Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

Reversible dissociation of singly-bonded (C60−)2 dimers in (MV˙+)2(C60−)2·solvent salt containing paramagnetic methyl viologen MV˙+ radical cations

Interaction of MV⁰ with C₆₀ produces salt (MV˙⁺)₂(C₆₀⁻)₂⋅solvent (1) containing singly-bonded (C₆₀⁻)₂ dimers dissociated at 235–375 K. There is exchange interaction between MV˙⁺ and C₆₀˙⁻ in the monomeric phase which is switched off in the dimeric phase.

Control of binding of C60 molecules to the substrate by Coulomb blockade

We report on a transition in a monolayer of C₆₀ molecules deposited on a WO₂/W(110) substrate. The transition from a static state, where the molecules are rigidly bound to the surface by a coordination bond, to a state where the molecules are loosely bound to the surface by van der Waals force and rotate continuously, has been studied using scanning tunnelling microscopy (STM). The separation between the molecules and the surface increases by 1.2 Å across the transition. The transition from the static state into the rotating state takes place at 259 K. The energy of the spinning state with respect to the lowest energy state, having a single coordinated bond, can be obtained from the statistics of the molecules switching. The binding energy of the molecule in the spinning state can be easily altered by changing the polarity of the bias voltage applied between the STM tip and the surface. The binding energy decreases by 80 meV when the bias polarity of the sample changes from positive to negative with respect to the tip. The results are consistent with the Coulomb blockade model: when electrons travel from the surface to the C₆₀ molecule, and then to the tip; charge accumulates on the molecule due to the Coulomb blockade. This increases the electrostatic interaction between the molecule's charge and a corresponding image charge generated on the metallic surface.

Molecular Structure and Magnetic and Optical Properties of Endometallonitridofullerene Sc3 N@Ih -C80 in Neutral, Radical Anion, and Dimeric Anionic Forms

A series of compounds with Sc₃ N@I_h -C₈₀ in the neutral, monomeric, and dimeric anion states have been prepared in the crystalline form and their molecular structures and optical and magnetic properties have been studied. The neutral Sc₃ N@I_h -C₈₀ ⋅3 C₆ H₄ Cl₂ (1) and (Sc₃ N@I_h -C₈₀ )₃ (TPC)₂ ⋅5 C₆ H₄ Cl₂ (2, TPC=triptycene) compounds both crystallized in a high-symmetry trigonal structure. The reduction of Sc₃ N@I_h -C₈₀ to the radical anion resulted in dimerization to form diamagnetic singly bonded (Sc₃ N@I_h -C₈₀ ^- )₂ dimers. In contrast to {[2.2.2]cryptand(Na⁺ )}₂ (Sc₃ N@I_h -C₈₀ ^- )₂ ⋅2.5 C₆ H₄ Cl₂ (3) with strongly disordered components, we synthesized new dimeric phases {[2.2.2]cryptand- (K⁺ )}₂ (Sc₃ N@I_h -C₈₀ ^- )₂ ⋅2 C₆ H₄ Cl₂ (4) and {[2.2.2]cryptand- (Cs⁺ )}₂ (Sc₃ N@I_h -C₈₀ ^- )₂ ⋅2 C₆ H₄ Cl₂ (5) in which only one major dimer orientation was found. The thermal stability of the (Sc₃ N@I_h -C₈₀ ^- )₂ dimers was studied by EPR analysis of 3 to show their dissociation in the 400-460 K range producing monomeric Sc₃ N@I_h -C₈₀ ^.- radical anions. This species shows an EPR signal with a hyperfine splitting of 5.8 mT. The energy of the intercage C-C bond was estimated to be 234±7 kJ mol^-1 , the highest value among negatively charged fullerene dimers. The EPR spectra of crystalline (Bu₃ MeP⁺ )₃ (Sc₃ N@I_h -C₈₀ ^.- )₃ ⋅C₆ H₄ Cl₂ (6) are presented for the first time. The salt shows an asymmetric EPR signal, which could be fitted by three lines. Two lines were attributed to Sc₃ N@I_h -C₈₀ ^.- . Hyperfine splitting is manifested above 180 K due to the hyperfine interaction of the electron spin with the three scandium atoms (a total of 22 lines with an average splitting of 5.32 mT are observed at 220 K). Furthermore, each of the 22 lines is additionally split into six lines with an average separation of 0.82 mT. The large splitting indicates intrinsic charge and spin density transfer from the fullerene cage to the Sc₃ N cluster. Both the monomeric and dimeric Sc₃ N@I_h -C₈₀ ^- anions show an intrinsic shift of the IR bands attributed to the Sc₃ N cluster and new bands corresponding to these species appear in the NIR range of their UV/Vis/NIR spectra, which allows these anions to be distinguished from neutral species.

Negatively charged singly-bonded dimers of C1-[C70(CF3)10] and bare C70 fullerene

Singly-bonded {C₇₀(CF₃)₁₀⁻}₂ and (C₇₀⁻)₂ dimers are obtained as crystalline salts allowing their molecular structure, and optical and magnetic properties to be studied.

