22596
The synthesized compounds , especially tris ( 4 - ( pyridin - 4 - yl ) phenyl ) amine , presented pH - dependent absorptions and emissions , indicating that these compounds might be used as pH sensors .
 Chemical: tris ( 4 - ( pyridin - 4 - yl ) phenyl ) amine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
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Answer:
 Chemical: tris ( 4 - ( pyridin - 4 - yl ) phenyl ) amine