Study On Synthesis And Characteristics Of10-Hydroxybenzo[h]Quinoline And Its Derivatives

Owing to their excellent electroluminescent properties,10-hydroxybenzo[h]quinoline (HBQ) and its complexes have great potential for applications in the field of organic light emitting devices (OLEDs). The applications of HBQ have been extensively investigated during the past years. However, the number of studies on HBQ derivatives is still limited. This dissertation focuses on the synthesis and spectroscopic properties of novel HBQ derivatives. The molecular structures of the ground state(So) and the first singlet excited state (S1) for HBQ and its derivatives in CH3CN were optimized at the B3LYP/6-31G(d, p) level using the polarizable continuum model.The frontier molecular orbital characteristics and energy levels of HBQ and its derivatives have been analyzed. Electronic spectrum property have been investigated with time-dependent density functional theory (TD-DFT). The relationship between the structure and properties are discussed. We have mainly focused our discussion on the substituent effect and solvent effect. The major contents in this thesis are described as follows:1. Eight compounds were synthesized, including10-hydroxybenzo[h]quinoline(HBQ),7,7’-methylenebis-10-hydroxybenzo [h] quinoline(PMDHBQ),7,9-methylenebis-10-hydr-oxy-benzo[h]quinoline(OMDHBQ),10-methoxybenzo[h]quinoline(MBQ),2-benzyl-10-methoxybenzo[h]quinoline(NMBQ),2-(2-naphthyl)-10-methoxybenzo[h]quinoline,2-anthryl-10-methoxybenzo[h]quinoline(AMBQ) and ionic supramolecular complex bis(10-hydroxybenzo[h]quinoline) zinc chloride. All of the compounds were characterized and confirmed by IR, NMR and elemental analysis.The single crystals of five target compounds have been obtained, and their structures were further confirmed by single-crystal X-ray diffraction analysis.a. Compounds PMDHBQ and OMDHBQ are bis-10-hydroxybenzo[h]quinoline bridged by methylene, with the two conjugate planes of HBQ perpendicular to each other. The angle between the two HBQ rings are82.1(2)°and79.0(4)°for PMDHBQ and OMDHBQ, respectively. The two compounds form strong intramolecular hydrogen bond between the O-H proton and the N atom.b. In BMBQ, the hydroxybenzo[h]quinoline and benzene rings lie almost in the same plane, the angle between the two aromatic rings being0.70(1)°. In AMBQ, however, the conjugate planes of hydroxybenzo[h]quinoline and anthracene rings are perpendicular to each other with the angle of84.9(2)°.c. For the ionic supramolecular compound MBQZn, there exists static interaction between the cationic ([C14H12NO]-)2) and anionic ([ZnCl4]2-) species.2、The molecular structures of the ground state(S0) and the first singlet excited state (S1) for HBQ and its derivatives in CH3CN were optimized at the B3LYP/6-31G(d, p) level using the polarizable continuum model. The frontier molecular orbital characteristics and energy levels of HBQ and its derivatives have been analyzed. Electronic spectrum property have been investigated with time-dependent density functional theory (TD-DFT). The main conclusion include:1) HBQ (OMDHBQ) has a strong six-membered ring intramolecular hydrogen bond between the O-H proton and the N atom. This hydrogen bond permits a highly efficient generation of the proton-transfer tautomer. The molecule mainly exists in the enol form in the ground state, whereas the keto form is dominant in the excited state.Due to the lack of hydroxyl proton, no hydrogen bond is formed and therefore no proton transfer reaction takes place in the molecule of MBQ、BMBQ and NMBQ. The electronic configuration does not change significantly from the ground state to the excited state.2) The election density of HOMO is mainly localized on the phenol ring and the election density of LUMO is mainly localized on the pyridine ring. The electronic transition from the ground state to the excited state is mainly about electron flowing from the phenol ring including O to the pyridine ring including N.3) An increase of energy gaps between LUMO and HOMO would lead to a blue shift of the absorption spectra. The calculation result of the electronics spectrum is in accordance with the regulation of energy gaps between LUMO and HOMO.4) The calculated absorption and emission wavelengths were in good agreement with the experimental ones, indicating that the theory methods can be used to predict the spectroscopic parameters.3. The spectroscopic properties of HBQ and its derivatives were investigated. We have mainly focused our discussion on the substituent effect and solvent effect. The main conclusions include:1) HBQ, PMDHBQ and PMDHBQ exhibited similar UV/Vis and emission spectral properties. All exhibited dual emissions, and the long wavelength emission band was attributed to the excited proton transferred keto form. A red spectral shift (18nm) and a decrease in intensity of PMDHBQ emission relative to that of HBQ were observed. MBQ and its derivatives exhibited only one enol emission due to the lack of a hydroxyl proton. Compared with MBQ, the fluorescence spectra of BMBQ and NMBQ revealed a red spectral shift and a marked increase in intensity. In the case of AMBQ, a slight red shift and a marked decrease in intensity relatively to that of MBQ were observed. The results indicated that the fluorescence properties of fluophors are greatly influenced by both the steric and electronic effects of substituents.2) The UV-vis absorption of MBQ and its derivatives, independent of solvent polarity, exhibits similar spectral features. The absorption maxima of HBQ and PMDHBQ, however, show blue shifts with increasing solvent polarity. The emission maxima of HBQ and PMDHBQ show blue shifts with increasing solvent polarity. By contrast, a red shift of the emission maximum and an increase of quantum yield occurred in the emission of MBQ and its derivatives.3) The effects of electron donor and acceptor were examined. The emission intensity of the title compounds as a function of electron donor (DMA) concentration initially increases with DMA concentration and then decreases. The electron acceptor, DMTP, can efficiently quench the fluorescence of the compounds and the quenching behavior follows the Stern-Volmer relationship, implying that the title compounds could potentially be used as electroluminescent materials in OLED technology.It was found that HBQ, PMDHBQ and OMDHBQ are good red light-emitting materials.In summary, novel10-hydroxybenzo[h]quinoline derivatives have been synthesized and characterized. The structural and spectroscopic properties of the title compounds were investigated using experimental and theoretical approaches. The calculated absorption and emission wavelengths were in good agreement with the experimental ones. The results derived from the above research could contribute to the development of new luminescent materials.