Trinuclear Intro-Vertere Circular Helicate and Its Columnar Hexagonal Stacking

Abstract

A self-assembled discrete Pd3L′3L3 type circular helicate of hitherto unknown architecture is disclosed in this work where L′ stands for 1,10-phenanthroline (phen) and L for a triazole appended bidentate nonchelating ligand, i.e., 1,4-bis((1H-1,2,3-triazol-1-yl)methyl)benzene. The coordination environment of palladium(II) in any given PdN4 coordination planes of the helicate is described by one phen moiety and two triazole moieties belonging to different ligand strands. All the three bound phen moieties are uniquely turned inside and lodged in the internal cavity of the molecule; hence the term “intro-vertere circular helicate” is introduced. One of the PdN4 square planes is sandwiched between the other two via phen-inspired intramolecular π-stacking making a cylindrical stacking arrangement. A racemic pair designated as MPP and PMM isomers, where M and P stand for the handedness of the ligand L, is observed in the crystal structure. In the crystal packing, the trinuclear intro-vertere circular helicate m...