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

Abstract

Refluxing 1,2-bis(2-cyanoguanidino)ethane (L 1 ) in methanol or ethanol containing copper() sulfate resulted in the formation of [CuL 3m ][MeOSO 3 ] 2 {L 3m = [HN᎐ ᎐ C(OMe)NHC(NH 2 )᎐ ᎐ NCH 2 ] 2 } and [CuL 3e ][EtOSO 3 ] 2 {L 3e = [HN᎐ ᎐ C(OEt)NHC(NH 2 )᎐ ᎐ NCH 2 ] 2 }. Structural analysis of these complexes has revealed hydrogen-bonded supramolecular architectures constructed from [CuL i ] 2ϩ cations with square planar CuN 4 chromophores and [ROSO 3 ] Ϫ anions. The basic supramolecular synthon is a 1-D chain of alternating cations and anions, a motif which is also found with Cl Ϫ and [BF 2 (OMe) 2 ] Ϫ anions. The [ROSO 3 ] Ϫ 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 hydrophilic SO 3 Ϫ moiety forms N-H ؒ ؒ ؒ O hydrogen bonds with their amino and imino functionalities. In [CuL 3m ][MeOSO 3 ] 2 the chains, which are linear, are 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 elongated octahedral geometry for the copper() centre. In [CuL 3e ][EtOSO 3 ] 2 the chains, which are sinusoidal, are hydrogen bonded through a second ethyl sulfate anion to give a bilayered arrangement. The bilayers aggregate into 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() centre. Despite the fit between [CuL i ] 2ϩ cations and alkyl sulfate anions in the chain, when a mixture of anions (chloride and ethyl sulfate) is present in the crystallisation medium, the preferred chain supramolecular synthon of the product, [CuL 3e ][EtOSO 3 ]Clؒ2H 2 O, is that containing chloride. The ethyl sulfate anions are involved, together with water molecules, in a complex hydrogen-bonding network which connects the chains into 2-D sheets, which are assembled, in turn, into a 3-D network structure by a combination of hydrogen bonding networks and exceedingly weak Cu ؒ ؒ ؒ Cl co-ordinative interactions, which give rise to a square pyramidal copper() co-ordination geometry.

A brief review on structural concepts of novel supramolecular proton transfer compounds and their metal complexes

“…Also, a polymeric complex formulated as [Zn 12 (hypydc) 12 (H 2 O) 10 .12H 2 O] n [130] is synthesized using the title ion pair that shows three different coordination numbers 4, 5 and 6 for Zn II ion. In addition to covalent and coordination bonds, there are -interactions and hydrogen bonds binding the fragments to each other (Fig.…”

“…E-mail: aghabozorg@saba.tmu.ac.ir networking. In one approach, which is the more frequently used, coordinative covalent bonds engaged between main group, transition or lanthanide elements and various organic linkers, propagate the coordination geometry into infinite architectures of various dimensionality and topology [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The other method, still far less common, exploits weaker intermolecular forces (particularly -stacking, hydrogen bonding, and ion pairing) as a guide to the assembly of molecular coordination complexes into extended organized networks [9][10][11][12].…”

An unexpected in situ formation of a substitute tetrazole ligand and its Mn(II) and Cu(II) complexes

“…There is currently considerable interest in selfassembly and construction of supramolecular compounds with fantastic architectures via noncovalent interactions such as coordination bonds, hydrogen bonds and other weak intermolecular interactions [1][2][3]. Hydrogen bonds, combining directionality, strength and selectivity, have been noted as the most versatile organizing force to assemble superstructures [4].…”

Synthesis and spectroscopic studies on novel Cu(II)–Cu(II) binuclear adducts. EPR evidence for ferromagnetic interactions

“…It is pertinent to note that the reaction of cupric sulfate with 1,2-bis(2-cyanoguanidino) ethane in methanol or ethanol gives the formation of complex cations with square planar CuN 4 chromophores and forming [(alkyl)OSO 3 ] À anions resulting hydrogenbonded supramolecular architectures [10]. The solutions were kept for several days to form complexes in methanol or ethanol having very weak CuÁ Á ÁO coordinative interactions.…”