A new Schiff‐base molecule, 4‐chloro‐2‐((2‐(pyridin‐4‐yl)hydrazono)methyl)phenol (LH₂) has been found as a fluorescent chemosensor for high pH. It has been synthesized by condensation of 4‐hydrazinylpyridine and 5‐chlorosalicylaldehyde (1:1) in methanol. It has been characterized by elemental analysis and different spectroscopic methods. LH₂ shows emission peak at 571 nm (λ_ex=390 nm) upto pH 10.5 and a new peak at 504 nm emerges with increasing intensity with higher pH value of the media. Several cations and anions do not have any significant effect on the emission intensity of LH₂. Color of LH₂ changes distinctly when pH of aqueous medium is changed from 10.5 to 11 when observed under both visible and UV light. Some theoretical calculations have been performed to look into the spectral transitions. This probe has been used for the detection of pH regions using sea water.

中文翻译：

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新型席夫碱化合物的高pH传感特性

已发现一种新的席夫碱分子4-氯-2-（（2-（吡啶-4-基）肼基）甲基）苯酚（LH ₂）作为高pH值的荧光化学传感器。它是通过在甲醇中缩合4-肼基吡啶和5-氯水杨醛（1：1）合成的。它已通过元素分析和不同的光谱方法进行了表征。LH ₂在最高pH值为10.5的情况下，在571 nm（_λex = 390 nm）处显示出发射峰，并且随着介质pH值的增加，随着强度的增加，在504 nm处出现了一个新的峰。几种阳离子和阴离子对LH ₂的发射强度没有任何显着影响。LH _2的颜色当在可见光和紫外光下观察时，当水性介质的pH从10.5变为11时，其变化都会明显。已经进行了一些理论计算来研究光谱跃迁。该探针已用于使用海水检测pH值区域。