Tautomerism and hydrogen bonding in guaninium phosphite and guaninium phosphate salts

Abstract

The crystal structures of three similar guaninium salts, guaninium monohydrogenphosphite monohydrate, C5H6N5O+·H2O3P−·H2O, guaninium monohydrogenphosphite dihydrate, C5H6N5O+·H2O3P−·2H2O, and guaninium dihydrogenmonophosphate monohydrate, C5H6N5O+·H2O4P−·H2O, are described and compared. The crystal structures have been determined from accurate single‐crystal X‐ray data sets collected at 100 (2) K. The two phosphite salts are monoclinic, space group P21/c, with different packing and the monophosphate salt is also monoclinic, space group P21/n. An investigation of the hydrogen‐bond network in these guaninium salts reveals the existence of two ketoamine tautomers, the N9H form and an N7H form.

Correlation between structural studies and third order NLO properties of selected new quinolinium semi-organic compounds

“…the dihedral angle) is 1.15(2)°and this puckering along the C4-C9 bond is commonly found in quinolinium salts structures [36,37]. The presence of such puckering has already been noticed in compounds containing similar pyridinium rings [38]. The interplanar separation between quinolinium layers is 3.398(2) Å leading to a p-p stacking interactions between the cations as also observed in (I).…”

Pd-NHC (PEPPSI) Complexes: Synthetic Utility and Computational Studies into Their Reactivity

“…[145][146][147][148] Although traditionally used for theoretical and in silico determinations, it may also be applied to experimentally derived X-ray diffraction results with the X-ray density method, developed by Lecomte. [149][150][151][152][153] The X-ray density method has recently been applied to protein structure determination, 154 characterisation of hydrogen-bonding in nucleotides, 155 metallic superionic conduction, 156 as well as adding to fundamental understanding in crystallography. 157 The topological properties of the electron density distribution of a molecule are based on the gradient vector field of the electron density r (r) , and on the Laplacian of the electron density ∇ 2 r (r) , where r is the positional vector of an electron in three-dimensional space.…”

Guanine‐Stabilized Formamidinium Lead Iodide Perovskites

“…Analogous qualitative changes are visible in 15 N (Supporting Information, Figure S3 a,b) and 1 H (Supporting Information, Figure S3 d–f) solid‐state NMR spectra. This spectral complexity may be partly associated with guanine adopting several tautomeric forms (Figure g) . Previous reports suggest that G exists in the aqueous phase as a mixture of two tautomers (Figure g), the N 9H (85 %) and a N 7H form (15 %).…”

“…Previous reports suggest that G exists in the aqueous phase as a mixture of two tautomers (Figure g), the N 9H (85 %) and a N 7H form (15 %). Moreover, N 7H has been shown to be more stable than N 9H form in solution, although the latter was found to be the only tautomer in polar solvents or in the solid state . Protonation was reported to predominantly occur at position N7 , which is also suggested by the corresponding p K a values .…”

“…The 13 C CP MAS spectrum of unprotonated guanine shows five well‐resolved resonances, corresponding to the inequivalent sites of the purine ring system (Figure a). Protonation of guanine with HI, yielding GI, leads to changes in the chemical shift of all peaks, as well as to the appearance of new peaks, which are most likely due to the protonation of both the primary and secondary amine group of guanine (Figure b) . The formation of G 2 PbI 4 is evidenced by changes in the 13 C NMR spectrum as compared to neat GI (Figure c), although peak assignment is difficult due to the high level of disorder.…”