  To verify the effect of geometrical frustration, we artificially distort the
triangular lattice of quasi-two-dimensional organic conductor
$\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ [BEDT-TTF:
bis(ethylenedithio)terathiofulvalene] by analogous-molecular substitution and
apply $^{13}$C NMR of bulk and substituted sites, electric conductivity, and
static magnetic susceptibility measurements. The results indicate that the
magnetic characteristics of the substituted sample are quantitatively similar
to those of the pure sample. Moreover the magnetic characteristics at the
substituted sites are also the same as in the bulk. These results suggest that
the observed magnetic properties may not be due to the geometrical frustration
but the importance of disorder.
