Special feature: Perspective. Host–guest chemistry in the mass spectrometer

Abstract

The study of host-guest chemistry in the gas phase has been pursued systematically only in the last 5 years, after sporadic interest in the 1980s, despite extensive investigation of this chemistry in the condensed phase and the success encountered in several Ðelds of application. Most gas-phase studies have been performed under the controlled conditions that can be achieved inside a mass spectrometer, where solvent e †ects are not present. At this point, the Ðrst evaluation of the achievements and knowledge emerging from these mass spectrometric investigations can be attempted. At the same time, it is possible to evaluate the most promising subjects for future research. This review undertakes these tasks, by presenting (i) applications where mass spectrometry was used to investigate condensed phase equilibria and, more extensively, (ii) experiments where host-guest complexes were formed directly in the gas phase. The latter processes are discussed in detail in relation to the structural and electronic e †ects, the energetic requirements and the dependence on size, rigidity, spatial geometry and functional groups of both hosts and guests. All these e †ects combined are likely to contribute to the strength and multiplicity of the non-covalent bonds that allow the complex to be formed. The macro(poly)cyclic hosts considered include crown ethers, cryptands, cyclodextrins, calixarenes, cryptophanes, cavitands, carcerands and macrolides. The guests are either metal cations or organic molecules and ions.

Effect of Ring Size on the Complexation and Decomposition of Benzenediazonium Ion in the Presence of Crown Ethers in 1,2-Dichloroethane and the Gas Phase

“…Under comparable conditions, homolytic decomposition reactions are faster than the corresponding heterolysis reactions, and thus the increasing destabilization with increasing concentration of 12-crown-4 can be explained as being due to the increase in homolysis (see Scheme 1). 6,18 In accordance with Laali and Lattimer's 8 observation, and in contrast to crown ether-metal ion systems, sandwich complexes 1,7 were not detected by FAB-MS; only 1:1 complexes were observed under FAB conditions. Using field desorption mass spectrometry (FD-MS), Laali + (m/z 633).…”

“…[7][8][9] The same method was used in this work for the observation and characterization of the host-guest complexation between crown ethers containing 4-10 oxygen atoms and benzenediazonium ion. The mass spectrum of benzenediazonium tetrafluoroborate in the presence of 15-crown-5 was recently presented in connection with our investigations of polyether-tropylium ion systems.…”

“…[1][2][3][4][5][6] In addition, it is observed that fast atom bombardment mass spectrometry (FAB-MS) is a rapid and good method for the characterization of complexation in the gas phase. [7][8][9][10] Arenediazonium salts possess considerable importance in the chemical industry, which has initiated a great number of the studies. 11 According to Bunnett,12 all reactions, independent of their mechanism, where the two nitrogen atoms of azo or diazo compounds are replaced by any other group, are dediazoniation reactions.…”

New Fluorenocrownophanes Containing Benzene or Biphenyl Fragments: Synthesis, Properties and Interaction with Paraquat

“…Возможность образования таких комплексов и качественную оценку их относительной устойчи-вости проводили с помощью масс-спектрометрии в условиях бомбардировки быстрыми атомами (ББА), которая позволяет зафиксировать их образование. [32,33] В масс-спектре раствора эквимольных количеств краунофанов 2a-г и десяти эквивалентов параквата + (m/z = 867, 955, 943, и 1031, соот-ветственно). Такая спектральная картина характерна для большинства ротаксанов и псевдоротаксанов [34] и свидетельствует об образовании достаточно устой-чивых комплексов флуоренофанов 2a-г с паракватом 6·2PF 6 + в 1,5 раза.…”

New Fluorenocrownophanes with Naphthalene Fragments: Synthesis, Structure, Properties and Interaction with Paraquat

“…[25][26][27] Two solutions containing equimolar amounts of crownophanes 2b-d or 2e-g and 3 equivalents of 6•2PF 6 in 3-nitrobenzyl alcohol were subjected to mass spectral analysis. In the mass spectra, besides the initial crownophanes peaks, the peaks of ions corresponding to the formation of a crownophaneparaquat 1:1 complex with the loss of a hexafluorophosphate anion were observed (Table 2).…”