My doubts are about NMR saturation. Saturation is caused by a continued impulse and cause the equalization in spin popolation with a lost in coherence, so there is no NMR signal. Why is not possible invertion after saturation, even of it is possible using a longer RF impulse (180º instead of 90º)? Why there is lost in coherence sending a long impulse? What happens to net magnetization and to the magnetization components during this process?

My second doubt is about the anti aromatic compound behavior in diamagnetic anisotropy. What causes this change in behavior?