Charge-transfer heptamethine dyes for NIR singlet oxygen generation

Jarman, John B.; Dougherty, Dennis A.

doi:10.1039/c9cc01096c

Cited by 10 publications

(9 citation statements)

References 24 publications

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“…101 Additionally, the absorption spectrum of [L2] + roughly corresponds to the sum of those of (i) the terdentate binding unit 6 and (ii) the IR-780 iodide dye 8 taken separately (Figure S20). Due to the existence of chargetransfer (CT) bands in the cyanine part, 102 [L2] + slightly absorbs in the visible domain from 22,000 to 28,000 cm −1 with a fluctuating ε = 4800−6000 M −1 •cm −1 (Figures 8a and S20).…”

Section: Photophysical Properties Of Ligand [L2] + and Molecular Ligh...mentioning

confidence: 99%

Seeking Brightness in Molecular Erbium-Based Light Upconversion

et al. 2023

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Whereas dye-sensitized lanthanide-doped nanoparticles represent an unquestionable advance for pushing linear near-infrared (NIR) to visible-light upconversion within the frame of applications, analogous improvements are difficult to mimic for related but intramolecular processes induced at the molecular level in coordination complexes. Major difficulties arise from the cationic nature of the target cyanine-containing sensitizers (S), which drastically limits their thermodynamic affinities for catching the lanthanide activators (A) required for performing linear light upconversion. In this context, the rare previous design of stable dye-containing molecular SA light-upconverters required large S···A distances at the cost of the operation of only poorly efficient intramolecular S → A energy transfers and global sensitization. With the synthesis of the compact ligand [L2]+, we exploit here the benefit of using a single sulfur connector between the dye and the binding unit for counterbalancing the drastic electrostatic penalty which is expected to prevent metal complexation. Quantitative amounts of nine-coordinate [L2Er(hfac)3]+ molecular adducts could be finally prepared in solution at millimolar concentrations, while the S···A distance has been reduced by 40% to reach circa 0.7 nm. Detailed photophysical studies demonstrate the operation of a three times improved energy transfer upconversion (ETU) mechanism for molecular [L2Er(hfac)3]+ in acetonitrile at room temperature, thanks to the boosted heavy atom effect operating in the close cyanine/Er pair. NIR excitation at 801 nm can thus be upconverted into visible light (525–545 nm) with an unprecedented brightness of B up(801 nm) = 2.0(1) × 10–3 M–1·cm–1 for a molecular lanthanide complex.

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Section: Photophysical Properties Of Ligand [L2] + and Molecular Ligh...mentioning

confidence: 99%

Seeking Brightness in Molecular Erbium-Based Light Upconversion

et al. 2023

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“…As emphasized in Table 1 ,

is used as a counter anion in IR-1040, IR-1048, and IR-1061 ( Figure 1 c,d). Among them, IR-1061 has been embedded in a variety of nanostructures such as polymeric micelles and solid nanoparticles and used for biophotonic applications [ 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Thinking about why such heavy anions are coordinated with the NIR organic dyes gives a hint on selecting proper surroundings in organic/inorganic hybrid nanostructures.…”

Section: Design Basics Of Near Infrared Fluorescent Nanostructurementioning

confidence: 99%

Near Infrared Fluorescent Nanostructure Design for Organic/Inorganic Hybrid System

Okubo¹,

Umezawa²,

Soga³

2021

Biomedicines

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Near infrared (NIR) light offers high transparency in biological tissue. Recent advances in NIR fluorophores including organic dyes and lanthanide-doped inorganic nanoparticles have realized the effective use of the NIR optical window for in vivo bioimaging and photodynamic therapy. The narrow energy level intervals used for electronic transition that involves NIR light, however, give rise to a need for guidelines for reducing heat emission in luminescence systems, especially in the development of organic/inorganic hybrid structures. This review presents an approach for employing the polarity and vibrational energy of ions and molecules that surround the luminescence centers for the development of such hybrid nanostructures. Multiphonon relaxation theory, formulated for dealing with heat release in ionic solids, is applied to describe the vibrational energy in organic or molecular systems, referred to as phonon in this review, and we conclude that surrounding the luminescence centers either with ions with low vibrational energy or molecules with small chemical polarity is the key to bright luminescence. NIR photoexcited phosphors and nanostructures in organic/inorganic mixed systems, designed based on the guidelines, for photodynamic therapy are reviewed.

