Co(cyclam) Complexes of Triarylamine-acetylide: Structural and Spectroscopic Properties and DFT Analysis
journal contributionposted on 25.08.2020, 12:40 by Susannah D. Banziger, Adharsh Raghavan, Matthias Zeller, Tong Ren
Any type of content formally published in an academic journal, usually following a peer-review process.
Reported herein are the syntheses of mono- and bis-C2TPA (HC2TPA = 4-ethynyl-N,N-bis(4-methoxyphenyl)aniline) complexes of CoIII(cyclam) (cyclam = 1,4,8,11-tetraazacyclotetradecane) complexes, and the formation of η2-adducts of Cu(I)/Ag(I) to the acetylenic bond of TPAC2 ligand. The reaction between trans-[Co(cyclam)Cl2]Cl and HC2TPA in the presence of Et2NH yielded trans-[Co(cyclam)(C2TPA)Cl]Cl (Cl) and subsequent treatment of Cl with CuCl or AgNO3 afforded trans-[Co(cyclam)(C2TPA-η2-CuCl2)Cl] (2a) or trans-[Co(cyclam)(C2TPA-η2-Ag(NO3)2)(NO3)] (2b), respectively. The reaction between [Co(cyclam)Cl2]Cl and 3 equiv of LiC2TPA afforded trans-[Co(cyclam)(C2TPA)2]Cl (Cl). X-ray diffraction studies of compounds Cl, 2a/b, and Cl established their molecular structures. All four compounds display redox couples that are characteristic of TPA (reversible oxidation) and CoIII (irreversible reduction) center. The reversible TPA oxidation in compounds Cl and Cl enables further UV–vis/near-IR spectroelectrochemical studies to elucidate the change of electronic structures upon oxidation. The electronic spectra of both compounds Cl and Cl and their oxidized derivatives have been rationalized based on DFT and TD-DFT analysis.