Solvation Structure and Stability of [(CH3)2NH] m (NH3) n –H Hypervalent Clusters: Ionization Potentials and Switching of Hydrogen-Atom Localized Site

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 115; no. 30; pp. 8380 - 8391
• Main Authors: Yamada, Yuji, Ishikawa, Haruki, Fuke, Kiyokazu
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 04.08.2011
• Subjects: A: Dynamics, Clusters, Excited States; Clusters; Excimer lasers; Femtosecond; Ionization potentials; Mathematical analysis; Radicals; Stability; Switching
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp204331q

Ionization potentials (IPs) of [(CH3)2NH] m (NH3) n –H hypervalent radical clusters produced by an ArF excimer laser photolysis of dimethylamine (DMA)–ammonia mixed clusters are determined by the photoionization threshold measurements. The IPs of the DMA1(NH3) n –H hypervalent radicals decrease rapidly with the number of ammonia up to n = 4, and then its decrease rate becomes much slower for n ≥ 5. This trend is very similar to that found for NH4(NH3) n clusters. The calculated results on the stable structures and IP as well as the observed IP for DMA1(NH3) n –H indicate that the hydrogen atom-localized site is the NH3 moiety for n = 1, while the doubly coordinated DMA–H is favorable for n = 2–4, and then 4-fold-coordinated NH4 is again more stable for n ≥ 5. These changes are consistent with the results on the femtosecond pump–probe experiments of DMA n –H clusters. Switching of the hydrogen atom-localized site is ascribed to the instability of DMA–H against a hydrogen-atom dissociation.