Jarosław Kowalski

Macrocyclic Metal Complex-DNA Conjugates for Electrochemical Sensing of Single Nucleobase Changes in DNA

The direct incorporation of macrocyclic cyclidene complexes into DNA via automated synthesis results in a new family of metal-functionalized DNA derivatives that readily demonstrate their utility through the ability of one redox-active copper(II)-containing strand to distinguish electrochemically between all four canonical DNA nucleobases at a single site within a target sequence of DNA.

Neutral Nickel(II) and Copper(II) Tetraazamacrocyclic Complexes as Molecular Rods Attached to Gold Electrodes

New dithiolated derivatives of neutral Cu(II) and Ni(II) tetraazamacrocyclic complexes have been synthesized and characterized by spectroscopic and diffractional methods. These rod-shaped molecules were assembled in monocomponent and mixed monolayers on gold electrodes. In the mixed monolayers, the active molecules were embedded in a hexanethiol matrix. The dithiolated complexes are oriented perpendicularly to the electrode, and reveal faster kinetics of electron transfer than those assembled in a single-component monolayer. They appear as protrusions, which are easily addressed by using the STM method. In the presence of a suitable electron acceptor in the solution, the donor properties of the anchored Cu complex were weakened, which revealed donor-acceptor interactions with the monolayer. The peak position in the voltammogram indicates a stronger interaction of the solution-based acceptor with the reduced Cu(II) form than with the Cu(III) complex. This suggests the possibility of switching the association on or off by applying an appropriate potential.

Self-assembly of a nickel(II) pseudorotaxane nanostructure on a gold surface

Tetraazamacrocyclic complexes of NiII and CuII can be used as components of catenanes or rotaxanes showing electrochemically switched intramolecular motion in solution. In our present studies, we modify these compounds with organothiol chains to attach them to the surface of the electrode using the self-assembly method and employ them next as molecular switches, which change conductivity upon applying appropriate potential. The electrochemical properties of these compounds are studied in the solution and, in the case of thiol derivative, immobilized on the electrode surface. The macrocyclic complex of NiII, immobilized on the Au surface, forms the axis of the rotaxane. This compound can be anchored to the surface by one or two thiol groups. The data obtained from scanning tunneling microscopy (STM) experiments using colloidal Au confirm that the orientation normal to the surface dominates. The electrochemical experiments reveal reversible one-electron oxidation of metal center from +2 to +3. The behavior of the electrode modified with the macrocyclic complex of NiII upon immersion in a solution containing bismacrocyclic complex of NiII points to the formation of a new rotaxane-like nanostructure on the surface of the electrode.

Face-to-face dinuclear scaffolds composed of tetraazamacrocyclic charged and neutral complexes.

A new family of bismacrocyclic homo- and heteronuclear Ni and Cu complexes has been synthesized and characterized. The ligand scaffold is comprised of two 14-membered tetraazamacrocyclic sites held in cofacial orientation. The dinuclear complexes are unique in that one macrocyclic center is neutral while the other one is charged, although the ligand backbones are nearly identical. This leads to a binuclear system of two structurally similar components, differing in their electron-donor abilities. The crystallographically characterized structures in the solid state revealed similarity of the four dinuclear complexes studied. The metal-metal separations are between 4 and 5 A. The strongest electrostatic intramolecular interactions occur in the molecules with neutral and charged components, most differing in donor abilities.

Molecular Necklaces Composed of Tetraazamacrocyclic and Crown Ether Building Blocks

A series of catenanes was synthesized via self-assembly of dibenzo-24-crown-8, ethylenediamine, and either three, four, or five cyclidene units coordinating nickel(II) or copper(II) ions. A number of molecular necklaces were successfully isolated and characterized. ESI mass spectrometry proved to be the most useful analytical tool to establish the exact composition of synthesized catenanes. Additionally, single crystal of a grand macrocycle composed of four tetraazamacrocyclic units complexing copper(II) ions was obtained and its X-ray structure has been successfully determined.