With ligand (Z)-1 in hand, we initially focussed our efforts on evaluating its photophysical properties. In particular, the nature of the cationic N-methylated pyridinium groups on the photochemistry of the cyclic azobenzene was unknown, and our previous studies have demonstrated this moiety can significantly affect the photochemistry of conjugated chromophores by virtue of its strongly inductive and mesomeric electron withdrawing properties. In conditions relevant to G4 folding (namely 100 mM potassium phosphate buffer, pH 7.4), the thermodynamically-stable Z isomer exhibits a π-π* absorbance band at 394 nm (compared to 404 nm in the corresponding unsubstituted cyclic azobenzene). Upon irradiation close to this maximum (λ = 405 nm), we observed rapid spectral changes (reaching a photostationary state after approximately 4.5 minutes, Krel = (15.37 ± 0.43)x10 -3 s -1 ) namely a decrease in absorbance at 400 nm and the emergence of a red-shifted absorbance band at 480 nm, corresponding to the n-π* transition of the E isomer (Figure ).