Effect of the Cooling Rate on Dimerization of C₆₀^•– in Fullerene Salt (DMI⁺)₂·(C₆₀^•–)·{Cd(Et₂NCS₂)₂I^–}

The salt (DMI⁺)₂·(C₆₀^•–)·{Cd­(Et₂NCS₂)₂I^–} (<b>1</b>) containing fullerene radical anions, the anions of cadmium diethyldithiocarbamate iodide, and <i>N</i>,<i>N</i>′-dimethylimidazolium cations was obtained. Fullerenes are monomeric in <b>1</b> at 250 K and form three-dimensional packing in which each fullerene has nearly tetrahedral surroundings from neighboring fullerenes. Fullerenes with a shorter interfullerene center-to-center distance of 10.031(2) Å form spiral chains arranged along the lattice <i>c</i> axis. The convolution consists of four fullerene molecules. Dimerization realized in <b>1</b> within the spiral chains below 135 K manifests a strong dependence on the cooling rate. The “frozen” monomeric phase was obtained upon instant quenching of <b>1</b>. This phase is stable below 95 K for a long time but slowly converted to the dimeric phase at <i>T</i> > 95 K. It exhibits a weak antiferromagnetic interaction of spins below 95 K (the Weiss temperature is −4 K), which results in the splitting of the electron paramagnetic resonance (EPR) signal into two components below 10 K. A disordered phase containing both C₆₀^•– monomers and singly bonded (C₆₀^–)₂ dimers with approximately 0.5/0.5 occupancies is formed at an intermediate cooling rate (for 20 min). The position of each fullerene in this phase is split into three positions slightly shifted relative to each other. The central position corresponds to nonbonded fullerenes with interfullerene center-to-center distances of 9.94–10.00 Å. Two other positions are coincided to dimeric fullerenes formed with the right and left fullerene neighbors within the spiral chain. This intermediate phase is paramagnetic with nearly zero Weiss temperature due to isolation of C₆₀^•– by diamagnetic species and exhibits a strongly asymmetric EPR signal below 20 K. A diamagnetic phase containing ordered singly bonded (C₆₀^–)₂ dimers can be obtained only upon slow cooling of the crystal for 6 h

Linear Coordination Fullerene C₆₀ Polymer [{Ni(Me₃P)₂}(μ‑η²,η²‑C₆₀)]_∞ Bridged by Zerovalent Nickel Atoms

Coordination nickel-bridged fullerene polymer [{Ni­(Me₃P)₂}­(μ-η²,η²-C₆₀)]_∞ (<b>1</b>) has been obtained via reduction of a Ni^II(Me₃P)₂Cl₂ and C₆₀ mixture. Each nickel atom is linked in the polymer with two fullerene units by η²-type Ni–C­(C₆₀) bonds of 2.087(8)–2.149(8) Å length. Nickel atoms are coordinated to the 6–6 bonds of C₆₀ as well as two trimethylphosphine ligands to form a four-coordinated environment around the metal centers. Fullerene cages approach very close to each other in the polymer with a 9.693(3) Å interfullerene center-to-center distance, and two short interfullerene C–C contacts of 2.923(7) Å length are formed. Polymer chains are densely packed in a crystal with interfullerene center-to-center distances between fullerenes from neighboring polymer chains of 9.933(3) Å and multiple interfullerene C···C contacts. As a result, three-dimensional dense fullerene packing is formed in <b>1</b>. According to optical and electron paramagnetic resonance spectra, fullerenes are neutral in <b>1</b> and nickel atoms have a zerovalent state with a diamagnetic d¹⁰ electron configuration. The density functional theory calculations prove the diamagnetic state of the polymer with a singlet–triplet gap wider than 1.37 eV

Negatively Charged Iron-Bridged Fullerene Dimer {Fe(CO)₂‑μ₂‑η²,η²‑C₆₀}₂^2–

The interaction of {Cryptand(K+)}(C60•–) with Fe3(CO)12 produced {Cryptand(K+)}2{Fe(CO)2-μ2-η2,η2-C60}22–·2.5C6H4Cl2 (1) as the first negatively charged iron-bridged fullerene C60 dimer. The bridged iron atoms are coordinated to two 6–6 bonds of one C60 hexagon with short and long C(C60)–Fe bonds with average lengths of 2.042(3) and 2.088(3) Å. Fullerenes are close to each other in the dimer with a center-to-center interfullerene distance of 10.02 Å. Optical spectra support the localization of negative electron density on the Fe2(CO)4 units, which causes a 50 cm–1 shift of the CO vibration bands to smaller wavenumbers, and the C60 cages. Dimers are diamagnetic and electron paramagnetic resonance silent and have a singlet ground state resulting from the formation of an Fe–Fe bond in the dimer with a length of 2.978(4) Å. According to density functional theory calculations, the excited triplet state is higher than the ground state by 6.5 kcal/mol. Compound 1 shows a broad near-infrared band with a maximum at 970 nm, which is attributable to the charge transfer from the orbitals localized mainly on iron atoms to the C60 ligand

