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Paper
Phys. Chem. Chem. Phys., 2000, 2, 2245 - 2250, DOI: 10.1039/b000225i
PCCP does exist
Mark Brönstrup, Jochen Gottfriedsen, Ilona Kretzschmar, Stephen J. Blanksby, Helmut Schwarz and Herbert Schumann
Neutral and cationic [C2,P2] were investigated by a combination of mass spectrometry and electronic structure calculations. The cationic [C2 ,P2]
+ potential energy surface including all relevant minima, transition states and fragmentation products was calculated at the B3LYP/6-311G(3df) level of theory. The most stable structures are linear PCCP+1+ (Erel=0 kcal mol–1), a three-membered ring with exocyclic phosphorus c-(PCC)-P 2+ (Erel=40.8 kcal mol–1), and the rhombic isomer 3+ (Erel=24.9 kcal mol–1). All fragmentation channels are significantly higher in energy than any of the [C2,P2]+ isomers. Experimentally, [C2,P2]+ ions are generated under high vacuum conditions by electron ionization of two different precursors. The fragmentation of [C2 ,P2]+ on collisional activation is preceded by rearrangement reactions which obscure the structural connectivity of the ions. The existence and the high stability of neutral [C2,P2] were proved by a neutralization–reionization (NR) experiment. Although an unambiguous structural assignment of the neutral species cannot be drawn, both theory and experiment suggest that the long-sought neutral, linear PCCP 1 is generated using the NR technique.
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