Products Cited in Publications Worldwide Development of Redox-Active Pt2+–Linked Porphyrin Nanocages and Modulation of Their Host–Guest Properties

Development of Redox-Active Pt2+–Linked Porphyrin Nanocages and Modulation of Their Host–Guest Properties

Kaitlyn Grace Dutton

Abstract

Metal-organic cages are often targeted for applications in which it is useful to tune the encapsulation of guest molecules inside a nanoporous environment. Modulating uptake and release of cargo from a host-guest complex usually requires control over the thermodynamic forces that favor association, and this control is commonly attained via addition of an external stimulus to interrupt the favorability of the inclusion complex. However, the stimuli used to alter guest binding often employ harsh conditions (eg, reducing or acidic conditions), so robust nanocages that can withstand these additives are of interest for investigating guest affinity. In this thesis, we present four related electroactive Pt 2+-porphyrinic nanocages that differ primarily in the capping substituents at the linkers and structure types (M 6 L 3 vs M 4 L 2). The incorporation of additional electroactive sites into the linkers of one cage increased its stability to reducing conditions relative to the cages without added redox activity. The affinity for anions to bind to the hosts was investigated using cages that differ only by the size of the cavity or the hydrogen-bond-donation ability of the linkers. The affinity for a host to bind strongly-or weakly-associating guests could be swapped via an acid stimulus. Redox stimuli could be used to form thermodynamically unfavored cation-in-cation complexes with two hosts, where metallocene cations bind in the reduced hosts and become trapped (for weeks to months) upon reoxidation of the host. Redox stimuli could also be used to tune the pK a of benzoic acid guests encapsulated in the metallated versions of one host. The presence and oxidation state of Lewis acidic metal centers in the porphyrin walls of a cage gave rise to ap K a swing of 12 units for the bound benzoic acid guest. The last chapter details common misconceptions found in interpretations of Frost diagrams and introduces means to clarify confusion surrounding these diagrams.

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Dipotassium tetrachloroplatinate

A12848810025-99-798%

Dipotassium tetrachloroplatinate

317.0/10g

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