Spin Crossover in Anionic Cobalt-Bridged Fullerene (Bu₄N⁺){Co(Ph₃P)}₂(μ₂‑Cl^–)(μ₂‑η²,η²‑C₆₀)₂ Dimers

A spin crossover phenomena is observed in an anionic (Bu₄N⁺)­{Co­(Ph₃P)}₂(μ₂-Cl^–)­(μ₂-η²,η²-C₆₀)₂·2C₆H₁₄ (<b>1</b>) complex in which two cobalt atoms bridge two fullerene molecules to form a dimer. The dimer has a triplet ground state with two weakly coupling Co⁰ atoms (<i>S</i> = 1/2). The spin transition realized above 150 K is accompanied by a cobalt-to-fullerene charge transfer that forms a quintet excited state with a high spin Co^I (<i>S</i> = 1) and C₆₀^•– (<i>S</i> = 1/2)

Spin Crossover in Anionic Cobalt-Bridged Fullerene (Bu₄N⁺){Co(Ph₃P)}₂(μ₂‑Cl^–)(μ₂‑η²,η²‑C₆₀)₂ Dimers

A spin crossover phenomena is observed in an anionic (Bu₄N⁺)­{Co­(Ph₃P)}₂(μ₂-Cl^–)­(μ₂-η²,η²-C₆₀)₂·2C₆H₁₄ (<b>1</b>) complex in which two cobalt atoms bridge two fullerene molecules to form a dimer. The dimer has a triplet ground state with two weakly coupling Co⁰ atoms (<i>S</i> = 1/2). The spin transition realized above 150 K is accompanied by a cobalt-to-fullerene charge transfer that forms a quintet excited state with a high spin Co^I (<i>S</i> = 1) and C₆₀^•– (<i>S</i> = 1/2)

Magnetic and Optical Properties of Layered (Me₄P⁺)[M^IVO(Pc^•3–)]^•–(TPC)_0.5·C₆H₄Cl₂ Salts (M = Ti and V) Composed of π‑Stacking Dimers of Titanyl and Vanadyl Phthalocyanine Radical Anions

Two isostructural salts with radical anions of titanyl and vanadyl phthalocyanines (Me₄P⁺)­[M^IVO­(Pc^•3–)]^•–­(TPC)_0.5­·C₆H₄Cl₂ (M = Ti (<b>1</b>), V (<b>2</b>)), where TPC is triptycene, were obtained. These salts contain phthalocyanine layers composed of the {[M^IVO­(Pc^•3–)]^•–}₂ dimers with strong π–π intradimer interaction. The reduction of metal phthalocyanines was centered on the Pc macrocycles providing the appearance of new bands in the near infrared range and a blue shift of Q- and Soret bands. That results in the alternation of shorter and longer C–N_imine bonds in Pc^•3–. Only one <i>S</i> = 1/2 spin is delocalized over Pc^•3– in <b>1</b> providing a χ_M<i>T</i> value of 0.364 emu K mol^–1 at 300 K. Salt <b>1</b> showed antiferromagnetic behavior approximated by the Heisenberg model for isolated pairs of antiferromagnetically interacting spins with exchange interaction of <i>J</i>/<i>k</i>_B = −123.0 K. The χ_M<i>T</i> value for <b>2</b> is equal to 0.617 emu K mol^–1 at 300 K to show the contribution of two <i>S</i> = 1/2 spins localized on V^IV and delocalized over Pc^•3–. Magnetic behavior of <b>2</b> is described by the Heisenberg model for a four-spin system with strong intermolecular coupling between Pc^•3– in {[V^IVO­(Pc^•3–)]^•–}₂ (<i>J</i>_inter/<i>k</i>_B = −105.0 K) and weaker intramolecular coupling between the V^IV and Pc^•3– (<i>J</i>_intra/<i>k</i>_B = −15.2 K)

