Supramolecular self-assembly and anion-dependence of copper(II) complexes with cationic dihydro-imidazo phenanthridinium (DIP)-containing ligands

Abstract

We present two new ligands, 2,3-dihydro-1-(2-pyridyl-methyl)-imidazo[1,2-f]phenanthridinium bromide (L1·Br) and 2,3-dihydro-1-(4-pyridyl-methyl)-imidazo[1,2-f]phenanthridinium bromide (L2·Br), which have been synthesized and fully characterized as coordinating cations. The reactions of Cu(BF₄)₂ (compound 1), Cu(NO₃)₂ (compound 2), CuBr₂ (compound 3), Cu(NO₃)₂ and NaN₃ (compound 4), Cu(NO₃)₂ and NaSCN (compound 5) with L1·Br and CuBr₂ with L2·Br (compound 6) have been carried out. The crystal structures of the resulting metal–organic assemblies have been determined and the intermolecular interactions of the compounds in the crystalline phase have been analysed. A mononuclear copper(II) compound has been obtained with CuBr₂, in which the copper(II) ion adopts a tetrahedral geometry with a CuNBr₃ coordination motif. With Cu(BF₄)₂, two L1⁺ cations and two bromide anions chelate the copper ion giving a CuN₂Br₂ motif, while the BF₄⁻ is present as a non-coordinating counterion. With Cu(NO₃)₂, a five coordinated copper complex is obtained whereas when bridging ligands such as NaN₃ and NaSCN are added into the reaction mixture of L1·Br and Cu(NO₃)₂, two novel dinuclear copper coordination cores of [Cu₂(μ_1,1-N₃)₂(N₃)₄]²⁻ and Cu(CH₃O)₂(SCN)₄]²⁻ form. The presence of the large heteroaromatic cationic DIP moiety within the ligand system leads to the formation of 1-, 2- and 3-D supramolecular arrays based on the interactions of the π systems between adjacent molecules.