Yousef Fakhri O, Ghanem Raed, Almashaqbeh Omar K, Shehadi Ihsan A
Department of Chemistry, Al-Hussein Bin Talal University, Ma'an, Jordan.
Department of Chemistry, Al Al-Bayt University, P.O. Box 130040, Mafraq, 25113, Jordan.
J Fluoresc. 2024 Oct 23. doi: 10.1007/s10895-024-04002-2.
The photophysical properties of valsartan (VAL), a potent phenyl tetrazole derivative sartan, were investigated. Valsartan has absorption bands at 230 nm and 255 nm and a fluorescence band at about [Formula: see text] = 346 nm in butanol which is red shifted depending on the H-bonding capability of the solvent. The role of H-bonding in the excited state was approved through the linear correlation of the emission energy of VAL with Camlet-Taft acidity and basicity parameters, α and β, of polar protic solvents. The position and intensity of fluorescence emission bands of VAL are found to be pH dependent, shifting from 425 nm at pH 2 to 375 nm at pH 4 with enhancement of intermolecular H-bonding and fluorescence intensity depletion beyond pH 5 with formation of tetrazole anion. The results were supported by time-resolved fluorescence measurements which indicated the presence of different species with different lifetimes in the excited state depending on solution pH value. Computational results based on time dependent density functional methods (TDDFT) show that the tetrazole moiety is involved in the [Formula: see text] absorption transitions, while natural bond analysis (NBO) shows that VAL adopts a dimer conformation in water because of effective intermolecular H-bonding.
研究了缬沙坦（VAL）这种强效苯基四氮唑衍生物沙坦的光物理性质。缬沙坦在230纳米和255纳米处有吸收带，在丁醇中约在λ = 346纳米处有荧光带，该荧光带会根据溶剂的氢键能力发生红移。通过VAL发射能量与极性质子溶剂的Camlet - Taft酸度和碱度参数α和β的线性相关性，证实了氢键在激发态中的作用。发现VAL荧光发射带的位置和强度与pH有关，随着分子间氢键增强，在pH 2时从425纳米移至pH 4时的375纳米，且在pH 5以上随着四氮唑阴离子的形成，荧光强度减弱。时间分辨荧光测量结果支持了这些结果，表明根据溶液pH值，激发态中存在具有不同寿命的不同物种。基于含时密度泛函方法（TDDFT）的计算结果表明，四氮唑部分参与了π - π*吸收跃迁，而自然键分析（NBO）表明，由于有效的分子间氢键作用，VAL在水中采取二聚体构象。
