Magnetoresistance of the metallic polyacetylene

Magnetoresistance studies of polymer nanotube/wire pellets and single polymer nanotubes/wires

“…For instance, polyaniline [3][4][5][6], polypyrrole [7][8][9], PEDOT [10] films, and polyaniline composites [11,12] usually exhibit a positive magnetoresistance (MR, defined as MR = R(H )/R(0) = [R(H ) − R(0)]/R(0)) at low temperatures (T < 10 K) and MR ∝ H 2 (H is not very large); the reason could be the shrinkage of localized wavefunctions of electrons in the presence of a magnetic field [13] or electron-electron interactions [14,15]. However, highly conductive polyacetylene films [16][17][18] usually show a negative magnetoresistance (or positive magnetoconductance) at low temperatures, which is mainly attributed to the weak localization effects [15].…”

Synthesis and characterization of copper(II) hexaazamacrotetracyclic complexes containing organic ligands

“…The synthesis of polyaza macrocyclic ligands and their metal complexes containing axial ligands has attracted considerable attention because of their structural and chemical properties, which are often quite different from those of the uncoordinated axial ligands [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. It has been widely observed that such compounds can be affected by various factors, such as the type and synthetic difference of the axial groups.…”

“…The coordination geometry around the copper(II) ions in these complexes is known to be mononuclear square pyramidal or axially elongated octahedral. For example, the compound [Cu(dttd)(N 3 )](ClO 4 )(H 2 O) (dttd ¼ 3,14-dimethyl-2,6,13,17-tetraazatricyclo [14,4,0 1.18 ,0 7.12 ]docosane) [8] exhibits a distorted square-pyramidal geometry, with four nitrogen atoms of the macrocycle and one nitrogen atom of the axial azido group. Also, [Cu(dttd) (SCH 3 ) 2 ] AE 2H 2 O reveals a tetragonally elongated octahedral geometry with two axial thiolate sulfur atoms [10].…”

“…Also, [Cu(dttd) (SCH 3 ) 2 ] AE 2H 2 O reveals a tetragonally elongated octahedral geometry with two axial thiolate sulfur atoms [10]. However, the dinuclear and polynuclear copper(II) complexes [{Cu II (dttd)} 2 (l-MoO 4 [14] show that two copper(II) ions are bridged by the tetraoxo anions in a distorted square-pyramidal and an elongated octahedral geometry. On the other hand, the complex {[Cu 2 (dttd)-(pdc) 2 (H 2 O) 2 ] AE 12H 2 O} n (pdc ¼ 2,3-pyrazinedicarboxylate) shows that each copper atom is bridged by pdc ligands to give a 3-D network through the covalent and intermolecular hydrogen-bonding interaction [15].…”

The Influence of Glassy Properties on the Anomalous Low-Temperature Transport in Highly-Doped Conjugated Polymers

“…Note that the dramatic change of the TCR sign at T % 1K accompanied by a change of the magnetoresistance behavior is not explained in the standard localization±interaction theory because the latter by no means predicts a crossover from a negative to positive TCR with increase of temperature. The incapability of the interaction±localization model to explain low temperature transport properties of conducting polymers was also emphasised in a recent paper [9].…”