title: Synthesis and structural studies of two pyridine-armed reinforced cyclen chelators and their transition metal complexes.
abstract: Two novel pyridine pendant-armed macrocycles structurally reinforced by an ethyl bridge, either between adjacent nitrogens (for side-bridged) or non-adjacent nitrogens (for cross-bridged), have been synthesized and complexed with a range of transition metal ions (Co2+, Ni2+, Cu2+and Zn2+). X-ray crystal structures of selected cross-bridged complexes were obtained which showed the characteristic cis-V configuration with potential labile cis binding sites. The complexes have been characterized by their electronic spectra and magnetic moments, which show the expected high spin divalent metal complex in most cases. Exceptions are the nickel side-bridged complex, which shows a mixture of high-spin and low spin, and the cobalt cross-bridged complex which has oxidized to cobalt(III). Cyclic voltammetry in acetonitrile was carried out to assess the potential future use of these complexes in oxidation catalysis. Selected complexes offer significant catalytic potential enhanced by the addition of the pyridyl arm to a reinforced cyclen backbone.
authors.affiliation: Department of Chemistry and Physics, Southwestern Oklahoma State University, 100 Campus Drive, Weatherford, Oklahoma 73096, United States.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Wilson
authors.affiliation: Department of Chemistry and Physics, Southwestern Oklahoma State University, 100 Campus Drive, Weatherford, Oklahoma 73096, United States.
authors.forename: Desiray J
authors.initials: DJ
authors.lastname: Cannon-Smith
authors.affiliation: Department of Chemistry and Positron Emission Tomography Research Centre, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Burke
authors.affiliation: Department of Chemistry and Physics, Southwestern Oklahoma State University, 100 Campus Drive, Weatherford, Oklahoma 73096, United States.
authors.forename: Orry C
authors.initials: OC
authors.lastname: Birdsong
authors.affiliation: Department of Chemistry and Positron Emission Tomography Research Centre, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Archibald
authors.affiliation: Department of Chemistry and Physics, Southwestern Oklahoma State University, 100 Campus Drive, Weatherford, Oklahoma 73096, United States.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Hubin
keywords: cross-bridged; cyclen; pendant-armed; pyridyl; reinforced macrocycles; tetraazamacrocycles