Fourier transform infrared and theoretical studies of alkylimines complexed with hydroxylic proton donors

Migchels, P.; Zeegers‐Huyskens, Th.; Peeters, Daniel

doi:10.1021/j100173a010

Cited by 14 publications

(6 citation statements)

References 1 publication

(1 reference statement)

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“…[1] Furthermore, an indirect but independent and precise estimation of the basicity of the carbonyl group can also be made from the frequency of the carbonyl absorption [ν (C=O) = 1695.3 cm -1 ] by using the calibration frequencies of the acetophenones given in Table 2, with the fluorine and trifluoromethyl substituents being selected to surround the en-docyclic aza substituent. [36] This approach cannot be used for myosmines because, as already mentioned, the corresponding ν (C=N) vibrations of the three derivatives 1d-f at around 1619 cm -1 are insensitive to the association [19] and are strongly coupled with other C=C vibrations so that no further information can be gained from the IR spectra of this series of molecules. …”

Section: Experimental Analysismentioning

confidence: 99%

“…Moreover, the C=N absorption is known to be very insensitive to HB formation. [19] In these compounds, an additional complication arises from the direct conjugation between the two sites (see below) so that the association at one site influences the basicity of the second site more strongly than in the nicotinic analogues in which conjugative interactions cannot occur. [14] Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen‐Bond Accepting Strength of Five‐Membered N‐Heterocycles:The Case of Substituted Phenylpyrrolines and Myosmines

et al. 2009

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The hydrogen‐bond (HB)accepting strengths of a series of five‐membered N‐heterocycles have been measured in CCl4 solution and/or calculated by theoretical methods. These molecules present a great chemical versatility, ranging from very weak π bases up to strongly HB acceptors, imines and amines. Among these compounds, special attention has been paid to myosmines, which are bifunctional molecules containing two very similar pyridinic and pyrrolinic sp2 nitrogen atoms. Infrared measurements provided the global HB basicities of these molecules, but the individual accepting strength of each nitrogen atom could not be achieved experimentally and had to be determined by theoretical calculations. Owing to their flexibility, the geometries of their different isomers were optimized and their basicities weighted by the calculated relative populations. To accurately estimate the individual HB strength of a nitrogen site, it was necessary to take into account a specific halogen bond between the second nitrogen atom and a solvent molecule. 1‐Pyrroline is a significantly stronger base than pyridine, but irrespective of the substituent on the pyridine ring, the pyrrolinic site is always the weakest HB acceptor in the myosmine molecules.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Section: Experimental Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydrogen‐Bond Accepting Strength of Five‐Membered N‐Heterocycles:The Case of Substituted Phenylpyrrolines and Myosmines

et al. 2009

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“…It is noteworthy that in the complexes involving the same proton donors and saturated Schiff bases, the intensity of the vc=, vibration does not increase upon hydrogen bond formation (23). The difference can be ascribed to the electronic delocalization in the retinylidene system, which increases upon complex formation.…”

Section: Characteristics Of the V= Vibrationmentioning

confidence: 88%

FT-infrared study of the interaction between all-trans retinylidene isopropylamine and model proton donors

Migchels¹,

Zeegers‐Huyskens²

1992

Can. J. Chem.

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The interaction between all-trans retinylidene isopropylamine (tRiPA) and phenols covering a large pKa domain is investigated by FT-infrared spectrometry. For phenols having pKa between 10.2 and 8.18, only normal OH … N hydrogen bonds are formed. The thermodynamic parameters (K, −ΔH, −ΔS0) determined in carbon tetrachloride solution show that tRiPA possesses a good proton acceptor ability. The spectral characteristics (frequency and integrated intensity) of the νC=N vibration are also investigated. From a pKa of 6, proton transfer takes place. The proton transfer constants determined in 1,2-dichloroethane are linearly related to ΔpKa (pKa of the protonated base minus pKa of the phenol). Comparison with previously studied imine systems shows that the proton transfer constant increases with the number of C=C double bonds in the base.

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“…Comparison of the protein-bound to the ''free'' retinal spectra reveals two major differno contribution from side reactions which would complicate the analysis, such as self-association. 41 ences: First, the maximum scattering intensity is shifted to lower frequencies (1664 cm 01 in CCl 4 ; The apparent association constant extracted from this fit is shown in Table II for complexes between 1650 and 1645 cm 01 when bound to RBP and CRBP-I, respectively). Second, the C|O-stretchall-trans retinal and donors of varying acidity (phenol, 4-nitrophenol, 3,5-dichlorophenol, 3,4-diing vibration broadens considerably upon binding with the proteins (FWHM Å 12 cm 01 in CCl 4 , 24 methylphenol, and 4-bromophenol).…”

Section: C|c Vibrations C|o Vibration the Most Intense Band In The Ramentioning

confidence: 99%

The interactions between cellular retinol-binding protein (CRBP-I) and retinal: A vibrational spectroscopic study

Senak

Noy

et al. 1997

Biospectroscopy

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Preresonance Raman difference spectra have been obtained for all‐trans retinal in dilute CCl4 solution, complexed with cellular retinol‐binding protein (CRBP‐I) and retinol‐binding protein (RBP). These spectra indicate that retinal is of a slightly more planar conformation within the binding pocket of CRBP‐I than in solution or hydrophobically complexed with RBP. Compared to retinal in solution or bound to RBP, the conformation of the polyene tail of the retinal chromophore is perturbed from C8 through C11. This perturbation is probably due to the close proximity of the Lys40 in the CRBP‐I binding pocket to the above‐mentioned carbons. The C(DOUBLE BOND)O stretching vibration of bound retinal carbonyl has been found to shift from 1664 cm−1 solubilized in CCl4 to 1650 and 1645 cm−1 in RBP and CRBP‐I, respectively, and significantly broadened in both cases. The frequency shift and broadening have been attributed to hydrogen bonding. These have been compared to calibrations of frequency shift (ΔνC(DOUBLE BOND)O) vs. ΔH and ΔG of all‐trans retinal complexed with a series of phenol derivatives of incremental proton‐donating ability as obtained by the relationship of van't Hoff. By this relationship, the binding enthalpy of the all‐trans retinal carbonyl moiety bound to CRBP‐I and RBP is −28.1 kJ/mol (−6.7 kcal/mol) and −23.5 kJ/mol (−5.6 kcal/mol), respectively. The free energy of binding of the retinal carbonyl bound to CRBP‐I and RBP has been determined to be −10.5 kJ/mol (−2.5 kcal/mol) and −7.2 kJ/mol (−1.7 kcal/mol), respectively. The hydrogen‐bonded C(DOUBLE BOND)O moiety of retinal complexed with CRBP‐I accounts for a substantial (25%) but not overriding amount of the binding energy of CRBP‐I for retinal, and it also accounts for the protein's preference for binding retinol. © 1997 John Wiley & Sons, Inc. Biospect 3: 131–142, 1997

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Fourier transform infrared and theoretical studies of alkylimines complexed with hydroxylic proton donors

Cited by 14 publications

References 1 publication

Hydrogen‐Bond Accepting Strength of Five‐Membered N‐Heterocycles:The Case of Substituted Phenylpyrrolines and Myosmines

Hydrogen‐Bond Accepting Strength of Five‐Membered N‐Heterocycles:The Case of Substituted Phenylpyrrolines and Myosmines

FT-infrared study of the interaction between all-trans retinylidene isopropylamine and model proton donors

The interactions between cellular retinol-binding protein (CRBP-I) and retinal: A vibrational spectroscopic study

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