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The Use of Electrospray Mass Spectrometry to Determine Speciation in a Dynamic Combinatorial Library for Anion Recognition
Author(s) -
Phillips Hazel I. A.,
Chernikov Aleksey V.,
Fletcher Nicholas C.,
Ashcroft Alison E.,
Ault James R.,
Filby Maria H.,
Wilson Andrew J.
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201201302
Subject(s) - chemistry , amide , bipyridine , chloride , acetonitrile , bromide , tetrafluoroborate , carboxylic acid , polymer chemistry , mass spectrometry , electrospray , medicinal chemistry , ionic liquid , inorganic chemistry , organic chemistry , ion , chromatography , catalysis , crystal structure
The composition of a dynamic mixture of similar 2,2′‐bipyridine complexes of iron(II) bearing either an amide (5‐benzylamido‐2,2′‐bipyridine and 5‐(2‐methoxyethane)amido‐2,2′‐bipyridine) or an ester (2,2′‐bipyridine‐5‐carboxylic acid benzylester and 2,2′‐bipyridine‐5‐carboxylic acid 2‐methoxyethane ester) side chain have been evaluated by electrospray mass spectroscopy in acetonitrile. The time taken for the complexes to come to equilibrium appears to be dependent on the counteranion, with chloride causing a rapid redistribution of two preformed heteroleptic complexes (of the order of 1 hour), whereas the time it takes in the presence of tetrafluoroborate salts is in excess of 24 h. Similarly the final distribution of products is dependent on the anion present, with the presence of chloride, and to a lesser extent bromide, preferring three amide‐functionalized ligands, and a slight preference for an appended benzyl over a methoxyethyl group. Furthermore, for the first time, this study shows that the distribution of a dynamic library of metal complexes monitored by ESI‐MS can adapt following the introduction of a different anion, in this case tetrabutylammonium chloride to give the most favoured heteroleptic complex despite the increasing ionic strength of the solution.