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The transient conductivity induced by nanosecond pulse radiolysis of octa-n-nonyloxyphthalocyanine has been studied as a function of accumulated radiation dose, ED, from 10 Gy to 250 kGy. The end-of-pulse conductivity, AamplD, is unaffected by ED up to 150 kGy. Above this, AaWp/D begins to decrease and at 250 kGy is 65% of the low-dose value. An increase in the rate of decay of the transient conductivity in the solid state can be observed at values of ED as low as 10 kGy. On heating to the liquid crystalline phase and resolidifying, the conductivity decay returns to that found for the virgin material. However, Aacpp/D remains low. The solid to mesophase transition temperature, as monitored by differential scanning calorimetry, was found to be a few degrees lower after a total accumulated dose of 260 kGy.

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 Dh* 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 (Dh* → Dr 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 Dh* 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.

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