Should 4-amino-tempo has an imaginary frequency?

[xiongyan21]

When 4-aminotempo has been optimized using ROHF DFTB3, the subsequent vibrational analysis with 6-31G+(d,p) has a small imaginary frequency around 96 cm^-1. Is this structure suitable, although the reorganzation energy, outer and total, obtained in the existence of a self-assembled monolayer is quite close to the experimental data published in an article? Perhaps this means the a little proloned C-N bond length.