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Ionic liquids (ILs) have attracted increasing attention since last few decades due to their high molecular design abilities and wide applications in different fields. In this study, four novel fluorescent isoquinolino [2,1-a]quinoxalin-5-ium ILs were designed and synthesized via a two-step process including a simple dual Schiff's base formation and a subsequent [RhCp∗Cl2]2-catalyzed oxidative C–H activation/annulation reaction. The as-synthesized ILs were extensively characterized using FT-IR, 1H-NMR, 13C-NMR, 19F-NMR, HSQC-NMR, HMBC-NMR and HR-MS. Their photophysical properties were determined by steady-state fluorescence spectroscopy. The results demonstrate that all these ILs showed dual or triple emissions, large stokes shift (90 nm) and mechanochromic behaviors. Basing on solvatochromism and titration experiments, it is thought that the emission bands of the ILs are raised from their local excited states, charge transfer states or excited state proton transfer of cations, while the substitute effect of these quinoxaline derived ILs on their stokes shifts is negligible.

Several 2D nanosheets of porphyrin MOFs with various transition-metal clusters as metal nodes were prepared via a simple solvothermal method to apply in the photocatalytic hydrogen evolution, in which the hydrogen production rate of the optimal NS-Cu was as high as 15.39 mmol•g−1•h−1. A series of experimental technologies especially cyclic voltammetry (CV) and Mott-Schottky (M-S) had been adopted to investigate the charge-transfer property of photo-generated electron-hole pairs, it was found that the uniformly dispersed Cu-clusters nodes in the original 2D MOFs played a key role in the electron transfer process, that was, the photo-generated electron transferred from excited state eosin-Y to the Cu-clusters nodes for the efficient hydrogen evolution. The excellent photocatalytic performance could be attributed to the reversible oxidation-reduction process of CuII/CuI, which had excellent electron-receiving and electron-outputting capabilities. Our results provided a novel avenue to adapt the uniformly dispersed metal nodes in the original MOFs as cost-effective noble-metal-free cocatalysts with very high atom-utilization efficiency to improve the photocatalytic hydrogen evolution performance in dye-sensitized system.

Upconversion nanosensitizers have been widely considered to have important applications in the treatment of major diseases such as tumors and the utilization of solar energy. Majority of the efforts so far have been focused on improving the efficiency of energy transfer (ET) between upconversion nanoparticles (UCNPs) and the anchored sensitizers with premise that high ET efficiency will lead to high acceptor efficacy. This premise is, however, proved by our current work to be invalid for commonly used load. Interaction between adjacent sensitizing molecules was found to be critical which undermines the amount of excited monomer sensitizers and thus fades the efficacy. Here NaYF4:Yb3+,Er3+ UCNPs and rose bengal (RB) photosensitizer molecules were used as the model energy donors and acceptors, respectively. Contrary to monotonous increase of the ET efficiency from UCNPs to RB species with increasing RB loading, acceptor efficacy characterized by the reactive oxygen species, as well as the RB fluorescence, exhibits bizarre dependence on the RB loading. The underlying mechanism was well studied by the steady-state and time-resolved spectroscopy of a series of samples. RB aggregates are believed to be responsible for the severe deviation between the ET efficiency and acceptor efficacy. The conclusion was validated by in vitro test where the photodynamic therapy with the most monomer RB in UCNPs-RB nanosensitizers kills 35.8% more cells than that with the highest RB loading. This understanding sheds light on construction of new ET based nanosystems for broad applications, such as medicine, solar energy utilization and optical storage.

Luminescent metal–organic frameworks (MOFs) are of interest for sensing, theranostics, dosimetry, and other applications. The use of lanthanoids in MOF metal nodes allows for intrinsic met-al-based luminescence. In this work, a facile route for modulat-ing the photoluminescent and radioluminescent properties of Tb(III)-based MOFs is reported. By using Tb(III)-cluster nodes as X-ray attenuators, and organic linkers with varying excited state energies as sensitizers, MOFs with metal-based, linker-based, and metal+linker-based photo- and radioluminescence are reported.

Here, we report a finding on light-mediated CO2-responsiveness. It is found on the microgels that are made of side-chain type metallopolymers containing metalla-aromatics. Turbidity and laser light scattering studies on dilute aqueous dispersion of these microgels in dark indicate high CO2-responsivity, but poor reversibility upon N2 purge, which can be improved by exposing to light. This light-mediated CO2-responsiveness can be elucidated by the loss of aromaticity from initial photoexcitation and concurrent formation of a less reactive, antiaromatic excited state of relatively low CO2 binding affinity, and by subsequent relief of antiaromaticity that can enhance the CO2 removal. The finding is also checked by CO2 uptake-release experiments on the microgels, which enables both CO2 capture of high capacity and CO2 removal of good reversibility under a mild condition, allowing effective and reversible response to dilute CO2.

