1H, 13C, 15N NMR and Ab Initio/IGLO/GIAO-MP2 Study of Mono-, Di-, Tri-, and Tetraprotonated Guanidine1

Oláh, George A.; Burrichter, Arwed; Rasul, Golam; Hachoumy, and Mohammed; Prakash, G. K. Surya

doi:10.1021/ja972553o

Cited by 50 publications

(41 citation statements)

References 15 publications

(36 reference statements)

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“…The global minimum does not reflect the experimental result of the X-ray structure analysisb ecause this ion does not have ap lanar geometry.T he local minimum, however,e xhibits planar geometry and is in good agreementw ith the crystal structure of 4.T his phenomenon has already been reported. [17,28] The energetic difference between the globala nd local minima is 0.284 kJ mol À1 .D ue to the very small energetic difference and the improved agreement with our experimental results, we used the structure with ap lanar geometry for the calculations of the molecular orbitals. We assumeaplanar geometry would be accessible only through simulation of the solid-state interactions.T herefore, we suggest that the high stabilityo ft he guanidinium(1 +)c ation does not depend on either electron delocalization or hydrogen-bonding interactions, buti saproduct of both properties together.…”

Section: Theoretical Calculationsmentioning

confidence: 72%

“…[27] The geometry of the guanidinium(2 +) cation is also consistent with resultso faprevious study from 1997 when the calculated and predicted geometries of the dication were comparedt oe xperimental and calculated 1 H, 13 C, and 15 Nc hemical shifts. [28] Furthermore, the protons were found in the differenceF ouriers ynthesis and were refinedi sotropically.…”

Section: Vibrational Spectra Of 1-3mentioning

confidence: 99%

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Diprotonation of Guanidine in Superacidic Solutions

Morgenstern

Zischka

Kornath

2018

Chemistry A European J

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Guanidinium chloride reacts with the superacidic solutions HF/MF (M=As, Sb) at a molar ratio of 1:2 under formation of the diprotonated guanidinium salts [C(NH ) (NH )][AsF ] and [C(NH ) (NH )][SbF ] . The compounds were characterized by using infrared and Raman spectroscopy. Furthermore, single-crystal X-ray structure analysis of the guanidinium(2+) salts [C(NH ) (NH )][SbF ] ⋅HF, [C(NH ) (NH )] [Ge F ]⋅HF, and [C(NH ) (NH )] [Ge F ]⋅2 HF and the guanidinium(1+) salt [C(NH ) ][SbF ] is reported. The discussion of the experimental data is supported by quantum-chemical calculations of the [C(NH ) (NH )] and [C(NH ) ] ions to investigate the modification of the resonance stabilization during the protonation process at the PBE1PBE/6-311G++(3df,3pd) level of theory. The planar CN skeleton of the guanidinium(2+) ion has two carbon-nitrogen bonds in the range 1.286(4)-1.293(4) Å and one carbon-nitrogen bond of 1.453(4) Å, which can be explained with a decreased resonance stabilization relative to the guanidinium(1+) ion.

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Section: Theoretical Calculationsmentioning

confidence: 72%

Section: Vibrational Spectra Of 1-3mentioning

confidence: 99%

Diprotonation of Guanidine in Superacidic Solutions

Morgenstern

Zischka

Kornath

2018

Chemistry A European J

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“…Actually, if −44.1 ppm is the absolute shielding ( σ ), it can be transformed into the corresponding chemical shift ( δ , ppm) by means of the equation δ 13 C = 175.7 – 0.963 σ 13 C, affording 218 ppm. The measured value is 157 ppm , but the transformation equation was established to B3LYP/6‐311++G(d,p) calculations. Note that 157 ppm is a value typical for a C = N, for instance, of hydrazones .…”

Section: Resultsmentioning

confidence: 99%

Solvent effects on guanidinium-anion interactions and the problem of guanidinium Y-aromaticity

