Tetraazamacrocyclic transition metal complexes depending on the properties of the components may act as a donor or an acceptor of electrons. Changing the oxidation state of the metal center by applying an appropriate potential allows to control the redox properties of the whole molecule. Depending  on the redox state their complexing properties can be switched on and off.[1] Our aim was to use mono- and polymacrocyclic complexes as receptors for binding guest on the surface of the electrode as well as in the solution.

Pseudorotaxane systems in the solution or on the gold surface.

The monomacrocyclic Cu(II) complex was chosen to play the role of axis of the rotaxane molecule and dibenzo-24-crown-8 to act as the ring (Fig. 1). In the first approach, both components were dissolved in the solution phase. Next, disulfide derivative of monomeric Cu(II) complex was attached to the gold substrate and the crown ether dissolved in the solution phase was the ring able to thread onto the axis. (Fig.2)

Host – guest systems used to bind selected guests.

Tris – and tetramacrocyclic complexes were used to bind small guests molecules[2]. The interactions with two molecules: 9,10-dimethyltriptycene and fullerene, were examined.

The formation of complexes between the trismacrocyclic cyclidene hosts and π-electron-rich aromatic guests was confirmed by NMR and electrochemical studies. The 9,10-dimethyltriptycene molecule fits into the cavities formed by the macrocyclic complex of copper and nickel . Based on the decrease of the diffusion coefficients we were able to determine the association constants of dimethyltriptycene and copper and nickel cations using the equation of Osa et al.[3] and compare them with NMR results[4].

For binding the molecule of C₆₀, two four-center macrocyclic compunds with short, two-carbon alkyl chains were chosen. The size of the cavity in those complexes is appropriate to accept the guest molecule. The radius of the molecule of the fullerene is approximately 7Å and the dimensions of the cavity of the macrocyclic complex is ca. 15x15Å. The changes observed in the cyclic voltammetry allowed us to confirm the formation of a new complex, which is demonstrated in the decrease of the diffusion coefficient value and in the shift of the voltammetric peaks corresponding to the redox processes of  both fullerene and the metal ion center of the receptor.

[1]A. Więckowska, M. Wiśniewska, M. Chrzanowski, J. Kowalski, B. Korybut-Daszkiewicz, R. Bilewicz, Pure Appl. Chem. 2007, 79, 1077

[2]R. Bilewicz, A. Wieckowska, B. Korybut-Daszkiewicz, A. Olszewska, N. Feeder, K. Woniak, J. Phys. Chem. B 2000, 104, 11430-11434

[3] T. Osa, T. Matsue, T. Fujihira, Heterocycles, 1977, 6, 1833

[4] J. Małecka, U. Lewandowska, R. Kamiński, I. Mames, A. Więckowska, R. Bilewicz, B. Korybut-Daszkiewicz, K. Wozniak, Chem. Eur.J. 2011, in press

1. POSTER: Tetraazamacrocyclic copper(II) and nickel(II) complexes in host - guest systems., JPEG image data, JFIF standard 1.01, 0MB

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