Highly Efficient Mechanochemical Scission of Silver-Carbene Coordination Polymers

Abstract

The ultrasound-induced scission of silver carbene coordination complexes with polytetrahydrofuran-functionalized N-heterocyclic carbene ligands is reported. In solution, scission is very efficient, with complete conversion within 10 min when the polymers have a molecular weight of 6.7 kDa. The mechanochemical origin of the scission is supported by the molecular weight dependence of the scission rate and by the low reactivity of the silver complex with low molecular weight ligands. The mechanochemical process at room temperature is much faster than thermal scission at 60 degreesC, which has a conversion of 30% in 18 h.

Theoretical Approaches for Understanding the Interplay Between Stress and Chemical Reactivity

“…Measuring F for multiple values of R yields a force-extension curve, which can be useful in determining the values of F needed to induce processes such as the unfolding proteins [35,56,57] or the rupture of polymers [58,59]. At the other end of the spectrum, isotensional conditions involve subjecting a molecule to a constant tensile force, F, and allowing the affected degrees of freedom to change as needed to accommodate F. Such conditions have been achieved in AFM experiments of stretched macromolecules [7,60] and the ultrasonic cleavage of metalligand coordination complexes [61][62][63], for example. Of course, in practice, the need to move between different values of F or R, as well as phenomena such as thermal fluctuations, lead to deviations from strictly controlled separation or isotensional conditions in experiments.…”

Mechanochemical Reactions Reporting and Repairing Bond Scission in Polymers

“…Furthermore, polymers which include both Pd II and Pt II were sonicated and it was shown that force selectively breaks the weaker Pdphosphine bonds which were randomly distributed along the polymer backbone [80]. Following the work on metal-phosphine coordination polymers, the group started investigating mechanical dissociation of silver(I)-coordination complexes with N-heterocyclic carbene (NHC) functionalised polymers [81]. It has been shown that polymers with an Ag(NHC) 2 coordination complex in the pTHF main chain have significantly lower M lim values.…”

Sonophotocatalytic Degradation of Poly (Vinyl Pyrrolidone) in the Presence of Fe (III)/H2O2

“…Ultrasound can be used to apply force to dilute polymer solutions. Since its initial use to degrade starch and agar [2], this technique has also been employed to degrade cellulose [3], polypeptides, polysaccharides [4,5], proteins [6], DNA [7], transition metal-coordinated polymers [8][9][10], and various organic polymers [11,12].…”