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As a model system we have chosen a rigid molecular module , 1 , 3 , 5 - tris ( pyridine - 4 - ylethynyl ) benzene , which can undergo self - association via hydrogen bonding ( H - bonding ) to form ordered 2D nanostructures .
 Chemical: 1 , 3 , 5 - tris ( pyridine - 4 - ylethynyl ) benzene; Chemical: hydrogen; Chemical: H
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: 1 , 3 , 5 - tris ( pyridine - 4 - ylethynyl ) benzene; Chemical: hydrogen; Chemical: H