Selective formation of integrated stacks of (α-diimine)(ethylenediamine)platinum(II) and neutral π systems of the phenanthrene type

Abstract

The [Pt(en)(L)]²⁺ (L = bipy or phen) complexes with a planar α-diimine ligand and a non-planar diamine ligand formed 1∶1 integrated stacks taking up free phen and phenanthrene (phe) selectively. The stacking structures of the composite crystals [Pt(en)(L)][PF₆]₂·phen·2H₂O (L = bipy or phen) and [Pt(en)(bipy)][PF₆]₂·phe have been elucidated by X-ray analysis. Both π–π interactions and hydrogen bonds lead to easy and selective uptake of phen to form the integrated stack while it is possible for phe with no hydrogen bonding ability to form a similar integrated stack. The composite crystals exhibit emission spectra which originate from the ³ππ*(L) state of [Pt(en)(L)]²⁺ in the integrated stack. The emission properties indicate facile energy transfer from free phen or phe to [Pt(en)(L)]²⁺ in the stacks.