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Copper complexes formed by 3,5-bis(2,2′-bipyridin-4-ylethynyl)benzoic acid and its methyl and ethyl esters as studied by electrospray ionization mass spectrometry

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Frański R., Kowalska M., Czerniel J., Zalas M., Gierczyk B., Cegłowski M., Schroeder G.

Open Chemistry

2013

vol. 11

issue 12

2066-2075

Electrospray ionization mass spectrometry was used to study the complexes of ligands containing two bipyridine units, namely 3,5-bis(2,2-bipyridin-4-ylethynyl)benzoic acid (1) and its methyl and ethyl esters (2, 3), with copper cation, with CuCl2 as a source of copper. It was found that the type of complexes formed strongly depends on CuCl2 concentration. At lower CuCl2 concentration, the detected complexes were rather simple and some of them were formed upon electrospray ionization conditions e.g. ions [22+Cu2]2+ and [32+Cu2]2+ (complexes ligand-Cu(I) of stoichiometry 2:2) which are analogical to the well known, for quaterpyridine, helical complexes. At higher CuCl2 concentration, the detected complexes were more complicated, and most of them contained copper cations bridged by chlorides. The largest ions were [L2+Cu4Cl6]2+. The CID MS/MS spectra of these ions allowed determination of their mass spectrometric fragmentation pathways and as a consequence their structure elucidation. [...]

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

100%

Frański R., Zalas M., Gierczyk B., Cegłowski M., Schroeder G., Kozik T., Hoffmann M.

Open Chemistry

2015

vol. 13

issue 1

[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.

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2 Open Chemistry

1 2015

1 2013

2 Cegłowski M.

2 Frański R.

2 Gierczyk B.

2 Schroeder G.

2 Zalas M.

1 Czerniel J.

1 Hoffmann M.

1 Kowalska M.

1 Kozik T.

Search results

Copper complexes formed by 3,5-bis(2,2′-bipyridin-4-ylethynyl)benzoic acid and its methyl and ethyl esters as studied by electrospray ionization mass spectrometry

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