Gas-phase lithium cation basicity of histamine and its agonist 2-(β-aminoethyl)-pyridine

Hallmann, M.; Raczyńska, Ewa D.; Gal, Jean‐François; Maria, Pierre‐Charles

doi:10.1016/j.ijms.2007.02.058

Cited by 8 publications

(6 citation statements)

References 40 publications

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“…scale 30 is currently limited to about 200 kJ mol −1 and potentially up to 230 kJ mol −1 using diaminoalkanes as chelating ligands, 42 including 2-(β-aminoethyl)-pyridine (AEP) and histamine (HA). 43 The development of the LiCB scale by relative basicity determinations may benefit from the close relative basicities estimated for monodentate and bidentate ligands listed in Table 4. S1 in the Supporting Information) contain a 10-electron system, i.e., three pairs of n-electrons at the amino N atoms and two pairs of π-electrons in the imino CN group, which are conjugated in a different way; I1, I3, and I5 are doubly n-π-cross-conjugated system, whereas I2 and I4 possess two differently bonded Yconjugated fragments.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“… a B3LYP/6-311+G(d,p)//B3LYP/6-311+G(d,p) for 298 K. b This work. c Averaged value calculated for reaction taking the percentage contents of the neutral and lithiated isomeric mixtures of imeglimin into account at the DFT, G2, G2MP2, and G4 levels, respectively. d Ref . e B3LYP/6-311+G(d,p)//B3LYP/6-31G(d,p) for 298 K. f Ref . Difference between Exp.…”

Section: Resultsmentioning

confidence: 99%

“…The macroscopic lithium-cation basicity data have been estimated as the enthalpy and Gibbs energy changes of reaction . Although the estimated macroscopic LiCB and LiCA for bidentate imeglimin (Table ) are smaller than those for metformin, they seem to be higher than those for monodentate bicyclic guanidine MTBD . The higher range of the LiCB scale is currently limited to about 200 kJ mol –1 and potentially up to 230 kJ mol –1 using diaminoalkanes as chelating ligands, including 2-(β-aminoethyl)-pyridine ( AEP ) and histamine ( HA ) . The development of the LiCB scale by relative basicity determinations may benefit from the close relative basicities estimated for monodentate and bidentate ligands listed in Table .…”

Section: Resultsmentioning

confidence: 99%

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Biguanide Antidiabetic Drugs: Imeglimin Exhibits Higher Proton Basicity but Smaller Lithium-Cation Basicity than Metformin in Vacuo

et al. 2018

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Compounds containing biguanide moiety, such as buformin, phenformin, and metformin are well recognized for their antihyperglycaemic action. Imeglimin is a dihydro-1,3,5-triazine that can be considered as a cyclic metformin derivative, which has been tested as a promising new antidiabetic drug. Quantum-chemical calculations have been carried out to examine its structure and its gas-phase basicity toward the proton and the lithium cation. Owing to various structural isomeric rearrangements possible for imeglimin, 23 isomers have been considered for the neutral molecule in vacuo at the B3LYP/6-311+G(d,p) level. Four isomers (two major and two minor) have been selected and their exceptional energetic stabilities additionally confirmed by the G2, G2MP2, and G4 methods. The major isomers (>95%) correspond to the push−pull biguanide systems, which are similar to those for neutral metformin. The minor isomers (<5%) have nonanalogous metformin structures. The basicity properties in the gas phase have been examined by computing the energetics of protonation and adduct formation with Li + . The same protocol (starting by density functional theory, then Gn procedures) used for the neutral molecule was applied to the monoprotonated and monolithiated forms of imeglimin to select the favored isomers. When compared to metformin, the proton affinity of imeglimin is larger by more than 10 kJ mol −1 , this increase being attributed to the effect of the additional >CH−CH 3 group. The cyclic form of imeglimin precludes the possibility of chelation effect by two imino groups as it occurs for metformin. Consequently, imeglimin has a lower lithium-cation affinity than that of metformin by ca. 30 kJ mol −1 . The lithium cation seems however to be weakly chelated by the neighboring imino and amino N atoms of imeglimin, an effect that is weaker than that of the two terminal imino N atoms of metformin. Gas-phase proton basicity of imeglimin falls between that of bicyclic amidine DBU and guanidine TBD, whereas lithium-cation basicity is situated between that of bicyclic guanidine MTBD and tricyclic vinamidine TTT. Electron delocalization in the biguanide moiety of imeglimin is analogously related to isomerism as that in the parent biguanide and metformin.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Biguanide Antidiabetic Drugs: Imeglimin Exhibits Higher Proton Basicity but Smaller Lithium-Cation Basicity than Metformin in Vacuo

et al. 2018

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“…Generally, bidentate adducts have smaller Gibbs energies than monodentate ones in the gas phase [77,91,92]. The lowest G value at the DFT level (Table S5 in SM) possesses the bidentate adduct P739M + , formed from the neutral minor tautomer P7 with the lithium or sodium cation (Chart 2).…”

