Abstract
Two dyads built with a co-facial slipped bis(zinc(
ii
)porphyrin), a free base and a bridge, [Zn
2
]–bridge–[Fb] (bridge = C
6
H
4
CC, 1 and C
6
H
4
CCC
6
H
4
, 2), exhibit S
1
energy equilibrium [Zn
2
]* ↔ [Fb]* at 298 K, an extremely rare situation, which depends on the degree of MO coupling between the units. At 77 K, 2 becomes bi-directional due to the two large C
6
H
4
–[Zn
2
] and C
6
H
4
–[Fb] dihedral angles.
