title: Synthesis and luminescence properties of Cr(III) complexes with cyclam-type ligands having pendant chromophores, trans-[Cr(L)Cl(2)]Cl.
abstract: The synthesis and spectroscopic properties of new cyclam-type ligands 5,7-dimethyl-6-R-1,4,8,11-tetraazacyclotetradecane (L), where R is a pendant chromophore such as an anthracene derivative, are reported. These ligands were prepared according to a nickel(II) template procedure, and the X-ray crystal structures of several Ni(II) intermediates are described. Reaction of the free base ligands L with CrCl(3)x3THF resulted in facile formation of trans-[Cr(L)Cl(2)]Cl complexes, and the structures and spectroscopic characterizations of these complexes are also described. Examination of the photophysical properties of trans-[Cr(L)Cl(2)]Cl solutions at 77 K demonstrated the emission spectra to be dominated by phosphorescence from the ligand field doublet of the chromium(III) center. This also applies to the Cr(III) complex trans-[Cr(mac)Cl(2)]Cl, where mac is the anthracene derivative 5,7-dimethyl-6-anthracenylcyclam. Excitation into the pi-pi(*) states of the anthracene leads to marked quenching of the fluorescence from this chromophore and sensitized phosphorescence from the metal-centered doublet state.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Derosa
authors.forename: Xianhui
authors.initials: X
authors.lastname: Bu
authors.forename: Kristina
authors.initials: K
authors.lastname: Pohaku
authors.forename: Peter C
authors.initials: PC
authors.lastname: Ford
mesh_terms: D002857:Chromium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000138:chemical synthesis*; D008024:Ligands; D008163:Luminescent Measurements; D008968:Molecular Conformation; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010777:Photochemistry; D013237:Stereoisomerism
chemical_list: D006571:Heterocyclic Compounds; D008024:Ligands; D009942:Organometallic Compounds; D002857:Chromium; C024560:cyclam; D009569:Nitric Oxide; D009532:Nickel