Preliminary explorations of the annihilation electrogenerated chemiluminescence (ECL) of mixed metal complexes have revealed opportunities to enhance emission intensities and control the relative intensities from multiple luminophores through the applied potentials. However, the mechanisms of these systems are only poorly understood. Herein, we present a comprehensive characterisation of the annihilation ECL of mixtures of tris(2,2'-bipyridine) ruthenium(II) hexafluorophosphate ([Ru(bpy)(3)](PF6)(2)) and fac-tris(2-phenylpyridine)iridium(III) ([Ir(ppy)(3)]). This includes a detailed investigation of the change in emission intensity from each luminophore as a function of both the applied electrochemical potentials and the relative concentrations of the two complexes, and a direct comparison with two mixed (Ru/Ir) ECL systems for which emission from only the ruthenium-complex was previously reported. Concomitant emission from both luminophores was observed in all three systems, but only when: (1) the applied potentials were sufficient to generate the intermediates required to form the electronically excited state of both complexes; and (2) the concentration of the iridium complex (relative to the ruthenium complex) was sufficient to overcome quenching processes. Both enhancement and quenching of the ECL of the ruthenium complex was observed, depending on the experimental conditions. The observations were rationalised through several complementary mechanisms, including resonance energy transfer and various energetically favourable electron-transfer pathways. Refereed/Peer-reviewed

We investigate the long-range, two-body interactions between rubidium and potassium atoms in highly excited ($n=70$) Rydberg states. After establishing properly symmetrized asymptotic basis states, we diagonalize an interaction Hamiltonian consisting of the standard Coulombic potential expansion and atomic fine structure to calculate electronic potential energy curves. We find that when both atoms are excited to either the $70s$ state or the $70p$ state, both the $\Omega=0+$ symmetry interactions and the $\Omega=0-$ symmetry interactions demonstrate a deep potential well capable of supporting many bound levels; the size of the corresponding dimer states are on the order of 2.25 $\mu$m. We estabish $n$-scaling relations for the equilibrium separation $R_e$ and the dissociation energy $D_e$ and find these relations to be consistent with similar calculations involving the homonuclear interactions between rubidium and cesium. We discuss the specific effects of $\ell$-mixing and the exact composition of the calculated potential well \textit{via} the expansion coefficients of the asymptotic basis states. Finally, we apply a Landau-Zener treatment to show that the dimer states are stable with respect to predissociation., Comment: 8 pages, 4 figures, 4 tables

Recent developments in quantum hardware and quantum algorithms have made it possible to utilize the capabilities of current noisy intermediate-scale quantum devices for addressing problems in quantum chemistry and condensed matter physics. Here we report a demonstration of solving the dynamical mean-field theory (DMFT) impurity problem for the Hubbard-Holstein model on the IBM 27-qubit Quantum Falcon Processor Kawasaki, including self-consistency of the DMFT equations. This opens up the possibility to investigate strongly correlated electron systems coupled to bosonic degrees of freedom and impurity problems with frequency-dependent interactions. The problem involves both fermionic and bosonic degrees of freedom to be encoded on the quantum device, which we solve using a recently proposed Krylov variational quantum algorithm to obtain the impurity Green's function. We find the resulting spectral function to be in good agreement with the exact result, exhibiting both correlation and plasmonic satellites and significantly surpassing the accuracy of standard Trotter-expansion approaches. Our results provide an essential building block to study electronic correlations and plasmonic excitations on future quantum computers with modern ab initio techniques.

It is of great significance to understand the role of carrier in piezocatalysis of composites by studying the separation mode of carriers under dynamic polarization field. Herein, the separation and migration pathways of carriers under piezoelectric field are investigated by synthesizing heterojunctions with Bi2WO6 (BWO) nanosheets grown vertically on g-C3N4 (CN) coated ZnO nanorods and directly on ZnO. Compared with the photocatalysis, the piezocatalytic efficiency of Rhodamine B (RhB) by BWO/ZnO is significantly increased to 0.121 min−1, which indicated the polarization field promotes band tilt and Z-scheme formation. After introducing the CN interlayer, the piezocatalytic efficiency of BWO/CN/ZnO is further improved (0.217 min−1), which can be attributed to the unique core–shell structure with Z-scheme heterojunctions. This unique structure provides more active sites and excited carrier concentration, the intermediate layer CN also reduces the direct contact and recombination of electrons and holes controlled by polarization potential at the interface between BWO and ZnO. This work deeply analyzes the influence of carrier concentration, separation efficiency and transport process on piezocatalysis, which provides a reference for the design of efficient catalysts.

