Supramolecular Architectures of Metal Complexes Controlled by a Strong π···π Stacking, 1,8-Naphthalimide Functionalized Third Generation Tris(pyrazolyl)methane Ligand

Abstract

A new hetero-bifunctional ligand designed to form supramolecular structures with a combination of covalent and noncovalent forces has been prepared. The ligand, (1,8-naphthalimide)CH2C6H4CH2OCH2C(pz)3 (Ltris, pz = pyrazolyl ring), contains both a tris(pyrazolyl)methane coordination unit and a 1,8-naphthalimide strong π···π stacking unit. The reactions of iron(II), copper(II), and cadmium(II) tetrafluoroborate salts with 2 equiv of Ltris yield [Fe(Ltris)2](BF4)2 (1), [Cd(Ltris)2](BF4)2 (2), and [Cu(Ltris)2](BF4)2 (3), respectively. Vapor diffusion crystallization yielded two pseudopolymorphs for 1. In the solid-state structures of both forms, the iron is in an octahedral environment with bond distances expected for low-spin iron(II); both tris(pyrazolyl)methane donor sets are in a κ3-coordination mode with each Ltris ligand in a U-shaped, syn arrangement. In one pseudopolymorph, the 1,8-naphthalimide side chains are on the same side of the molecule when viewed down the metal axis (syn-1), twisted only 30° ...