Unusual complex between 18-Crown-6 and tetramethylammonium cation—detection by electrospray ionization mass spectrometry

On the charge partitioning between c and z fragments formed after electron-capture induced dissociation of charge-tagged Lys-Lys and Ala-Lys dipeptide dications

“…For comparison, photodissociation mass spectroscopy of complexes between protonated tryptophan and CE and between protonated tryptamine and CE also displayed mobility of CE since ammonia was lost without the CE [67,68]. In the z ϩ• (CE) fragment, the CE likely interacts with a methyl of the ϪNMe 3 ϩ group [69]. (CE) and [KK= ϩ H] 2ϩ either, and z ϩ• are formed in both cases, likely together with a c zwitterion.…”

Cation–π interactions in gas‐phase complexes formed by benzo‐crown ethers and alkali metal cations

“…[9][10][11][12][13] For example, because of cation-p interactions, the complexes of benzo-crown ethers with tetramethylammonium cation are more stable than complexes of simple crown ethers with tetramethylammonium cation. [12,14] Interactions of the aromatic ring of benzo-crown ethers with transition metal cations, namely Cu 2þ and Hg 2þ , have been also found to take place. [13,15] Crown ethers with aromatic side-arms exhibited cation-p interactions between K þ and a benzene ring; [16] however, cation-p interactions have not yet been observed for complexes of benzo-crown ethers with alkali metal cations.…”

An electrospray ionization mass spectrometric study of the interactions between crown ethers and tetramethylammonium(‐phosphonium) cations

“…[18C6 þ (CH 3 ) 4 N] þ ion -a complex based on the C-HO interaction (obviously, participation of ion-induced dipole interaction and ion-dipole interaction cannot be definitely excluded). 21 The stability of the complexes between benzo-crown ethers and the tetramethylammonium cation (e.g. [DB18C6 þ (CH 3 ) 4 N] þ ion) is enhanced by the cation-p interaction (because the distance between the charge and the p cloud is rather large, this interaction could be also considered as ion-induced dipole interaction).…”

“…[DB18C6 þ (CH 3 ) 4 N] þ ion) is enhanced by the cation-p interaction (because the distance between the charge and the p cloud is rather large, this interaction could be also considered as ion-induced dipole interaction). 21,22 The goal of this paper is to compare the complexing ability of crown ethers towards the tetramethylammonium cation and the tetramethylphosphonium cation ((CH 3 ) 4 N þ and (CH 3 ) 4 P þ ) by ESI-MS.…”

“…The abundances of these complexes are comparable, but evidently 24C8 is more prone to complexing (CH 3 ) 4 N þ than (CH 3 ) 4 P þ , and evidently DB24C8 is more prone to complexing (CH 3 ) 4 P þ than (CH 3 ) 4 4 P] þ , we deal also with cation-p interaction; as mentioned earlier this interaction could be also considered as ion-induced dipole interaction). 21 Thus, it is clear that 24C8 is more prone to form hydrogen bonds with (CH 3 …”