10 research outputs found
Efficient Syntheses of New Super Lewis Basic Tris(dialkylamino)âSubstituted Terpyridines and Comparison of Their Methyl Cation Affinities
Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy
Multivalent biomolecular interactions allow for a balanced interplay of mechanical stability and malleability, and nature makes widely use of it. For instance, systems of similar thermal stability may have very different rupture forces. Thus it is of paramount interest to study and understand the mechanical properties of multivalent systems through well-characterized model systems. We analyzed the rupture behavior of three different bivalent pyridine coordination complexes with Cu2+ in aqueous environment by single-molecule force spectroscopy. Those complexes share the same supramolecular interaction leading to similar thermal off-rates in the range of 0.09 and 0.36 sâ1, compared to 1.7 sâ1 for the monovalent complex. On the other hand, the backbones exhibit different flexibility, and we determined a broad range of rupture lengths between 0.3 and 1.1 nm, with higher most-probable rupture forces for the stiffer backbones. Interestingly, the medium-flexible connection has the highest rupture forces, whereas the ligands with highest and lowest rigidity seem to be prone to consecutive bond rupture. The presented approach allows separating bond and backbone effects in multivalent model systems
Mechanical Rupture of Mono- and Bivalent Transition Metal Complexes in Experiment and Theory
Biomolecular
systems are commonly exposed to a manifold of forces,
often acting between multivalent ligands. To understand these forces,
we studied mono- and bivalent model systems of pyridine coordination
complexes with Cu<sup>2+</sup> and Zn<sup>2+</sup> in aqueous environment
by means of scanning force microscopy based single-molecule force
spectroscopy in combination with <i>ab initio</i> DFT calculations.
The monovalent interactions show remarkably long rupture lengths of
approximately 3 Ă
that we attribute to a dissociation mechanism
involving a hydrogen-bound intermediate state. The bivalent interaction
with copper dissociates also via hydrogen-bound intermediates, leading
to an even longer rupture length between 5 and 6 Ă
. Although
the bivalent system is thermally more stable, the most probable rupture
forces of both systems are similar over the range of measured loading
rates. Our results prove that already in small model systems the dissociation
mechanism strongly affects the mechanical stability. The presented
approach offers the opportunity to study the force-reducing effects
also as a function of different backbone properties