A new, one step functionalization of C60 with lactones has been developed. This photochemical approach utilizes a variety of lactonyl radicals deriving from lactones through a hydrogen atom ...abstraction process mediated by tetrabutylammonium decatungstate (n-Bu4N)4W10O32. This reaction provides access to a previously unknown class of materials, namely 1-lactonyl-2-hydro60fullerenes. A mechanism for this new reaction has been proposed based mainly on the structure of reaction products and deuterium-incorporated experiments.
Crown ether decorated phthalocyanines were designed to form rigidly eclipsed aggregates with metal ions being sandwiched between the molecules. We studied tetra-18crown-6 ether functionalized zinc ...phthalocyanine (ZnPcTetCr) in the presence of excess NaCl by electrospray ionization mass spectrometry. ZnPcTetCr was found to form aggregates in the gas phase to which several neutral NaCl molecules are attached. Collision-induced dissociation experiments revealed that the ions observed in the positive- and negative-ion modes possess remarkably different structures. Their fragmentation behavior indicates that the sodium ions providing the charge of the positively charged aggregates are strongly bound inside the crown ether moieties, while the neutral salt units are less strongly attached. However, in the negatively charged ions, none of the sodium ions is embedded in the crown ether moieties, and the NaCl molecules were found to be attached as one large, weakly bound cluster.
Singly and doubly charged adducts of LiCl with β-cyclodextrin (βCD) of the type (βCD)(LiCl)
n
Li
+
and (βCD)
2
(LiCl)
p
Li
2
2+
were studied using electrospray ionization mass spectrometry (ESI-MS). ...Insight into their structural composition was gained by analysis of their collision-induced dissociation (CID) mass spectra. The conditions the ions experience in the transfer region interfacing the ESI source and the mass analyzer were found to have a marked influence on the nature of the detected ions. In one instrument incorporating a single skimmer, individually attached LiCl ion pairs were observed, whereas the dual funnel ion guides of the second instrument allow the detection of previously unknown labile inclusion complexes of (LiCl)
n
clusters in βCD.
Graphical Abstract
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A systematic scanning tunnelling microscopy study of the self-assembly, intramolecular conformation and supramolecular ordering of different tetraphenylporphyrins (xTPP) with or without a central ...metal atom (x = 2H, Fe, Co) on Ag(111) at room temperature is presented. The investigation covers a wide range,
i.e.
the adsorption behaviour from the low sub-monolayer up to the multilayer regime is described in detail and conclusively discussed in regard to molecule-molecule and molecule-substrate interactions. At monolayer coverage the molecules self-assemble in domains with a square unit cell caused by "T-type" intermolecular interactions, while the orientation of the domains along the symmetry axes is determined by adsorbate-substrate interactions. Interestingly for ordered monolayers domain boundaries always separate domains of different organizational chirality but same orientation of the square unit cell. This demonstrates that in the particular system chirality obviously restricts the long range order of the supramolecular TPP assemblies. In combination with DFT calculations it is also demonstrated that the previously reported intramolecular saddle shape deformation of TPPs upon adsorption is more pronounced for metallo-TPP than for 2HTPP.
The specific interaction characteristics of tetraphenylporphyrins on Ag(111) trigger their assembly into interlocked mirror domains limiting the long range order.
The in situ metalation of monolayers and multilayers of 2H-tetraphenylporphyrin (2HTPP) with Fe atoms on Ag(111) was studied with scanning tunneling microscopy (STM) and X-ray photoelectron ...spectroscopy (XPS). This surface-confined coordination reaction results in the formation of adsorbed iron(II)-tetraphenylporphyrin (FeTPP). It is demonstrated that metalation of 2HTPP is achieved either by depositing iron atoms onto a monolayer of 2HTPP at room temperature or, alternatively, by depositing 2HTPP onto a Ag(111) surface with predeposited iron. The latter route requires elevated temperatures, indicating that this reaction includes at least one step with an activation barrier. In addition, it is demonstrated that vapor deposited Fe atoms also react with multilayers of the porphyrin at room temperature under the formation of FeTPP.
Crown ether fullerenes, C60H(cr – H), form two different dimers in electrospray ionization mass spectrometry, a noncovalently bound, metal-bridged dimer C60H(cr – H)2M+, and a singly bonded ...fullerene dimer of the type (cr – H)–C60–C60–(cr – H)M n n+, with n = 1, 2. In this work, the dependence of both the formation and the dissociation of these dimers on the respective sizes of the crown ether moiety (12cr4, 15cr5, 18cr6) and of the alkali metal ion (M+ = Li+, Na+, K+, Rb+, Cs+) is studied. The size ratio of crown ether cavity to metal cation size has a profound influence on the formation of the noncovalent dimers, C60H(cr – H)2M+. These are only formed if the cation is larger than the crown ether cavity. Also, the doubly charged, covalent dimers C60(cr – H)2M2 2+ show a dependence on the size ratio. The proposed formation mechanism involves the recombination of two C60(cr – H)M•+ radical cations, which can only occur if the repulsion between the two charges is sufficiently reduced by encapsulating the metal cations within the crown ether moiety. Only the formation of the singly charged covalent dimer C60(cr – H)2M+ was found to be independent of the size ratio, in line with a radical-based dimerization mechanism. The fragmentation behavior, however, is strongly dependent on the size ratio, revealing the influence of intramolecular crown–metal–crown complexes.