Naphthalene diimides (NDIs) are a promising material for n-type polymer acceptors in thin-film devices such as organic light-emitting diodes. The intersystem crossing (ISC) pathway of NDIs has been...

Herein we demonstrate the synthesis and investigation of organic D-A type fluorophores, named Np-TPA and Np-2TPA, comprising of twisted triphenylamine (TPA) as electron-donor and planar 1,8-naphthalenimide (Np) as electron-acceptor. These fluorophores emit strong fluorescence not only in dilute solutions but also in the solid state with quantum yields up to 0.74 and 0.92, respectively. From theoretical and structural analysis, the conformation planarization of Np-TPA and Np-2TPA in the excited state could effectively diminish the molecular motions thus allowing intense emission in solution, while highly restricted π-π stacking permits their bright emission in crystalline state. Efficient yellow bioimaging in the cytoplasm of multiple of various cells can be achieved after the incubation with even extremely low concentrations of Np-2TPA (about 30 nM). All the results imply that the dual-state emissive fluorophore represents a new paradigm for bioimaging.

A direct boost the emission efficiency is presented based on the strategy of link multiple weak AIE-active anthracenyl-o-carborane dyad together for improving solid-state luminescence. Multiple anthracenyl-o-carborane dyad, linked with benzyl (CA1), 1,3-bismethyl-benzene (CA2), 1,3,5-trismethyl-benzene (CA3), were prepared and fully characterized, and compared their optical properties. Various types of substituent groups at the adjacent carbon atom of o-carborane can restrict vibration of Ccage–Ccage bonds and rotational motion of the o-carborane moiety and regulate the orientation of ICT from the electron-donating moiety to the o-carborane cluster. CA1, CA2 and CA3 are all AIE-active molecules. The emission efficiencies of CA1, CA2 and CA3 were 8- to 16-fold greater than that of anthracenyl-o-carborane dyad (F = 4.3%) in solid state, clearly indicating that the combination of multiple anthracenyl-o-carborane dyads should be valid for enhancing luminous efficiency. DFT calculations on the structures of excited state suggested that the ICT emission is via the twisted intramolecular charge transfer (TICT) mechanism in the multi-linked anthracenyl-o-carborane dyads.

Conjugated molecular thin films have potential for novel optoelectronic devices such as flexible solar cells and display devices. However, a detailed understanding of their excited state dynamics is crucial for their technological applications. Tetrapyrrole complexes are an important class of conjugated organic molecules for optoelectronic applications due to their high light gathering ability and thermal stability. In this review, we summarize excited state dynamics of porphyrin and phthalocyanine molecular thin films investigated by pump–probe techniques. The relaxation dynamics for metallo-phthalocyanine molecules are observed to be ultrafast in nature and are in femtosecond time scale while that for metal free phthalocyanine are moderately fast. In case of metallo-phthalocyanines exciton lifetime is much longer than for metal free phthalocyanines. The central metal atom plays an important role in the excited state dynamics of porphyrin molecular thin films thus providing additional excitation channels. Time-resolved photoemission spectroscopy reveals about the evolution of charge transfer excitons at donor–acceptor interfaces and their dissociation mechanism. In case of metallo-phthalocyanines the exciton transport is dominated by hopping mechanism rather than spatial coherent length of excitons. The pump–probe studies provide a basis for appropriate selection of molecules for technological applications.

Two series of cyclometalated PtII and IrIII complexes with general formula [Pt(pbt){PPh2(R)-P,O)}] (2a-2c) and [Ir(pbt)2{PPh2(R)-P,O)}] (3a-3c), where Hpbt is 2-phenylbenzothiazol and PPh2(R) is a diphenylphosphino donor functionalized deprotonated based acid (R = o-C6H4CO2 a, o-C6H4SO3 b, CH2CH2CO2 c) are presented. The structures of 1, 2a-2c, 3a and 3b were confirmed by single X-ray diffraction analyses, and the intermolecular interactions in 2a were studied using Hirshfeld surface analysis and Non Covalent Interaction (NCI) methods on its X-ray structure. Their photophysical properties were investigated by absorption and emission [CH2Cl2, solid (298, 77 K) and doped polystyrene (PS) films], supported by TD-DFT calculations on 1, 2a-2c and 3a. The PtII complexes exhibit bright phosphorescence in the region 525-543 nm, adscribed to a mixed 3IL/3MLCT excited state with predominant 3IL contribution. The IrIII derivatives (3a-3c) show orange photoluminescence (534-584 nm, 298 K), blue shifted at 77 K (527-560 nm), originated from admixture of 3IL/3MLCT/3LLCT excited states. Interestingly, the photoluminescence quantum yields of the Pt complexes 2a-2c ( = 46.5-66.5%) in PS films are remarkably higher than those of the iridium corresponding complexes ( = 17.3-32%) and the precursor 1 ( = 17%). The calculated 3MC-3IL/3MLCT energy gap for 2a and 3a accounts for the higher quantum yield of the Pt in relation to the Ir complexes.

