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The adjustment of the main helical scaffold in helicenes is a fundamental strategy for modulating their optical features, thereby enhancing their potential for diverse applications. This work explores the influence of helical elongation (n = 5–9) on the structural, photophysical, and chiroptical features of symmetric oxa[n]helicenes. Crystal structure analyses revealed structural variations with helical extension, impacting torsion angles, helical pitch, and packing arrangements. Through theoretical investigations using density functional theory (DFT) calculations, the impact of helical extension on aromaticity, planarity distortion, and heightened chiral stability were discussed. Photophysical features were studied through spectrophotometric analysis, with insights gained through time‐dependent DFT (TD‐DFT) calculations. Following optical resolution via chiral high‐performance liquid chromatography (HPLC), the chiroptical properties of both enantiomers of oxa[7]helicene and oxa[9]helicene were investigated. A slight variation in the main helical scaffold of oxa[n]helicenes from [7] to [9] induced an approximately three‐fold increase in dissymmetry factors with the biggest values of|glum| of oxa[9]helicene (2.2 × 10−3) compared to|glum|of oxa[7]helicene (0.8 × 10−3), findings discussed and supported by TD‐DFT calculations. [ABSTRACT FROM AUTHOR]

A series of four novel heteroleptic Cu(I) complexes, bearing bis(1H-indazol-1-yl)methane analogues as N,N ligands and DPEPhos as the P,P ligand, were synthesised in high yields under mild conditions and characterised by spectroscopic and spectrometric techniques. In addition, the position of the carboxymethyl substituent in the complexes and its effect on the electrochemical and photophysical behaviour was evaluated. As expected, the homoleptic copper (I) complexes with the N,N ligands showed air instability. In contrast, the obtained heteroleptic complexes were air- and water-stable in solid and solution. All complexes displayed green-yellow luminescence in CH2Cl2 at room temperature due to ligand-centred (LC) phosphorescence in the case of the Cu(I) complex with an unsubstituted N,N ligand and metal-to-ligand charge transfer (MLCT) phosphorescence for the carboxymethyl-substituted complexes. Interestingly, proper substitution of the bis(1H-indazol-1-yl)methane ligand enabled the achievement of a remarkable luminescent yield (2.5%) in solution, showcasing the great potential of this novel class of copper(I) complexes for potential applications in luminescent devices and/or photocatalysis. [ABSTRACT FROM AUTHOR]

In this paper, several Ir (III) complexes with transition metal as the central atom formed by the corresponding combination of two main ligands and three auxiliary ligands have been studied theoretically. The electronic structure, frontier molecular orbital, and spin orbit coupling data are used to analyze its application value in light emitting devices. The density functional theory is used to study (tbi)2Ir(bpp), (tbi‐c)2Ir(bpp), (tbi)2Ir(dbm), (tbi‐c)2Ir(dbm), (tbi)2Ir(pic), and (tbi‐c)2Ir(pic). bpp = (2Z)‐3‐hydroxy‐13‐diphenylprop‐2‐en‐1‐one; dbm = 1,3‐di‐phenyl‐1, 3‐propanedione; pic = picolinate. [ABSTRACT FROM AUTHOR]

Graphene derivatives such as reduced graphene oxide and graphene-based composites are regarded as highly promising materials for optoelectronics and photodetection applications. Recently, considerable interest has arisen in using facile and environmentally friendly methods of graphene production. Despite significant progress in experimental studies of graphene and graphene-based composites, some fundamental questions about their structures, and the interaction between components in these systems, remain open. In the present work, several atomistic models of oxidized graphene fragments have been proposed based on XPS compositional analysis and DFT calculations, representing reduced graphene oxide produced by laser irradiation. The composition of the oxygen-containing functional groups, their equilibrium configuration and influence on the electronic and optical properties of graphene sheets were determined. The nature of the low-lying excited states, as well as the photoactive regions, has also been studied for the proposed models. The calculated absorption spectra of the graphene sheets were compared with experimental UV-Vis spectrum of rGO produced by laser ablation. [ABSTRACT FROM AUTHOR]

A series of four novel heteroleptic Cu(I) complexes, bearing bis(1H-indazol-1-yl)methane analogues as N,N ligands and DPEPhos as the P,P ligand, were synthesised in high yields under mild conditions and characterised by spectroscopic and spectrometric techniques. In addition, the position of the carboxymethyl substituent in the complexes and its effect on the electrochemical and photophysical behaviour was evaluated. As expected, the homoleptic copper (I) complexes with the N,N ligands showed air instability. In contrast, the obtained heteroleptic complexes were air- and water-stable in solid and solution. All complexes displayed green-yellow luminescence in CH2Cl2 at room temperature due to ligand-centred (LC) phosphorescence in the case of the Cu(I) complex with an unsubstituted N,N ligand and metal-to-ligand charge transfer (MLCT) phosphorescence for the carboxymethyl-substituted complexes. Interestingly, proper substitution of the bis(1H-indazol-1-yl)methane ligand enabled the achievement of a remarkable luminescent yield (2.5%) in solution, showcasing the great potential of this novel class of copper(I) complexes for potential applications in luminescent devices and/or photocatalysis.

