Coordination polymers of perylenetetracarboxylate with Cs(I) ions: 3D structures with 2D inorganic layers or triple coordination nets

Abstract

The self-assembly of perylenetetracarboxylate (ptc) with Cs(I) ions at ambient temperature has been investigated with two coordination polymers being synthesized and structurally characterized. The diffusion of ethanol into a Cs-ptc solution led to the formation of compound 1 [(Cs4(ptc)(H2O)5·nH2O] displaying a compact three-dimensional (3D) structure constructed with 2D undulating layers of Cs polyhedra linked by ptc ligands in two types coordination modes. Extensive π···π interactions among stacking ptc ligands formed large hydrophobic organic channels between the inorganic layers. The addition of ethylenediamine (ED) to the reaction system afforded the formation of compound 2 [(H2ED)5Cs2(ptc)3(H2O)10] showing triple 2D coordination nets with protonated ethylene diammonium cations hydrogen-bonded to both non-bonded carboxyl oxygen and coordinated water molecules. The triple 2D nets are further linked via hydrogen bonding to form a 3D structure. The optical absorption, band gap analysis, vibrational modes and thermal stability of compound 1 were also investigated. Overall, the structural diversity was achieved in the studied self-assembly system at ambient temperature through varying Cs to ptc ratios by introducing ethylene diammonium as a non-metal cation.