Polymorphism and photoluminescence in a naphthalene-based ligand, and its supramolecular structures through second-sphere coordination with the [CoCl4]2− anion

A naphthalene-based ligand, N,N,N′,N′-tetrabenzyl-naphthalene-1,5-diamine (L1) has been synthesized and crystallized as two polymorphs, α and β. There are no strong hydrogen bonding donors, instead C–Hπ interactions play critical roles in the stabilization of the structures of the two polymorphs with different packing motifs. The ligand L1 can be doubly protonated and coordinate with the “second-sphere” of [CoCl4]2− using N–H hydrogen bond donors to form two neutral supramolecular complexes [H2L1]2+[CoCl4]2− (1) and EtOH ⊂ [H2L1]2+[CoCl4]2− (2). L1 in 1 and 2 adopts the arrangement manner of stable polymorph α. The [CoCl4]2− anions are connected with L1 through N–HCl interactions, meanwhile, the anion [CoCl4]2− acting as an “off–on” switching template controls the photoluminescence.