afni.nimh.nih.gov

It seems like sb_delim is using the literal characters of '\' and 'n' so I altered your code a bit and got something to work:

3dinfo -label -sb_delim "," ${FILE} | tr ',' '\n' | grep 'Coef' | grep 'not5_LL5'

It's a little round about but it should work as a workaround for know.