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Theoretical Studies on the Excited State Intramolecular Proton Transfer in Benzotriazole Derivatives with Chromphore

Author: XuXiaoFang
Tutor: GaoFang
School: Chongqing University
Course: Environmental Science
Keywords: Ab initio Density Functional Excited state intramolecular proton transfer Benzene Benzotriazole Tautomer
CLC: O621.13
Type: Master's thesis
Year: 2010
Downloads: 49
Quote: 0
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Abstract


Intramolecular proton transfer in the fields of chemistry and biochemistry and more and more people pay attention to. This article using ab initio (HF), density functional theory (DFT, TDDFT) and nitro stilbene chromophore connection 2 - (2 - hydroxy - benzene singlet excited state structure theory (CIS) yl) - benzo three triazole derivatives: 2 - hydroxy-5 - [4'-nitro - diphenyl vinyl - oxymethylene] - phenyl - (2H-benzene Pian three triazole) nitro -3,4 - bis [2 - hydroxy - (2H-benzo triazole) - benzyloxy] - stilbene (C1, C2) the possibility of occurrence of excited-state intramolecular proton transfer (ESIPT) replace in the C1-NO2 obtained as well as to replace the group-H,-F,-OCH3, and-N (C2H5) 2 C3 derivatives ESIPT reaction. System C1, C2 and C3 class occurred ESIPT tautomer ground state and excited states of the nature of change, including changes in the structural parameters of the bond length, bond angle of Mulliken charge and dipole moment changes frontline track as well as the potential energy curve trend. The calculation results show that for the C1, C2 terms in the ground state (S0), ketone (keto, K) do not exist in a stable structure, and the isomerization process as a whole need to absorb a lot of heat, so the ground state intramolecular proton transfer occurs ( GSIPT) unlikely. Keto form of the excited state of the hydrogen bond strength of the (keto *, K *) to be far stronger than the alcohol excited state (enol *, E *) of the hydrogen bond strength. Molecules in photoluminescence, the negative charge of the proton donor decreasing the negative charge of the proton acceptor increased (the substituent is-N (C2H5) 2, except). K *, the HOMO to LUMO electronic transitions causes the electron density from the phenol ring to the transfer of the protonated heterocyclic (substitution except-N (C2H5) 2). For C1, E * → K * transition only need to overcome the energy barrier smaller (about 41 kJ · mol-1), C3 class with different substituents ESIPT will need to cross the energy barrier from about 32.864 kJ · mol ranging from -1 to 63.343 kJ · mol-1. The calculation shows that the C1 occurs ESIPT great possibility, C3-based compound due to the isomerization process product energy slightly higher than the energy of the reactants can not occur at room temperature of ESIPT. For C2 is concerned, due to having a high energy, and the base state of the single proton transfer characteristics isomers EK (containing both the the enol structure E with ketone structure K Enol-keto) and the ground state of the transfer characteristics of the double proton isomers body 2K (containing double-enol structure enol-enol), as well as the structural characteristics of the enol excited state 2K * (keto *-keto *) do not exist in a stable structure, ground state molecules within single or double proton transfer and The excitation state intramolecular double proton transfer occurs very unlikely. EK excited state (EK *, enol *-keto *) the existence of a stable structure, and 2E * → EK * transition has a low energy barrier, and therefore C2 may occur excited singlet state intramolecular proton transfer (ESISPT). This article by quantum chemical calculations predicted molecular C1, C2 and C3 class UV-visible absorption spectra and fluorescence emission spectra obtained a larger the Stoke displacement of ESIPT fluorescence emission peak.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Theory of organic chemistry,physical organic chemistry > Organic Chemistry Structure Theory
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