Tomasz Kozik

Cationization versus surface activity--the effect on electrospray ionization.

Ethoxylated fatty alcohols, C12E1, C12E2, C18E1 and C18E2, were studied by electrospray ionization mass spectrometry (E is the ethoxylene unit –OCH2CH2–). For compounds containing two ethoxylene units, which form quite stable adducts with sodium cation, the abundances of [M + Na]+ ions were not affected by alkyl chain, so the hydrophobic effect was not observed. For the compounds containing one ethoxylene unit, forming rather unstable adducts with sodium, the hydrophobic effect was clearly seen since the [C18E1 + Na]+ ion was more abundant than the [C12E1 + Na]+ ion. Two ethoxylene units are not able to form stable adducts with potassium cations, therefore the hydrophobic effect was observed for the [C12E2 + K]+ and [C18E2 + Na]+ ions, the latter being more abundant than the former. For lithium cation adducts with C12E1 and C18E1, the hydrophobic effect was observed, but was less manifested than for sodium cations since lithium adducts are more stable than sodium ones. C18E1 and C18E2 gave more intense signals at higher cone voltage values than C12E1 and C12E2, respectively. However, this is not related to the hydrophobic effect but to the collisions being less effective for the former.

Electrospray ionization and liquid secondary ion mass spectrometric study of N-heterocyclic carbenes and their 1,2,4-triazolium salt precursors

Abstract N-Heterocyclic carbenes and their 1,2,4-triazolium salt precursors were analyzed by electrospray ionization (ESI) and liquid secondary ion mass spectrometry (LSIMS). It was found that under applied conditions the C5 carbene center is formed from [M+ClO 4 ] + ion, were M corresponds to the 1,2,4-triazolium dicationic system, by loss of HClO 4 molecule. Further decomposition of formed carbene ions, namely [M−H] + ion, consist in the breaking of triazolium ring and loss bulky substituents from N1 and N4 atoms through the hydrogen transfer to the carbene center. This is in contrast to the [M] 2+ carbene precursor ions for which only the loss of N1 substituent occurred as a simple heterolytic bond cleavage.

Phenylcopper(I) clusters in the gas phase obtained by laser desorption/ionization from bis(dibenzoylmethane)copper(II)

AbstractIt has been demonstrated that phenylcopper(I)-containing clusters are generated in the gas phase from bis(dibenzoylmethane) copper(II) (Cu(dbm)2) by laser desorption/ ionization (LDI) method. For example, the [Cu5dbm2(C6H5)2]+ ion can be considered as consisting of two Cudbm molecules, two CuC6H5 molecules and a Cu+ cation. The [Cu5(C6H5)4]+ ion can be considered as phenylcopper(I) cluster (consisting of four phenylcopper molecules) ionized by additional Cu+ cation. Results from MS/MS (tandem mass spectrometry) experiments have confirmed the presence of phenylcopper molecules in the analyzed clusters. Ease of preparation of dibenzoylmethane-metal complexes and straightforward method to obtain LDI mass spectra offer a wide range of possibilities to study similar organometallic clusters in the gas phase.

Complexation of phosphates by 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane.

RATIONALE Compounds containing a urea or thiourea moiety form complexes with anions thanks to the ability to form quite strong hydrogen bonds. We have synthesized 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane (1). Compound 1 contains two urea moieties connected by a long flexible linker; thus, it should be able to adopt a structure suitable for formation of quite stable complexes with anions. METHODS The ability to form complexes of compound 1 with phosphates was tested by electrospray ionization mass spectrometry (ESI-MS). Full scan ESI mass spectra and collision-induced dissociation tandem mass (CID-MS/MS) spectra of the ions of interest were obtained on a quadrupole time-of-flight (QTOF) mass spectrometer. RESULTS It has been found that compound 1 is not only much more prone to form complexes with the phosphate anion than with other inorganic anions, but it is also able to form complexes with organic phosphates, namely nucleotides and phospholipids. However, compound 1 is not able to form complexes with organic compounds not containing a phosphate group (e.g. nucleosides, sugars, glycerolipids). CONCLUSIONS Compound 1 can be regarded as selective towards phosphate-containing organic compounds. Formation of such complexes may have some interesting applications for identification of organic phosphates in crude extracts from biological materials.

Unexpected formation of [M] 2+ from [M+CuCl+H] 2+ ions under CID conditions, where M is a moleculeof 3,5-bis(2,2’-bipyridin-4-ylethynyl)benzoic acidor its methyl ester

Abstract [M+CuCl+H]2+ ions were generated using electrospray ionization (ESI); where M is a molecule of 3,5-bis(2,2’-bipyridin-4-ylethynyl)benzoic acid or its methyl ester (1 and 2, respectively). The ions were subjected to CID-MS/MS analysis. It was found that their gas phase decomposition lead to the formation of rare di-cations [M]2+, namely [1]2+ and [2]2+ ions. The formation of [1]2+ ion from [3+H+CuCl]2+ ion in the second fragmentation, where 3 is ethyl ester of 3,5-bis(2,2-bipyridin-4-ylethynyl)benzoic acid, was also observed since in the first fragmentation step the loss of ethylene molecule from [3+H+CuCl]2+ ion took place. To the best of our knowledge, it is the first time that [M]2+ ions formation from respective metal complexes has been reported. It is also unusual that formation of [M]2+ ions is not accompanied by formation of [M]+∙ ions. Furthermore, as expected, theoretical calculation and electron ionization mass spectra show that 1 and 2 are not especially prone to form [M]2+ ions. Thus formation of [M]2+ ions under CID conditions is very surprising. Graphical Abstract