Carbon dots (CDs) are the unique class of luminescent nanomaterials consist of various chromophoric units heterogeneously distributed throughout the nanoparticle, resulting intriguing multistate emissive properties. Herein, we have critically investigated the specific locations of the blue and green-emitting centers inside dual emissive CDs by steady-state and time-resolved polarized emission study. It is further clarified by a temperature-dependent fluorescence study for both the emitting domains. Results suggest that the blue chromophoric units are located at the interior part of CDs, while green units are mostly at the exterior region. Furthermore, we have investigated the solvent-dependent inter-chromophoric interactions between the two emissive domains by the Time-Resolved Area Normalized Emission Spectroscopy (TRANES). Results suggest that at polar aprotic solvent acetone, time-dependent positive evolution of green-emitting states and negative evolution of blue emissive domains have been observed. This reversible emitting properties evolve due to the excited state energy migration from blue emissive domains to green emissive domains at polar aprotic medium, while in the case of polar protic solvent water, this phenomenon is missing. This switchable inter-chromophoric interaction are correlated further with the inter-particle interactions of CDs.

International audience; Three room-temperature metallomesogens based on Zn(II) cations pentacoordinated by different chelating N^N^N terpyridines and two monodentate gallate co-ligands were designed and synthesized. Depending on the terpyridine ligand's tip functionality, the complexes self-assemble into either a 3D hexagonal mesophase or into a columnar hexagonal mesophase. A systematic study between the structure (molecular architecture, arrangement of the molecules and columns, and chains in both types of mesophases) and photophysical properties (emission maxima and yields, lifetimes of the excited states in the mesophase), correlated with investigations of single molecules in solution, was conducted. Remarkably, one complex exhibited a record quantum yield of 95.0% in solution, while in the mesophase, despite quenching due to the radiative deactivation from the ILCT state, still retained a considerable emission yield of ϕ = 20.2%. The polarized emission of an oriented film, determined for the first time in columnar metallomesogens, shows a dichroic emission ratio (I||/I⊥) of 1.30. DFT and TDDFT computational studies confirmed the origin of the observed fluorescence anisotropy from the transition dipole moment oriented along the C2 symmetry axis of the molecule combined with a high level of order in the 3D mesophase.

In this study, a new series of zinc oxide (ZnO) with high specific surface area and narrow energy band gap are prepared using a facile microwave-induced method. The corresponding formation mechanism is also discussed for the first time. Due to the introduction of C, these ZnO can be excited by long wave temperature light without harmful short wave radiation, and play an efficient photocatalytic activity. This valuable property fundamentally improves the biological safety of its photocatalytic application. Herein, taking teeth whitening as an example, the photocatalytic performance of ZnO is evaluated. The “pure” yellow light-emitting diode (PYLED) with high biological safety is used as the excitation source. It is found that this method could effectively remove pigment on the tooth surface through physical adsorption. In addition, these ZnO could generate active oxygen to degrade the pigment on the tooth surface under the irradiation of yellow light. Some further optimization of these “warm light” responsive ZnO is also discussed in this systematical study, which could open up new opportunities in biomedical field., Graphical abstract Image 1, Highlights • A series of ZnO (PZCs, ZnO-BC) with high specific surface area and low band gap were synthesized by simple microwave-induced synthesis. • The introduction of C or BC can effectively reduce the band gap of ZnO. • Long wavelength warm light can effectively stimulate the photocatalytic activity of PZCs and ZnO-BC. • Under the yellow light, ZnO can effectively decompose the pigment on the tooth surface. • Warm light whitening, from the light source and material two levels to reduce the stimulation of teeth, and no obvious damage to enamel.