Coordination Complexes of Pentamethylcyclopentadienyl Iridium(III) Diiodide with Tin(II) Phthalocyanine and Pentamethylcyclopentadienyl Iridium(II) Halide with Fullerene C₆₀^– Anions

Synthetic approaches to iridium complexes of metal phthalocyanines (Pc) and fullerene anions have been developed to give three types of complexes. The compound­{(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}·2C₆H₄Cl₂ (<b>1</b>) (Cp* is pentamethylcyclopentadienyl) is the first crystalline complex of a metal phthalocyanine in which an iridium­(III) atom is bonded to the central tin­(II) atom of Pc via a Sn–Ir bond length of 2.58 Å. In (TBA⁺)­(C₆₀^•–)­{(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}·0.5C₆H₁₄ (<b>2</b>), the {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)} units cocrystallize with (TBA⁺)­(C₆₀^•–) to form double chains of C₆₀^•– anions and closely packed chains of {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}. Interactions between the fullerene and phthalocyanine subsystems are realized through π–π stacking of the Cp* groups of {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)} and the C₆₀^•– pentagons. Furthermore, the spins of the C₆₀^•– are strongly antiferromagnetically coupled in the chains with an exchange interaction <i>J</i>/<i>k</i>_B = −31 K. Anionic (TBA⁺)­{(Cp*Ir^IICl)­(η²-C₆₀^–)}·1.34C₆H₄Cl₂ (<b>3</b>) and (TBA⁺)­{(Cp*Ir^III)­(η²-C₆₀^–)}·1.3C₆H₄Cl₂·0.2C₆H₁₄ (<b>4</b>) are the first transition metal complexes containing η²-bonded C₆₀^– anions, with the Cp*Ir^IICl and Cp*Ir^III units η²-coordinated to the 6–6 bonds of C₆₀^–. Magnetic measurements indicate diamagnetism of the {(Cp*Ir^IICl)­(η²-C₆₀^–)} and {(Cp*Ir^III)­(η²-C₆₀^–)} anions due to the formation of a coordination bond between two initially paramagnetic Cp*Ir^IICl or Cp*Ir^III groups and C₆₀^•– units. DFT calculations support a diamagnetic singlet ground state of <b>4</b>, in which the singlet–triplet energy gap is greater than 0.8 eV. DFT calculations also indicate that the C₆₀ molecules are negatively charged

Coordination Complexes of Pentamethylcyclopentadienyl Iridium(III) Diiodide with Tin(II) Phthalocyanine and Pentamethylcyclopentadienyl Iridium(II) Halide with Fullerene C₆₀^– Anions

Synthetic approaches to iridium complexes of metal phthalocyanines (Pc) and fullerene anions have been developed to give three types of complexes. The compound­{(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}·2C₆H₄Cl₂ (<b>1</b>) (Cp* is pentamethylcyclopentadienyl) is the first crystalline complex of a metal phthalocyanine in which an iridium­(III) atom is bonded to the central tin­(II) atom of Pc via a Sn–Ir bond length of 2.58 Å. In (TBA⁺)­(C₆₀^•–)­{(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}·0.5C₆H₁₄ (<b>2</b>), the {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)} units cocrystallize with (TBA⁺)­(C₆₀^•–) to form double chains of C₆₀^•– anions and closely packed chains of {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}. Interactions between the fullerene and phthalocyanine subsystems are realized through π–π stacking of the Cp* groups of {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)} and the C₆₀^•– pentagons. Furthermore, the spins of the C₆₀^•– are strongly antiferromagnetically coupled in the chains with an exchange interaction <i>J</i>/<i>k</i>_B = −31 K. Anionic (TBA⁺)­{(Cp*Ir^IICl)­(η²-C₆₀^–)}·1.34C₆H₄Cl₂ (<b>3</b>) and (TBA⁺)­{(Cp*Ir^III)­(η²-C₆₀^–)}·1.3C₆H₄Cl₂·0.2C₆H₁₄ (<b>4</b>) are the first transition metal complexes containing η²-bonded C₆₀^– anions, with the Cp*Ir^IICl and Cp*Ir^III units η²-coordinated to the 6–6 bonds of C₆₀^–. Magnetic measurements indicate diamagnetism of the {(Cp*Ir^IICl)­(η²-C₆₀^–)} and {(Cp*Ir^III)­(η²-C₆₀^–)} anions due to the formation of a coordination bond between two initially paramagnetic Cp*Ir^IICl or Cp*Ir^III groups and C₆₀^•– units. DFT calculations support a diamagnetic singlet ground state of <b>4</b>, in which the singlet–triplet energy gap is greater than 0.8 eV. DFT calculations also indicate that the C₆₀ molecules are negatively charged