Molecular solar‐thermal systems (MOST) have emerged in these last years as a novel concept to store solar light. They rely on two state molecular switches that can absorb a photon to convert the initial state A to a higher‐in‐energy state B. The chemical energy stored by B can be then released to reconstitute A. Although simple in its principle, an optimal MOST needs to satisfy several requirements: incoming photon energy in the solar spectrum range, high photoreaction quantum yield, high storage density, no degradation. The first challenge is therefore the search for molecular switches that accomplish all such properties. Until now, trial‐and‐error experiments have been performed, led by physicochemical intuition. The result is that most of the initially proposed switches have been abandoned in favor of the preferred norbornadiene/quadricyclane system, together with its derivatives. Nevertheless, most of the solar spectrum is still out of the MOST absorption region, hence requiring novel approaches. Here, it is shown how mechanochemistry can be applied to improve the principally desired characteristics of a MOST: photon absorption energy, storage energy, and thermal B‐to‐A energy barrier. It is especially shown how azobenzene—a paradigmatic photoswitch still attracting much attention—can be proposed, within certain limits, as a MOST when applying external forces. [ABSTRACT FROM AUTHOR]

Graphene derivatives such as reduced graphene oxide and graphene-based composites are regarded as highly promising materials for optoelectronics and photodetection applications. Recently, considerable interest has arisen in using facile and environmentally friendly methods of graphene production. Despite significant progress in experimental studies of graphene and graphene-based composites, some fundamental questions about their structures, and the interaction between components in these systems, remain open. In the present work, several atomistic models of oxidized graphene fragments have been proposed based on XPS compositional analysis and DFT calculations, representing reduced graphene oxide produced by laser irradiation. The composition of the oxygen-containing functional groups, their equilibrium configuration and influence on the electronic and optical properties of graphene sheets were determined. The nature of the low-lying excited states, as well as the photoactive regions, has also been studied for the proposed models. The calculated absorption spectra of the graphene sheets were compared with experimental UV-Vis spectrum of rGO produced by laser ablation.

The UV–visible spectra of a series of subphthalocyanines (SubPcs) characterized by three different axial substituents (An) in combination with H, F, NO2, SO2H and SO2CH3 peripheral substituents (Ri) were predicted and analyzed by means of time-dependent DFT calculations, including chloroform as a solvent. In this analysis, we paid particular attention to the Q band, which remained almost unchanged regardless of the nature of the axial substituent. For the same axial substituent, changes in the Q band were also rather small when hydrogens at the periphery were replaced by R1 = SO2H and R1 = R2 = SO2H. However, the shifting of the Q band was almost 10 times larger when R1 = NO2 and R1 = R2 = NO2 due to the participation of this substituent in the π SubPc cloud. In most cases, the characteristics of the spectra can be explained considering only the transitions involving the HOMO-1, HOMO, LUMO and LUMO + 1 orbitals, where the Q band can be decomposed into two main contributions, leading to charge separation. Only for SubPc(A3,F,F,H) would one of the two contributions from the deepest orbital involved not lead to charge transfer. For this latter case, the HOMO-2 orbital must also be taken into account. In summary, the results obtained with the analysis of the MO indicate that the studied SubPcs are appropriate for photochemical devices.

