Three 2,4,6-trimethylpyridine–benzoic acid complexes at 150K

Foces‐Foces, Concepción; Llamas-Saíz, Antonio L.; Lorente, Phillipe; Golubev, N. S.; Limbach, Hans−Heinrich

doi:10.1107/s0108270198013766

Cited by 11 publications

(19 citation statements)

References 3 publications

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“…The bond angles of the benzene ring show significant deviations from 120 , probably because of the presence of the electronwithdrawing nitro and carboxylic groups. These findings are in agreement with earlier X-ray crystallographic studies on complexes of 2,4,6-trimethylpyridine (collidine) with derivatives of benzoic acids (Foces-Foces et al, 1999).…”

Section: Resultssupporting

confidence: 92%

X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1:1 hydrogen-bonded complexes with benzoic acid derivatives: evidence for coupled inter- and intramolecular proton transfer

Sharif

Powell

Schagen

et al. 2006

Acta Crystallogr Sect B

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Crystal structures of Schiff bases containing pyridoxal (PL), N-(pyridoxylidene)-tolylamine, C(15)H(16)N(2)O(2) (I), N-(pyridoxylidene)-methylamine, C(9)H(12)N(2)O(2) (III), and their 1:1 adduct with 2-nitrobenzoic acid, (I)(+) C(7)H(4)NO_4;- (II), and 4-nitrobenzoic acid, (III)(+) C(7)H(4)NO_4;- (IV), serve as models for the coenzyme pyridoxal-5'-phosphate (PLP) in its PLP-dependent enzymes. These models allow the study of the intramolecular OHN hydrogen bond of PL/PLP Schiff bases and the H-acceptor properties of their pyridine rings. The free base (I) forms hydrogen-bonded chains involving the hydroxyl side groups and the rings of adjacent molecules, whereas (III) forms related hydrogen-bonded cyclic dimers. The adducts (II)/(IV) consist of 1:1 hydrogen-bonded complexes, exhibiting strong intermolecular bonds between the carboxylic groups of the acids and the pyridine rings of (I)/(III). In conclusion, the proton in the intramolecular O-H...N hydrogen bond of (I)/(III) is located close to oxygen (enolamine form). The added acids protonate the pyridine ring in (II)/(IV), but only in the latter case does this protonation lead to a shift of the intramolecular proton towards the nitrogen (ketoimine form). All crystallographic structures were observed in the open form. In contrast, the formation of the pyridinium salt by dissolving (IV) leads to the cyclic aminal form.

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Section: Resultssupporting

confidence: 92%

X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1:1 hydrogen-bonded complexes with benzoic acid derivatives: evidence for coupled inter- and intramolecular proton transfer

Sharif

Powell

Schagen

et al. 2006

Acta Crystallogr Sect B

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“…This curve constitutes a good approximation to the correlation of the equilibrium distances. The squares originate data obtained by Lorente et al for 1:1 hydrogen‐bonded complexes of 2,4,6‐trimethylpyridine (collidine) with various acids by using a combination of dipolar solid state NMR6a and X‐ray crystallography 6b…”

Section: Resultsmentioning

confidence: 99%

NMR Parameters and Geometries of OHN and ODN Hydrogen Bonds of Pyridine–Acid Complexes

Limbach

Pietrzak

Sharif

et al. 2004

Chemistry A European J

101

175

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In this paper, equations are proposed which relate various NMR parameters of OHN hydrogen-bonded pyridine-acid complexes to their bond valences which are in turn correlated with their hydrogen-bond geometries. As the valence bond model is strictly valid only for weak hydrogen bonds appropriate empirical correction factors are proposed which take into account anharmonic zero-point energy vibrations. The correction factors are different for OHN and ODN hydrogen bonds and depend on whether a double or a single well potential is realized in the strong hydrogen-bond regime. One correction factor was determined from the known experimental structure of a very strong OHN hydrogen bond between pentachlorophenol and 4-methylpyridine, determined by the neutron diffraction method. The remaining correction factors which allow one also to describe H/D isotope effects on the NMR parameters and geometries of OHN hydrogen bond were determined by analysing the NMR parameters of the series of protonated and deuterated pyridine- and collidine-acid complexes. The method may be used in the future to establish hydrogen-bond geometries in biologically relevant functional OHN hydrogen bonds.

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“…In Table 2 we compare the hydrogen bond geometries of the complexes 2, 5 and 6 obtained by low-temperature x-ray crystallography 12 with those obtained by NMR. First, we note that in addition to the experimental error of the dipolar coupling constants, the distances derived from these couplings are affected by a well-known systematic error, as the NMR distances represent average reversed cubic distances whereas neutron data represent mean distances.…”

Section: X-ray Diffraction and Nmr Hydrogen Bond Distancesmentioning

confidence: 98%

“…For the complexes 2, 5 and 6 crystal structures at 150 K have been reported. 12 Two structures, those of 2 and 5, are depicted in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 1. Crystallographic structures for the complexes 2 and 5 determined by x-ray diffraction at 150 K. Adapted from Foces-Foces et al 12 We chose collidine instead of pyridine whose 15 N chemical shielding tensor in the free compound and in pyridinium salts has been studied previously, 13 because in spite of many attempts we were not able to obtain solid 1 : 1 complexes of pyridine with the less acidic carboxylic acids such as benzoic acid where the competition between cyclic dimer and the 1 : 1 acid-base complex formation and the interplay with other intermolecular interactions apparently favors the former.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

1H/15N NMR chemical shielding, dipolar15N,2H coupling and hydrogen bond geometry correlations in a novel series of hydrogen-bonded acid-base complexes of collidine with carboxylic acids

et al. 2001

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Three 2,4,6-trimethylpyridine–benzoic acid complexes at 150K

Cited by 11 publications

References 3 publications

X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1:1 hydrogen-bonded complexes with benzoic acid derivatives: evidence for coupled inter- and intramolecular proton transfer

X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1:1 hydrogen-bonded complexes with benzoic acid derivatives: evidence for coupled inter- and intramolecular proton transfer

NMR Parameters and Geometries of OHN and ODN Hydrogen Bonds of Pyridine–Acid Complexes

1H/15N NMR chemical shielding, dipolar15N,2H coupling and hydrogen bond geometry correlations in a novel series of hydrogen-bonded acid-base complexes of collidine with carboxylic acids

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