2 2' 6' 2''-terpyridine July 8, 2019 16 32 64 128 4 4 methylphenyl 2 2 6 2 terpyridine 4 chloro 2 2 6 2 terpyridine 2 2' 2''-terpyridine 2 2'-pyridyl 2 2'-pyridil