An Electrochemically Controlled Molecular Shuttle

Abstract

Usurping the crown: A controlled intramolecular motion of the crown moiety from around the Ni to the Cu center takes place in a transition‐metal hetero‐dinuclear [2]catenane in response to an applied potential (see picture).

Tetraaza[14]macrocyclic Transition Metal Complexes as DNA Intercalators

“…The synthesis was carried out in an analogous way to the methods used for the synthesis of other cyclidene systems that were obtained previously by the group of KorybutDaszkiewicz. [14][15][16][17]31] The complexes were separated using reversed-phase silica gel and crystallised from water/acetonitrile mixture with an excess of ammonium hexafluorophosphate upon slow evaporation of solvents. The corresponding chlorides were precipitated from acetonitrile solutions of hexafluorophosphate salts by adding a large excess of anhydrous tetrabutylammonium chloride.…”

“…They are waterstable π-electron rich tetraazamacrocyclic systems (also called Jäger complexes), that during the last decade they have been used by the group of Korybut-Daszkiewicz as building blocks for the synthesis of a range of macrocycles, including linear compounds, oligomacrocycles, [14,15] catenanes, [16,17] pseudorotaxanes [18] and rotaxanes. [19] It has been demonstrated Six tetraazamacrocyclic copper(II) and nickel(II) complexes have been synthesised and their interactions with doublestranded DNA (calf-thymus DNA) have been studied using circular and linear dichroism, as well as other spectroscopic methods.…”

“…that some of those can act as molecular devices, [17] while others are able to recognise small aromatic systems. [20] The 14-membered cyclidene units are relatively easy to obtain [21][22][23] and able to coordinate various transition metal ions, such as copper(II), nickel(II), but also iron(II), cobalt(II, III), palladium(II) and platinum(II, IV).…”

“…The dissociation to metal cation and free tetraaza [14]macrocyclic ligand was never observed in nickel(II) and copper(II) cyclidenes, as confirmed many times using NMR and mass spectrometry. [14][15][16][17][18][19][20][21][22] The removal of the metal ion can only occur in the presence of strong acids in dry solvents. Moreover, a large number of heterodinuclear bismacrocyclic complexes, containing both copper and nickel ion in one molecule have been previously obtained and neither the presence of free ligand in solution nor metal scrambling was observed.…”

“…As a result, the ring becomes relatively hydrophobic, what can be observed in catenanes, where the benzene ring of the crown ether moiety is located in the cavity between two opposite cyclidene rings. [16,17] Very close analogues of the studied compounds, namely 16-membered cyclidenes, do also form a hydrophobic cavity, that is in aqueous media able to host aliphatic and aromatic alcohols. NMR relaxation techniques indicated their hydroxyl groups remaining outside the cavity [27][28][29][30] which also confirms the hydrophobic nature of cyclidene rings.…”