Studying On The Gas Phase "H/D Scrambling" Phenomenon For Two Types Of Indoles In Electrospray Ionization Mass Spectrometry

In this thesis,a combination of high-resolution electospray ionization high-energy collisional dissociation mass spectrometry?ESI-HCD-MS/MS?,electosprayionizationcollision-induceddissociationmassspectrometry?ESI-CID-MS/MS?,regiospecific hydrogen-deuterium labeling experiments and density functional theory?DFT?calculation was applied to investigate the gas phase fragmentation reactions of 4,5-bisindolyl-1,2,4-triazol-3-ones and cyclic indolyl?-amino esters.Meanwhile,the“H/D scrambling”phenomenon in the formation of characteristic product ions from their protonated ions was discussed.Firstly,thegasphasefragmentationreactionsofprotonated4,5-anthraquinone-1,2,4-triazol-3-one derivatives were investigated.As a result,two kinds of characteristic product ions including product ion a?protonated3-?hydrazonomethyl?-1H-indoles?andproductionb?protonated3-isocyanato-1-methyl-1H-indoles?were observed in their HCD-MS/MS spectra.Besides the product ions a-d₃ and b-d₁,the product ions a-d₂,a-d₁ and b were also observed in the HCD-MS/MS spectrum of the entirely labile hydrogen-deuterium exchanged ion[M-d₂+D]⁺for compound 1.Density functional theory?DFT?calculations demonstrated that the N¹ position and O¹³ position were the possible protonation sites for these compounds.The external proton can easily transfer from N¹ position to C⁷ position or C⁹ position or from O¹³ position to C¹⁰ position,C¹²position or N² position with a lower energy barrier than fragmentation energy barrier,which indicated that the external proton on N¹ position and O¹³ position can undergo reversible intramolecular proton exchange reaction with C⁷ or C⁹ position and C¹⁰,C¹²or N² position,respectively,resulting in gas phase“H/D scrambling”phenomenon in HDX experiments,which gave rise to the the product ion a-d₂,a-d₁and b.Secondly,the gas phase fragmentation mechanisms of protonated cyclic indolyl?-amino esters were studied in quadrupole/orbitrap?Q/Orbitrap?and quadrupole time-of-flight?QTOF?mass spectrometers,respectively,and the gas phase fragmentation mechanisms of lithiated cyclic indolyl?-amino esters were studied in Q/Orbitrap mass spectrometer.In Q/Orbitrap MS/MS,owing to the enough dwell time in the C-trap,besides the proton transfer reaction within the ion-neutral complexes,the gas phase“H/D scrambling”phenomenon was observed for protonated cyclic indolyl?-amino esters due to H/D exchange with residual water in the collision cell.In contrast,the gas phase“H/D scrambling”phenomenon was not observed in QTOF MS/MS.In addition,due to the coordination action of lithium ion in the lithiated cyclic indolyl?-amino esters,the water complex ions are relatively stable,so that gas phase"H/D scrambling”phenomenon was not observed in the HDX experiments.