The K+ adducts of the crown ether–60fullerene conjugate of the form (12cr4 – H)–C60–H are investigated by electrospray mass spectrometry (ESI-MS), focusing on the dimeric species produced from two ...different solvent mixtures. A singly bonded fullerene dimer of the type (12cr4 – H)–C60–C60–(12cr4 – H)K+ is generated in aprotic solvents, while in protic solvents, a metal-bridged, noncovalently bound dimer predominates. The dimerization reaction is proposed to occur during the ESI process via the radical intermediate (12cr4 – H)–C60 •. The fragmentation behavior of the different dimers is studied by collision-induced dissociation (CID), showing characteristic product ions for each species.
The aggregation of phthalocyanines is well-known in solution but has never before been studied in the gas phase. We investigated the tetra-18crown-6 ether functionalized zinc–phthalocyanine ...(ZnPcTetCr, M) with electrospray ionization mass spectrometry (ESI-MS) in the absence of coordinating metal cations. Apart from the molecular ion M +•, singly and multiply charged aggregates M n z(+•) were observed, bound together by electrostatic interactions, without alkali metal cations inside the crown ethers. Collision-induced dissociation (CID) experiments indicate that these clusters consist of stacked neutral M and radical cations M +•. After the oxidation of individual molecules at the electrospray needle, the aggregation occurs during desolvation of the charged droplets created in the source. Complete evaporation of the solvent and detection of the aggregates was found to require an additional acceleration of the droplets in the transfer region of the instrument, the resulting collisions with neutral gas assisting the desolvation process.
Metalfluoride anions are produced from reaction of fluorinated fullerenes with activated metal surfaces.
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•Metalfluoride anions are produced from reaction of fluorinated fullerenes ...with activated metal surfaces.•In a plasma ion source, C60Fx react with the Mo and W of the filament and sample holder yielding MoF5/6− and WF5/6−.•In laser desorption/ionisation (LDI) of C60Fx on Al, Cu and Fe foils, the respective metalfluoride anions are generated.•The metalfluoride yields strongly depend on the fluorine content of the fullerene.
A comparative investigation into the chemical reactions of a series of fluorinated fullerenes (C60F18, C60F36 and C60F48) with a variety of activated metal surfaces is reported. New ways of generating intense beams of metal fluoride anions are demonstrated: either in reactions of fluorinated fullerene vapours with hot W and Mo metal surfaces in a plasma ion source or by laser desorption/ionisation (LDI) of solid fluorinated fullerenes from various metal substrates (Al, Fe, Cu, Pt, W). In both cases, the resulting metal fluorides and their anions are formed in the highest oxidation state, yielding molybdenum and tungsten hexafluoride anions (plasma ion source), aluminium and iron tetrafluoride anions, and copper trifluoride anions (LDI). No reactions were observed with Pt and W in LDI. The reactivity of the metals towards fluorination correlates with their positions in the metal activity series. Relative yields of bare metal cations are dictated by their ionisation energy. The yield of metal fluoride anions is strongly dependent on the fluorine content of the fluorofullerenes.
The ion formation of crown ether-60fullerene conjugates of the type (crown - H)-C60-H with crown = 12cr4, 15cr5 and 18cr6 has been studied with matrix-assisted laser desorption/ionisation (MALDI) and ...electrospray ionisation mass spectrometry (ESI MS). In total five different ways of ion formation are presented, including metalation (MALDI, ESI), protonation and oxidation (both in MALDI) in the positive-ion mode and deprotonation (MALDI, ESI) and reduction (MALDI) in the negative-ion mode. In line with thermochemistry, the deprotonation and electron transfer processes involve the C60 moiety as the charge-carrying entity, while protonation and metalation occur at the crown ether. Particular emphasis has been placed on the study of metal cation attachment in MALDI varying the crown ether size in the conjugate and using different alkali metal chlorides in the target preparation. Dissociation reactions of the metalated conjugates are influenced by the interaction strength of the metal cation to the crown ether fullerene conjugate. The data confirm an increase in bond strength with smaller metal cations, supporting the notion of charge density-driven interactions.
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