Superbasic alkyl-substituted bisphosphazene proton sponges: a new class of deprotonating matrices for negative ion matrix-assisted ionization/laser desorption mass spectrometry of low molecular weight hardly ionizable analytes

Abstract

For the first time, the usefulness of novel superbasic proton sponges is demonstrated for MALDI detection of hardly ionizable compounds such as sterols, steroids, fatty alcohols and saccharides. The leading candidate TPPN has been successfully applied for negative ion MAILD-MS analysis of cholesterol, fatty acids and phospholipids in egg yolk and brain tissue extracts. Copyright © 2016 John Wiley & Sons, Ltd.

Development of an Unsymmetrical Cyclopropenimine‐Guanidine Platform for Accessing Strongly Basic Proton Sponges and Boron‐Difluoride Diaminonaphthalene Fluorophores

“…The cyclopropenium and guanidine rings are also more coplanar with the naphthalene backbone, as evidenced by the smaller torsion angles f of 33.4(5)8 and 60.8(6)8 between the bestp laneso ft heset wo rings and the best plane throught he naphthalene rings, respectively ( Figures 3c and d). This greater degree of planarity of the cyclopropenium and guanidine rings relative to the naphthalene backbone is further reflected in the reduced torsional dihedral angles q (C(14)-N(2)-C(7)-C(6)) = 171.0(7)8 and q (C(11)-N(1)-C(1)-C(6)) = 152.0(1)8.F inally,m uch like other proton sponges, [7] the protonated cation displays ac oplanar torsion angle between the cyclopropenium and guanidine rings in relation to the naphthalene backbones uch that q (C(14)-N(2)-C(7)-C(8)) = 11.4(8)8 and q (C(11)-N(1)-C(1)-C(2)) = 33.5(4)8,c onsistent with significant conjugation between the p-systems that is significantly absent in the free base (6). Like its Janus counterpart (5), the unsymmetrical sponge (6) does not undergo diprotonation in the presenceo fs trong acids such as conc.…”

“…[39] On the other hand, the unique coordinationa nd associated reactivity of di-, tri-, and tetracoordinate boron compounds incorporating BÀN bondingi so ft imely interest [40] as evidenced by:( i) organic reactivity, [41] (ii)the broad range of organic light emitting diodes (OLEDs), [42] (iii)the previously mentioned small molecule BODIPY fluorophores, [29] and (iv) the recently well-documented value of boron isosteric replacements affording boron heterocyclic systems with important biological andm aterials applications. [43] With this precedent in mind, our interest turned to preparing the BF 2 derivative, DAGBO (7). To this end, the approach outlined in Scheme 3w as followed, where deprotonation by KHMDS, followed by the addition of BF 3• OEt 2 ,a fforded the tetracoordinated boron adduct DAGBO (7)i n9 4% yield after purificationv ia column chromatography (Scheme 3, See Supporting Information section 2f or details).…”

“…Over the past 50 years, the development of proton sponges has greatlyb enefited fundamental branches of chemistry and chemicalp rocesses that include catalysis, [1] aciditya nd basicity, [2] hydrogen transfer, [3] hydrided onation, [4] and hydrogen bonding. [5] By the same token, proton sponges lend themselves to ab road range of applicationst hat include directing agents for the synthesis of crystalline microporous materials, [6] deprotonating matrices in mass spectrometry, [7] and catalysts or reactants for chemical transformations. [8,9] In our laboratory, proton sponges and relateds uperbases have been employed as phase-transfer catalysts, [10] small molecule fluorophores, [11] as well as fort he fundamentals tudy of intra-versus intermolecular hydrogen bonding interactions within molecules.…”

Characterization of bioactive and nutraceutical compounds occurring in olive oil processing wastes

“…29 One of the first binary components tested was 1,8bis(dimethylamino)naphthalene (DMAN), 30,31 called also "proton sponge", a strongly basic matrix (pK BH+ value of 18 in acetonitrile (ACN)), 32 which allows the proton extraction from very weak acids even in the liquid phase. 33 Since DMAN was reported to be unstable under high vacuum conditions, 34 leading to variable matrix-to-analyte ratio and contamination of the mass spectrometer ion optics, novel proton sponges were suggested to overcome this issue. 24,31,35 Among them TMGN (1,8-bis(tetramethylguanidino)naphthalene) is a possible candidate being a commercial proton sponge matrix (pK BH+ = 25.1 in ACN) first proposed for the determination of perfluorinated compounds in water samples.…”

1,8-Di(piperidinyl)-naphthalene – rationally designed MAILD/MALDI matrix for metabolomics and imaging mass spectrometry

“…However, this class of sponges produce matrix-related signals. 13 In this study, we searched for new superbasic ion-less matrices with a low vapour pressure to address these shortcomings. We also focused on increasing the sensitivity of the analysis.…”