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 NiII and CuII, or octahedral complexes upon coordination of additional ligands, such as with CoII/III and CrII/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, CrIII 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 CrIII(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.