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Details van artikel 120 van 131 gevonden artikelen
| Titel: |
Thermal and optical behaviour of octa-alkoxy substituted phthalocyaninatovanadyl complexes |
| Auteur: |
Sleven, Jurgen Cardinaels, Thomas Binnemans, Koen Guillon, Daniel Donnio, Bertrand |
| Verschenen in: |
Liquid crystals |
| Paginering: | Jaargang 29 (2002) nr. 11 pagina's 1425-1433 |
| Jaar: |
2002-11-01 |
| Inhoud: |
This paper deals with the synthesis of vanadyl phthalocyanines substituted with eight alkoxy chains in the peripheral (2, 3, 9, 10, 16, 17, 23, 24) positions. The alkoxy chain length was varied, and octa-octyloxy (C8H17O), octa-dodecyloxy (C12H25O) and octa-hexadecyloxy (C16H33O) substituted vanadyl phthalocyanine complexes were prepared. Studies by polarizing optical microscopy and small angle X-ray diffraction (XRD) revealed that all the complexes are liquid crystalline and that these metallomesogens exhibit a columnar phase. The symmetry of the 2D lattice is rectangular, with a c2mm space group, as determined by the indexation of the XRD reflections; hence a rectangular columnar phase (Colr) was assigned. A double periodicity, although weak, along the axis of the columns was found, which indicates some degree of pairing or dimerization. A tentative explanation based on an antiferroelectric stacking is given. Transition enthalpies were determined by differential scanning calorimetry. The compounds start to decompose above 250°C before reaching the clearing temperatures. A significant bathochromic shift of the Q-band in the UV/Vis spectra of the vanadyl complexes compared with the metal-free ligands and other metallophthalocyanines (M=CoII, NiII, CuII, ZnII) was also observed. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 120 van 131 gevonden artikelen
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