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A selected series of dipole functionalized triphenylene-based discotic liquid crystals (DLCs) was synthesized and investigated in a systematic way to reveal the phase behavior and molecular dynamics.

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All chemicals were, unless stated otherwise, provided by the supplier and used without further purification. Dry solvents were dried by conventional laboratory methods. The eluents for chromatography petroleum ether (low-boiling) and ethyl acetate were distilled prior to use.For thinlayer chromatography silica gel 60 F254 glass plates with a layer thickness of 0.25 mm on aluminium (pore size 60 Å) from the company Merck were used. Column chromatography was performed using silica gel with a particle diameter of 40 -60 µm from the company Fluka.1 H NMR spectra were measured using the Bruker Avance 300 and Bruker Avance 500 spectrometers at 300 MHz and 500 MHz, respectively and 13 C-NMR spectra at 75 MHz and 126 MHz, respectively. Deuterated chloroform (CDCl3) and deuterated dimethyl sulfoxide (DMSO-d6) were used as solvents. The chemical shift δ in ppm (parts per million) refers to the standard tetramethylsilane. The numbering of atoms can be different from the IUPAC nomenclature in order to ensure better comparison of various compounds. In order to assign the signals of the 1 H and 13 C NMR spectra, COSY, HSQC and HMBC measurements were carried out.

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Scheme1.Neutral N and charge-separated zwitterionic Z resonance structures of merocyanines. [9,10] [a] J.

A series of phenylguanidinium salts 3 . X, which are linked via an alkoxy spacer either to a 4-decyloxy-or 4-cyanosubstituted biphenyl mesogen, was prepared and the mesomorphism studied. A decyloxybiphenyl core and a spacer of at least C6 chain length were required for mesophase formation. Replacement of the chloride counterion by other anions like bromide or tetrafluoroborate improved the thermal stability of the mesophase. A comparison of substitution pattern (meta v. para) on the phenyl ring revealed decreased melting and clearing points for the bent cationic head group. All guanidinium ionic liquid crystals 3 displayed only smectic A (SmA) phases. A packing model is assumed where the molecules in a bilayer stack over each other in opposite direction with interdigitated terminal decyloxy groups and spacers.bromides 9 giving the tethered compounds p-10a,b and m-10b-e in 78-88 % yield. N-Boc-deprotection to derivatives p-11a,b and m-11b-e was achieved very cleanly with methane sulfonic acid in CHCl 3 . Derivative m-11a was obtained in 94 % yield by acidic hydrolysis [62] of acetamide m-7a. The aniline derivatives 11 were finally treated with chloro-N,N,N 0 ,N 0tetramethylformamidinium chloride [63] and either NEt 3 or NaHCO 3 . Workup strictly required an inert gas atmosphere to provide the neat target guanidinium salts 3 . Cl in 70-98 % yield. To further study the anion effect, decyloxybiphenyl guanidinium chloride m-3a . Cl was submitted to salt metathesis with NaBr, KI, NaOTf, NaBF 4 , KPF 6 , KOAc, and KSCN yielding the corresponding guanidinium ILCs m-3a . X (Scheme 2). Anion Effect in Guanidinium ILCsComparison of the 1 H NMR spectra of phenylguanidinium salts m-3a . X revealed a significant downfield shift of the N-H signal from ,7.5 to 12.0 ppm in the following order: PF 6 , BF 4 , OTf , I , SCN , Br ECl (Fig. 1).This correlation between the anion and the N-H proton shift indicates the presence of contact between the ion pairs that also led to small chemical shifts of the aromatic protons of the phenylguanidinium moiety (Fig. 1, grey). To estimate the effect of concentration on the N-H signal, 1 H NMR measurements of m-3b . Cl with concentrations varying from 0.83 to 2.50 mg mL À1 were carried out. The N-H signal shift of 0.1 ppm turned out to be negligible with respect to the strong dependence of the NH signal on the anion (see Supplementary Material for details). This effect rather might be due to either the interaction of the anion with the anisotropic cone of the aryl ring than due to the conjugation between the guanidinium cation and the aryl ring. Previous DFT calculations of several guanidinium salts revealed no or only very little conjugation, i.e. the guanidinium moiety behaves like an isolated cation. [39] In agreement with these studies, the N-H signal shifted upfield with increasing anion radii [64,65] with an almost linear correlation (Fig. 2).

All chemicals were obtained from the supplier and used without further purification. Dry solvents were prepared by common laboratory methods. The eluents for chromatography petroleum ether (low-boiling) and ethyl acetate were distilled prior to use.Thinlayer chromatography silica gel 60 F254 glass plates (layer thickness of 0.20 mm on aluminium, pore size 60 Å) from the company Merck were used. Column chromatography