Charged Clusters of C₆₀ and Au or Cu: Evidence for Stable Sizes and Specific Dissociation Channels

Abstract

We have doped helium nanodroplets with C60 and either gold or copper. Positively or negatively charged (C60)mMn± ions (M = Au or Cu) containing up to ≈10 fullerenes and ≈20 metal atoms are formed by electron ionization. The abundance distributions extracted from high-resolution mass spectra reveal several local anomalies. The sizes of the four most stable (C60)mAun± ions identified in previous calculations for small values of m and n (m ≤ 2 and n ≤ 2, or m = 1 and n = 3) agree with local maxima in the abundance distributions. Our data suggest the existence of several other relatively stable ions including (C60)2Au3± and (C60)3Au4–. Another feature, namely the absence of bare (C60)2±, confirms the prediction that (C60)2M± dissociates by loss of C60± rather than loss of M. The experimental data also reveal the preference for loss of (charged or neutral) C60 over loss of a metal atom from some larger species such as (C60)3M3+. In contrast to these similarities between Au and Cu, the abundance distributions of (C60)3Aun– and (C60)3Cun– are markedly different. In this discussion, we emphasize the similarities and differences between anions and cations, and between gold and copper. Also noteworthy is the observation of dianions (C60)mAun2– for m = 2, 4, and 6.

Phenanthrene: establishing lower and upper bounds to the binding energy of a very weakly bound anion

“…1a: He n Ph À , He n H 2 Ph À , and He n H 2 OPh À . Mass peaks due to ions that contain the main isotopes of each element ( 1 H, 4 He, 12 C, and 16 O) are marked by symbols; connecting lines are drawn to guide the eye. The first member of each series (i.e.…”

“…In the extreme case, one may try to form the anion within a liquid helium nanodroplet (HND) whose temperature is 0.37 K. 3 Excess helium may then be removed by collisions with a helium gas, until the bare M À emerges. 4 But what if it doesn't? There is another trick that the experimenter has in her toolbox, namely complexing M À with a ligand X.…”

Complexes with Atomic Gold Ions: Efficient Bis-Ligand Formation

“…The experiments utilize the ultracold environment of helium nanodroplets (HND) as a nano matrix for the formation of cold, mixed complexes with gold as described in [10][11][12][13][14]16,51,63]. The experimental setup which is schematically shown in Figure 9 has been described previously in [64].…”

Helium Droplet Mass Spectrometry

“…In complexes of C 60 and ammonia, the signal of [(C 60 ) p (NH 3 )] + is also found to be strongly suppressed for n = 1 and p = 2, 3 [405]. Certain small ionic complexes are also found to be absent in complexes of C 60 and either Cu or Au), although no consistent, simple pattern is observed for these compounds [375] (also see previous discussion on C 60 -metal complexes).…”

“…Licensed under CC BY 4.0 which has also been found to be surprisingly stable, considering it consists of a noble metal and two rare gas atoms [319,374]. A follow-up study by Martini and coworkers examined larger anionic and cationic clusters of up to ~10 C 60 molecules and up to ~20 metal atoms (either gold or copper) formed in helium droplets and subsequently ionized by electron impact or EA [375] 2with m = 2, 4, 6 and odd n can be observed in the mass spectra (compounds with even n might also be present, but would be buried in the ion signals of singly charged species), significantly smaller than the smallest bare C 60 dianion observed in helium droplets, (C 60 ) 5…”