Azaporphine guest–host complexes in solution and gas-phase: evidence for partially filled nanoprisms and exchange reactions

Patrick Weis,Manfred Kappes,Frank Hennrich,Ulrike Schwarz,Stefan Bräse,Danny Wagner

doi:10.1039/c3cp55486d

Abstract

Supramolecular guest-host complexes comprising various azaporphines stacked in a coordination nanoprism consisting of tris(4-pyridyl)triazines as panels, 1,4-bis(pyridyl)benzenes as pillars and (en)Pd as hinges were synthesized according to the procedure of Fujita and coworkers and characterized as ions in the gas-phase by high-resolution electrospray ionization mass spectrometry and collision induced dissociation as well as in solution by analytical ultracentrifugation. Apart from fully filled nanoprisms we have also prepared and observed partially filled as well as empty congeners in aqueous solutions. Upon mixing room temperature solutions of two types of nanoprisms, we observe that azaporphine guest exchange reactions occur on a timescale of minutes, indicating that the formation of the guest-host complexes is reversible.

Highlights

The goal of the present study was to further investigate the influence of the azaporphine guest on the energetics of these fascinating host–guest complexes
As part of our effort on completely filled nanoprisms, we have explored whether partially or even empty nanoprisms can be formed and whether the formation of the guest–host complex is reversible under room temperature solution conditions
Supramolecular guest–host complexes, ‘‘nanoprisms’’, consisting of a prismatically shaped coordination box filled with 2H and Cu-azaporphines were prepared according to the method of Fujita and coworkers.[11]

Summary

Introduction

The goal of the present study was to further investigate the influence of the azaporphine guest on the energetics of these fascinating host–guest complexes. For this we have applied a novel combination of analytical ultracentrifugation (AUC) and high resolution electrospray ionization mass spectrometry (ESI-MS) to determine the compositions of solutions containing the host–guest complexes. We have used collision induced dissociation studies to compare the gas-phase stabilities of nanoprism hosts filled with different sets of guests. Paper (17.39 mmol) of a violet, fluffy powder were obtained. For sample ‘‘2’’ we use the same protocol with 80 mmol of Cu-tetraazaporphine (which contained small amounts of metal-free tetraazaporphine, see below).

Objectives

Results

Conclusion