Spectral and Photophysical Properties of Thioxanthone in Protic and Aprotic Solvents: The Role of Hydrogen Bonds in S1-Thioxanthone Deactivation

Organocatalytic [2 + 2] Photopolymerization under Visible Light: Accessing Sustainable Polymers from Cinnamic Acids

Herein, the successful development of a metal-free, solution [2 + 2] photopolymerization of natural cinnamic acid-derived bisolefinic monomers is reported, which is enabled by a strategy based on direct triplet state access via energy transfer catalysis. 2,2'-Methoxythioxanthone has been identified as an effective organic photocatalyst for the [2 + 2] photopolymerization in solution, which can be excited by visible light and activate the biscinnamate monomers via triplet energy transfer. This method features its metal-free conditions, visible light utilization, solution polymerization, and abundant biomass-based feedstock, as well as processable polymer products, which is different from the rigid, insoluble products obtained from solid-state photopolymerization. This solution polymerization method also shows a good compatibility to monomer structures; cinnamic acid-derived bisolefinic monomers with different linkers, including diamine, natural diol, and bisphenol, can all readily undergo [2 + 2] photopolymerization, and be transformed into colorless, sustainable polymers.

Allyl amino-thioxanthone derivatives as highly efficient visible light H-donors and co-polymerizable photoinitiators

Allyl-amino thioxanthone derivatives as new visible-light photoinitiators for efficient free-radical, cationic and thiol–ene polymerizations.

Thioxanthone in apolar solvents: ultrafast internal conversion precedes fast intersystem crossing

The photophysics of thioxanthone dissolved in cyclohexane was studied by femtosecond fluorescence and transient absorption spectroscopy.

Deactivation of 6-aminocoumarin intramolecular charge transfer excited state through hydrogen bonding

This paper presents results of the spectral (absorption and emission) and photophysical study of 6-aminocoumarin (6AC) in various aprotic hydrogen-bond forming solvents. It was established that solvent polarity as well as hydrogen-bonding ability influence solute properties. The hydrogen-bonding interactions between S₁-electronic excited solute and solvent molecules were found to facilitate the nonradiative deactivation processes. The energy-gap dependence on radiationless deactivation in aprotic solvents was found to be similar to that in protic solvents.

Novel thermally activated delayed fluorescence materials-thioxanthone derivatives and their applications for highly efficient OLEDs

Thermally activated delayed fluorescence emitters with small energy gap between the triplet and singlet (ΔEST ), TXO-PhCz and TXO-TPA, have been successfully synthesized by combining a hole-transporting TPA/PhCz moiety and an electron-transporting TXO moiety. Both compounds display efficient solid-state luminescence with an efficient up-conversion of the triplet to singlet. OLEDs based on them exhibt high performance up to 21.5%, which is among the best reported for OLEDs.

Thioxanthone functionalized silver nanorods as smart photoinitiating assemblies to generate photopolymer/metal nano-objects

Silver nanorods (AgNRs) with lengths in the 50-60 nm range were synthesized and functionalized with 2-(2-mercaptoethyl)thioxanthone (C2TX) to generate AgNR@C2TX nanoassemblies. When irradiated at 377 nm in the presence of a diacrylate monomer, these dispersed nanoassemblies initiate radical photopolymerization, indicating that the excited singlet to triplet intersystem crossing process of C2TX in the vicinity of AgNRs was favored while the fluorescence of C2TX was completely quenched at the surface of NRs. SEM and TEM images confirmed the formation of a AgNR-polymer nanocomposite and the homogeneous dispersion of AgNRs in the polymer film. Moreover, under specific experimental conditions allowing the spatial extent of the polymerization to be limited, polymer-capped AgNRs were obtained (polymer diameter of ca. 1 nm).

Solvent dependence of the photophysical properties of 2-chlorothioxanthone, the principal photoproduct of chlorprothixene

2-chlorothioxanthone (CTX) is used as photoinitiator for the reticulation of synthetic resins and for the preparation of pharmaceuticals. It was previously determined that CTX is the primary photoproduct of z-chlorprothixene (CPTX) when irradiated at 313 nm and is formed in an autocatalyzed reaction through an energy-transfer mechanism (Piñero et al. [2009] Photochem. Photobiol., 85, 895-900). In this work, the photophysical properties of CTX were measured in acetonitrile/water solutions to determine if their magnitude can affect the side effects of CPTX. The results show that CTX has higher absorption coefficients in the visible region (400-420 nm) and higher triplet quantum yields than its parent compound. Similar to TX, both properties strongly depend on the solvent polarity/hydroxylicity. The quantum yield of the triplet intermediate is very close to the value of the phenothiazine triplets. The phenothiazines are the most phototoxic antidepressants. Therefore, given the appropriate microenvironment, the photosensitization side effects of CPTX can be intensified on the production of CTX.