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“…16,17 The ISC enhancement can also be achieved by introducing a covalently-linked radical species, such as 2,2,6,6-tetramethyl-1piperidinyloxyl (TEMPO), 18 J-aggregation, 19 or charge transfer. 20,21 Electron-donating substituents in the C4′ positions or electron-withdrawing groups in the C3′ position of the Cy7 chain were also shown to improve ISC, but the effect is relatively small. 22 Triplet-excited Cy7s can be used as singlet oxygen generators in organic synthesis, 23 wastewater treatment, 24 or photodynamic therapy.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Heptamethine cyanines (Cy7) are small organic chromophores with strong absorption and emission in the near-infrared (NIR) region that are used in diverse biological applications, such as fluorescence probes, pH and metal cation − sensors, and DNA and protein markers, or for tumor visualization and photocaging. , The best-known Cy7 derivative, indocyanine green (ICG), is a fluorescent probe approved by the Federal Drug Administration (FDA) for various clinical applications . Some Cy7 derivatives, bearing heavy halogen atomsusually on the indole corehave been reported to act as photosensitizers. − Heavy atoms enhance intersystem crossing (ISC) due to strong spin–orbit coupling between the singlet and triplet states (heavy-atom effect, HAE). , The ISC enhancement can also be achieved by introducing a covalently-linked radical species, such as 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO), J-aggregation, or charge transfer. , Electron-donating substituents in the C4′ positions or electron-withdrawing groups in the C3′ position of the Cy7 chain were also shown to improve ISC, but the effect is relatively small . Triplet-excited Cy7s can be used as singlet oxygen generators in organic synthesis, wastewater treatment, or photodynamic therapy …”

Section: Introductionmentioning

confidence: 99%

Spin–Vibronic Control of Intersystem Crossing in Iodine-Substituted Heptamethine Cyanines

et al. 2023

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Spin–orbit coupling between electronic states of different multiplicity can be strongly coupled to molecular vibrations, and this interaction is becoming recognized as an important mechanism for controlling the course of photochemical reactions. Here, we show that the involvement of spin–vibronic coupling is essential for understanding the photophysics and photochemistry of heptamethine cyanines (Cy7), bearing iodine as a heavy atom in the C3′ position of the chain and/or a 3H-indolium core, as potential triplet sensitizers and singlet oxygen producers in methanol and aqueous solutions. The sensitization efficiency was found to be an order of magnitude higher for the chain-substituted than the 3H-indolium core-substituted derivatives. Our ab initio calculations demonstrate that while all optimal structures of Cy7 are characterized by negligible spin–orbit coupling (tenths of cm–1) with no dependence on the position of the substituent, molecular vibrations lead to its significant increase (tens of cm–1 for the chain-substituted cyanines), which allowed us to interpret the observed position dependence.

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Charge-transfer heptamethine dyes for NIR singlet oxygen generation

Abstract: A heptamethine-based charge-transfer dye was designed based on previous evidence of triplet state formation in orthogonal charge-transfer partners and calculations suggesting the formation of a charge-transfer state in heptamethine dye derivatives.

Cited by 10 publications

References 24 publications

Seeking Brightness in Molecular Erbium-Based Light Upconversion

Seeking Brightness in Molecular Erbium-Based Light Upconversion

Near Infrared Fluorescent Nanostructure Design for Organic/Inorganic Hybrid System

Spin–Vibronic Control of Intersystem Crossing in Iodine-Substituted Heptamethine Cyanines

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