Collision-induced dissociation mass spectrometry of phosphorus cluster anions P2m+1− (3 ≤ m ≤ 20)

• Phosphorus cluster anions are investigated with CID MS.
• The CID MS results of P2m+1− are very different with those of P2m+1+.
• For P2m+1− (3 ≤ m ≤ 11), their dissociation channels are characterized by the loss of a P2 unit.

Phosphorus cluster anions were generated and investigated using collision-induced dissociation mass spectrometry. Results show that the primary dissociation channels of P2m+1− (3 ≤ m ≤ 11) are generally characterized by the loss of a P2 unit, which distinguishes them from their counterpart cations. However, P11− and P13− are two exceptions. The former is characterized by the loss of a P4 unit, and the latter is characterized by two parallel dissociation channels, which lead to the loss of P2 and P6 units. The dissociation behaviors of larger cluster anions of P8k+1− (k = 3–5) are more complex. The primary dissociation pathway of P25− is the loss of a P8 unit, and those of P33− and P41− are the loss of P16 and P2 units respectively. Theoretical calculations were performed for anions of P2m+1− (3 ≤ m ≤ 9). Results show that their dissociation channels characterized by the loss of the P2 unit are more thermodynamically favored, which is generally consistent with the experimental results.

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