| Research Abstract |
In this research project, systematic crystal growth of 1,6-diaminopyrene (DAP) charge-transfer complexes has been carried out to study on their crystal structures and physical properties. Fifteen electron acceptors, of which acceptor strength distributes in a wide renge, were selected to combine with DAP.These complexes can be categorized into two groups from their structure and electronic state, as follows.
1. Complexes with Neutral Mixed-Stack Structure : The complex with p-chloranil (CHL) belongs to the first group. The crystal comprises mixed-stack columns of neutral donors and acceptors. In general, the electrical conductivity of such a crystal is expected to be very poor. However, it has been found that the complexes with not only CHL but also p-bromanil and 2,5-dibromo-3,6-dichloro-p-benzoquinone shows high conductivity. Furthermore, it has been found that there are two distinguishable trends in their electrical conductiviity and temperature dependence of the magnetic susceptibil
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2. Complexes with Ionic Segregated-Stack Structure : We have found new five complexes which have ionic segregated-stack structure similar to DAP-TCNQ.In all the complexes, component molecules are completely ionized. The electrical resistivities are quite low ; 10^<-1>-10^3 OMEGA cm at room temperature. However, the activation energies of conduction are extremely large. Though the interplanar spacing between the molecules is uniform, they are suggested to be a spin-Peierls system, since totally symmetric vibrational modes have been observed.
A common characteristic in these two groups is hydrogen-bonds between donors and acceptors. Since rather small anisotropy of the conduction has been found, it has been suggested that the hydrogen-bonding plays some important role in their unusual transport mechanism. Systematic comparison has not been complete due to lack of some structural data. The systematic study on the interaction between the pi-electron systems and the relation with the hydrogen-bonding will be performed after completion of the structure analyzes. Less
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