8517
Computational study of the spin - state energies and UV - Vis spectra of bis ( 1 , 4 , 7 - triazacyclononane ) complexes of some first - row transition metal cations .
 bis ( 1 , 4 , 7 - triazacyclononane ), transition metal
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 bis ( 1 , 4 , 7 - triazacyclononane ), transition metal