ABSTRACT
Molecular spintronics is currently attracting a lot of attention due to its great advantages over traditional electronics. A variety of self-assembled molecule-based devices are under development, but studies regarding the reliability of the growth process remain rare. Here, we present a method to control the length of molecular spintronic chains and to make their terminations chemically inert, thereby suppressing uncontrolled coupling to surface defects. The temperature evolution of chain formation was followed by X-ray photoelectron spectroscopy to determine optimal growth conditions. The final structures of the chains were then studied, using scanning tunneling microscopy, as a function of oligomerization conditions. We find that short chains are readily synthesized with high yields and that long chains, even exceeding 70mers, can be realized under optimized growth parameters, albeit with reduced yields.
ABSTRACT
The structure of the title compound, [Cu4(CH3O)4(C11H13O2)4], consists of dimeric dinuclear copper(II) complexes oriented around a centre of inversion. Within each dinuclear fragment, the two Cu(II) atoms are in a distorted square-planar coordination sphere. Two neighbouring fragments are linked by four apical Cu-O contacts, yielding an overall square-pyramidal coordination environment for each of the four Cu(II) atoms. The mol-ecules are arranged in layers parallel to (101). Non-classical C-Hâ¯O hydrogen-bonding inter-actions are observed between the layers.
ABSTRACT
An important development in recent synthesis strategies is the formation of electronically coupled one and two-dimensional organic systems for potential applications in nanoscale molecule-based devices. Here, we assemble one-dimensional spin chains by covalently linking basic molecular building blocks on a Au(111) surface. Their structural properties are studied by scanning tunneling microscopy and the Kondo effect of the basic molecular blocks inside the chains is probed by scanning tunneling spectroscopy. Tunneling spectroscopic images reveal the existence of separate Kondo regions within the chains while density functional theory calculations unveil antiferromagnetic coupling between the spin centers.
Subject(s)
Models, Chemical , Models, Molecular , Nanostructures/chemistry , Nanostructures/ultrastructure , Organic Chemicals/chemistry , Polymers/chemistry , Computer Simulation , Particle SizeABSTRACT
Previous empirical assignments of the normal modes of Ru(η(5)-C(5)H(5))(2) were checked against the results of a calculation applying density functional theory (DFT). After some reassignments, following those recently suggested for Fe(η(5)-C(5)H(5))(2) (after theoretical model calculations), a satisfactory agreement was observed. Recently communicated polarized Raman spectra of an oriented Ru(η(5)-C(5)Me(5))(2) single crystal were used here for the identification of the irreducible representations of a number of Raman active normal modes (assuming molecular D(5h) symmetry) which agree well with the results of the DFT calculation. The energies of IR active fundamental vibrations, extracted from recently communicated FIR/MIR spectra (pellets), were correlated with comparable energies of IR allowed irreducible representations of the DFT calculation and assigned. Both the skeletal and the intra-ligand normal modes could be correlated with the idealized standard motions (ν(i)s) of the model sandwich complex Ru(C(5)C(5))(2), and previous assignments had to be revised. Neglecting the νCH vibrations (which are off by ca. 50cm(-1)) an r.m.s. deviation of 9.8cm(-1) (for 47 assignments) of the remaining normal modes could be achieved.
Subject(s)
Cyclopentanes/chemistry , Organometallic Compounds/chemistry , Ruthenium/chemistry , Electrons , Models, Molecular , Quantum Theory , Spectrophotometry, Infrared , Spectrum Analysis, RamanABSTRACT
The disubstitution of 1,8-diiodonaphthalene (1) with cyclopentadienyl nucleophiles reveals 1,8-(dicyclopentadienyl)-naphthalene, which rapidly undergoes Diels-Alder reaction forming 1,8-(3a',4',7',7a'-tetrahydro-4',7'-methanoindene-7a',8'-diyl)-naphthalene (2). A subsequent retro-Diels-Alder reaction in the presence of sodium hydride yields the disodium salt of 1,8-(dicyclopentadiendiyl)-naphthalene 3. The disodium salt 3 was the starting material to obtain the paramagnetic bisnickelocene derivative 4, which structure was obtained by X-ray structure analysis, revealing two nickelocenes kept together in a stacked fashion by a 1,8-naphthalene clamp. An electronic interaction between the two nickel atoms is found as a result of cyclic voltammetry, indicating five different oxidation states +4, +3, +2, +1, and 0. The magnetic properties of 4 in solution were studied by variable temperature paramagnetic (1)H NMR spectroscopy and Evans method and revealed Curie behavior between 213 and 293 K. The magnetic susceptibility of a powdered sample of 4 was measured, and an antiferromagnetic interaction with an exchange coupling of J(12) = -31.49 cm(-1) is found. In accord with experimental data, broken symmetry density functional theory (DFT) calculations revealed four antiferromagnetically coupled electrons resulting in an open shell singlet ground state.
ABSTRACT
In the title compound, [Pt(NO(3))(2)(C(42)H(42)O(2)P(4))(2)]·4CH(3)OH, the Pt atom positioned on a crystallographic centre of inversion. The two symmetry-equivalent nitrate anions are weakly coordinated to the Pt(II) ion, creating, together with four P ligand atoms, a distorted octa-hedral coordination environment. In addition, several close C-Hâ¯O contacts between the nitrate O atoms and phenyl H atoms are found. Hydrogen bonds from two methanol solvent mol-ecules to one of the O-P groups complete the crystal structure.
ABSTRACT
The title compound, [PtCl(C(42)H(78)OP(4))]Cl·0.5CH(2)Cl(2)·4H(2)O, crystallizes as a contact ion-pair with two close inter-molecular C-Hâ¯Cl(-) contacts between CH acidic αH atoms of the phosphane ligand and the chloride anion. A chloride ligand together with three coordinating P ligand atoms create a slightly distorted square-planar coordination environment around the Pt(II) center. An inter-molecular water O-Hâ¯Cl(-) and water O-Hâ¯OP hydrogen-bond network completes the coordination around the anion. In addition, a disordered CH(2)Cl(2) solvent mol-ecule cocrystallized within a hydro-phobic cavity spanned by the dicyclo-hexyl-phosphane ligands.