Near-infrared (NIR) fluorophores are emerging tools for biophotonics because of their reduced scattering, increased tissue penetration and low phototoxicity. However, the library of NIR fluorophores is still limited. Here, we report the NIR fluorescence of two benzene-fused oligo-BODIPYs in their hexameric (H) and octameric (O) forms. These dyes emit bright NIR fluorescence (H: maxima 943/1075 nm, O: maxima 976/1115 nm) that can be excited in the NIR (H = 921 nm, O = 956 nm) or non-resonantly over a broad range in the visible region. The emission bands of H show a bathochromic shift and peak sharpening with increasing dye concentration suggesting the presence of J-aggregates. Furthermore, the emission maxima of both H and O shift up to 20 nm in solvents of different polarity. These dyes can be used as NIR ink and imaged remotely on the macroscopic level with a stand-off distance of 20 cm. We furthermore demonstrate their versatility for biophotonics by coating microscale beads and performing microrheology via NIR video particle tracking (NIR-VPT) in biopolymer (F-actin) networks. No photodamaging of the actin filaments takes place, which is typically observed for visible fluorophores and highlights the advantages of these NIR dyes.

The nitric oxide vibrationally excited levels in the daytime are studied, at altitudes between 80 and 200 km. For that, we use a coupled 1D Boltzmann kinetic-fluid model to find density profiles of the major ions: O 2 + ; N 2 + ; NO + ; N + ; O + , nitrogen atoms: N ( 4 S ) ; N ( 2 D ) and vibrationally excited levels: NO ( v ⩽ 7 ) . A variety of processes are included in the model calculations that are neutrals chemistry, ions chemistry, photoabsorption, energetic electrons acting on the neutral atmosphere, molecular diffusion, and turbulent diffusion transport. The vibrational excitation of the nitric oxide is under strong solar control, reaching its maximum value near noon, when the solar zenith angle has the smallest value and then decreases away from noon. Data measurements of NO 5.3 μ m volume emission rate (VER) provided by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite instrument corroborate our numerical results.

The synthesis, structural characterization and photophysical properties of a series of platinum(II) complexes of benzannulated pincer-type diarylamido ligands are described. The ligands all contain tricyclic phenanthridine (3,4-benzoquinoline) rings as donor arms, which were elaborated into N∧N−∧O-coordinating β-enaminoketonato chelates via partial condensation with acetylacetone. The proligands are easily deprotonated, and metallation can be achieved under mild conditions using simple Pt(II) salts and Ag2O as a base. The resulting Pt(II) complexes exhibit strong metal-to-ligand charge-transfer absorptions in the region of ∼450–575 nm and are phosphorescent in solution at room temperature, emitting bright orange light (λmax ∼ 600 nm) with quantum yields of up to 16% and excited-state lifetimes on the order of ∼20 μs, representing significant improvements to these photophysical properties compared with many previously reported N∧N∧O or N∧N∧N-ligated systems. Computational modelling reveals that the lowest-lying triplet state is populated efficiently thanks to strong coupling between singlet and triplet excited state manifolds, as in cyclometallated compounds of Pt(II). Substituents (CH3, tBu, or CF3) in the 2-position of the phenanthridinyl unit are found to have little influence on the optical properties, but the emission is severely quenched when a methyl substituent is introduced ortho to the coordinating nitrogen. Molecular distortions in the excited state are shown to be primarily responsible for the quenching in this complex.

Until recently, the many classes of non-fullerene acceptor (NFA) molecules and polymers exhibited lower power conversion efficiencies than polymer:fullerene counterparts in organic photovoltaic (OPV) cells. We sought to understand the shortcomings of such NFAs, and provide insights for material design in the new era of efficient NFA acceptors. Our study applies broadband transient absorption spectroscopy to a series of donor:acceptor blends, comprising a fixed donor component (PPDT2FBT), and a varying acceptor component of a NFA polymer (N2200), an earlier generation NFA small molecule (NIDCS-HO), or [6,6]-phenyl-C71-butyric acid methyl ester (PCBM) for reference. Our results show that the poor performance of the polymer:polymer blend is explained by incomplete exciton dissociation and rapid geminate recombination. In the case of the small-molecule NFA (NIDCS-HO), we reveal the presence of CT-excitons in the NFA phase, as well as a significant photocurrent generation channel via hole transfer from the NFA. We find that a simple kinetic model of measured charge separation and recombination rates can adequately account for observed photoccurent quantum efficiencies, but the advantage of hole-transfer mediated charge photogeneration (which is less available in fullerene-based devices) may be offset by higher disorder and sub-optimal thin-film morphology for these NFA materials. These results provide valuable insight into how new intrinsic excited states and interfacial excited states need to be accounted for in charge generation dynamics of NFA based OPVs.

