Table 2. Experimentally and Computationally Determined Parameters Important to the Upconversion Process.

	ΦUCa	Ithb (mW/cm2)	kTETc (×109 M–1 s–1)	kTTAd (×109 M–1 s–1)	τTe (ms)	kTf (×103 s–1)	E(S1)g (eV)	E(T1)h (eV)	2 × E(T1) – E(S1)j (eV)
DPA	0.240	15	1.78	3.01	5.5	0.18	3.05/3.15	1.72i	0.29
9,9′-PA2	0.150	605	0.99	3.73	0.56	1.79	2.86/3.08	1.72	0.36
1,2-DPA2	0.140	142	0.95	2.89	0.80	1.25	2.85/3.08	1.71	0.34
1,3-DPA2	0.212	44	1.04	2.81	4.7	0.21	3.04/3.12	1.72	0.32
1,4-DPA2	0.149	1343	0.96	4.00	0.29	3.44	3.06/3.12	1.72	0.32

^aUpconversion quantum yield relative to a theoretical maximum of 0.5 (50%).

^bThreshold intensity. Individual values have been normalized with respect to slight deviations in [S] between samples.

^cRate constant for triplet energy transfer from PtOEP.

^dRate constant for triplet–triplet annihilation.

^eFirst triplet excited-state lifetimes.

^fRate constant for intrinsic triplet decay.

^gEnergy of the first singlet excited state as calculated with TD-DFT (B3LYP/6-31G**)/calculated from the 0 → 0 transition of the absorption spectra. See the Supporting Information for calculation details.

^hEnergy of the first triplet excited state as calculated with TD-DFT.

ⁱExperimental literature value⁵⁰ is 1.77 eV.

^jThermodynamic driving force for TTA.