A 3D supramolecular framework assembled via π⋅⋅⋅π interactions and CH⋅⋅⋅Cl hydrogen-bonds with second-harmonic generation response

Abstract

A three-dimensional (3D) supramolecular framework [CuII2Cl3(tpen)]2⋅[CuIICl4] (1) (tpen = N,N,N',N'-tetra(2-pyridylmethyl) ethylenediamine) assembled from [CuII2Cl3(tpen)]+ and [CuIICl4]2– via π⋅⋅⋅π interactions and CH⋅⋅⋅Cl hydrogen-bonds has been obtained by solvothermal synthesis. The π-stacked supramolecular layers of the [CuII2Cl3(tpen)]+ ions are connected by the [CuIICl4]2– anions in a distorted tetrahedral geometry to form a 3D architecture via CH⋅⋅⋅Cl hydrogen-bonds. Due to the helical alignment of the [CuII2Cl3(tpen)]+ and the oriented [CuIICl4]2–, compound 1 crystallizes in the tetragonal non-centrosymmetric (NCS) space group P–421/c. The compound shows a moderate band-gap of 2.48 eV and a UV cutoff edge of 420 nm. For the NCS structure of compound 1, a phase-matchable second harmonic generation (SHG) response of ~0.009 times that of KH2PO4 (KDP) was observed.