Conformation, Spectra And Property Study Of Photochromic Compound: 1-phenyl-3- Methyl-4-(4-bromobenzal) Pyrazolone-5 Thiosemicarbazone

Quantum chemistry calculation is a researching method being used comprehensively by chemists recently. The issue of 1998 Nobel chemistry Prize is an important sign that the position of quantum chemistry calculation is established and obtained the widely acknowledged in chemistry and the whole natural science. Through untiring efforts, quantum chemistry calculation has been widely already applied to all fields of chemistry and forms many new developing discipline, eg. quantum organic chemistry, solid quantum chemistry, quantum catalysis, quantum surface chemistry, quantum medicine chemistry ,etc. which has become the important bridge between experiment chemistry and modern theoretical chemistry as well as powerful tool solving the chemical problem. For deeper research the photochromic properties of pyrazolone thiosemicarbazone compounds synthesized by us, the quantum chemistry calculation method is used to analyze their conformation ,spectrum and photochromic mechanism for the first time. The conformation of 1-phenyl-3-methyl-4-(4-bromobenzal) pyrazolone-5 thiosemicarbazone is researched in the first part. Compared with crystal structure of some series compounds, there is a methanol molecule in the PM4BrBP-TSC crystal structure, the thiosemicarbazone part deflects relative to the pyrazolone part and no intramolecular hydrogen bond exists. Because the hydrogen bond play a key role in the photochromic proton transfer process, the research under what conditions methanol molecule can enter the crystal lattice will contribute to synthesize the photochromic molecule with special conformation. The calculated results show that the reason why methanol can enter the crystal lattice of the PM4BrBP-TSC is because the stable energy of intermolecular hydrogen bond is bigger than that of intramolecular hydrogen bond. The NBO charge comparison results among PM4BrBP-TSC, PM4FBP-MTSC and methanol molecule also indicate that the charge distribution is favor of the formation of the intermolecular hydrogen bond. According to the analysis for computed result, stable energy of hydrogen bond and charge distribution should have a threshold point and if exceed this threshold point, the methanol molecule can enter the crystal lattice, whereas then not go. The IR spectra and UV-Vis reflectance spectra of 1-phenyl-3-methyl-4-(4-bromobenzal) pyrazolone-5 thiosemicarbazone is studied in the second part. The comparison result of the calculated IR spectra and experimental IR spectra enunciate that getting the basic and consistent result with experimental IR spectra is possible if the method having certain accuracy is adopted, which means the quantum chemistry calculation method can be used to analyze the experimental IR spectra. in addition, the calculated output result still contain the thermodynamics property of the system, such as the thermal capacity,the entropy and enthalpy, etc., so the quantum chemistry calculation is also a powerful assistant that research the thermodynamics property. The UV calculation result is not good consistent with the experiment value, this is relative to the calculated method that we have selected. However from the perspective of determining-quality research, it is still useful because the calculation result show that the hypothesis from enol form to keto form is reasonable. The photochromic property of 1-phenyl-3-methyl-4-(4-bromobenzal) pyrazolone-5 thiosemi carbazone is studied in the third part. Based on the analysis for the experiment result, we put forward the following five problems: (1) Is the hypothesis from enol form to keto from reasonable? (2) Why only can intermolecular hydrogen bond exist? (3) Which intermolecular hydrogen bond plays the key role in proton transfer process? (4) What function does the light make in the photochromic proton transfer process? (5) Why is the proton transfer irreversible? The CIS calculation results show that the hypothesis from enol form to keto form is reasonable; the conformation analysis of both enol form and keto form indicate that only intermolecular hydrogen bond can exist; the molecular orbital analysis of keto form suggest that the hydrogen bond that function in proton transfer process is the O ┄H-N(5) rather than the O ┄H-N(8); the energy and NBO charge comparison results between the ground state and excited state of the...