1,5,9-Triazacyclododecane macrocyclic systems

The complex [ZnL(H20)2]2+ (L = 2,2,4-trimethyl-l,5,9-triazacyclododecane) loses a proton from an aqua group with a pKa of 9.56.1102 Macrocycles such as (151), with a pyridine group incorporated into the structure, react slowly with Zn2+ compared to other 14-membered cyclic aliphatic tetraaza systems,1103 probably as a result of the rigidity introduced into their structure by the pyridine ring. 

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