title: Intermolecular binding modes in a novel [1 + 1] condensation 1H-pyrazole azamacrocycle: a solution and solid state study with evidence for CO2 fixation.
abstract: The synthesis of a novel cyclophane (L1) consisting of a 1H-pyrazole moiety linked through methylene groups to a 1,5,9,13-tetraazadecane chain is described. As far as we know, this is one of the first reported syntheses of a [1 + 1] condensation 1H-pyrazole azamacrocyclic ligand. The crystal structures of the complexes [Cu2(H(H(-1)L1))(H(-1)L1)](ClO4)3·3.75H2O (1) and ([Cu2(H(H(-1)L1))(0.5)(H(-1)L1)(1.5)]2(ClO4)3Br2·4.2H2O (2) show that Cu(2+) coordination leads to formation of 2:2 Cu(2+):L dinuclear dimeric complexes in which the 1H-pyrazole units lose a proton behaving as bis(monodentate) bridging ligands. Unlike previously reported complexes of [2 + 2] pyrazole azamacrocycles, the pyrazolate units in 1 are pointing outward from the macrocyclic cavity to bind the Cu(2+) ions. Inner coordination with formation of 1:1 Cu(2+):L complexes is however observed in [1 + 1] pyridine azamacrocycles as shown by the crystal structure here presented of the complex [CuL2](ClO4)2 (3). Crystals of [Cu3(H(-1)L1)2(CO3)(H2O)](ClO4)2·8H2O (4) grown by evaporating aqueous solution at pH 9 containing Cu(2+) and L1 in 3:2 molar ratio show the presence of a further Cu(2+) coordinated to the two free amine groups found in structures 1 and 2. The metal ion fills its coordination sphere capturing atmospheric CO2 as a η(1),η(2)-bidentate carbonate anion placed in the equatorial position and an axial water molecule. pH-metric data, UV-vis spectroscopic data, EPR measurements, and HR-ESI-MS data support that the outer coordination mode with formation of 2:2 dinuclear dimeric and 3:2 trinuclear complexes is preserved in aqueous solution.
authors.affiliation: Instituto de Ciencia Molecular, Universidad de Valencia , C/Catedrático José Beltrán Martínez, no. 2, 46980 Paterna, Valencia, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Belda
authors.forename: Javier
authors.initials: J
authors.lastname: Pitarch-Jarque
authors.forename: Conxa
authors.initials: C
authors.lastname: Soriano
authors.forename: José M
authors.initials: JM
authors.lastname: Llinares
authors.forename: Salvador
authors.initials: S
authors.lastname: Blasco
authors.forename: Jesús
authors.initials: J
authors.lastname: Ferrando-Soria
authors.forename: Enrique
authors.initials: E
authors.lastname: García-España
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D011720:Pyrazoles / Q000737:chemistry*
chemical_list: D001372:Aza Compounds; D056831:Coordination Complexes; D047028:Macrocyclic Compounds; D011720:Pyrazoles; D002245:Carbon Dioxide