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Tremendous attention in recent years has been devoted to the design of multifunctional purely organic emitters owing to their diverse emissive mechanism and widespread applications in the luminescent field. Herein, we describe the synthesis and photophysical investigation of D3A-type tris(triazolo)triazine (TTT) multifunctional emitters with unprecedented dual thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), aggregation-induced emission enhancement (AIEE), and aggregation-induced delayed fluorescence (AIDF). We demonstrate that the presence of methyl substituents at different positions of the emitter offers the possibility to switch between RTP and TADF processes by choosing appropriate hosts and controlling the singlet–triplet energy gap (ΔEST). TTT-PTZ, in particular, is a very strong TADF emitter (DF/PF ratio 9.3) in Zeonex®, even with a ΔEST around 0.20 eV, displaying high external quantum efficiency (EQE) of up to 12.4% in solution-processed organic light-emitting diodes (OLEDs). [ABSTRACT FROM AUTHOR]

This study explores the synthesis, characterization, and application of a heterofunctional initiator derived from 2-hydroxypropyl cyclodextrin (HP-β-CD), having eight bromoester groups and thirteen hydroxyl groups allowing the synthesis of mikto-arm star-shaped polymers. The bromoesterification of HP-β-CD was achieved using α-bromoisobutyryl bromide as the acylation reagent, modifying the cyclodextrin (CD) molecule as confirmed by electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy analysis, and differential scanning calorimetry (DSC) thermograms. The initiator's effectiveness was further demonstrated by obtaining star-comb and mikto-arm polymers via an enzymatically assisted atom transfer radical polymerization (ATRP) method and subsequent ring-opening polymerization (ROP). The ATR polymerization quality and control depended on the type of monomer and was optimized by the way of introducing the initiator into the reaction mixture. In the case of ATRP, high conversion rates for poly(ethylene oxide) methyl ether methacrylate (OEOMA), with molecular weights (Mn) of 500 g/mol and 300 g/mol, were achieved. The molecular weight distribution of the obtained polymers remained in the range of 1.23–1.75. The obtained star-comb polymers were characterized by different arm lengths. Unreacted hydroxyl groups in the core of exemplary star-comb polymers were utilized in the ROP of ε-caprolactone (CL) to obtain a hydrophilic mikto-arm polymer. Cloud point temperature (TCP) values of the synthesized polymers increased with arm length, indicating the polymers' reduced hydrophobicity and enhanced solvation by water. Atomic force microscopy (AFM) analysis revealed the ability of the star-comb polymers to create fractals. The study elucidates advancements in the synthesis and utilization of hydrophilic sugar-based initiators for enzymatically assisted ATRP in an aqueous solution for obtaining complex star-comb polymers in a controlled manner. [ABSTRACT FROM AUTHOR]

An efficient and convenient method for the synthesis of 1-hydroxyalkylphosphonium salts is described. Reactions were carried out at room temperature, in a short time, and without chromatography for product isolation. The properties of the obtained phosphonium salts were examined and discussed. In this paper, primary attention was paid to the stability of phosphonium salts, depending on the structure of the aldehydes used as substrates in their preparation. Other conditions such as the type of solvent, temperature, and molar ratio of the substrates were also investigated. Finally, the high reactivity of 1-hydroxyalkylphosphonium salts was demonstrated in reactions with amide-type substrates and (hetero)aromatic compounds. The developed step-by-step procedure (with the isolation of 1-hydroxyphosphonium salts) was compared to the one-pot protocol (in situ formation of such phosphonium salts). [ABSTRACT FROM AUTHOR]

A new series of multifunctional compounds displaying thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) have been developed, and their optical properties investigated. The materials are based on a twisted donor–acceptor (D–A) motif using acenaphtopyridopyrazine as the acceptor core, and various donors are used for tuning their photophysical behaviour. Time-resolved spectroscopy analysis using different matrices gives a detailed image of their photophysical properties. Solution-processed organic light-emitting diodes (OLEDs) using the new compounds as emitters gave high external quantum efficiency (EQE) of up to 15.3% in the CBP matrix. The triplet excited state of the new emitters poses an opportunity for the photochemical formation of singlet oxygen (1O2) species in solution. We demonstrate that the efficiency of 1O2 generation correlates with the ΔEST and triplet decay lifetime. The maximum 1O2 quantum efficiency obtained is ∼48% for NQPy-CBZ. [ABSTRACT FROM AUTHOR]

Fullerenes have been long investigated for application as singlet oxygen sources. Even though they possess high photosensitizing efficiency, their practical use is still limited, mostly because of insufficient absorption of visible and/or near-infrared light. This limitation can be overcome by introducing organic chromophores that absorb longer-wavelength light, either by covalent attachment to C60 or by its encapsulation in a polymeric matrix. In this work, we investigated the photosensitizing properties of the C60 molecule functionalized with organic units comprising thiophene or selenophene rings. The chemical structures of the synthesized dyads were characterized by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. The influence of the S/Se atoms and vinyl linkage between the organic unit and C60 on the absorptive and emissive properties of the dyads was investigated and correlated with their photosensitizing activity. For the latter, we used a standard chemical singlet oxygen trap. A selected dyad C60ThSe2 was also applied as a source of singlet oxygen in a model photocatalyzed synthesis of the fine chemical juglone from 1,5-dihydroxynapthalene. [ABSTRACT FROM AUTHOR]

A series of Re(I) carbonyl complexes with the 1H-imidazo[4,5-f][1,10]phenanthroline (imphen) ligand functionalized with electron-donating amine groups attached to the imidazole ring via phenylene linkages were designed to investigate the impact of remote amine substituents on the ground- and excited-state properties of [ReCl(CO)3(R-C6H4-imphen)]. The complexes [ReCl(CO)3(R-C6H4-imphen)] belong to the family of [ReCl(CO)3(diimine)] systems, but contrary to strongly related phenanthroline Re(I) carbonyl complexes with a rich history in coordination chemistry, they are really sparse. The effects of electron-rich N-donor groups in [ReCl(CO)3(R-C6H4-imphen)] were fully studied with the use of cyclic voltammetry, absorbance and emission spectroscopy, and transient absorption spectroscopy, and they were simulated by density functional theory. The attachment of electron-rich amine groups to C6H5-imphen resulted in a decrease in oxidation potentials and a noticeable bathochromic shift of the longest absorption wavelength of [ReCl(CO)3(R-C6H4-imphen)] compared with the parent compound [ReCl(CO)3(C6H5-imphen)] due to a significant destabilization of the HOMO energy level. Regarding the excited-state properties, the triplet emission red-shift of [ReCl(CO)3(R-C6H4-imphen)] induced by appended electron-rich N-donor groups was accompanied by a significant increase in excited state lifetimes, up to a 12-fold enhancement compared with the parent chromophore. The lifetime prolongation of [ReCl(CO)3(R-C6H4-imphen)] bearing amine substituents was rationalized by the population of the ligand-localized triplet state, while the solvent-dependent photoluminescence characteristics of [ReCl(CO)3(R-C6H4-imphen)] were correlated with strong hydrogen bonding interactions between the acidic imidazole NH proton and highly polar solvents. The present findings are of high importance for understanding and controlling the excited-state nature of transition metal complexes. [ABSTRACT FROM AUTHOR]