Since I have really become obsessed about point groups of objects and molecules, I decided to post some practice and tips about them.
Tip : Octahedral complexes with 3 chelating ligands have D3 point groups. Well if you don't want to believe this, you can always draw the molecule and see it yourself. Trischelates are tricky. So, I suggest that you should always draw a Newman Projection to see the perpendicular C2 axis.