In this work, a series of acenaphthene derivatives (AC-derivatives) were designed and synthesized by incorporating imidazole as an electron deficient moiety and triphenylamine (TPA) as an electron rich moiety with different functional groups at the N1 position of imidazole. All the dyes were structurally characterized by spectroscopic methods (1H NMR, 13C NMR, IR, and Mass) and some of the dyes were characterized by single crystal X-ray diffraction. The detailed thermal, photophysical and electrochemical properties were systematically investigated. All the dyes showed good thermal stability with high thermal decomposition (Td) temperatures ranging from 400 to 430 °C. All the dyes had similar absorption behaviour, with peak wavelengths at 240 nm and 350 nm assigned to the π → π* transitions of the aromatic segments. All the dyes exhibited a broad bluish-white to yellowish-orange emission with the emission maximum in the range of 520–600 nm. Electrochemical analysis was performed to discover the HOMO and LUMO energy levels of the dyes, which were verified using DFT calculations. Theoretical investigations, such as optimization, singlet–triplet and HOMO and LUMO energy levels calculations, were calculated using DFT and TD-DFT analysis. The excited singlet–triplet energy gaps of the dyes were estimated and correlated to the structural and energetic characteristics of the known host materials. In addition, examinations were carried out to find the optical, electronic, charge transport and stability properties of dyes for use as emissive and charge transport materials in organic light emitting devices (OLEDs). All the dyes are good emissive materials with their hole transporting nature more favourable than the electron transporting nature. The theoretical investigations clearly indicate that AC-mCF3 has more potential as an emitter for OLED applications.

Organic light-emitting device (OLED) is an attractive technology for display application in high-end electronics. Tetradentate Pt(II) complexes are phosphorescent emitters of great importance for OLED fabrications. A novel series of N-Heterocyclic carbene (NHC), benzocarbene (Ph/NHC) and pyridinocarbene (Py/NHC)-based tetradentate Pt(II) complexes with fused 5/6/6 metallocycles was designed and developed. Their electrochemical and photophysical properties were systematically studied through experimental and theoretical investigations, which greatly affected by the NHC, Ph/NHC and Py/NHC. Pt(NHC-1) shows dominant emission peak at 509 nm with a quantum efficiency of 40% and excited lifetime of 1.8 µs in 5 wt% doped PMMA film at room temperature. Pt(NHC-1)-doped green OLED using 26mCPy as host material demonstrated a very high Lmax of 64416 cd/m2, which was a record-high value for the reported Pt(II) complexes-based phosphorescent OLEDs. The OLED also achieved a peak EQE of 13.1% with small efficiency roll-off, which yet maintained EQEs of 12.8%, 11.6% and 8.6% at a high brightness of 100, 1000 and 10000 cd/m2.

Organic room temperature phosphorescent materials have attracted a lot of research interest due to their wide applications. Herein, a series of intramolecular-locked triphenylamine derivatives have been synthesized with adjustable room temperature phosphorescence (RTP) properties, in which the RTP lifetime ranged from 30 to 288 ms and the emission color varied from sky blue to green. These results are mainly related to the substituent effect, which can tune the intramolecular charge transfer and intermolecular interactions, contributing to different intersystem crossing (ISC) processes, and the stability and energy levels of excited triplet states.

Copper hexadecafluorophthalocyanine (CuFPc) has excellent environmental and thermal stability and stable n-type semiconducting properties under ambient conditions. We investigated the exciton diffu...

Surface damage produced by single MeV-GeV heavy ions impacting ultrathin polymer films has been shown to be weaker than those observed under bulk (thick film) conditions. The decrease in damage efficiency has been attributed to the suppression of long-range effects arising from excited atoms lying deeply in the solid. This raises the possibility that the substrate of the films itself may be relevant to the radiation effects seen at the top surface. Here, the role of the substrate on cratering induced by individual 1.1 GeV Au ions in ultrathin poly(methyl methacrylate) (PMMA) layers is investigated. Materials of different thermal and electrical properties (Si, SiO2, and Au) are used as substrates to deposit PMMA thin films of various thicknesses from ∼1 to ∼300 nm. We show that in films thinner than ∼40 nm craters are modulated by the underlying substrate to a degree that depends on the transport properties of the medium. Crater size in ultrathin films deposited on the insulating SiO2 is larger than in similar films deposited on the conducting Au layer. This is consistent with an inefficient coupling of the electronic excitation energy to the atomic cores in metals. On the other hand, the damage on films deposited on SiO2 is not very different from the Si substrate with a native oxide layer, suggesting, in addition, poor energy transmission across the film/substrate interface. The experimental observations are also compared to calculations from an analytical model based on energy addition and transport from the excited ion track, which describe only partially the results.

