Datensatz

Zusammenfassung

Aseries of mono- and divalent fluorinatedpyri- dine derivatives is investigated by electrospray ionization (tandem) mass spectrometry and quantum chemical calcula- tions with respect to their capability to bind anions in the gas phase. The pyrid ine derivativ es differ not only in valency , but also with regard to the degree of fluorination of the pyr- idine rings, the positions of the fluorine atoms, the rigidity of the spacers connec ting the two pyridines in the divalent compounds, and the relative configuratio n. While the mono- valent compounds did not form anioncomplexes, the diva- lent analoguesexhibit anion binding even to weakly coordi- nating anionssuch as tetrafluoroborate.Three different tandem mass spectrometric experimentswereappliedto rank the gas-phase binding energies:(i) collision-induceddis- sociation (CID)experiments in aFourier transform ion-cyclo- tron-resonance (FTICR) mass spectrometer on two different, simultaneously mass-selected complexes with different re- ceptors, (ii)determination of the collisionenergy required to fragment 50 %ofthe mass-selected complexes in an ESI- QToF mass spectrometer,and (iii)CID of heterodimers formed from two different, competing pyridine receptor s and indigo carmine,adianionwith two identical binding sites. All three experimentsresult in consistent binding energyranking. This ranki ng reveals surprising features, whichare not in agreement with binding through anion–p interactions. Densityfunctionaltheory (DFT) calculations comparing different potentialbinding modes provide evi- dencethat the ranking can insteadnicely be explained, when C@H···anion interactions with the spacers are invoked. Theseresults are supported by gas-phase IR spectroscopy and ion mobility-mass spectrometry (IM-MS)onaselected set of chloridepyridine comp lexes.