Table 1.

Comparison of acidity, log(D_o/w) (previously reported)^{10–11, 13}, quantum yields for photodissociation (Φ_PD) (previously reported)^9–11, and quantum yields for singlet oxygen (Φ_Δ) (reported herein) upon irradiation at 450 nm for complexes 1–5.

compound	Structure	pKa avg	log(Do/w)a at pH 7.4	ΦPD at pH 5.0b	ΦPD at pH 7.5c	ΦΔ for XAd	ΦΔ for XBd
1A	[(bipy)2Ru(6,6’-dhbp)]2+	6.3	1.4(1)	0.0058(5)	0.0012(1)	0.041(2)	0.18(2)
2A	[(phen)2Ru(6,6’-dhbp)]2+	6.0(1)	1.6(1)	0.0020(2)	0.000036(1)	0.048(2)	0.87(9)
3A	[(dop)2Ru(6,6’-dhbp)]2+	5.9(1)	1.8(1)	0.001(1)	0.00022(3)	0.048(2)	0.48(5)
4	[(phen)2Ru(6,6’-dmbp)]2+	N/A	−1.3(2)	0.024(6)	N/A	0.01(1)e	N/A
5	[(dop)2Ru(6,6’-dmbp)]2+	N/A	−1.1(1)	0.0030(2)	N/A	0.01(1)e	N/A

^aLog(D_o/w) is the octanol-water partition coefficient measured as described in our prior publication.¹³ D_o/w is defined as the total concentration of all ruthenium complex (in various protonation states) in octanol divided by the total concentration of all ruthenium complex in water for the equilibrated biphasic mixture.

^bIn aqueous solution at pH 5.0, mostly the X_A form is present if using a protic ligand (in 1-3).

^cIn aqueous solution at pH 7.5, mostly the X_B form is present if using a protic ligand (in 1-3).

^dIsolated X_A or X_B (in 1-3) was used in CD₃OD. The aprotic complexes 4 and 5 are included in the X_A column because they carry the same charge as 1_A-3_A.

^ePhotodissociation also occured during these experiments to quantify singlet oxygen, thereby reducing the accuracy of this measurement. Incident photons could have led to either product.