Selection of Betaine Building Blocks for the Construction of Quadrupolar Heterophane Frameworks

Abstract

The synthesis of a set of [(azolio)methyl]azolate betaines 3−6 designed by combination of a variety of heterocyclic fragments based on pyrazole, 1,2,4-triazole, and benzimidazole is reported. The dipolar nature of the betaines is discussed on the basis of 1 H and 13 C NMR spectroscopic data and dipole moment values, which range between 13.4 and 16.5 D. By exploitation of the sensitivity of electrospray ionization mass spectrometry in both the positive and negative modes, sev-

Imidazolium-Based Dicationic Cyclophanes. Solid-State Aggregates with Unconventional (C–H)+···Cl− Hydrogen Bonding Revealed by X-ray Diffraction

“…The negative-ion ESI-MS experiments were first performed on a VG-Quattro mass spectrometer from Micromass Instruments, as previously described [7,13]. Then, negative-ion ESI-MS analyses were recorded on a ZQ mass spectrometer from Waters- Single-crystal X-ray diffraction analysis.…”

“…Positive-ion electrospray ionization mass spectrometry was used for characterizing imidazoliun-based frameworks, with prime examples derived from [1 4 ]metaheterophanes 1·2X (MH 2 ·2X), 2 and 4.2X (M·2X) [6b,9,13,14]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 In the negative-ion mode ESI-MS experiments, we examined azolophanes 1·2X [13] together with a set of [{imidazolio}methyl] azolate betaines B and their corresponding salts BH·X [7]. The negative-ion ESI responses displayed peaks attributable to non-covalent self-aggregates: further study to confirm this was restricted to instrumental limitation.…”

“…The negative-ion ESI responses displayed peaks attributable to non-covalent self-aggregates: further study to confirm this was restricted to instrumental limitation. Under the same experimental conditions [7,13] [4,14,15a]. Thereafter, a variety of quaternary imidazolium-linked frameworks were reported for anion recognition driven by ( For the X-ray diffraction analysis of 4b·2Cl·3.5H 2 O·0.5CH 3 CN, many different crystals were used but crystals deteriorated so fast that, in consequence, the final refinement values were inappropriate for a detailed discussion of non-covalent interactions.…”

“…Quaternary imidazolium units were selected due to their recognized chemical stability [4,[6][7][8][9]. Dicationic [1 4 ]imidazoliophanes 4·2X are simple prototypes for intermolecular interactions driven by unconventional (C-H) + ···X hydrogen bond.…”

Imidazolium‐Based [14]Heterophanes as Models for Anion Recognition

“…As part of our ongoing research of imidazolium‐based frameworks,7,9 we have examined cyclophanes 1·2X and 2 9b together with dicationic pincers 3·2X (Figure 1);9c for bis(betaines) 2 and dications 1·2X , quaternary imidazolium units were selected because of the recognized chemical stability of the methyleneimidazolium azolate betaine building blocks 10. Maintaining the two imidazolium moietiespresent in the heterophanes 1·2X , dicationic [1 4 ]imidazoliophanes 4·2X arise as models for intermolecular interactions driven by unconventional (C–H) + ··· X hydrogen bonds7 (Figure 1).…”