Diimines obtained from 3,3′-diaminobenzidine and tert-butyl-substituted salicylaldehydes in MeOH can be readily isolated in 60-90% yield and were obtained as a mixture of geometrical isomers. Two distinct diimine intermediates (4 and 5) with a higher molecular symmetry as related to the other isomeric diimine products were both isolated by crystallization of which 5 was subsequently used to demonstrate that nonsymmetrical bis-salphen complexes with different functional groups and metal centers can be assembled via a three-component one-pot procedure.
![Facile isolation of bisimines based on 3,3’-diaminobenzidine: Direct access to unsymmetrical bimetallic salphen building blocks](https://www.iciq.org/wp-content/uploads/2014/03/Facile-isolation-of-bisimines_eng_noticies_articles_2007_60.gif)