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

Paramagnetic {[Fe(CO)2]2-μ2-η2:η2-η2:η2-(C60)2}2- Dimer Bridged by Iron Atoms and C-C Bonds: Effect of Starting Iron Carbonyls on Structures and Properties of Negatively Charged Iron-Bridged Fullerene Dimers

The reaction between an excess of Fe(CO)5 with {Cryptand(K+)}(C60•-) produced the salt {Cryptand(K+)}2{[Fe(CO)2]2-μ2-η2:η2-η2:η2-(C60)2}2-·4C6H4Cl2 (1) containing negatively charged iron-bridged fullerene dimers. In these dimers, the C60 cages are linked via two Fe(CO)2 fragments, forming short Fe-C(C60) bonds with a length of 2.070(3) Å and via two intercage C-C bonds with a length of 1.566(3) Å. Interfullerene center-to-center distance is short, being 9.02 Å. Thus, the coordination-induced dimerization of fullerenes is observed in 1. The dimer is negatively charged, with additional negative electron density mainly localized on iron atoms and, to a lesser extent, on the C60 cages, as revealed by optical and electron paramagnetic resonance spectra. These dimers have a diamagnetic singlet ground state with a small singlet-triplet gap of 25 K; consequently, they transfer to a paramagnetic state with two S = 1/2 spins per dimer above 50 K. Previously, different dimers with isomeric structures were obtained starting from {Cryptand(K+)}(C60•-) and Fe3(CO)12. However, these dimers exhibit diamagnetic properties, owing to the formation of a Fe-Fe bond. In contrast, in dimer 1, the Fe atoms are positioned too far apart to form such a bond, preserving the spin on Fe. We assume that both dimers are formed through the same [Fe(CO)3](C60•-) intermediate, but the subsequent interaction of this intermediate with Fe3(CO)12 or its dimerization yields different dimers. Therefore, the starting carbonyls can control the structures and properties of the resulting dimers.

Negatively Charged Iron-Bridged Fullerene Dimer {Fe(CO)2-μ2-η2,η2-C60}22

The interaction of {Cryptand(K⁺)}(C₆₀^•-) with Fe₃(CO)₁₂ produced {Cryptand(K⁺)}₂{Fe(CO)₂-μ₂-η²,η²-C₆₀}₂^2-·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 C≡O 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.

A 1D Mixed-Valence Cuprofullerene Pyrazolate Polymer as a Semiconductor Material

Polymeric {Cu₆[(μ₃-η²:η²:η²)₂-C₆₀](FPz)₆Cl·3C₆H₅Cl}_∞ [FPz = 4-(trifluoromethyl)pyrazolate], synthesized solvothermally with chlorobenzene as the solvent, is a doubly-connecting trans bis-adduct hexanuclear cuprofullerene that has copper in mixed valence. The compound is an example of a metallofullerene having semiconductivity character.

Regioisomeric core-shell cuprofullerene C60@Cu24

The controlled synthesis of high-nuclear regioisomeric core-shell exohedral metallofullerenes (ExMFs) is challenging. Herein, we demonstrated the synthesis of regioisomeric core-shell cuprofullerene C₆₀@Cu^I₂₄ and its 3-D coordination polymer using heteroleptic ligands, realizing high-nuclear regioisomeric ExMFs and a polymeric ExMF structure.

The directional character of the piperazine double addition product, e{N(CH2CH2)2N}2C60, as a building block for forming crystalline fullerene polymers

The piperazine double addition product, ^e{N(CH₂CH₂)₂N}₂C₆₀, has its donor atoms positioned to bind Lewis acids in two orthogonal directions. It has been used to construct crystalline, 1-d and 2-d polymers through reactions with diiodine and the rhodium(ii) acetate dimer.

Theoretical investigation of interactions between palladium and fullerene in polymer

Applying density functional theory (DFT) calculations, we predict the structural and electronic properties of different types of palladium–fullerene polymers.

P,C-Chelation versus P,P-coordination of unsymmetrical phosphorus ylides in palladacyclopropa[60]fullerene complexes; synthetic, spectroscopic, and theoretical studies

New palladacyclopropa[60]fullerene complexes containing P,C-chelated and P,P-coordinated unsymmetrical phosphorus ylides were synthesized and characterized successfully.

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.

Synthesis and Preliminary Characterization of a PPE-Type Polymer Containing Substituted Fullerenes and Transition Metal Ligation Sites

A substituted fullerene was incorporated into a PPE-conjugated polymer repeat unit. This subunit was then polymerized via Sonogashira coupling with other repeat units to create polymeric systems approaching 50 repeat units (based on GPC characterization). Bipyridine ligands were incorporated into some of these repeat units to provide sites for transition metal coordination. Photophysical characterization of the absorption and emission properties of these systems shows excited states located on both the fullerene and aromatic backbone of the polymers that exist in a thermally controlled equilibrium. Future work will explore other substituted polyaromatic systems using similar methodologies.