Electronic and Spectroscopic Properties of Avobenzone Derivatives Attached to Mo₂ Quadruple Bonds: Suppression of the Photochemical Enol-to-Keto Transformation.
Electronic and Spectroscopic Properties of Avobenzone Derivatives Attached to Mo₂ Quadruple Bonds: Suppression of the Photochemical Enol-to-Keto Transformation.
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DOI：
10.1021/jacs.5b01495
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发表时间：
2015-04
影响因子：
15
通讯作者：
M. Chisholm;C. Durr;T. Gustafson;William T Kender;Thomas F. Spilker;P. Young
中科院分区：
文献类型：
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作者：
M. Chisholm;C. Durr;T. Gustafson;William T Kender;Thomas F. Spilker;P. Young
由Mo2(T(i)PB)4（其中T(i)PB为2,4,6-三异丙基苯甲酸酯）与2种等量酸（4-甲酰苯甲酸HBzald）之间的反应；4-（3-氧-3-苯丙基）苯甲酸；和4-(2,2-二氟-6-苯基- 2h -1λ（3),3,2λ(4)-二恶aborinin-4-基）苯甲酸，HAvoBF2，化合物Mo2(T(i)PB)2(Bzald)2, i；Mo2 (T(我)PB) 2 (Avo) 2,第二;分离得到Mo2(T(i)PB)2(AvoBF2)2， III。化合物I和II是红色的，化合物III是蓝色的。用H NMR、MALDI-TOF MS、稳态吸收和发射光谱、飞秒和纳秒时间分辨瞬态吸收和红外光谱对新化合物进行了表征。利用密度泛函理论和时变密度泛函理论进行电子结构计算，以帮助解释这些数据。这些化合物具有很强的金属到配体的电荷转移、MLCT和光谱可见区跃迁，它们包括寿命为5- 15ps的S1态。三重态为Mo2δδ*，寿命为微秒级。I和II的光谱性质相似，而III中配体的平面性大大降低了MLCT的能量，增强了时间分辨光谱的强度。Mo2单元将基态平衡完全转变为烯醇形式，并淬灭了阿伏苯宗部分的降解途径。
From the reactions between Mo2(T(i)PB)4, where T(i)PB is 2,4,6-triisopropylbenzoate, and 2 equiv of the acids 4-formylbenzoic acid, HBzald; 4-(3-oxo-3-phenylpropanoyl)benzoic acid, HAvo; and 4-(2,2-difluoro-6-phenyl-2H-1λ(3),3,2λ(4)-dioxaborinin-4-yl)benzoic acid, HAvoBF2, the compounds Mo2(T(i)PB)2(Bzald)2, I; Mo2(T(i)PB)2(Avo)2, II; and Mo2(T(i)PB)2(AvoBF2)2, III, have been isolated. Compounds I and II are red, and compound III is blue. The new compounds have been characterized by (1)H NMR, MALDI-TOF MS, steady-state absorption and emission spectroscopies, and femtosecond and nanosecond time-resolved transient absorption and infrared spectroscopies. Electronic structure calculations employing density functional theory and time-dependent density functional theory have been carried out to aid in the interpretation of these data. These compounds have strong metal-to-ligand charge transfer, MLCT, and transitions in the visible region of their spectra, and these comprise the S1 states having lifetimes ∼5-15 ps. The triplet states are Mo2δδ* with lifetimes in the microseconds. The spectroscopic properties of I and II are similar, whereas the planarity of the ligand in III greatly lowers the energy of the MLCT and enhances the intensity of the time-resolved spectra. The Mo2 unit shifts the ground state equilibrium entirely to the enol form and quenches the degradation pathways of the avobenzone moiety.