The number of substituted pyridine pyridinophanes found in the literature is limited due to challenges associated with 12-membered macrocycle and modified pyridine synthesis. Most notably, the electrophilic character at the 4-position of pyridine in pyridinophanes presents a unique challenge for introducing electrophilic chemical groups. Likewise, of the few reported, most substituted pyridine pyridinophanes in the literature are limited to electron-donating functionalities. Herein, new synthetic strategies for four new macrocycles bearing the electron-withdrawing groups CN, Cl, NO 2 , and CF 3 are introduced. Potentiometric titrations were used to determine the protonation constants of the new pyridinophanes. Further, the influence of such modifications on the chemical behavior is predicted by comparing the potentiometric results to previously reported systems. X-ray diffraction analysis of the 4-Cl substituted species and its Cu(II) complex are also described to demonstrate the metal binding nature of these ligands. DFT analysis is used to support the experimental findings through energy calculations and ESP maps. These new molecules serve as a foundation to access a range of new pyridinophane small molecules and applications in future work.

A library of novel tetra-aza macrocyclic molecules, specifically 3,6,9,15-tetraazabicyclo [9.3.1]pentadeca-1(15),11,13-trienederivatives, capable of chelating metal ions in vivo have been synthesized. Applications of these complexes are currently being pursued as a 1) therapeutic, focusing on radical scavenging and metal chelation, and 2) diagnostic tool such as magnetic resonance imaging (MRI) contrast agents when complexed with specific metal ions. However, a full study of the electronic effects imparted by substitution to the pyridyl moiety and the subsequent impact on the metal center have not been explored. The objective of the present study is to characterize metal complexes of four tetra-aza macrocyclic metal chelating molecules. The pyridyl functional groups studied include: A) uper (II) complexes. Analysis of the resulting copper (II) complex of the p-nitrile tetra-aza macrocycle (L6) indicate a six-coordinate metal center based on X-ray diffraction. UV-visible spectroscopy and electrochemistry help to confirm donor strength among the ligand series as well as a comparison to other tetra-aza macrocycles of interest. modified pyridyl (L1), B) p-hydroxyl (L2), and C)p-nitrile modified pyridyls (L6) on a pyclen base structure. Notable progress has been made in developing an optimal procedure for obtaining cop. Click here to listen to our interview with Brian Niebuhr on Soundcloud.

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