Interligand Charge Transfer in a Complex of Deprotonated <i>cis</i>-Indigo Dianions and Tin(II) Phthalocyanine Radical Anions with Cp*Ir^III

A diamagnetic complex, {(<i>cis</i>-indigo-<i>N</i>,<i>N</i>)^2–(Cp*Ir^III)} (<b>1</b>), in which deprotonated <i>cis</i>-indigo dianions coordinate an iridium center through two nitrogen atoms was obtained. By employment of the ability of the iridium center in <b>1</b> to coordinate an additional ligand, the complex [(Bu₄N⁺)₂{[Sn^II(Pc^•3–)]­(<i>cis</i>-indigo-<i>N</i>,<i>N</i>)^2–Cp*Ir^III}^•–₂·0.5­(H₂Indigo)·2.5C₆H₄C_l2 (<b>2</b>), which has two functional ligands coordinating an Ir^III center, was obtained. This complex has a magnetic moment of 1.71 μ_B at 300 K, in accordance with an <i>S</i> = 1/2 spin state. The spin density is mainly delocalized over the Pc^•3– macrocycle and partially on (<i>cis</i>-indigo-<i>N</i>,<i>N</i>)^2–. Due to an effective π–π interaction, a thermally activated charge transfer from [Sn^II(Pc^•3–)]^•– to (<i>cis</i>-indigo-<i>N</i>,<i>N</i>)^2– is observed, with an estimated Gibbs energy (−Δ<i>G</i>°) of 9.27 ± 0.18 kJ/mol. The deprotonation of indigo associated with the coordination of Ir^III by the indigo releases H⁺ ions, which protonate noncoordinating indigo molecules to produce leuco <i>cis</i>-indigo (H₂Indigo). One H₂indigo links two (<i>cis</i>-indigo-<i>N</i>,<i>N</i>)^2– dianions in <b>2</b> to produce strong N–H···OC and O–H···OC hydrogen-bonding interactions

Coordination Complexes of Pentamethylcyclopentadienyl Iridium(III) Diiodide with Tin(II) Phthalocyanine and Pentamethylcyclopentadienyl Iridium(II) Halide with Fullerene C₆₀^– Anions

Synthetic approaches to iridium complexes of metal phthalocyanines (Pc) and fullerene anions have been developed to give three types of complexes. The compound­{(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}·2C₆H₄Cl₂ (<b>1</b>) (Cp* is pentamethylcyclopentadienyl) is the first crystalline complex of a metal phthalocyanine in which an iridium­(III) atom is bonded to the central tin­(II) atom of Pc via a Sn–Ir bond length of 2.58 Å. In (TBA⁺)­(C₆₀^•–)­{(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}·0.5C₆H₁₄ (<b>2</b>), the {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)} units cocrystallize with (TBA⁺)­(C₆₀^•–) to form double chains of C₆₀^•– anions and closely packed chains of {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)}. Interactions between the fullerene and phthalocyanine subsystems are realized through π–π stacking of the Cp* groups of {(Cp*Ir^IIII₂)­Sn^IIPc­(2−)} and the C₆₀^•– pentagons. Furthermore, the spins of the C₆₀^•– are strongly antiferromagnetically coupled in the chains with an exchange interaction <i>J</i>/<i>k</i>_B = −31 K. Anionic (TBA⁺)­{(Cp*Ir^IICl)­(η²-C₆₀^–)}·1.34C₆H₄Cl₂ (<b>3</b>) and (TBA⁺)­{(Cp*Ir^III)­(η²-C₆₀^–)}·1.3C₆H₄Cl₂·0.2C₆H₁₄ (<b>4</b>) are the first transition metal complexes containing η²-bonded C₆₀^– anions, with the Cp*Ir^IICl and Cp*Ir^III units η²-coordinated to the 6–6 bonds of C₆₀^–. Magnetic measurements indicate diamagnetism of the {(Cp*Ir^IICl)­(η²-C₆₀^–)} and {(Cp*Ir^III)­(η²-C₆₀^–)} anions due to the formation of a coordination bond between two initially paramagnetic Cp*Ir^IICl or Cp*Ir^III groups and C₆₀^•– units. DFT calculations support a diamagnetic singlet ground state of <b>4</b>, in which the singlet–triplet energy gap is greater than 0.8 eV. DFT calculations also indicate that the C₆₀ molecules are negatively charged