From Molecular Design to Supramolecular Design: Synthesis and Size-Selective Coordination Chemistry of 1,2-Bis(2‘-pyrazineethynyl) Benzene

The synthesis and coordination chemistry of 1,2-bis(2‘-pyrazineethynyl)benzene are presented. With
four Lewis base sites, the ligand may adopt a conformation in which two nitrogen atoms face inward and two nitrogens
face out. In this conformation, it may complex transition metal cations either “internally” or “externally”. An “internal”
1:1 complex is formed with silver(I) nitrate, while the larger dicopper(II) tetraacetate moiety does not fit in the
internal cavity and is thus externally coordinated by two separate ligands as a 2:2 coordination complex. When
mixed with 1 equiv each of silver(I) cation and copper(II) acetate the ligand selectively complexes the cations and
a coordination complex with two “internally coordinated” silver(I) cations and an “externally coordinated” dimeric
copper(II) acetate moiety is obtained. Self-assembly with 1 equiv of silver(I) nitrate and 2 equiv of copper(II) acetate
results in the formation of a mixed-metal coordination polymer with alternating silver and copper centers. In the
presence of an excess of silver(I) cations, an infinite one-dimensional coordination polymer is formed with one
“internal” and one “external” silver(I) cation.