Twisted Tethered Tolanes: Unanticipated Long-Lived Phosphorescence at 77 K

Influencing the communication within a conjugated system
as diphenylacetylene
is a challenging subject in molecular electronics. Some examples of
twisted tolanes are known, where high twists have been achieved in
the solid state by steric encumbrance. The insertion of a spacer system
is an alternative way to tailor rotation. Only a few examples of such
tethered tolanes exist, and they all suffer from small twist angles
(<35°). We report on tolanophanes containing a malonyl tether,
where twist angles of almost 80° were reached. Long-lived phosphorescence
(4 s at 77 K) was recorded, and quantum-chemical calculations were
performed to confirm the experimental results.