Time-resolved diffuse reflectance of electron trapping by alkali-metal cation clusters in zeolites and clays following far-UV Excitation

1995 ◽  
Vol 91 (4) ◽  
pp. 759 ◽  
Author(s):  
Xinsheng Liu ◽  
J. Kerry Thomas
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Diffuse Reflectance ◽  
Alkali Metal Cation ◽  
Electron Trapping ◽  
Time Resolved ◽  
Uv Excitation

Influence of alkali metal cations on the photoheterolysis of 9-cyclopropyl-9-fluorenol and the reactivity of the 9-cyclopropyl-9-fluorenyl cation in non-acidic zeolites

2003 ◽  
Vol 81 (6) ◽  
pp. 647-659 ◽  
Author(s):  
Melanie A O'Neill ◽  
Frances L Cozens
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Diffuse Reflectance ◽  
Bond Cleavage ◽  
Alkali Metal Cation ◽  
Zeolite Framework ◽  
Time Resolved ◽  
Highly Sensitive ◽  
Cation Size ◽  
Acidic Zeolites

Alkali metal cation regulation of carbocation formation and reactivity in non-acidic zeolites is probed using the photoheterolysis reaction of 9-cyclopropyl-9-fluorenol. Nanosecond time-resolved diffuse reflectance is employed to directly observe the 9-cyclopropyl-9-fluorenyl cation as a transient species within the non-acidic zeolites. The efficiency of carbocation formation via photoheterolysis and the dynamics of other reaction pathways available to photoexcited 9-cyclopropyl-9-fluorenol are found to be strongly dependent on the zeolite alkali metal counterion. In particular, the yield of carbocation decreases with increasing counterion size in a manner consistent with the zeolite assisting the excited state C—O bond cleavage via Lewis acid catalysis involving the metal cation. Zeolite encapsulation is also found to modulate the ability of water and methanol to assist photoheterolysis. For instance, the influence of coadsorbed water on the photoheterolysis reaction within zeolites is found to be highly sensitive to the alkali metal cation. The rate constant for intrazeolite decay of the 9-cyclopropyl-9-fluorenyl cation increases significantly as the alkali metal cation size increases and as the Si–Al ratio decreases. These reactivity trends suggest that the intrazeolite decay of the 9-cyclopropyl-9-fluorenyl cation involves nucleophilic addition at the active site [Si-O-Al]– bridges of the zeolite framework. In addition, the reactivity of the 9-cyclopropyl-9-fluorenyl cation within alkali metal zeolites can be regulated by the co-inclusion of reagents such as methanol, water, and 1,1,1,3,3,3-hexafluoro-2-propanol.Key words: cation-exchanged zeolites, 9-cyclopropyl-9-fluorenyl cation, laser photolysis, reactivity.

Conformational effect on the preferential binding of alkali metal cation with crown ether: A molecular level investigation

2009 ◽  
Vol 12 (1-3) ◽  
pp. 93-99 ◽  
Author(s):  
Sulagna De ◽  
Sk. Musharaf Ali ◽  
M.R.K. Shenoi ◽  
Sandip K. Ghosh ◽  
Dilip K. Maity
Keyword(s):  
Crown Ether ◽  
Alkali Metal ◽  
Metal Cation ◽  
Molecular Level ◽  
Alkali Metal Cation ◽  
Conformational Effect ◽  
Preferential Binding

Dynamic chiral-at-metal stability of tetrakis(d/l-hfc)Ln(iii) complexes capped with an alkali metal cation in solution

2012 ◽  
Vol 41 (22) ◽  
pp. 6696 ◽  
Author(s):  
Yiji Lin ◽  
Fang Zou ◽  
Shigang Wan ◽  
Jie Ouyang ◽  
Lirong Lin ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Metal Cation ◽  
Alkali Metal Cation

The Influence of Alkali Metal Cation Size on the Formation and Dissociation of Crown Ether Fullerene Dimers in Electrospray Mass Spectrometry

2015 ◽  
Vol 120 (1) ◽  
pp. 786-792 ◽  
Author(s):  
Ina D. Kellner ◽  
Marc S. von Gernler ◽  
Manolis D. Tzirakis ◽  
Michael Orfanopoulos ◽  
Thomas Drewello
Keyword(s):  
Mass Spectrometry ◽  
Crown Ether ◽  
Alkali Metal ◽  
Metal Cation ◽  
Electrospray Mass Spectrometry ◽  
Alkali Metal Cation ◽  
Fullerene Dimers ◽  
Cation Size
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