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Gas‐Phase Reactions of Atomic Lanthanide Cations with D 2 O: Room‐Temperature Kinetics and Periodicity in Reactivity
Author(s) -
Cheng Ping,
Koyanagi Gregory K.,
Bohme Diethard K.
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600248
Subject(s) - lanthanide , chemistry , exothermic reaction , atom (system on chip) , electron transfer , reactivity (psychology) , analytical chemistry (journal) , activation energy , ion , crystallography , organic chemistry , medicine , alternative medicine , pathology , computer science , embedded system
Reactions of atomic lanthanide cations (excluding Pm + ) with D 2 O have been surveyed in the gas phase using an inductively coupled plasma/selected‐ion flow tube (ICP/SIFT) tandem mass spectrometer to measure rate coefficients and product distributions in He at 0.35±0.01 Torr and 295±2 K. Primary reaction channels were observed corresponding to O‐atom transfer, OD transfer and D 2 O addition. O‐atom transfer is the predominant reaction channel and occurs exclusively with Ce + , Nd + , Sm + , Gd + , Tb + and Lu + . OD transfer is observed exclusively with Yb + , and competes with O‐atom transfer in the reactions with La + and Pr + . Slow D 2 O addition is observed with early lanthanide cation Eu + and the late lanthanide cations Dy + , Ho + , Er + and Tm + . Higher‐order sequential D 2 O addition of up to five D 2 O molecules is observed with LnO + and LnOD + . A delay of more than 50 kcal mol −1 is observed in the onset of efficient exothermic O‐atom transfer, which suggests the presence of kinetic barriers of perhaps this magnitude in the exothermic O‐atom transfer reactions of Dy + , Ho + , Er + and Tm + with D 2 O. The reaction efficiency for O‐atom transfer is seen to decrease as the energy required to promote an electron to make two non‐f electrons available for bonding increases. The periodic trend in reaction efficiency along the lanthanide series matches the periodic trend in the electron‐promotion energy required to achieve a d 1 s 1 or d 2 excited electronic configuration in the lanthanide cation, and also the periodic trends across the lanthanide row reported previously for several alcohols and phenol. An Arrhenius‐like correlation is also observed for the dependence of D 2 O reactivity on promotion energy for early lanthanide cations, and exhibits a characteristic temperature of 2600 K.