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Supramolecular Structure, Physical Properties, and Langmuir‐Blodgett Film Formation of an Optically Active Liquid‐Crystalline Phthalocyanine
Author(s) -
van Nostrum Cornelus F.,
Bosman Anton W.,
Gelinck Gerwin H.,
Schouten Pieter G.,
Warman John M.,
Kentgens Arno P. M.,
Devillers Marinus A. C.,
Meijerink Andries,
Picken Stephen J.,
Sohling Ulrich,
Schouten ArendJan,
Nolte Roeland J. M.
Publication year - 1995
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.19950010306
Subject(s) - mesophase , phthalocyanine , mesogen , crystallography , langmuir–blodgett film , materials science , lyotropic , phase (matter) , circular dichroism , hexagonal phase , liquid crystal , chemistry , monolayer , organic chemistry , nanotechnology , liquid crystalline , hexagonal crystal system , optoelectronics
The structure and physical properties of optically active, metal‐free 2,3,9,10,16,17,23,24‐octa ( S ‐3,7‐dimethyloctoxy)phthalocyanine (( S )‐Pc(8,2)) are reported and compared with those of the phthalocyanine with ( R , S ) side chains (mixture of 43 stereoisomers). Unlike the latter compound, ( S )‐Pc(8,2) lacks a crystalline phase. A freshly prepared sample is in a distorted mesophase and reorganizes irreversibly to a more ordered phase above 65 °C. X‐ray diffraction and circular dichroism studies indicate that the molecules are stacked in columns which have a hexagonal arrangement and a left‐handed helical superstructure, that is, a novel chiral D h * mesophase. Solid state NMR measurements reveal that the phthalocyanine units in the columns begin to vibrate laterally when the temperature is increased. At 111 °C (D h * → D r transition) they start to rotate around their columnar axes and at the same time the side chains become liquidlike. Energy migration is very efficient in the chiral D h * phase and also in the frozen mesophase below 3 °C, as follows from luminescence spectroscopy. Intracolumnar charge transport, studied by the time‐resolved microwave conductivity technique, turns out to be slower in the helically distorted columns than in linear columns. ( S )‐Pc(8,2) forms a very stable bilayer at the air‐water interface, which can be transferred to give a high quality Langmuir‐Blodgett film. The fact that this phthalocyanine is mesogenic at room temperature is thought to be responsible for this behavior.