Singlet oxygen photogeneration from X-O2 van der Waals complexes: double spin-flip vs. charge-transfer mechanism

• Published in: Physical chemistry chemical physics : PCCP Vol. 17; no. 43; pp. 28565 - 28573
• Main Authors: Baklanov, Alexey V, Bogomolov, Alexandr S, Pyryaeva, Alexandra P, Bogdanchikov, Georgii A, Kochubei, Sergei A, Farooq, Zahid, Parker, David H
• Format: Journal Article
• Language: English
• Published: England 21.11.2015
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c5cp03129j

The channel of singlet oxygen O 2 ( 1 Δ g ) photogeneration from van der Waals complexes of oxygen X-O 2 has been investigated to discriminate between two possible mechanisms based on charge-transfer (CT) or double spin-flip (DSF) transitions. The results obtained in this work for complexes with X = ethylene C 2 H 4 , 1,3-butadiene C 4 H 6 , deuterated methyl iodide CD 3 I, benzene C 6 H 6 and water H 2 O and for those investigated previously indicate the DSF mechanism as a source of singlet oxygen. The formation of O 2 ( 1 Δ g ) is observed only when the energy of exciting quantum is sufficient for DSF transition. Universally detected low vibrational excitation of O 2 ( 1 Δ g ) arising in the photodissociation of van der Waals complexes X-O 2 indicates the DSF mechanism as its source. For complex of ethylene C 2 H 4 -O 2 ab initio calculations of vertical energy Δ E vert for DSF and CT transitions have been carried out. The positive results of singlet oxygen formation from C 2 H 4 -O 2 can be explained by the DSF but not by the CT mechanism. The channel of singlet oxygen O 2 ( 1 Δ g ) photogeneration from van der Waals complexes of oxygen X-O 2 has been investigated to discriminate between two mechanisms based on charge-transfer or double spin-flip transitions.