If we are interested in self-complementary chords in the division of the octave in 12 parts we have to look for hexachords.
The lisp-function 'first' takes the first chord (the green one). To be sure that it is self-complementary double-click on the n-cercle editor and type the letter 'c'. You will obtain the complementary chord that has the same intervallic structure.
Here is the usual score representation: