THE SYNTHESIS AND PHOTOPHYSICAL CHARACTERIZATION OF MACROCYCLIC CHROMIUM(III) COMPLEXES

Tetraazamacrocycles, such as cyclam (1,4,8,11-tetraazacyclotetradecane), are useful ancillary ligands in the formation of organometallic complexes. Coordination of a 3d metal can lead to the formation of square planar complexes, such as with Ni^II and Cu^II, or octahedral complexes upon coordination of additional ligands, such as with Co^II/III and Cr^II/III. Notably with Cr, a mixture of cis- and trans-octahedral complexes are formed, and the isomerism can be influenced through C-substitution of the cyclam macrocycle. Herein, Cr^III complexes featuring C-substituted cyclam derivatives and either redox-active ligands or alkynyl ligands are reported.

Chapter 1 features an introduction to the photophysical processes of Cr(III), an overview of cyclam and its derivatives, and a brief review of Cr^III(cyclam/cyclam’) bis-alkynyl complexes for various applications. Chapter 2 discusses the structural, optical, electronic, and magnetic characterizations of cis-[Cr(HMC)catecholate]⁺ and cis-[Cr(HMC)semiquinonate]²⁺ complexes, which feature redox-active catecholate and semiquinonate ligands. Chapter 3 highlights a series of trans-[Cr(HMC)(C₂Ar)Cl]⁺ complexes, which expands upon prior research on bis-alkynyl complexes. Chapter 4 discusses how a different C-substituted cyclam derivative, MPC, is used to produce trans-[Cr(MPC)Cl₂]⁺ starting material in higher quantity than the HMC derivative. This allows for higher amounts of trans-[Cr(MPC)(C₂Ar)₂]⁺ complexes to be synthesized, making it a more practical macrocycle for the future pursuit of dissymmetric bis-alkynyl complexes.