboxylate ligand: synthesis, structural diversity, reversible SCSC transformation and magnetic properties

The reversible SCSC transformation of a paddle-wheel cluster to a 1D linear polymer could be accomplished.