Fig. 1. Representative structures for the most commonly studied square-planar Pt(II) complexes

Fig. 2. Structures of Pt(Ⅱ) terpyridine acetylide complexes 1-22 with different substituents on the acetylide ligand or on the terpyridine ligand

Fig. 3. (a) Linear absorption spectra of complexes 1-3 (8.8×10⁻⁵ mol/L) in CH₂Cl₂/CH₃OH (8∶2) in a 2 mm cell, (b) triplet transient difference absorption (TA) spectra of 2 (2.39×10⁻⁵ mol/L) and 3 (2.09×10⁻⁵ mol/L) in a 1-cm cell. The TA spectrum of 1 was similar to that of 2, thus was not shown in Fig.3(b), (c) Z-scan experimental data and fitting curve for 3 in CH₂Cl₂/CH₃OH (8∶2) with a concentration of 3×10⁻⁴ mol/L and a linear transmission of 95% at 532 nm in a 1 mm cell. Figures a and b are modified from Ref. [50] with permission, copyright © American Institute of Physics

Fig. 4. (a) and (b) Linear absorption spectra of complexes 4-12 (1×10⁻⁵ mol/L) in acetonitrile in a 1 cm cuvette, (c) ns TA spectra of 4, 5, 6 and 10 in acetonitrile in a 1 cm cell (A = 0.4 at 355 nm). See Ref. [51] for the ns TA spectra of 11 and 12 in acetonitrile, (d) time-resolved fs TA spectra of 11 in acetonitrile, (e) optical limiting curves of 4, 5, 10, 11 and 12 in acetonitrile in a 2 mm cell at 532 nm for 4.1 ns laser pulses. The linear transmission for all solutions was adjusted to 70% in the 2 mm cell. Figures are modified from Refs. [51] and [52] with permission, copyright © Chinese Optical Society and American Chemical Society, respectively

Fig. 5. (a) Linear absorption spectra of 19-22 (2.0×10⁻⁵ mol/L) in acetonitrile in a 1 cm cuvette, (b) ns TA spectra of 19-22 in acetonitrile in a 1 cm cell (A= 0.4 at 355 nm), (c) optical limiting curves of 19-22 in acetonitrile in a 2 mm cell at 532 nm for 4.1 ns laser pulses. The linear transmission for all solutions was adjusted to 70% at 532 nm in the 2 mm cell. Figures are modified from Ref. [53] with permission, copyright © American Chemical Society

Fig. 6. Structures of Pt(N^N^N) complexes 23-32

Fig. 7. (a) Linear absorption spectra of 23-27 in CH₂Cl₂, (b) ns time-resolved TA spectra of 25 in CH₂Cl₂ in a 1 cm cell (6.2×10⁻⁵ mol/L (A₃₅₅ = 0.888)), (c) ns time-resolved TA spectra of 26 in CH₂Cl₂ in a 1 cm cell (3.9×10⁻⁵ mol/L (A₃₅₅ = 0.564)), (d) optical limiting curves of 25-27 in a 2 mm cell at 532 nm for 4.1 ns laser pulses. The linear transmission for all solutions was adjusted to 70% at 532 nm in the 2 mm cell. 25 and 26 were dissolved in CH₂Cl₂, and 27 was dissolved in DMF. Figures are modified from Ref. [5] with permission, copyright © American Chemical Society

Fig. 8. (a) Linear absorption spectra of 28-32 in acetonitrile, (b) ns TA spectra of 28-32 in acetonitrile in a 1 cm cell (λ_ex = 355 nm), (c) optical limiting curves of 28-32 in acetonitrile in a 2 mm cell at 532 nm for 4.1 ns laser pulses. The linear transmission for all solutions was adjusted to 75% at 532 nm in the 2 mm cell. Figures are modified from Ref.[56] with permission, copyright © American Chemical Society

Fig. 9. Structures of Pt(II) R-fluorenylterpyridine chloride complexes 33-37

Fig. 10. (a) UV-vis absorption spectra in CH₃CN for 33-35, (b) time-resolved fs transient difference absorption spectra of 33 in CH₃CN, (c) open-aperture Z-scan experimental data and fitting curve for 34 in CH₃CN at 740 nm. The energy used for the experiment was 6.6 μJ, and the beam waist at the focal point was 31 μm. Figures are modified from Ref.[67] with permission, copyright © Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Fig. 11. (a) UV-vis absorption spectra of 36 and 37 in DMSO, (b) nanosecond TA spectra of 36 and 37 in CH₃CN immediately after laser excitation. λ_ex = 355 nm. A₃₅₅ = 0.4 in a 1 cm cuvette. (c) optical limiting curves of 36 and 37 in DMSO solution for 4.1 ns laser pulses at 532 nm. The linear transmission of the solution was adjusted to 95% in a 2 mm cuvette. The beam waist at the focal plane was 72 μm, (d) wavelength dispersion of the ratios of excited-state absorption cross section to that of the ground-state absorption (σ_ex/σ₀) and TPA cross section (σ₂) for 36 and 37 in DMSO solution. Figures are modified from Ref.[72] with permission, copyright © American Chemical Society

Fig. 12. Structures of mononuclear or multinuclear alkynylplatinum(Ⅱ) terpyridine complexes 38-44

Fig. 13. Structures of a trinuclear RuPt₂ and heptanuclear RuPt₆ complexes 45 and 46

Table 1. Optical limiting parameters at 532 nm for ns laser pulses^a

Table 2. Photophysical parameters and optical limiting data for 4, 5, 10, 11, 12, and 19-22 in acetonitrile^[51,53]

Table 3. Photophysical parameters of 28-32 in CH₃CN

Table 4. Ground-state and excited-state absorption cross sections of 28-32 in CH₃CN at 532 nm

Table 5. Singlet excited-state absorption cross sections of 28 at different wavelengths^a

Table 6. Excited-state absorption and two-photon absorption cross sections for 33-35 at different wavelengths in CH₃CN

Table 7. Photophysical parameters of 36 and 37^a

Table 8. Absorption cross sections of 36 and 37 at selected wavelengths determined by fitting of Z-scan data