Abstract
The synthesis and properties of 16 tris(dialkylamino)cyclopropenium (TDAC) cations with the dicyanamide (DCA) anion, [N(CN)2]−, are described. D3h- and C3h-symmetric cations ([C3(NR2)3]DCA (R = Me, Et, Pr, Bu, Pent, Hex, Dec) and [C3(NRMe)3]DCA (R = Bu, St), respectively) were synthesised by reaction of C3Cl5H with the corresponding amine. Reaction of the alkoxydiaminocyclopropenium salt [C3(NEt2)2(OMe)]+ with amines led to a series of C2v-symmetric salts [C3(NEt2)2(NR2)]DCA (R = Me, Bu, Hex) and two Cs-symmetric salts and [C3(NEt2)2(NRMe)]DCA (R = Me, Bu). Similarly, [C3(NMe2)2(OMe)]+, was used to prepare the Cs-symmetric salts [C3(NMe2)2(NRMe)]DCA (R = Pr, Bu). In addition to characterisation by NMR, mass spectrometry and microanalysis, the salts were characterised by DSC, TGA, density, viscosity, conductivity and miscibility/solubility studies. Comparisons have been made with similar series of bistriflimide (NTf2−) salts that have been previously reported to see whether the same trends are observed with a different anion.
Highlights
Ionic liquids (ILs) are an increasingly important class of so materials that have undergone rapid development in recent years; many of these materials are commercially available.[1]
Density data were determined from 20–90 C where possible; the results for the 20 C and 50 C data are given in Table 2 and molar volumes are provided in the Electronic supplementary information (ESI).† Unlike melting points, viscosities and conductivities, vide infra, densities for TDAC DCA salts are effectively independent of cation shape and depend only on the cation size
We have prepared a series of TDAC DCA salts for comparison with a similar series of NTf2À salts
Summary
Ionic liquids (ILs) are an increasingly important class of so materials that have undergone rapid development in recent years; many of these materials are commercially available.[1]. 4) and the triaminocyclopropenium (TAC) salts have been known for more than 40 years,[5] we did not report on the IL properties of TAC salts until 2011.6 TAC salts are remarkably stable due to a combination of the aromaticity of the 2p-electron ring system. Any hydrogen bonding, impact on the intermolecular forces and their physical properties. We sought to investigate how exchanging from one anion to another impacts on trends in the physical properties of TAC ILs. Following our detailed study on bistri imide salts, we report on the corresponding dicyanamide ([N(CN)2]À, DCA) TDAC salts, an anion which would be expected to produce lower viscosities, higher conductivities and greater hydrophilicity. Some of this work has been communicated.[6,14]
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