... Volume: Page: ... These issues have been considered, in detail, for 1,3-diphenylpropynylidene (13).(42, 43) In terms of chemical reactivity, trapping and/or ... at cryogenic temperatures produces triplet propynylidene (2: IR (Ar, 8 K) 3265 s, 1621 w, 550 m, 403 m, 249 ...