[Display omitted] • Dimethylacridan and phenothiazine-5,5-dioxide-based compounds were synthesized. • Media polarity influenced emission properties ranging from LE to HLCT and CT. • Para -isomer demonstrated more efficient triplet harvesting in OLEDs than the meta -one. Aiming to combine the advantages of both prompt fluorescence and thermally activated delayed fluorescence in single emitter, molecular design of emitters with hybridized locally excited and charge transfer states were investigated by computational approaches and optical spectroscopy. Taking into account the results of the theoretical screening, the most promising derivatives of 9,9-dimethyl-9,10-dihydroacridine and 10-phenyl-10 H -phenothiazine-5,5-dioxide based with the different linking topology (meta - and para -isomers) were selected for the synthesis and experimental investigations. Both the compounds exhibit ultraviolet LE emission peaking at ca. 360 nm, green ICT peaking at ca. 510 nm, and deep-blue HLCT emission peaking at ca. 430 nm when they are molecularly dispersed in the solid media of the different polarity. The developed emitters allow to obtain deep-blue electroluminescence for the host-containing OLEDs and green electroluminescence of host-free devices with the efficiency of exciton production of 42 and 73%, respectively. Efficient exciton production is due to the spin-flip switching via thermally activated processes which is much more efficient than prompt fluorescence. Showing the impact of the linking topology, the para -isomer demonstrated more efficient triplet harvesting in OLEDs than meta -isomer. A detailed discussion on the structure–property relationships and on some discrepancies between the results of the results of theoretical calculations and spectral analysis allows to obtain important insights on the photophysical properties of these compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydration structure of caffeine diluted in ambient liquid water has been studied using classical MD simulations. • The results obtained have revealed that the first hydration shell of caffeine contains on average 56 water molecules. • Hydrated caffeine forms in total 3 hydrogen bonds with its neighbor water molecules. • The water molecules within the first hydration shell of caffeine significantly change their translational and reorientational dynamics relative to the bulk. • Quantum chemical calculations have predicted the UV–Vis and fluorescence spectra of hydrated caffeine, in agreement with recent experimental data. The hydration structure and related dynamics of caffeine diluted in ambient liquid water have been extensively studied by performing classical molecular dynamics simulations, using our previously developed potential model of caffeine and the TIP4P/2005 water model. The results obtained have revealed that the first hydration shell of caffeine contains on average 56 water molecules. Hydrated caffeine forms in total 3 hydrogen bonds with its neighbor water molecules, with the O caffeine ... H water hydrogen bonds exhibiting similar lifetimes with the ones corresponding to O water ... H water hydrogen bonds in liquid water. The self-diffusion coefficient of caffeine has been found to be four times lower than the corresponding value for water, being also in agreement with recent experimental measurements. The presence of water molecules inside the solvation shell of caffeine changes significantly their low-frequency intermolecular vibrations, as reflected on the calculated atomic velocity time correlation functions and corresponding spectral densities. Using the estimated average intermolecular structure of the first hydration shell of caffeine, the molecular cluster caffeine@W 56 was optimized via quantum chemical calculations and subsequently the time-dependent density functional theory was used in order to predict the ultraviolet–visible and fluorescence spectra of hydrated caffeine. The results obtained are in agreement with recent experimental studies, which have proposed that such spectroscopic measurements can be used for the direct determination of alkaloids in aqueous extracts of natural products. In this framework, multi-scale molecular modelling providing accurate predictions of experimental data could also be a very useful tool, linking theoretical physical chemistry with analytical chemistry applications. [ABSTRACT FROM AUTHOR]

A series of four novel heteroleptic Cu(I) complexes, bearing bis(1 H -indazol-1-yl)methane analogues as N , N ligands and DPEPhos as the P,P ligand, were synthesised in high yields under mild conditions and characterised by spectroscopic and spectrometric techniques. In addition, the position of the carboxymethyl substituent in the complexes and its effect on the electrochemical and photophysical behaviour was evaluated. As expected, the homoleptic copper (I) complexes with the N , N ligands showed air instability. In contrast, the obtained heteroleptic complexes were air- and water-stable in solid and solution. All complexes displayed green-yellow luminescence in CH 2 Cl 2 at room temperature due to ligand-centred (LC) phosphorescence in the case of the Cu(I) complex with an unsubstituted N,N ligand and metal-to-ligand charge transfer (MLCT) phosphorescence for the carboxymethyl-substituted complexes. Interestingly, proper substitution of the bis(1 H -indazol-1-yl)methane ligand enabled the achievement of a remarkable luminescent yield (2.5%) in solution, showcasing the great potential of this novel class of copper(I) complexes for potential applications in luminescent devices and/or photocatalysis.

Organic-based photovoltaic devices emerged as a complementary technology to silicon solar cells with specific advantages in terms of cost, ease of deployment, semi-transparency, and performance under low and diffuse light conditions. In this work, thin-film boron-doped diamond (B:NCD) electrodes are employed for their useful optical, electronic, and chemical properties, as well as stability and environmental safety. A set of oligothiophene perylene diimide (nT-PDI) donor-acceptor chromophores is designed and synthesized in order to investigate the influence of the oligothiophene spacer length when the nT-PDI molecule is attached to a B:NCD electrode. The chromophores are anchored to the diamond surface via diazonium grafting followed by Sonogashira cross-coupling. X-ray photoelectron spectroscopy shows that the surface coverage decreases with increasing oligothiophene length. Density functional theory (DFT/TDDFT) calculations reveal the upright nT-PDI orientation and the most efficient photogenerated charge separation and injection to diamond for elongated oligothiophene chains (8T-PDI). Yet, the maximum photovoltage is obtained for an intermediate oligothiophene length (3T-PDI), providing an optimum between decreasing transport efficiency and increasing efficiency of charge separation and reduced recombination with increasing oligothiophene length. Holes transferred from nT-PDI to diamond persist there even after the illumination is switched off. Such features may be beneficial for application in solar cells. [Display omitted] • Variable donor-acceptor chromophore/diamond system designed in-silico and fabricated. • Oligothiophene donor length adjusts valence band and charge transport with diamond. • Intermediate oligothiophene length (3 units) yields the maximum photovoltage. • Up to 0.87 electron per molecule transferred to diamond across 44 Å under excitation. [ABSTRACT FROM AUTHOR]

