From “naked” copper(II) ions and asymmetric macrocyclic complex linkers with a monodentate top and a bidentate top to molecular rectangle and infinite molecular rectangle strands

A molecular rectangle [Cu{CuL1(NO3)}(H2O)(NO3)]2 (1) and two infinite molecular rectangle strands {[Cu{CuL1(NO3)}2] · 2H2O}∞ (2) and [Cu{CuL2(ClO4)}2]∞ (3) were prepared by reaction of “naked” Cu(II) ions with macrocyclic complex ligands CuL1 for 1 and 2 and CuL2 for 3 in metal-to-ligand molar ratios of 1:1, 1:2 and 1:2, respectively. L1 and L2 denote the dianions of diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate and diethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate, respectively. The structures of 1–3 were determined by X-ray single-crystal analyses. CuL1 in 1 and 2 and CuL2 in 3 act as angular linkers with a monodentate coordination top and a bidentate one between two Cu(II) nodes to enclose the molecular rectangle of 1 and the rectangular subunits of 2 and 3. The angular shape, the monodentate top plus bidentate top coordination mode and the self-complementarity for π⋯π interactions of the macrocyclic complex linkers, the ratio between the reactants and the octahedral coordination geometry of the naked Cu(II) ions jointly determined the interesting structures of metallocyclophane 1 and 1D double chain coordination polymers 2 and 3. The cavities of the rectangular molecules of 1 are arranged into infinite strands so that parallel channels occur in the crystal. The molecules of 2 and 3 all pack parallel in the crystals.

The features, i.e. the monodentate top plus bidentate top coordination mode, the self-complementarity for π⋯π interactions and the angular shape, of the macrocyclic linkers are important for the formation of the molecular metallorectangle and the two infinite metallorectangle strands.Figure optionsDownload as PowerPoint slide