The ability to access panchromatic absorption and long-lived charge-transfer (CT) excited states is critical to the pursuit of abundant-metal molecular photosensitizers. Fe(II) complexes supported by benzannulated diarylamido ligands have been reported to broadly absorb visible light with nanosecond CT excited state lifetimes, but as amido donors exert a weak ligand field, this defies conventional photosensitizer design principles. Here, we report an aerobically stable Fe(II) complex of a phenanthridine/quinoline diarylamido ligand, Fe(ClL)2, with panchromatic absorption and a 3 ns excited-state lifetime. Using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) at the Fe L-edge and N K-edge, we experimentally validate the strong Fe-Namido orbital mixing in Fe(ClL)2 responsible for the panchromatic absorption and demonstrate a previously unreported competition between ligand-field strength and metal-ligand (Fe-Namido) covalency that stabilizes the 3CT state over the lowest energy triplet metal-centered (3MC) state in the ground-state geometry. Single-crystal X-ray diffraction (XRD) and density functional theory (DFT) suggest that formation of this CT state depopulates an orbital with Fe-Namido antibonding character, causing metal-ligand bonds to contract and accentuating the geometric differences between CT and MC excited states. These effects diminish the driving force for electron transfer to metal-centered excited states and increase the intramolecular reorganization energy, critical properties for extending the lifetime of CT excited states. These findings highlight metal-ligand covalency as a novel design principle for elongating excited state lifetimes in abundant metal photosensitizers.

The delta self-consistent field (ΔSCF) method was applied to the simulation of low-lying singlet and triplet excited states of multiple-resonance (MR)-type thermally activated delayed fluorescence (TADF) molecules, which form a promising group for organic light-emitting diode (OLED) emitters. A comparison with the experimental values of 13 emitters from the literature showed that ΔSCF gave fairly accurate S1 and T1 excitation energies (mean absolute errors (MAEs) of 0.092 and 0.055 eV, respectively) as well as quite accurate ΔEST (S1-T1 gap, MAE of 0.041 eV), which could not be calculated with sufficient accuracy by the conventional time-dependent density functional theory (TDDFT). ΔSCF also demonstrated its utility for the analysis of photophysical properties through a simulation of the reverse intersystem crossing (RISC) process of an MR-type emitter.

Understanding excited states is vital to photochemistry and spectroscopy, yet the study of excited states from a theoretical viewpoint is often much more challenging than that of ground states due to the more complicated nature of excited states systems. This thesis is primarily focused on a series of topics regarding excited state electronic structure theory, aiming to improve the accuracy, efficiency and interpretability of computational methods. In particular, we generalize the recently developed ALMO-CIS approach, which is a formulation of configuration interaction singles (CIS) for molecular complexes or clusters based on absolutely-localized molecular orbitals (ALMOs), in two ways. The first is to reintroduce charge-transfer (CT) effects, and the resulting ALMO-CIS+CT method is shown to provide better accuracy in simulating spectra of large helium clusters. Secondly, a multi-reference version of ALMO-CIS is formulated, and shown to be a promising method for systems where pure charge-transfer excitations are important. We also develop and implement an energy decomposition analysis (EDA) method for studying intermolecular interactions in excited molecular systems. This EDA scheme brings insight to interesting excited-state phenomena such as solvatochromism, charge-transfer-to-solvent (CTTS) spectrum and the formation of excimers.

An asymmetric two-way proton transfer molecule 3-(benzo[d]-thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) with the function of white-light emission was synthesized in a recent experiment (Bhattacharyya, A.; Mandal, S. K.; Guchhait, N. J. Phys. Chem. A 2019, 123, 10246). The particularity of this molecule is that there are two possible forms, one of which contained a six-membered H-bonded network toward a N atom (BTHMB-NH) present in the molecule as a proton acceptor and the other was toward an O atom (BTHMB-OH). Unfortunately, the experimental work lacked the theoretical explanation about the determination of the BTHMB-NH form and its excited-state intramolecular proton transfer (ESIPT) process under different solvents. Therefore, this study has explored these two points by means of the time-dependent density functional theory (TDDFT) method. The calculated relative energy and potential energy profile (PEP) of the transformation between BTHMB-NH and BTHMB-OH forms illustrated that BTHMB-NH was more stable, and the transfer from BTHMB-NH to BTHMB-OH was almost impossible at both S0 and S1 states under all solvents due to high potential energy barriers (PEBs) (11.67-21.59 kcal/mol). These calculated results provided the theoretical explanation and verification for the conclusion that the BTHMB molecule exists in the BTHMB-NH form in the experiment. Subsequently, the constructed PEPs of the ESIPT process for BTHMB-NH have proved that it was prone to the ESIPT process due to low PEBs (0.11-0.28 kcal/mol) at the S1 state. In particular, as the solvent polarity increased, the intensity of the intramolecular hydrogen bond (IHB) (O3-H4···N5) increased and the ESIPT process was more likely to occur. In addition, the twisted intramolecular charge-transfer (TICT) process was studied to explore the possible fluorescence quenching pathway of BTHMB-NH. Based on the PEPs of BTHMB-NH-T as a function of the N5-C6-C7-C8 dihedral angle at the S0 and S1 states, it is seen that the S0 state TICT process was inhibited due to the large PEBs (16.45-23.93 kcal/mol). Although the S1 state PEBs have been greatly reduced, they were still maintained at about 3.60 kcal/mol (3.60-3.84 kcal/mol), and hence, this process was still relatively difficult to occur. Due to the fact that BTHMB can be regarded as a standard in future designs involving red light and solvent-specific white-light emitters, a certain amount of investigative work on the ESIPT process was done in detail, and it paved the way for future research on the directionality of ESIPT in double ESIPT probes.