Fullerene C60dianion salt, (Me4N+)2(C602−)·(TPC)2·2C6H4Cl2, where TPC is triptycene, obtained by a multicomponent approach

The hexagonal TPC network accommodates small Me₄N⁺cations and becomes a template to build zigzag closely packed chains from the C₆₀²⁻dianions in (Me₄N⁺)₂(C₆₀²⁻)·(TPC)₂·2C₆H₄Cl₂(1) (figure).

Synthesis, Structure, and Properties of the Fullerene C60 Salt of Crystal Violet, (CV(+) )(C60 (.-) )⋅0.5 C6 H4 Cl2 , which Contained Closely Packed Zigzagged C60 (.-) Chains

The reduction of fullerene C60 by zinc dust in the presence of crystal violet cations (CV(+) ) yielded a deep-blue solution, from which crystals of (CV(+) )(C60 (.-) )⋅0.5 C6 H4 Cl2 (1) were obtained by slow mixing with n-hexane. The salt contained isolated, closely packed zigzagged chains that were composed of C60 (.-) radical anions with a uniform interfullerene center-to-center distance of 9.98 Å. In spite of the close proximity of the fullerenes, they did not dimerize, owing to spatial separation by the phenyl substituents of CV(+) . The room-temperature conductivity of compound 1 was 3×10(-2)  S cm(-1) along the fullerene chains. The salt exhibited semiconducting behavior, with an activation energy of Ea =167 meV. Spins localized on C60 (.-) were antiferromagnetically coupled within the fullerene chains, with a Weiss temperature of -19 K without long-range magnetic ordering down to 1.9 K.

Effective magnetic coupling with strong spin frustration in (Ph3MeP+)(C60˙−) and reversible C60˙− dimerization in (Ph3MeP+)(C60˙−)·C6H5CN. Effect of solvent on structure and properties

Antiferromagnetic coupling of spins with spin frustration and fullerene dimerization are observed for (Ph₃MeP⁺)(C₆₀˙⁻) (left) and (Ph₃MeP⁺)(C₆₀˙⁻)·C₆H₅CN (right).

Anionic coordination complexes of C60 and C70 with cyclopentadienyl and pentamethylcyclopentadienyl molybdenum dicarbonyl

Crystalline molybdenum η²-complexes with fullerenes C₆₀ and C₇₀ in the neutral and negatively charged form were obtained and studied.

Coordination complex of boron subphthalocyanine (BSubPc) with fluorenone pinacolate: effective π–π interaction of concave BSubPc macrocycle with fullerene C60

Dimeric coordination assembly of fluorenone pinacolate (C₂₆H₁₆O₂²⁻) with boron subphthalocyanine (BSubPc) was obtained and studied in the complex with fullerene {(BSubPc)₂(C₂₆H₁₆O₂)}·C₆₀.

Design, crystal structures and magnetic properties of anionic salts containing fullerene C60 and indium(iii) bromide phthalocyanine radical anions

Salts containing fullerene C₆₀ and indium(iii) bromide phthalocyanine (Pc) radical anions, (TBA⁺)₃(C₆₀˙⁻){In^III(Br)(Pc)˙⁻}(Br⁻)·C₆H₄Cl₂ (1) and (TEA⁺)₂(C₆₀˙⁻){In^III(Br)(Pc)˙⁻}·C₆H₄Cl₂·C₆H₁₄ (2), have been obtained and their structures, optical and magnetic properties are discussed.

Effect of the Co-C(C60(-)) bond formation on magnetic properties of the ionic complex {cryptand[2,2,2] x (Na+)} x {Co(II)TPP x (C60(-))} x (C6H4Cl2)2

A new ionic complex {cryptand[2,2,2] x (Na(+))} x {Co(II)TPP x (C(60)(-))} x (C(6)H(4)Cl(2))(2) has been obtained as single crystals by a diffusion technique. It involves coordination {Co(II)TPP x u(C(60)(-))} units and bulky {cryptand[2,2,2] x (Na(+))} cations. The Co-C(C(60)(-)) coordination bond is short (2.262(2) A at 100 K) which provides ordering in the C(60)(-) anions. This is the first ordered structure of {Co(II)TPP x (C(60)(-))}. The coordination bonds weaken upon heating to be 2.316(4) A at 250 K. As a result, the C(60)(-) anions begin to rotate at 250 K about the Co-C bond between two orientations. The complex is diamagnetic from 4 up to 320 K. The Co-C bonds dissociate above 320 K only to form unbound paramagnetic Co(II)TPP and C(60)(*-) species. The process is accompanied by the reversible increase in magnetic susceptibility of the complex and the appearance of a new broad EPR signal with g = 2.1187 and a linewidth of approximately 120 mT (350 K). The signal was attributed to both paramagnetic Co(II)TPP and C(60)(*-), which showed strong exchange interaction.