Section: Metal Cation Adduct Formationmentioning

confidence: 99%

“…High stability of bidentate metal cation adducts has also been reported for other neutral bases containing more than one Nbasic sites, e.g., biguanide, metformin, imeglimin, and histamine. [77,91,92]. In the case of the purine monoanion P − , the N sites can also interact with a metal cation, and monodentate or bidentate adducts can be formed as in the case of neutral purine.…”

Section: Metal Cation Adduct Formationmentioning

confidence: 99%

Purine tautomeric preferences and bond-length alternation in relation with protonation-deprotonation and alkali metal cationization

et al. 2020

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Quantum chemical calculations were carried out for deprotonated (P−) and protonated purine (PH+) and for adducts with one alkali metal cation (P−M+ and PM+, where M+ is Li+ or Na+) in the gas phase {B3LYP/6-311+G(d,p)}, a model of perfectly apolar environment, and for selected structures in aqueous solution {PCM(water)//B3LYP/6-311+G(d,p)}, a reference polar medium for biological studies. All potential isomers of purine derivatives were considered, the favored structures indicated, and the preferred sites for protonation/deprotonation and cationization reactions determined. Proton and metal cation basicities of purine in the gas phase were discussed and compared with those of imidazole and pyrimidine. Bond-length alternations in the P, PH+, P−M+, and PM+ forms were quantitatively measured using the harmonic oscillator model of electron delocalization (HOMED) indices and compared with those for P. Variations of the HOMED values when proceeding from the purine structural building blocks, pyrimidine and imidazole, to the bicyclic purine system were also examined. Generally, the isolated NH isomers exhibit a strongly delocalized π-system (HOMED > 0.8). Deprotonation slightly increases the HOMED values, whereas protonation and cationization change the HOMED indices in different way. For bidentate M+-adducts, the HOMED values are larger than 0.9 like for the largely delocalized P−. The HOMED values correlate well in a comprehensive relationship with the relative Gibbs energies (ΔG) calculated for individual isomers whatever the purine form is, neutral, protonated, or cationized. When PCM-DFT model was utilized for P−, PH+, PM+, and P−M+ (M+ = Li+) both electron delocalization and relative stability are different from those for the molecules in vacuo. The solvation effects cause a slight increase in HOMEDs, whereas the ΔEs decrease, but in different ways. Hence, contribution of particular isomers in the isomeric mixtures of PH+, PM+, and P−M+ also varies.

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Gas‐Phase Cation Affinity and Basicity Scales

Laurence

Gal

2009

Lewis Basicity and Affinity Scales

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The study of the formation of complexes between cations and chemical species in the gas phase offers the unique possibility of measuring the intrinsic (i.e. free of solvent and counter ion influences) Lewis basicity of these species. Although the charge-transfer component of the interaction energy in cation adducts is normally smaller than the electrostatic and polarization components, gas-phase cations are generally considered as archetypal Lewis acids because the full positive charge of the naked cation allows strong binding with classical Lewis bases. In fact, almost any entity bearing some electron density, such as the rare gases, can form complexes with cations that may be observable in the gas phase.There is a large array of cations that have been studied in the gas phase for their interaction with Lewis bases (generally neutral organic molecules) and are still being actively investigated today. The most studied is the proton [1-6]. This special cation will not be dealt with in this chapter (however, see Section 1.3 in Chapter 1), since the proton and its transfer serve to define the Brönsted acids and bases, as opposed to Lewis acids and bases, which do not exchange protons. Moreover, although the proton and a cation with an empty orbital may be seen as identical from the point of view of the Lewis theory, the special 'electronic structure' of the proton (in fact the absence of any electron) makes the proton affinity and basicity scales completely different, qualitatively and quantitatively, from any other cation scales. A significant part of the studies of the interaction of gas-phase metal cations with organic molecules was devoted to their chemical reactivity: bond insertion, bond cleavage, elimination and so on. This aspect is not considered here, although some of these reactions may be used as indirect routes for the formation of cation/molecule adducts.Apart from the proton, experimental studies have focused primarily on the binding of alkali metal cations and transition metal monocations. Few studies have considered alkaline Lewis Basicity and Affinity Scales: Data and Measurement

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Gas-phase lithium cation basicity of histamine and its agonist 2-(β-aminoethyl)-pyridine

Cited by 8 publications

References 40 publications

Biguanide Antidiabetic Drugs: Imeglimin Exhibits Higher Proton Basicity but Smaller Lithium-Cation Basicity than Metformin in Vacuo

Biguanide Antidiabetic Drugs: Imeglimin Exhibits Higher Proton Basicity but Smaller Lithium-Cation Basicity than Metformin in Vacuo

Purine tautomeric preferences and bond-length alternation in relation with protonation-deprotonation and alkali metal cationization

Gas‐Phase Cation Affinity and Basicity Scales

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