Azamacrocycles Basicity Effects and the Example of Cyclam

Nitrogen-containing macrocycles are highly complementary for hrst row transition metals as in the examples shown in Section 1.6. Common azamacrocycles include cyclen ([12]ane-N4) and cyclam (3.45) and many have a history that significantly pre-dates the crown ethers. Unlike the crown ethers which do not have donor atom substituents, the binding constants of azamacrocycles such as cyclam are greatly affected by N-alkylation. Alkylated amines are significantly more basic than ammonia, for 

Metal ion Cyclam Tetra-N -methylcyclam Ionic radius (A) 

Cyclam derivatives such as 3.75 with hydroxypropyl side arms engage in a lariat ether-like coordination of one hydroxyl group to give square pyramidal complexes that hydrogen bond to anions 

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