Syntheses, Crystal Structures And Properties Of Heterocyclic-azo Dyes And The Corresponding Metal Complexes

Remarkable progress has been achieved on the studies of functional dyes during the past decades in both academic and industrial fields, not only because of their various topologies and intriguing structures, but also their interesting physical and chemical properties such as textile dyeing and polyamide fiber coloring, non-linear optics, optical data storage, two photon absorptions, and dye-sensitized solar cells.Specifically, azo disperse dyes bearing aromatic heterocyclic components have shown brilliant color and chromophoric strength, especially for their excellent properties on light and sublimation fastness. In this dissertation, four aspects based on syntheis, structure and properties of azo disperse dyes and their coordination complexes are reported. I. Azo-hydrazone tautomerism observed from UV-vis spec tra by pH control and metal-ion complexation for two heterocyclic disperse yellow dyes. Ⅱ. Investgation on two pairs of 1:2 nickel(Ⅱ) and copper(Ⅱ) metal-complex dyes showing the same trans configuration and azo-hydrazone transformation but different thermal properties. Ⅲ. Oxidized coordination/ring-open reaction by in situ CuⅡ catalysis with the H2O2 oxidant of disperse dyes. Ⅳ. Comparisons between azo dyes and Schiff bases having the same benzothiazole/phenol skeleton:Syntheses, crystal structures and spectroscopic properties. Corresponding details are shown as follows:1. The azo-hydrazone tautomerism of two pyridine-2,6-dione based Disperse Yellow dyes 1 and 2, has been achieved by pH control and metal-ion complexation, respectively, which is evidenced by UV-visible spectra using the pH-titration,1H NMR and X-ray single-crystal diffraction techniques for two dyes and one neutral dinuclear dye-metal complex. pH-titration experiments under strong and weak acidic conditions (HC1 and HOAc) as well as strong and weak alkaline conditions (NaOH and ammonia) demonstrate that there is an equilibrium between the azo and hydrazone tautomers for two dyes in solution but the hydrazone form is dominant under conventional condition. The hydrazone proton is also observed in the 1H NMR spectra of 1 and 2 which can be verified by the Hydrogen-Deuterium exchange and the presence of cooperative six-membered intramolecular hydrogen rings involving the hydrazone proton in their X-ray single-crystal structures. Moreover, the azo-hydrazone tautomerism is evidenced by the formation of a novel neutral dinuclear dye-metal complex 3, where all the ligands are in the azo form and two types of coordination modes are present for four ligands. Namely, the side two ligands serve as the bidentate capping ligands, while the middle ones act as the quadridentate bridging ligands linking adjacent Cull centers in a reverse fashion.2. Two pairs of 1:2 neutral trans mononuclear transition-metal (M= NiⅡ and CuⅡ) complexes of pyridine-2,6-dione and quinoline-2,4-dione based heterocyclic dyes have been structurally and spectrally characterized and compared herein. X-ray single-crystal diffraction analyses of four complexes 4-7, reveal that they have the same trans configuration between the bidentate chelating dianionic ligands and two axially coordinated DMF molecules. Furthermore, a transformation from the hydrazone to azo configuration has been observed for both bidentate chelating ligands after metal-ion complexation. More importantly, simultaneous DSC/TG-MS-FTIR method has been used to explore the thermal stability of four neutral metal-complex dyes 4-7, where the two axially coordinated DMF molecules in NiⅡ and CuⅡ complexes exhibit distinguishable decomposition behavior because of their different M-O bond lengths originated from the Jahn-Teller distortions.3. One pair of 1:2 neutral trans mononuclear transition-metal (M= NiⅡ and CuⅡ) complexes of Y211 have been structurally characterized firstly. The H2O2 oxidant was added to the system in order to explore the stability of disperse dyes. In this case, azo dyes may be ether oxidized or decomposed.4. Three pairs of heterocyclic azo dyes and their corresponding Schiff bases were prepared by diazotization and Schiff-base condensation reactions between substituted 2-aminobenzothiazoles and either 3-(diethylamino) phenol or 3,5-dichloro-2-hydroxybenzaldehyde in order to obtain some high performance Disperse Red dyes and compare the structural and spectral differences between the azo dyes and Schiff bases. All azo dyes and Schiff bases in this work have the same benzothiazole/phenol skeleton but different substituent group in the phenyl ring. X-ray single-crystal diffraction analyses of selected compounds reveal that they have a similar planar conformation between the benzothiazole and phenol units but dissimilar dimeric crystal packing. Electronic spectra o f the dyes demonstrate that the presence of N=N and C=N double bond chromophore units as well as substituent effects of different auxochrome groups in the benzothiazole backbone leads to significant alterations of bathochromic and hypsochromic shifts despite only slight differences in their molecular structures.