1,5,9-Triazacyclododecane macrocyclic

Tri- and tetraaza macrocycles A-functionalized with imidazole and pyrazole groups have been coordinated to zinc. The zinc complexes of functionalized 1,5,9-trizacyclododecane and 1,4,8, 11-tetraazacyclododecane have been synthesized, (76) and (77).680-685 The formation constants with the mono-armed 1,5,9-triazacyclododecane were calculated and found to be higher than for the non-functionalized macrocycle and coordination was demonstrated to be through four nitrogen... 

The structures determined by X-ray analysis of the complexes [Ni(Me3[12]eneN3)2](NCS)2 (Me3[12]eneN3 = 2,4,4-trimethyl-l,5,9-triazacyclododec-l-ene) and [Ni(TRI)(H20)N03]N03 (TRI = tribenzo[b,/,/][l,5,9]triazacyclododecane) show that the two triaza macrocycles coordinate facially in both square pyramidal2721 and octahedral complexes.2724 Other complexes with triaza macrocycles have been prepared and are assumed to be either live- or six-coordinate.2721-2725 Selected examples of nickel(II) complexes with unsaturated macrocydes are reported in Table 106. 

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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