The UV–visible spectra of a series of subphthalocyanines (SubPcs) characterized by three different axial substituents (An) in combination with H, F, NO2, SO2H and SO2CH3 peripheral substituents (Ri) were predicted and analyzed by means of time-dependent DFT calculations, including chloroform as a solvent. In this analysis, we paid particular attention to the Q band, which remained almost unchanged regardless of the nature of the axial substituent. For the same axial substituent, changes in the Q band were also rather small when hydrogens at the periphery were replaced by R1 = SO2H and R1 = R2 = SO2H. However, the shifting of the Q band was almost 10 times larger when R1 = NO2 and R1 = R2 = NO2 due to the participation of this substituent in the π SubPc cloud. In most cases, the characteristics of the spectra can be explained considering only the transitions involving the HOMO-1, HOMO, LUMO and LUMO + 1 orbitals, where the Q band can be decomposed into two main contributions, leading to charge separation. Only for SubPc(A3,F,F,H) would one of the two contributions from the deepest orbital involved not lead to charge transfer. For this latter case, the HOMO-2 orbital must also be taken into account. In summary, the results obtained with the analysis of the MO indicate that the studied SubPcs are appropriate for photochemical devices. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) applications carried out with the assistance of ultrasound have attracted significant attention in recent years. The use of phthalocyanines, which are an important component as photosensitizers in PDT, is becoming more important day by day. In therapeutic applications, phthalocyanines can promote the production of reactive oxygen species. Motivated by this fact, the syntheses of metal-free ( 2 ), gallium ( 3 ), and indium ( 4 ) phthalocyanines have been achieved by substituting 4-(cinnamyloxy)phthalonitrile for the first time to evaluate their therapeutic applications. Additionally, photophysicochemical, sonophotochemical, and in vitro evaluations of phthalocyanines have been reported. To the best of our knowledge, this is the first study of the use of phthalocyanines with different metal ions as potential photosensitizers for sonophotodynamic therapy (SPDT) applications in gastric cancer cell lines. The results show that the quantum yield of the generation of singlet oxygen increased in sonophotochemical studies (Φ Δ = 0.55 ( 2 ), 0.85 ( 3 ), 0.96 ( 4 )), compared to photochemical studies (Φ Δ = 0.22 ( 2 ), 0.61 ( 3 ), 0.78 ( 4 )). The density functional theory (DFT) results are in good agreement with the experimental results and suggest increased reactivity of phthalocyanines 3 and 4 in various redox processes, thus implying their applicability and usefulness as potential therapeutic agents. These phthalocyanines are effective sensitizers for PDT, sonodynamic therapy (SDT), and SPDT against MKN-28 gastric cancer cell line in vitro. All three treatments decreased cell viability and induced apoptosis in the gastric cancer cell line. However, indium phthalocyanine ( 4 )-mediated SPDT was a more effective treatment modality compared to indium phthalocyanine ( 4 )-mediated PDT and SDT. Also, indium phthalocyanine ( 4 ) was found to be a more effective sensitizer to activate apoptosis compared to the other phthalocyanines. To sum up, phthalocyanine-mediated SPDT enhances the cytotoxic effect on gastric cancer cells more than the effect of SDT or PDT alone.

Magnetic field- and polarization-dependent measurements on bright and dark excitons in monolayer WSe 2 combined with time-dependent density functional theory calculations reveal intriguing phenomena. Magnetic fields up to 25 T parallel to the WSe 2 plane lead to a partial brightening of the energetically lower lying exciton, leading to an increase of the dephasing time. Using a broadband femtosecond pulse excitation, the bright and partially allowed excitonic state can be excited simultaneously, resulting in coherent quantum beating between these states. The magnetic fields perpendicular to the WSe 2 plane energetically shift the bright and dark excitons relative to each other, resulting in the hybridization of the states at the K and K' valleys. Our experimental results are well captured by time-dependent density functional theory calculations. These observations show that magnetic fields can be used to control the coherent dephasing and coupling of the optical excitations in atomically thin semiconductors.