A strategy for the propagation of hydrogen-bonding in bicyclic guanidinium salts

Abstract

Protonation of the {6,6}-and {5,5}-bicyclic guanidines 1, 3,4,6,7,8-hexahydro-2H-pyrimido [1,2-a] pyrimidine (hppH) and 1,4,6-triazabicyclo[3.3.0]oct-4-ene (Htbo), respectively, to afford the hydrochloride salts [hppH 2 ][Cl] (1a) and [HtboH][Cl] (2) was achieved using [NEt 3 H][Cl]. Anion exchange involving 1a and NaBPh 4 generated the borate salt [hppH 2 ][BPh 4 ] (1c). Crystal structure analysis of 1a and the analogous hydrobromide salt [hppH 2 ][Br] (1b) showed two NH/X hydrogenbonds between the cation and the anion, and association of the [hppH 2 ][X] ion-pairs into dimeric units.In salt 1c the [hppH 2 ] + cation was shown to be located within a cavity defined by phenyl substituents from the [BPh 4 ] À anion, with no hydrogen bonding present. Reducing the size of the heterocyclic rings from {6,6}-to {5,5}-in the [HtboH] + salt promotes formation of extended structures due to a wider angle between the projected hydrogen-bonds to the halide anion. Results from analysis of the bond parameters within the guanidinium cations are used to explain the distribution of p-electron density throughout the bicyclic framework.

Neutral and Anionic Antimony(III) Species Supported by a Bicyclic Guanidinate

“…Key features include a broad resonance at 7.57 ppm with a relative integral of 2H in the 1 H NMR spectrum, as well as two resonances at 159.2 and 152.5 ppm (corresponding to the C N 3 carbon atom) in the 13 C{ 1 H} NMR spectrum. These data indicate two different ligand environments and suggest that one may be associated with a guanidinium component as the low‐field resonance in the proton NMR spectrum is typical for the N H atoms of the [hppH 2 ] + cation 20…”

Guanidinium Ionic Liquids

“…In theory, they are formed by proton transfer from a Brønsted acid (AH) to a Brønsted base (B), otherwise the product of the reaction of AH with B will be better described as an adduct sustained by a AH• • •B hydrogen bond. NMR and IR techniques can give more informations about the ionicity and structure of proton ionic liquids [38]. For example, an upfield shift in 13…”

Improvement to the thermoelectric properties of PEDOT:PSS

“…545,546 (Please refer to Figure 7.6.2.1) showing the guanidinium oxidation states. 485,550,551 The oxidation state is dependent on the pH, temperature or any redox reactions it undergoes. 550,552 The designation of the peak around 289 eV to guanidinium/Guanidine is corroborated by the presence of the nitrogen 1s peak in the range reported for guanidinium compounds (Figure 7.6.2.2).…”

“…196,385 As seen in Figure 7.6.2.1 are 3 different oxidation state for the guanidine. 551 The guanidinium ion (a) has a positive charge on one of the nitrogen. 553 In reality the charge is delocalised across the whole molecule leading to a stabilized cation.…”

“…Another possible explanation and one which seems more likely is that because GuI treatment contained ionic charge carriers, a considerable amount of Gu + was adsorbed on the film surface of the SX films as confirmed by the SX film's C 1s and N 1s spectra. It is known that the charge is delocalised across the Gu + ion therefore it is possible that the ions form some cation-𝜋𝜋 interactions (guanidinium is known to make) 551,559,560 with PEDOT and improve bulk carrier concentration. This would be able to be proven via Hall effects measurements in future studies.…”