Chromoselective photocatalysis offers an intriguing opportunity to enable a specific reaction pathway out of a potentially possible multiplicity for a given substrate by using a sensitizer that converts the energy of incident photon into the redox potential of the corresponding magnitude. Several sensitizers possessing different discrete redox potentials (high/low) upon excitation with photons of specific wavelength (short/long) have been reported. Herein, we report design of molecular structures of two-dimensional amorphous covalent triazine-based frameworks (CTFs) possessing intraband states close to the valence band with strong red edge effect (REE). REE enables generation of a continuum of excited sites characterized by their own redox potentials, with the magnitude proportional to the wavelength of incident photons. Separation of charge carriers in such materials depends strongly on the wavelength of incident light and is the primary parameter that defines efficacy of the materials in photocatalytic bromination of electron rich aromatic compounds. In dual Ni-photocatalysis, excitation of electrons from the intraband states to the conduction band of the CTF with 625 nm photons enables selective formation of C‒N cross-coupling products from arylhalides and pyrrolidine, while an undesirable dehalogenation process is completely suppressed.

We report on the convenient synthesis of a CNC pincer ligand com¬po-sed of car¬ba¬zole and two mesoionic carbenes, as well as the corresponding lithium- and magnesium complexes. Mono-deprotonation affords a...

Among external stimuli used to promote a chemical reaction, photocatalysis possesses a unique one—light. Photons are traceless reagents that provide an exclusive opportunity to alter chemoselectivity of the photocatalytic reaction varying the color of incident light. This strategy may be implemented by using a sensitizer capable to activate a specific reaction pathway depending on the excitation light. Herein, we use potassium poly(heptazine imide) (K‐PHI), a type of carbon nitride, to generate selectively three different products from S‐arylthioacetates simply varying the excitation light and otherwise identical conditions. Namely, arylchlorides are produced under UV/purple, sulfonyl chlorides with blue/white, and diaryldisulfides at green to red light. A combination of the negatively charged polyanion, highly positive potential of the valence band, presence of intraband states, ability to sensitize singlet oxygen, and multi‐electron transfer is shown to enable this chromoselective conversion of thioacetates.

In photocatalysis,s mall organic molecules are converted into desired products using light responsive materials,e lectromagnetic radiation, and electron mediators.S ubstitution of low molecular weight reagents with redox active functional materials mayi ncrease the utility of photocatalysis beyond organic synthesis and environmental applications. Guided by the general principles of photocatalysis,w ed esign hybrid nanocomposites composed of n-type semiconducting potassium poly(heptazine imide) (K-PHI), and p-type conducting poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the redoxa ctive substrate.E lectrical conductivity of the hybrid nanocomposite,p ossessing optimal K-PHI content, is reversibly modulated combining as eries of external stimuli ranging from visible light under inert conditions and to dark conditions under an O 2 atmosphere.Using aconductive polymer as the redoxactive substrate allows study of the photocatalytic processes mediated by semiconducting photocatalysts through electrical conductivity measurements.

We report the fully fledged photophysical characterization of isomerically pure, empty-caged, tubular fullerenes D 5h -C 90 and D 5d -C 100 and compare their key properties. In particular, the focus was on cage sizes between 60 and 150 carbon atoms with D 3 , D 3d/h , and D 5d/h symmetry. The optical band gap of D 5d -C 100 is 1.65 eV, which is larger than 1.37 eV of D 5h -C 90 . In stark contrast to the nonluminescent D 5h -C 90 , D 5d -C 100 luminesces at room temperature. Transient absorption spectroscopy shows that photoexcited D 5d -C 100 is subject to a slow intersystem crossing that generates a triplet excited state. In contrast, a fast, nonradiative internal conversion governs the deactivation of D 5h -C 90 : In this case, exploring the corresponding triplet excited state required triplet−triplet sensitization experiments with anthracene. Density functional theory calculations revealed the electronic structure of the fullertubes, and calculations are consistent with our experimental findings. The calculated band gap systematically decreases with the number of carbon atoms within the D 3 and D 3d/h series. In contrast, an oscillating behavior is noted within the series of D 5d/h fullertubes. Finally, photoexcited D 5d -C 100 was found to undergo hole transfer with electron-donating triethylamines readily but not electron transfer with electron-accepting methyl viologens.

Deriving diverse compound libraries from a single substrate in high yields remains to be a challenge in cycloparaphenylene chemistry. In here, a strategy for the late-stage functionalization of shape-persistent alkyne-containing cycloparaphenylene has been explored using readily available azides. The copper-free [3 + 2]azide-alkyne cycloaddition provided high yields (> 90 %) in a single reaction step. Systematic variation of the azides from electron-rich to -deficient shines light on how peripheral substitution influences the characteristics of the resulting adducts. We find that among the most affected properties are the molecular shape, the oxidation potential, excited state features, and affinities towards different fullerenes. Joint experimental and theoretical results are presented including calculations with the state-of-the-art, artificial intelligence-enhanced quantum mechanical method 1 (AIQM1).

Epitaxial growth methods usually need dedicated equipment, high energy consumption to maintain pure vacuum conditions and evaporation of source materials, and elevated substrate temperatures. Solution epitaxial growth requires nothing of that but is rarely used because the achieved microstructures are of low quality, not homogeneous, and finally exhibit worse performances in devices. Here, an antisolvent‐vapor‐assisted‐crystallization of metal‐halide‐perovskites as a method overcoming these disadvantages is demonstrated. The methylammonium lead tribromide exhibits van‐der‐Waals type of epitaxial growth on mica substrates, resulting in micro‐crystallites whose shape can be controlled to be either triangular micro‐prism or micro‐cuboid. These micro‐crystallites act as optical resonators supporting various optical modes and lasing is achieved under optical excitation with low thresholds and record high environmental stability. Selecting suitable resonators from a large variety of sizes allows control of mode spacing and finally mono‐mode operation, considered to be an important feature of semiconductor laser devices. The achieved results are essentially competitive to those obtained by vapor phase epitaxial microstructures, highlighting that epitaxy of high‐quality optoelectronic device structures is feasible by minimum technological efforts and energy consumption, which are of increasing importance considering issues such as global warming and the current energy crisis.

success of epitaxial growth of conventional inorganic semiconductors for (opto) electronics, there are various attempts to obtain single-crystalline structures by the epitaxial growth of metal halide perovskites (MHPs), as promising materials for optoelectronic applications. While most attempts have been pursued by some ways of chemical vapor deposition (CVD) on various substrates and also by molecular beam epitaxy, [1][2][3][4][5][6][7][8] albeit with elaborate equipment, the advantages of the MHPs are enrolled by solution processing them. Solution epitaxy is an inexpensive and facile approach to obtain high-quality films and microstructures. Simple techniques such as spin coating delivered already epitaxial crystalline films operating as highly sensitive photodetectors. [9] Thereafter, spin coating was introduced by Kelso et al., as a general technique for the epitaxial growth of inorganic High-quality epitaxial growth of oriented microcrystallites on a semiconductor substrate is demonstrated here for formamidinium lead bromide perovskite, by drop casting of precursor solutions in air. The microcrystallites exhibit green photoluminescence at room temperature, as well as lasing with low thresholds. Lasing is observed even though the substrate is fully opaque at the lasing wavelengths, and even though it has a higher refractive index as the perovskite active material. Moreover, the lasing is stable for more than 10 9 excitation pulses, which is more than what is previously achieved for devices kept in the air. Such highly stable lasing under pulsed excitation represents an important step towards continuous mode operation or even electrical excitation in future perovskite-based devices.