Toward the Self-Assembly of Metal−Organic Nanotubes Using Metal−Metal and π-Stacking Interactions: Bis(pyridylethynyl) Silver(I) Metallo-macrocycles and Coordination Polymers

Shape-persistent macrocycles and planar organometallic complexes are beginning to show considerable promise as building blocks for the self-assembly of a variety of supramolecular materials including nanofibers, nanowires, and liquid crystals. Here we report the synthesis and characterization of a family of planar di- and tri-silver(I) containing metallo-macrocycles designed to self-assemble into novel metal−organic nanotubes through a combination of π-stacking and metal−metal interactions. The silver(I) complexes have been fully characterized by elemental analysis, high resolution electrospray ionization mass spectrometry (HR-ESI-MS), IR, <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, and the solution data are consistent with the formation of the metallo-macrocycles. Four of the complexes have been structurally characterized using X-ray crystallography. However, only the di-silver(I) complex formed with 1,3-bis(pyridin-3-ylethynyl)benzene is found to maintain its macrocyclic structure in the solid state. The di-silver(I) shape-persistent macrocycle assembles into a nanoporous chicken-wire like structure, and ClO<sub>4</sub><sup>−</sup> anions and disordered H<sub>2</sub>O molecules fill the pores. The silver(I) complexes of 2,6-bis(pyridin-3-ylethynyl)pyridine and 1,4-di(3-pyridyl)buta-1,3-diyne ring-open and crystallize as non-porous coordination polymers.