Rozas

Sánchez‐Sanz

Alkorta

et al. 2013

J. Phys. Org. Chem.

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We have calculated the complexes formed by guanidine/guanidinium and HCl/Cl−, HNO3/NO3− and H2SO4/HSO4− both in the gas and aqueous Polarizable Continuum Model (PCM) phase to understand the effect that solvation has on their interaction energies. In the gas phase, the cation–anion complexes are much more stable than the rest; however, when PCM‐water is considered, this energetic difference is not as large due to the extra stabilization that the ions suffer when in aqueous solution. All the complexes were analyzed in terms of their AIM and NBO properties. In all cases, water solvation seems to “dampen” those properties observed in the gas phase. The values of Nucleus Independent Chemical Shift (NICS)(1) and NICS(2) indicate a huge influence of the proximity of the carbon atom for short distances; thus, the 3D NICS values on the van der Waal isosurfaces have been used to evaluate the possible Y‐aromaticity of the guanidinium system. The isosurface in this system is more similar to cyclohexane than to benzene as indication of poor aromaticity. Copyright © 2013 John Wiley & Sons, Ltd.

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“…[24] We therefore chose to compare the signal of our products with the signal of the commercial products thiourea, Smethylisopseudothiourea hemisulfate salt and S-methylisopseudothiourea. In the spectrum of DDSTU/HCl-13 C 1a C13 (figure 4, A) the peak at 183 ppm could then be attributed to the thiourea function ( fig.…”

Section: Methodsmentioning

confidence: 99%

Iminothiol/thiourea tautomeric equilibrium in thiourea lipids impacts DNA compaction by inducing a cationic nucleation for complex assembly

Breton¹,

Bessodes²,

Bouaziz³

et al. 2009

Biophysical Chemistry

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 Abstract: Our research on lipidic vectors for transfection led us to develop thiourea lipids able to interact with DNA. Hence, we developed a series of lipopolythioureas based on the strong hydrogen bond donor ability of thiourea. More recently we have reported a branched hydroxylated bis-thiourea derivative with interesting transfecting properties. The last step of the syntheses involved a strong acidic condition, leading to an unstable product upon storage.Therefore we designed a new synthesis in mild acidic conditions. Though they exhibit the same mass, the lipids obtained in the two different conditions differ by their interaction with DNA. We therefore explored the physicochemical properties of these two lipids by different means that we describe in this article. In order to insure easier and reliable 13 C-NMR studies of the thiourea group we have designed the synthesis of the corresponding 13 C-labelled thiourea lipids. We have thus shown that when the lipid was submitted to mildly acidic medium; only the thiourea group was observed; while a thiourea/charged and/or uncharged iminothiol tautomeric equilibrium formed when the last step of the synthesis was submitted to low pH. NMR experiments showed that this tautomeric equilibrium could not form in polar solvents. However, UV experiments on the liposomal form of the lipopolythiourea showed the presence of the tautomers. Lipid/DNA interaction consequently differed according to the acidic treatment applied. Eventually, these results revealed that on this particular thiourea lipid, electrostatic interactions due to cationic thioureas are likely to be responsible for DNA compaction and that this tautomeric form of the thiourea could be stabilised by hydrogen bonds in a supramolecular assembly. Nevertheless, this does not reflect a general thiourea lipid/DNA interaction as other thiourea lipids that are able to compact DNA do not undergo an acidic treatment during the final stage of their synthesis.

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¹H, ¹³C, ¹⁵N NMR and Ab Initio/IGLO/GIAO-MP2 Study of Mono-, Di-, Tri-, and Tetraprotonated Guanidine¹

Cited by 50 publications

References 15 publications

Diprotonation of Guanidine in Superacidic Solutions

Diprotonation of Guanidine in Superacidic Solutions

Solvent effects on guanidinium-anion interactions and the problem of guanidinium Y-aromaticity

Iminothiol/thiourea tautomeric equilibrium in thiourea lipids impacts DNA compaction by inducing a cationic nucleation for complex assembly

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