Schiff-base template synthesis of tetra-aza macrocycles involving diethylmalonate as a padlock

• Published in: Inorganica Chimica Acta 1996-05, Vol.246 (1), p.379-385
• Main Authors: Fabbrizzi, Luigi, Licchellia, Maurizio, Poggi, Antonio, Vassalli, Omar, Ungaretti, Luciano, Sardone, Nicola
• Format: Article
• Language: English
• Subjects: Copper complexes; Crystal structure; Template syntheses; Tetra-aza-macrocycle complexes
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/0020-1693(96)05124-9

Diethylmalonate acts as an efficient locking fragment in the Cu II directed synthesis of 14-membered tetra-aza-macrocycles. In the reaction of [Cu II(en) 2+ (en = 1,2-diaminoethane) with 2 equiv. of diethylmalonate in the presence of formaldehyde and triethylamine the 1,4,8,11-tetraazacyclotetradecane-6,6,13,13-tetracarboxylic acid tetraethyl ester copper(II) diperchlorate complex salt is formed: monoclinic, space group C2/ c with a = 12.201(5) A ̊ , b = 12.464(5) A ̊ , c = 21.353(22) A ̊ , α = 90°, β = 91.30(6)°, γ = 90°, V = 3247(4) A ̊ 3 , and Z = 4 ( R = 0.072, R w = 0.072). The formaldehyde building block can be replaced by benzaldehyde in the same type of template procedure if the two en fragments are replaced by the tetra-amine 2.3.2-tet ( N/N′-bis-(2-amino-ethyl)-propane-1,3-diamine) and if the synthesis is carried out under strictly anhydrous conditions. The 5,7-diphenyl-1,4,8,11-tetraazacyclotetradecane-6,6-dicarboxylic acid diethyl ester copper(II) diperchlorate complex is obtained in good yield and exhibits a regular square coordination which is not disturbed by the bulky phenyl substituents: triclinic, space group P 1 with a = 11.742(5) A ̊ , β = 16.949(8) A ̊ , c = 8.718(4) A ̊ , α = 101.15(4)°, β = 105.92(4)°, γ = 96.21(4)°, V = 1613(1) A ̊ 3, and Z = 2 (R = 0.047, R w = 0.051) .