Experimental (XRD) and PCM (TD) DFT (ωB97X-D/6-31G(d,p)) optimised exocyclic C C/C–C bond lengths of a monomer in S₀ and S₁ states (SS = solid-state, all values in Å).

R1 = R2	State	Solvent	Bond length [Å]
			a	b	c	d	e
H	S0	SS (exp.)	—	—	—	—	—
		CH3Ph	1.469	1.340	1.472	1.477	1.334
	S1	CH3Ph	1.404	1.407	1.407	1.459	1.342
		CHCl3	1.402	1.410	1.405	1.459	1.343
		CH2Cl2	1.400	1.412	1.403	1.458	1.343
		CH3CN	1.399	1.414	1.402	1.458	1.344
COOMe	S0	SS (exp.)	1.458	1.338	1.465	1.463	1.342
		CH3Ph	1.467	1.341	1.470	1.466	1.344
	S1	CH3Ph	1.409	1.401	1.405	1.429	1.369
		CHCl3	1.406	1.404	1.402	1.426	1.372
		CH2Cl2	1.404	1.406	1.400	1.423	1.374
		CH3CN	1.402	1.408	1.397	1.421	1.376
CN	S0	SS (exp.)	1.462	1.338	1.465	1.454	1.351
		CH3Ph	1.467	1.341	1.469	1.457	1.357
	S1	CH3Ph	1.412	1.396	1.408	1.417	1.393
		CHCl3	1.408	1.400	1.404	1.412	1.398
		CH2Cl2	1.405	1.403	1.401	1.409	1.401
		CH3CN	1.402	1.406	1.398	1.405	1.404