ABSTRACT
A new 1D coordination polymer comprised of [Mn(III)(6)O(2)(Et-sao)(6)(EtOH)(4)(H(2)O)(2)](2+) units and bithiophene dicarboxylato was synthesized by mixing EtsaoH(2) (salicylaldoxime), H(2)btda (2,2'-bithiophene-5,5'-dicarboxylic acid) and Mn(ClO(4))(2)·6H(2)O in the presence of NEt(4)OH. The crystal structure was determined and consists of Mn(6) clusters bridged by the bithiophene dicarboxylato ligands coordinated to two of the Mn(III) ions of the Mn(6) polynuclear complex. Direct current magnetic measurements show an overall ferromagnetic interaction between the Mn(III) ions within the Mn(6) cluster leading to an S = 12 ground state for the Mn(6) unit. Furthermore, this compound presents single-molecule magnet behaviour. Slow relaxation of the magnetization is observed at low temperature following a thermal activated regime with U(eff) approximately 50 K and tau(0) approximately 2.2 10(-10) s. The magnetic measurements do not show any noticeable interaction between the Mn(6) clusters through the bithiophene dicarboxylato bridges.
ABSTRACT
Self-assembled monolayers (SAMs) of a bis(pyrazol-1-yl)pyridine-substituted thiol (bpp-SH) on Au (111)/mica were studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Using substrates precoated with perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA), preparation at elevated temperatures yields highly ordered layers whose structure is described by a rectangular (5 x radical3) unit cell containing one molecule. The bis(pyrazol-1-yl)pyridine (bpp) units exhibit pi-stacking along the 112 direction, and they are tilted significantly. We conclude the three imine nitrogen atoms in the bpp headgroup adopt a trans,trans arrangement.
Subject(s)
Gold Radioisotopes/chemistry , Pyrazoles/chemistry , Pyridines/chemistry , Carbon/chemistry , Carboxylic Acids/chemistry , Imines/chemistry , Microscopy, Scanning Tunneling/methods , Molecular Conformation , Nitrogen/chemistry , Perylene/chemistry , Photons , Sulfhydryl Compounds , Surface Properties , TemperatureABSTRACT
A tetrapodal pentadentate nitrogen ligand (2,6-bis(1,1-di(aminomethyl)ethyl)pyridine, 1) is used for the synthesis of the azido-iron(III) complex [(1)Fe(N3)]X2 where X is either Br or PF6. By means of electrospray ionization mass spectrometry, the dication [(1)Fe(N3)]2+ can be transferred into the gas phase as an intact entity. Upon collisional activation, [(1)Fe(N3)]2+ undergoes an expulsion of molecular nitrogen to afford the dicationic nitrido-iron species [(1)FeN]2+ as an intermediate, which upon further activation can intramolecularly activate C-H- and N-H bonds of the chelating ligand 1 or can transfer an NH unit in bimolecular reactions with activated olefins. The precursor dication [(1)Fe(N3)]2+, the resulting nitrido species [(1)FeN]2+, and its possible isomers are investigated by mass spectrometric experiments, isotopic labeling, and complementary computational studies using density functional theory.
