Synthesis and Characterization of the Europium Fullerides Eu_xC₆₀ (x = 1−6)

Abstract

Europium fullerides Eu x C60 (x = 1−6) were prepared by metal ammonia solution synthesis. The products were investigated by X-ray powder diffraction, optical spectroscopy, FTIR, mass spectrometry, and magnetic susceptibility. All products were amorphous by powder X-ray diffraction and were free of ammonia as determined by mass spectrometry. Products prepared with x = 1, 2, 3 showed the presence of unreacted C60 in the optical spectra, FTIR spectra, and the powder diffraction pattern. FTIR spectra of the Eu x C60 prepared with x = 3 show red-shifted frequencies of F1u(4) at 1399 and 1352 (1411) cm-1, suggesting the presence of C60 - and C60 6-. FTIR spectra of Eu x C60 samples prepared with x = 4, 5, 6 also show red-shifted frequencies and are discussed in detail. Magnetic susceptibility measurements show Curie−Weiss behavior above 50 K with experimental magnetic moments of 6.6 (1), 6.9 (1), and 5.9 (1) μB/Eu for x = 3, 4, 5 samples, respectively.

Effect of Lanthanide Metal Complexation on the Properties and Electronic Structure of Single-Walled Carbon Nanotube Films

“…22,35,36 Furthermore, there is the promise of new ferromagnetic and superconducting materials based on the organometallic single layer graphene and graphene sandwich compounds and their relationship to the graphite and C 60 intercalation compounds. 4,5,10,[12][13][14][15]21,35,37 …”

“…11,12 Indeed, the observation that some of these compounds (M = Yb, Sm) are superconductors strongly supports the idea that there are free electrons in these compounds which reside primarily on C 60 , 10,13,14 as do the physical properties of the Eu x C 60 compounds. 15 All of these authors assign the oxidation state of the lanthanide as +2 but the importance of covalent Special Issue: Advances towards Electronic Applications in Organic Materials character in these compounds is discussed at length. 14,15 In this respect, the C 60 compounds are rather different from the lanthanide complexes of benzene and SWNTs discussed above in that C 60 is strongly curved and possesses five-membered rings (5-MRs); these features of the geometric and electronic structure contribute to the ability of the fullerenes to stabilize excess electron density.…”

“…15 All of these authors assign the oxidation state of the lanthanide as +2 but the importance of covalent Special Issue: Advances towards Electronic Applications in Organic Materials character in these compounds is discussed at length. 14,15 In this respect, the C 60 compounds are rather different from the lanthanide complexes of benzene and SWNTs discussed above in that C 60 is strongly curved and possesses five-membered rings (5-MRs); these features of the geometric and electronic structure contribute to the ability of the fullerenes to stabilize excess electron density. 16,17 Although the fullerenes are incapable of forming stable π-complexes with transition metals requiring a hapticity greater than two, given the size and orbital extent of the lanthanides, they may be effective in facilitating η 5 -coordination of the 5-MRs. 14,18 Nevertheless, it is apparent that similar issues are relevant in the C 60 and SWNT complexes of the lanthanides; that is, the question of covalent and ionic bonding, although the fullerides prepared to date only include M = Sm, Eu, and Yb, which are known to readily form the +2 oxidation state.…”

Hexahapto-lanthanide interconnects between the conjugated surfaces of single-walled carbon nanotubes

“…There are uncertainties associated with the construction of this orbital correlation diagram but as much as possible we have followed the previous literature regarding the electronic structure of lanthanide complexes, 8,16,17,[19][20][21][22][25][26][27] theoretical analyses of organometallic bonding to SWNTs and graphene, 23,24,28 and frontier molecular orbital theory. 1 We have closed the gap between the highest occupied and lowest unoccupied arene molecular orbitals (HOMO and LUMO, respectively) in Fig.…”

Stereochemical effect of covalent chemistry on the electronic structure and properties of the carbon allotropes and graphene surfaces

“…Nevertheless it has been argued that some of the lanthanide compounds of C 60 possess significant covalent character, perhaps because the d-orbitals of these large metals are able to effectively overlap with the rehybridized C 60 p-orbitals [51][52][53]. The overlap of transition metal d-orbitals with the carbon nanotube p-orbitals has been extensively discussed previously and clearly constitutes an intermediate case between the fullerenes and graphene [32,54,55].…”