title: Aggregation of [Cu(II)4] building blocks into [Cu(II)8] clusters or a [Cu(II)4]infinity chain through subtle chemical control.
abstract: Coordination complexes of the ligand H3L [1,3-bis(3-oxo-3-phenylpropionyl)-2-hydroxy-5-methylbenzene] with Cu(II) are reported. Clusters showing various nuclearities or modes of supramolecular organization have been prepared by slightly changing the reaction conditions and have been crystallographically characterized. The reaction of H3L with one equivalent of Cu(OAc)2 in DMF yields the dinuclear complex [Cu2(HL)2(dmf)2] (1). Reaction in MeOH of H3L with an increased amount of metal, in the form of Cu(NO3)2, and excess strong base (nBu4NOH) affords the cluster [Cu8(L)2(OMe)8(NO3)2] (2). Complex 2 is a dimer of two linear [Cu4] arrays bridged by methoxide ligands, where the polynucleating ligand is fully deprotonated. The [Cu4]2 clusters are linked to each other by NO3- bridges to form one-dimensional coordination polymers. The link between [Cu8] units and their relative spatial positioning can be modified by changing the anion of the Cu(II) salt, as demonstrated by the synthesis of the cluster polymers [Cu8(L)2(OMe)8Cl2] (3) and [Cu8(L)(OMe)7.86Br2.14] (4), where only NO3- has been replaced by Cl- or Br-, respectively. Similarly, when ClO4- is used, compound [Cu8(L)2(OMe)8(ClO4)2(MeOH)4] (5) can be isolated. It contains independent [Cu8] units. A slight change in the stoichiometry of the reaction leading to 2 affords the related complex catena-[Cu4(L)(OMe)3(NO3)2(H2O)0.36] (6). This polymer contains essentially the same [Cu4] moiety as 2, albeit organized in a completely different arrangement. Each [Cu4] unit in 6 is linked by OMe- ligands to two such equivalent groups to form an infinite chain. Magnetic susceptibility measurements reveal weak antiferromagnetic exchange between Cu(II) centers in 1 (J = -0.73 cm(-1)) and strong antiferromagnetic coupling within [Cu4] chains in 2, 5, and 6 (most negative J values of -113.8 and -177.3 cm(-1) for 2 and 6, respectively).
authors.affiliation: Departament de Química Inorgànica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain. guillem.aromi@qi.ub.es
authors.forename: Guillem
authors.initials: G
authors.lastname: Aromí
authors.forename: Joan
authors.initials: J
authors.lastname: Ribas
authors.forename: Patrick
authors.initials: P
authors.lastname: Gamez
authors.forename: Olivier
authors.initials: O
authors.lastname: Roubeau
authors.forename: Huub
authors.initials: H
authors.lastname: Kooijman
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Spek
authors.forename: Simon
authors.initials: S
authors.lastname: Teat
authors.forename: Elizabeth
authors.initials: E
authors.lastname: MacLean
authors.forename: Helen
authors.initials: H
authors.lastname: Stoeckli-Evans
authors.forename: Jan
authors.initials: J
authors.lastname: Reedijk
mesh_terms: D001555:Benzene Derivatives / Q000138:chemical synthesis / Q000737:chemistry*; D003300:Copper; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009930:Organic Chemicals / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D008024:Ligands; D009930:Organic Chemicals; D003300:Copper