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. Author manuscript; available in PMC: 2012 Sep 5.
Published in final edited form as: Inorg Chem. 2011 Aug 5;50(17):7966–7979. doi: 10.1021/ic2012843

Figure 7.

Figure 7

Conformational changes that are hypothesized to occur during the formation of a chelate that positions the benzylic substituent on the corner of the macrocycle, shown for the S-SSSS- isomer of NB-DOTMA. The ligand structure is derived from the crystallographic data for RRSS-TCE-DOTA and the benzylic substituent located in the position found to afford the lowest energy conformation, vide infra. To flip the pendant arms on the left-hand sight of the macrocycle below the plane of the macrocycle as shown (blue arrows) the conformation of two ethylene bridges must flip λλ to δδ (blue arrows).