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The use of electrospray mass spectrometry to determine speciation in a dynamic combinatorial library for anion recognition.

Phillips HI, Chernikov AV, Fletcher NC, Ashcroft AE, Ault JR, Filby MH, Wilson AJ - Chemistry (2012)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry and Chemical Engineering, Queen's University Belfast, UK.

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ESI-MS spectrum of ligand L1 with FeCl2 in acetonitrile (metal ion concentration=50 μm).
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fig02: ESI-MS spectrum of ligand L1 with FeCl2 in acetonitrile (metal ion concentration=50 μm).

Mentions: Initial ESI-MS experiments indicated that a relatively straight forward spectrum, typical of the ionization of [Fe(L1)3]Cl2, could be obtained by taking a 10 μL solution of a 10 mm stock solution of anhydrous FeCl2 in methanol and mixing it with 60 μL of a 10 mm stock solution in acetonitrile of L1 and diluting the sample to 50 μm with acetonitrile (see the Experimental Section: Method A). Initially it was hoped to use only acetonitrile, however the solubility of the iron salt dictated that a small quantity of methanol was required to permit the initial dissolution. The detected spectrum (Figure 2) proved to be diagnostic, with signals for both [Fe(L1)3]2+ at m/z 461 and {[Fe(L1)3]Cl}+ at m/z 958 being particularly clear, in addition to peaks representing [L1H]+ at m/z 290, and {[Fe(L1)2]Cl}+ at m/z 669.


The use of electrospray mass spectrometry to determine speciation in a dynamic combinatorial library for anion recognition.

Phillips HI, Chernikov AV, Fletcher NC, Ashcroft AE, Ault JR, Filby MH, Wilson AJ - Chemistry (2012)

ESI-MS spectrum of ligand L1 with FeCl2 in acetonitrile (metal ion concentration=50 μm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569615&req=5

fig02: ESI-MS spectrum of ligand L1 with FeCl2 in acetonitrile (metal ion concentration=50 μm).
Mentions: Initial ESI-MS experiments indicated that a relatively straight forward spectrum, typical of the ionization of [Fe(L1)3]Cl2, could be obtained by taking a 10 μL solution of a 10 mm stock solution of anhydrous FeCl2 in methanol and mixing it with 60 μL of a 10 mm stock solution in acetonitrile of L1 and diluting the sample to 50 μm with acetonitrile (see the Experimental Section: Method A). Initially it was hoped to use only acetonitrile, however the solubility of the iron salt dictated that a small quantity of methanol was required to permit the initial dissolution. The detected spectrum (Figure 2) proved to be diagnostic, with signals for both [Fe(L1)3]2+ at m/z 461 and {[Fe(L1)3]Cl}+ at m/z 958 being particularly clear, in addition to peaks representing [L1H]+ at m/z 290, and {[Fe(L1)2]Cl}+ at m/z 669.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry and Chemical Engineering, Queen's University Belfast, UK.

Show MeSH