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Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives
Author(s) -
Kaller Martin,
Tussetschläger Stefan,
Fischer Peter,
Deck Christopher,
Baro Angelika,
Giesselmann Frank,
Laschat Sabine
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901173
Subject(s) - mesophase , chemistry , crystallography , differential scanning calorimetry , counterion , halide , ion , carbon 13 nmr , nuclear magnetic resonance spectroscopy , proton nmr , phase (matter) , stereochemistry , inorganic chemistry , organic chemistry , physics , thermodynamics
Dibenzo[18]crown‐6 derivatives 1 with two lateral tetraalkyloxy o ‐terphenyl units were prepared and converted to the corresponding complexes KX ⋅1 (X=halide, BF 4 , PF 6 , SCN) and NH 4 PF 6 ⋅1 . Complexation was probed by MALDI‐TOF spectrometry and NMR spectroscopy. Downfield shifts of 1 H NMR signals for complexes with soft anions Br, I, SCN, and PF 6 indicated the presence of tight ion pairs, whereas complexes with hard anions F, Cl, or BF 4 showed no or little shifts. In 13 C NMR spectra, upfield shifts were detected for soft anions. The character of the anion also influenced the mesomorphic properties of complexes MX ⋅1 (M=K, NH 4 ), which were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and XRD in comparison to neat 1 . Hard anions slightly stabilize or even destabilize the mesophase. Soft anions, however, improve the mesomorphic properties yielding mesophases with up to 70 °C phase widths in the case of KI ⋅1 , KPF 6 ⋅1 , and NH 4 PF 6 ⋅1 . For complexes KSCN ⋅1 with a soft and bridging anion, the balance between mesophase stabilization and high order is shifted in favor of the plastic crystal phase.