Summary of absorption properties and parameters for reversible photoisomerization.

			Photoisomerization
	λ max/nm (ε/M−1 cm−1)	K pi	Φ p→d, Φd→p
p-1Cl	528 (8700)	—	—
p-2Cl	552 (10 300)	—	—
p-3Cl	538 (10 600)	—	—
p-4Cl	537 (11 900)	—	—
p-1H2O	502 (8800)	3.2	8.3 × 10−3, 2.4 × 10−2
p-2H2O	515 (8100)	3.2	1.7 × 10−2, 5.7 × 10−2
p-3H2O	507 (10 700)	3.0	8.2 × 10−3, 2.7 × 10−2
p-4H2O	507 (12 300)	2.7	8.6 × 10−3, 2.0 × 10−2