This dissertation explores the structural modification of indigo into its rare cis form by substitution of a short organic bridge between the two indole nitrogen atoms. The synthesized N,N′-tethered cis-indigoids are assessed for their physicochemical properties in order to understand the effect of the organic tether on cis-indigoid systems. Three literature compounds containing “simple” tether structures are synthesized and subjected to complete characterization. Among them, alkyl group based cis-indigos, 2.5 and 2.6 exhibit similar absorption wavelengths as the parent indigo while oxalyl-tethered indigo 2.7 shows a large hypsochromic shift due to the strong electron-withdrawing nature of the oxalyl group. The electronics of the tether also affected the HOMO and LUMO energy levels; the oxalyl tether lowered both energy levels in comparison to the alkyl tethers. However, the indigoid co-planarity was strongly affected by the ring size from the tether rather than electronics. A new tethered cis-indigo structure type was discovered in reactions involving quinones. This new tether type consists of a 2,2′-dihydroindigo unit connected to the cis-indigo backbone through a central C–C bond of the former. Incorporation of the quinone moiety was observed in 3.2 where the final structure is comprised of two molecules of indigo and one naphthoquinone, while structures of 3.3 and 3.4 contained two indigoid units only. Investigation by CV revealed the strength of the quinone altered the early reaction intermediates. These dimeric cis-indigos show a small hypsochromic shift in the absorption compared to the parent indigo and relatively planar cis-indigoid backbone. 3.2 demonstrates rich redox behaviours. 3.3 and 3.4 display dynamic behaviours observed by solution VT 1H NMR spectroscopy. Oxalyl-tethered cis-Nindigo 4.6a and cis-indigo monoimine 4.7a were synthesized and compared with the indigoid counterpart 2.7 to examine the influence of the arylimine groups. Absorption wavelengths of the imine group containing species depended strongly on the electronics of the tether, yet the number of imine groups affected redox potentials. Protonation of 4.6a (to give H+oxalyl Nindigo 4.6aH+) causes a bathochromic shift in the absorption and allows for much easier reduction. The acidity (pKa) of 4.6aH+ is estimated between 3.6 – 4.46 in DMSO. A protonated cis-Nindigo derivative 4.9aH+ was obtained via reduction of the oxalyl group and is compared with 4.6aH+. / Graduate / 2022-08-13

Ligand design plays an important role in the development and control of new coordination compounds. A new ligand architecture, Nindigo, has previously been reported and this study represents an expansion of that research to gain better insights into the attributes of this multifunctional ligand family. Mono- and bis-palladium chelates of Nindigo have been synthesized with resulting electrochemical measurements allowing for the reversible redox-active nature of the ligand set to be identified. The electronic absorption properties of these complexes were also studied. The presence of the palladium centre was found to drastically perturb the ligand centered π-π* transition resulting in significant red shifts in the absorption spectra with respect to free Nindigo. The main group coordination chemistry of Nindigo was explored by generating mono- and bis-BF2 Nindigo chelates. The electrochemical and spectral properties of these compounds were investigated with both families displaying weak emission in the NIR region. The bis-BF2 chelates were found to be sensitive in nature and decompose to the mono-BF2 chelates. In addition, heteroleptic complexes of mono-BF2 Nindigo chelates with palladium were also synthesized. The redox chemistry as well as the electronic absorption characteristics of these compounds provides a conceptual bridge between the two homologues. Homoleptic zinc and copper complexes of mono-BF2 Nindigo chelates have been synthesized. The zinc derivative serves as an “innocent” system where all redox and spectral properties are ligand centered and the oxidation states of both the metal and surrounding ligands can be assigned. The copper complexes exhibit more diverse chemistry with the redox and electronic absorption properties differing dramatically from the zinc system. A combination of EPR, XPS and computational analysis suggests the copper systems to be non-innocent in nature. In addition to the bis-bidentate anionic Nindigo ligand system, the fully oxidized neutral analogue has also been synthesized. DehydroNindigo exhibits significantly different chemical behaviour from Nindigo. Bridged ruthenium dimers have been synthesized that are obtained as two isomers, cis and trans (with respect to the bridging ligand). Both isomers exhibit rich electrochemical behaviour. The mixed valence states of both species are found, electrochemically, to be extremely stable with respect to disproportionation. / Graduate / 0485 / 0488 / gnawn@uvic.ca