A Pd3L6 supramolecular cage incorporating photoactive [2.2]paracyclophane Units

Abstract

[2.2]Paracyclophane (pCp) scaffolds, unlike many -conjugated building blocks, have been rarely explored in supramolecular self-assembly. Herein we report the synthesis and characterization of two ligands, pCpd3py and pCpd4py , composed of a pCp core functionalized at its 7- and 15-positions respectively with 3-pyridyl and 4-pyridyl units. The self-assembly of pCpd4py with Pd2+ metal ions afforded a [Pd3( pCpd4py )6]6+ cage structure, pCpd4py-Pd , where the six pCpd4py ligands doubly bridge each edge of the Pd3 triangular core. The ligand pCpd4py and the palladium cage pCpd4py-Pd have been characterized by NMR spectroscopy, ESI-MS spectrometry and X-ray diffraction analyses and their photophysical properties investigated by steady-state and time-resolved emission spectroscopy as well as Time-Dependent Density Functional Theory calculations.