N-(2-{9,10-dimethoxy-4-oxo-2-[(E)-(2,4,6-trimethylphenyl)azanylidene]-6,7-dihydropyrimido[6,1-a]isoquinolin-3-yl}ethyl)-1-[(2-{9,10-dimethoxy-4-oxo-2-[(E)-(2,4,6-trimethylphenyl)azanylidene]-6,7-dihydropyrimido[6,1-a]isoquinolin-3-yl}ethyl)amino]methanamide