3d image of cyclen skeletal formula

cyclen tetrazacyclododecane aza-crown ether crown thorpe-ingold effect aromatic aromaticity macrocyclic heterocyclic heterocycle polycyclic ring nitrogen mass spectrometry propylene molecular spacer zinc diperchlorate chelating agent nitrogen secondary amines macrocycles ethyleneamines substance matter material compound component stuff reagent functional group precursor synthesis reaction production building block molecule molecular formula skeletal structural structure ball stick chemistry science scientific research organic chemical 3d