13 Photodynamic Therapy
461
Φ value (0.22) than OEJ-1 with Br
– (Φ = 0.17). This result is attributed to the
superior heavy atom effect of I
– to B
– .
Squalene dyes have been applied to optoelectronic devices including information
recording, OLED, and organic solar cells as red and near-infrared absorbing dyes
since the first synthesis in 1965. BTSQ (λ
abs
max = 682 nm, ε = 295,000 M
–1 cm
–1 ),
a squaraine dye developed as a photosensitizing dye for PDT, shows Φ = 0.05
(Salice et al. 2010). PyrrSQ-1–3 with two-photon absorption characteristics have
photoabsorption maximum wavelengths around 700 nm and show Φ values of
0.025–0.33 (Fig. 13.8c) (Beverina et al. 2008). It has been also reported that the
heavy atom effect of halogen atoms improves the Φ values (Fig. 13.8c, SQ-H,
SQ-Br, SQ-I) (Ramaiah et al. 1997).
Thus, pyrylium-, azinium-, and squalene-based photosensitizing dyes show low
1 O 2 generation efficiency, although they have excellent water solubility, tumor
affinity, and good photoabsorption properties in the phototherapeutic window. To
improve the problem, the relationship between the modification of dye skeletons and
1 O 2 generation efficiency is required to be elucidated.
13.9 Photosensitizing Dyes Based on Transition Metal (Ru,
Ir, Pt) Complex
Photosensitizing dyes based on complexes with transition metals such as Ru, Ir, and
Pt promise the use in PDT due to the broad photoabsorptions derived from metalto-ligand charge transfer (MLCT) in a visible region (350–550 nm), highly efficient
ISC (from S 1 to T 1 ) by the heavy transition metals, long-lived
3 MLCT excited states,
and phosphorescence characteristics.
1 O 2 generation properties of trisdiimine Ru(II) complexes ([Ru II (NˆN) 3 ] 2+ ) have
been extensively studied (Fig. 13.9a) (Fresnadillo et al. 1996; Stacey and Pope
2013). Most Ru(II) complexes have photoabsorption bands derived from MLCT
around 440–550 nm (ε = −10
4 M
–1 cm
–1 ). The Φ values of Ru(II) complexes are
significantly affected by the ligands. The Φ values of tris(2,2
-bipyridyl)ruthenium
(II) complex ([Ru(bpy) 3 ] 2+ ) are 0.22 in deuterated water and 0.73 in deuterated methanol, while those of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium (II)
complex ([Ru(dpp) 3 ] 2+ ) are 0.42 in deuterated water and 0.97 in deuterated
methanol. Ru (II) complex with benzenesulfonic acid sodium salts at the 4,7-positions
of the 1,10-phenanthroline ligands ([Ru(dpds) 3 ] 2+ ) has good water solubility and
shows Φ = 0.42 in deuterated water and Φ = ca. 1.0 in deuterated methanol.
Recently, the
1 O 2 generation characteristics of Ir(III) complexes and development of new Ir(III) complex-based photosensitizing dyes have been extensively
studied (Ashen-Garry and Selke 2014). In acetonitrile, the Φ value of tris(2,2
-
bipyridyl)iridium(III) complex ([Ir(bpy) 3 ] 3+ ) is ca. 0.1, which is lower than that
of [Ru(bpy) 3 ] 2+ (Φ = 0.57) (Fig. 13.9b). On the other hand, Thompson et al.
reported that dicyclometal-diketonated Ir(III) complexes ([Ir(CˆN) 2 (OˆO)]) exhibit
461
Φ value (0.22) than OEJ-1 with Br
– (Φ = 0.17). This result is attributed to the
superior heavy atom effect of I
– to B
– .
Squalene dyes have been applied to optoelectronic devices including information
recording, OLED, and organic solar cells as red and near-infrared absorbing dyes
since the first synthesis in 1965. BTSQ (λ
abs
max = 682 nm, ε = 295,000 M
–1 cm
–1 ),
a squaraine dye developed as a photosensitizing dye for PDT, shows Φ = 0.05
(Salice et al. 2010). PyrrSQ-1–3 with two-photon absorption characteristics have
photoabsorption maximum wavelengths around 700 nm and show Φ values of
0.025–0.33 (Fig. 13.8c) (Beverina et al. 2008). It has been also reported that the
heavy atom effect of halogen atoms improves the Φ values (Fig. 13.8c, SQ-H,
SQ-Br, SQ-I) (Ramaiah et al. 1997).
Thus, pyrylium-, azinium-, and squalene-based photosensitizing dyes show low
1 O 2 generation efficiency, although they have excellent water solubility, tumor
affinity, and good photoabsorption properties in the phototherapeutic window. To
improve the problem, the relationship between the modification of dye skeletons and
1 O 2 generation efficiency is required to be elucidated.
13.9 Photosensitizing Dyes Based on Transition Metal (Ru,
Ir, Pt) Complex
Photosensitizing dyes based on complexes with transition metals such as Ru, Ir, and
Pt promise the use in PDT due to the broad photoabsorptions derived from metalto-ligand charge transfer (MLCT) in a visible region (350–550 nm), highly efficient
ISC (from S 1 to T 1 ) by the heavy transition metals, long-lived
3 MLCT excited states,
and phosphorescence characteristics.
1 O 2 generation properties of trisdiimine Ru(II) complexes ([Ru II (NˆN) 3 ] 2+ ) have
been extensively studied (Fig. 13.9a) (Fresnadillo et al. 1996; Stacey and Pope
2013). Most Ru(II) complexes have photoabsorption bands derived from MLCT
around 440–550 nm (ε = −10
4 M
–1 cm
–1 ). The Φ values of Ru(II) complexes are
significantly affected by the ligands. The Φ values of tris(2,2
-bipyridyl)ruthenium
(II) complex ([Ru(bpy) 3 ] 2+ ) are 0.22 in deuterated water and 0.73 in deuterated methanol, while those of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium (II)
complex ([Ru(dpp) 3 ] 2+ ) are 0.42 in deuterated water and 0.97 in deuterated
methanol. Ru (II) complex with benzenesulfonic acid sodium salts at the 4,7-positions
of the 1,10-phenanthroline ligands ([Ru(dpds) 3 ] 2+ ) has good water solubility and
shows Φ = 0.42 in deuterated water and Φ = ca. 1.0 in deuterated methanol.
Recently, the
1 O 2 generation characteristics of Ir(III) complexes and development of new Ir(III) complex-based photosensitizing dyes have been extensively
studied (Ashen-Garry and Selke 2014). In acetonitrile, the Φ value of tris(2,2
-
bipyridyl)iridium(III) complex ([Ir(bpy) 3 ] 3+ ) is ca. 0.1, which is lower than that
of [Ru(bpy) 3 ] 2+ (Φ = 0.57) (Fig. 13.9b). On the other hand, Thompson et al.
reported that dicyclometal-diketonated Ir(III) complexes ([Ir(CˆN) 2 (OˆO)]) exhibit