Crystal structure of Ag · TCNQ

Abstract

High resolution electron microscopy (HREM) has been used for the direct imaging of complex crystal structures. High resolution at an atomic level cannot be expected from most organic crystals due to their high sensitivity to electron radiation damage, although we ¹ have previously considered the conspicuous images of chlorine and copper atoms in chlorinated copper phthalocyanine molecules as a special case dependent on the very radiation-resistant property of the compound. In practice, however, some organic crystals may be able to withstand the dosage necessary for the image recording itself but could not tolerate the extra dosage necessary for searching the proper image field and for successive careful focusing. In this respect, the principle of the minimum exposure proposed by Williams and Fisher² is attractive as it might reduce the unnecessary damage which takes place before the actual image recording. We describe here the structure images of a metal complex of 7 7′, 8, 8′–tetra-cyanoquinodimethane (TCNQ) with the resolution of an atomic level obtained by developing an automated device which is basically similar to that by Unwin and Henderson³. The electron microscope equipped with the low dosage device was JEM-200CX, which gives the instrumental resolution of 0.24 nm.