The Synthesis and Spectral Properties’ Study of Linear and Chiral Arylene-ethynylenes
|Keywords||Arylene-ethynylenes Synthesis Spectrum Solvent effect TICT|
Arylene-ethynylenes have been an important part of fluorescent materials, electroluminescent materials, liquid crystal materials, carbon-rich materials, organic semiconductor materials and light-emitting diode materials. Based on extensive literatures, a summary of arylene-ethynylenes’synthesis and their application in various fields was given in this paper. Based on the previous research which we did in our laboratory before, a series of arylene-ethynylenes were designed and synthesized, and the spectral properties were studied. This paper was consists of two parts: The first part is the study of linear type arylene-ethynylenes with different units or substituents; the second part is the study of chiral binaphthyl template contained arylene-ethynylenes.Under the irradiation of UV-light, fluorophores with amino group will result in TICT (Twisted Intramolecular Charge Transfer) state and emit florescent light. In chapter 2, Sonogashira reaction was adopted as a chief reaction for the synthesis of arylene-ethynylenes with NPh2 group, the UV-Vis absorption and fluorescence spectra of these compounds were measured and discussed. It mainly studied the solvent effect caused by TICT, proved that TICT state can exist in arylene-ethynylenes without Electron Withdrawinging Group (EWG) and cause the solvent effect in fluorescence spectra.) It revealed that expanded conjugation effectively increase the maximum wavelength of UV-Vis absorption. Arylene-ethynylenes containing three benzene rings in skeleton showed longer emitting wavelength and stronger solvent effect. Locating of EWG at opposite side of NPh2 group leads to a bathochromic shift, and the largest solvent effect can be observed in moderate EWG contained compounds.In chapter 3, a series of NPh2 substituted polyyne motif contained arylene-ethynylenes were synthesized by combination of Sonogashira coupling and double elimination protocol. By improvement of double elimination protocol, CN substituted polyyne contained arylene-ethynylenes were synthesized successfully. The UV-Vis absorption and fluorescence spectra of these compounds were measured and discussed. For further study, some compounds’life timeτwere measured, based on these data, reaction rates for radiative kr and nonradiative processes knr were obtained. Consider about the influence of the value of kr and knr by structure and solvent, the mechanism of solvent effect was elaborated theoretically. Molecules locating of EWG and NPh2 groups respectively at the opposite sides showed bathochromic shift apparently in fluorescence spectra. Diyne and triyne moieties located at the opposite side of NPh2 group could accommodate a negative charge which was generated in the excited state efficiently, so the stronger solvent effect was observed resulting in bathochromic shift.Because binaphthyl unit has a good property of configuration maintenance, enantiopure 2,2’-diethynyl-1,1’-binaphthyl was chosen as the starting materials for the synthesis of chiral arylene-ethynylenes. In chapter 4, a series of binaphthyl contained chiral arylene-ethynylenes with different substituents were synthesized. The UV-Vis absorption and Circular Dichroism (CD) spectra and Specific rotation ([α]D) of these compounds were measured and discussed. Compared with other compounds, Arylene-ethynylenes with NMe2 group showed obvious differences: the maximum wavelength of UV-Vis absorption showed a bathochromic shift; in CD spectra, the wavelength range of Cotton effect was enlarged, and moved to longer wavelength. Because of the containing of the CF3 group, the absolute value of [α]D of arylene-ethynylene 87 decreased a lot; because of the containing of two NMe2 groups, the absolute value of [α]D of arylene-ethynylene 86 became smaller; because of the cooperative functions of CF3 group and NMe2 group, the absolute value of [α]D of arylene-ethynylene 89 became bigger.In chapter 5, from enantiopure 2,2’-diethynyl-1,1’-binaphthyl, three binaphthyl contained chiral arylene-ethynylenes with similar structure were synthesized. Compound 90 was synthesized by combination of Sonogashira reaction and double elimination protocol which avoids the troubles resulting from the only use of Sonogashira reaction. Contrast the theoretical results with experimental results of the Vibrational Circular Dichroism(VCD) spectra of these three structural similar compounds, it finds that there is a well consistency between them. Based on this result, it is feasible to predict the real VCD spectra or to confirm the absolute configuration of this kind of compounds by theoretical calculation. Furthermore, the characteristic absorption maxima at 1512cm-1and 1519cm-1 can be used to figure out the absolute configuration of binaphthyl unit of these compounds.In chapter 6, enantiopure (R)- or (S)-binapythol was used as a starting material. The target molecular [(R,P),(R,P),(R,P)]-93 and [(S,M),(S,M),(S,M)]-93 ,[(R,P),(R,P),(R,P),(R,P)]-94 and [(S,M),(S,M),(S,M),(S,M)]-94 were synthesized by five steps: the control of competition reaction, cyclization reaction in dilute solution, introduction of acetylenic group and removal of protecting group, and finally, cyclization by the intermolecular Eglinton reaction. The CD spectra of the two isomer of the target molecular and compound 168 were measured and discussed. All of the compounds’[α]D were measured. As the difference of one double helix unit, compound 93 and 94 showed significant difference of their [α]D value, confirmed that the introduction of double helix units to one molecular can tune the [α]D value.All of the intermediates and target compounds were confirmed by 1H NMR, 13C NMR, Mass Spectrum and elementary analysis in this paper.