Structural diversity of a series of urea-based coordination complexes: from water tapes, water-sulfate chains, to supramolecular structures

Abstract

[Hg2(L1)2I4] (1), [Cd2(L1)2I4] (2), {[Cd(L1)2(SO4)(H2O)]·4H2O}n (3), {[Zn2(L2)2(Cl)4]·0.5H2O} (4), {[Cu2(L2)2(SO4)2(H2O)4]·2.5H2O} (5), and {[Cd(L2)2(SO4)(H2O)]·3H2O}n (6), based on N–(3–picolyl)–N′–(3–pyridyl)urea (L1) or N–(4–picolyl)–N′–(3–pyridyl)urea (L2), have been synthesized and characterized by elemental analyses, IR spectra, single-crystal and powder X-ray diffraction, and thermogravimetric analyses. Complexes 1 and 2 are isomorphous and feature similar rectangular metal organic loops, which were further extended into 2-D supramolecular structures through hydrogen bonds. Complex 3 possesses a 2-D sql sheet, and the channels between the neighboring sheets are filled with lattice water molecules, which formed a 1-D water tape. Complex 4 also exhibits a rectangular metal organic loop and a 3-D supramolecular structure with the help of hydrogen bonding interactions. Complex 5 also possesses a metal organic loop, and the water molecules interacted with sulfates, constructing a 1-D water–sulfate tube. Complex 6 features a 1-D loop polymeric chain. Moreover, the solid state luminescences of 1–4 and 6 have been investigated.