Data for Azo-UPy determined by NMR experiments in CDCl₃ at 298 K.

Compound	Chemical shift/ppm			D c/10−10 (m2 s−1)	K dim (M−1)
	H-a	H-b	H-c
E-Azo-UPy	11.8a	9.9a	12.1a	6.31	ndd
Z-Azo-UPy	12.9b	12.5b	12.3b	4.57	1.2 × 105e

^aThe concentration was 10 mM.

^bThe chemical shift of N–H signals for the 4[1H]-pyrimidinone dimer (isomer I).

^cThe diffusion coefficients.

^dThe value could not be determined as H-bonding dimerization between E-Azo-UPy was effectively restricted.

^eThis value refers to the apparent dimerization constant of Z-Azo-UPy.