3571
The effects of steric clashes between H atoms on polypyridyl ligands in decreasing complex stability are evaluated , as well as the effect of chelate ring size on metal ion selectivity .
 Chemical: H; Chemical: polypyridyl
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: H; Chemical: polypyridyl