title: Dinuclear versus tetranuclear cluster formation in zinc(II) nitrate/di-2-pyridyl ketone chemistry: synthetic, structural and spectroscopic studies.
abstract: The use of di-2-pyridyl ketone, (py)2CO, in zinc(II) nitrate chemistry has yielded a dinuclear complex and a cationic tetranuclear cluster. The 1:1 Zn(NO3)2.4H2O/(py)2CO reaction system in EtOH gives [Zn2(NO3)2{(py)2C(OEt)O}2].0.5H2O (1.0.5H2O), whereas the same reaction system in MeCN yields [Zn4(NO3)3{(py)2C(OH)O}4(H2O)](NO3) (2). The monoanionic derivatives of the hemiacetal and the gem-diol forms of di-2-pyridyl ketone have been derived from the ZnII-mediated addition of solvent (EtOH, H2O involved in MeCN) on the carbonyl group of (py)2CO. Each (py)2C(OEt)O- ion functions as an eta1:eta2:eta1:mu2 ligand in 1.0.5H2O chelating the two ZnII atoms through the 2-pyridyl nitrogen atoms and the common bridging, deprotonated oxygen atom; one asymmetric chelating nitrate completes six coordination at each metal center. The tetranuclear cluster cation of 2 has a cubane topology with the ZnII ions and the deprotonated oxygen atoms from the four eta1:eta3:eta1:mu3 (py)2C(OH)O- ligands occupying alternate vertices. Three monodentate nitrates and one aqua ligand complete the sixth coordination site at the metal ions. The two complexes have been characterized by IR and far-IR spectroscopies. Characteristic bands are discussed in terms of the known structures and the coordination modes of the nitrato ligands. Upon excitation at 371 nm, complex 2 displays blue photoluminescence in the solid state at room temperature with two emission maxima at 430 and 455 nm.
authors.affiliation: Department of Chemistry, University of Patras, 26504 Patras, Greece.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Katsoulakou
authors.forename: Vlasoula
authors.initials: V
authors.lastname: Bekiari
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Raptopoulou
authors.forename: Aris
authors.initials: A
authors.lastname: Terzis
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Lianos
authors.forename: Evy
authors.initials: E
authors.lastname: Manessi-Zoupa
authors.forename: Spyros P
authors.initials: SP
authors.lastname: Perlepes
mesh_terms: D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000737:chemistry; D002104:Cadmium / Q000737:chemistry; D018360:Crystallography, X-Ray; D007477:Ions; D008027:Light; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009566:Nitrates / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D013696:Temperature; D015032:Zinc / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: C418768:2,2'-dipyridylketone; D007477:Ions; D009566:Nitrates; D017967:Zinc Compounds; D002104:Cadmium; D015082:2,2'-Dipyridyl; C042103:zinc nitrate; D015032:Zinc