Anion recognition by conservation of hydrogen-bonding patterns in salts ofcopper(II) co-ordinated by tetradentate bis(amidino-O-alkylurea) ligands

Refluxing 1,2-bis(2-cyanoguanidino)ethane (L-1) in methanol or ethanol cont aining copper(II) sulfate resulted in the formation of [CuL3m][MeOSO3](2) { L-3m=[HN=C(OMe)NHC(NH2)=NCH2](2)} and [CuL3e][EtOSO3](2) {L-3e=[HN=C(OEt)NH C(NH2)=NCH2](2)}. Structural analysis of these complexes has revealed hydro gen-bonded supramolecular architectures constructed from [CuLi](2+) cations with square planar CuN4 chromophores and [ROSO3](-) anions. The basic supr amolecular synthon is a 1-D chain of alternating cations and anions, a moti f which is also found with Cl- and [BF2(OMe)(2)](-) anions. The [ROSO3](-) anion is an ideal fit for the space between two cations; its hydrophobic O- alkyl group is surrounded by the O-alkyl groups of the cations and its hydr ophilic SO3- moiety forms N-H . . .O hydrogen bonds with their amino and im ino functionalities. In [CuL3m][MeOSO3](2) the chains, which are linear, ar e hydrogen bonded through a second methyl sulfate anion to give a 2-D sheet motif. The sheets are bound together to form a 3-D framework through very weak Cu . . .O co-ordinative interactions which complete a tetragonally elo ngated octahedral geometry for the copper(II) centre. In [CuL3e][EtOSO3](2) the chains, which are sinusoidal, are hydrogen bonded through a second eth yl sulfate anion to give a bilayered arrangement. The bilayers aggregate in to a 3-D framework by a combination of hydrogen bonding and weak Cu . . .O co-ordinative interactions which result in a square pyramidal co-ordination geometry for the copper(II) centre. Despite the fit between [CuLi](2+) cat ions and alkyl sulfate anions in the chain, when a mixture of anions (chlor ide and ethyl sulfate) is present in the crystallisation medium, the prefer red chain supramolecular synthon of the product, [CuL3e][EtOSO3]Cl . 2H(2)O , is that containing chloride. The ethyl sulfate anions are involved, toget her with water molecules, in a complex hydrogen-bonding network which conne cts the chains into 2-D sheets, which are assembled, in turn, into a 3-D ne twork structure by a combination of hydrogen bonding networks and exceeding ly weak Cu . . . Cl co-ordinative interactions, which give rise to a square pyramidal copper(II) co-ordination geometry.