Study of anion-radicals of carboranes-12 in the gas phase by the mass spectrometry method of the resonance capture of electrons

1983 ◽  
Vol 32 (1) ◽  
pp. 197-199 ◽  
Author(s):  
V. A. Mazunov ◽  
Yu. S. Nekrasov ◽  
V. I. Khvostenko ◽  
V. I. Stanko
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Resonance Capture ◽  
Spectrometry Method ◽  
Mass Spectrometry Method ◽  
Resonance Capture Of Electrons ◽  
Anion Radicals

scholarly journals Study on the Influence of Chirality in the Threading of Calix[6]arene Hosts with Dialkylammonium Axles

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5323
Author(s):  
Carmen Talotta ◽  
Gerardo Concilio ◽  
Paolo Della Sala ◽  
Carmine Gaeta ◽  
Christoph A. Schalley ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
2D Nmr ◽  
Spectrometry Method ◽  
Mass Spectrometry Method ◽  
Reciprocal Influence ◽  
Chiral Centers ◽  
Stereogenic Center

The influence of chirality in calixarene threading has been studied by exploiting the “superweak anion approach”. In particular, the formation of chiral pseudo[2]rotaxanes bearing a classical stereogenic center in their axle and/or wheel components has been considered. Two kind of pseudo[2]rotaxane stereoadducts, the “endo-chiral” and “exo-chiral” ones, having the stereogenic center of a cationic axle inside or outside, respectively, the calix-cavity of a chiral calixarene were preferentially formed with specifically designed chiral axles by a fine exploitation of the so-called “endo-alkyl rule” and a newly defined “endo-α-methyl-benzyl rule” (threading of a hexaalkoxycalix[6]arene with a directional (α-methyl-benzyl)benzylammonium axle occurs with an endo-α-methyl-benzyl preference). The obtained pseudorotaxanes were studied in solution by 1D and 2D NMR, and in the gas-phase by means of the enantiomer-labeled (EL) mass spectrometry method, by combining enantiopure hosts with pseudoracemates of one deuterated and one unlabeled chiral axle enantiomer. In both instances, there was not a clear enantiodiscrimination in the threading process with the studied host/guest systems. Possible rationales are given to explain the scarce reciprocal influence between the guest and host chiral centers.

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