Table 1.

Calculated position of the ring‐opening excited state in the manifold and transannular bond length (q in Å) in this excited state. The value of q in the ground state is almost uniformly the same (1.535±0.001 Å). Comparison to experimental outcomes is given in the rightmost columns.

	closed‐closed		closed‐open		Experimental Observation
Molecule	State	q	State	q	1st Switching	Cooperative
DHP	S2	1.609	–	–	Yes	–
PyFm	S1	1.549	S1	1.579	Yes	Yes
PhCN	S1	1.564	S2	1.569	Yes	Yes
Ester	S3	1.582	S2	1.587	Yes	n.a.
CN	S1	1.545	S1	1.568	No	No
Isoin	S1 [a]	1.538	S2	1.550	No	No
PyCN	S1	1.547	S1	1.566	No	No

[a] For Isoin the S₁ state is the one with the largest f, but the state with a clear zwitterionic character is S₃.