Excited-state intramolecular proton transfer (ESIPT) dyes typically show strong solid-state emission, but faint fluorescence intensity is observed in the solution state owing to detrimental molecular motions. This article investigates the influence of direct (hetero)arylation on the optical properties of 2-(2'-hydroxyphenyl)benzoxazole ESIPT emitters. The synthesis of two series of ESIPT emitters bearing substituted neutral or charged aryl, thiophene, or pyridine rings is reported herein along with full photophysical studies in solution and solid states, demonstrating the dual solution-/solid-state emission behavior. Depending on the nature of substitution, several excited-state dynamics are observed: quantitative or partially frustrated ESIPT process or deprotonation of the excited species. Protonation studies revealed that pyridine substitution triggered a strong increase of quantum yield in the solution state for the protonated species owing to favorable quinoidal stabilization. These attractive features led to the development of a second series of dyes with alkyl or aryl pyridinium moieties showing strong tunable solution/solid fluorescence intensity. For each series, ab initio calculations helped rationalize and ascertain their behavior in the excited state and the nature of the emission observed by the experimental results.

Criegee intermediates make up a class of molecules that are of significant atmospheric importance. Understanding their electronically excited states guides experimental detection and provides insight into whether solar photolysis plays a role in their removal from the troposphere. The latter is particularly important for large and functionalized Criegee intermediates. In this study, the excited state chemistry of two small Criegee intermediates, formaldehyde oxide (CH2 OO) and acetaldehyde oxide (CH3 CHOO), was modeled to compare their specific dynamics and mechanisms following excitation to the bright ππ* state and to assess the involvement of triplet states to the excited state decay process. Following excitation to the bright ππ* state, the photoexcited population exclusively evolves to form oxygen plus aldehyde products without the involvement of triplet states. This occurs despite the presence of a more thermodynamically stable triplet path and several singlet/triplet energy crossings at the Franck-Condon geometry and contrasts with the photodynamics of related systems such as acetaldehyde and acetone. This work sets the foundations to study Criegee intermediates with greater molecular complexity, wherein a bathochromic shift in the electron absorption profiles may ensure greater removal via solar photolysis.

The inherent atomistic precision of synthetic chemistry enables bottom-up structural control over quantum bits, or qubits, for quantum technologies. Tuning paramagnetic molecular qubits that feature optical-spin initialization and readout is a crucial step toward designing bespoke qubits for applications in quantum sensing, networking, and computing. Here, we demonstrate that the electronic structure that enables optical-spin initialization and readout for S = 1, Cr(aryl)4, where aryl = 2,4-dimethylphenyl (1), o-tolyl (2), and 2,3-dimethylphenyl (3), is readily translated into Cr(alkyl)4 compounds, where alkyl = 2,2,2-triphenylethyl (4), (trimethylsilyl)methyl (5), and cyclohexyl (6). The small ground state zero field splitting values (

Excited state intramolecular proton transfer (ESIPT) has drawn much attention for its important applications in a variety of areas. Here, the steady-state and time-resolved absorption spectroscopic experiments as well as DFT/TD-DFT calculations are employed to study the photophysical properties and photochemical reaction mechanisms of 2-(2'-hydroxyphenyl) benzoxazole (HBO) and selected derivatives (compounds 1-3). Because of their larger π-conjugation framework, compounds 1-3 display red-shifted absorbance but blue-shifted fluorescence compared with HBO. A fast ESIPT process is observed directly for HBO while compound 3 has an enol/keto equilibrium type of ESIPT that exhibits dual emission. Interestingly, only the emission of the enol form is observed for compounds 1 and 2 which suggests that the ESIPT process is strongly inhibited. These results indicate the decoration with electron-withdrawing groups such as thiadiazol and pyrazine on the hydroxyphenyl ring (compounds 1 and 2) apparently suppresses the proton-transfer processes in their excited states. Whereas the ESIPT process is rarely increased for compound 3 that modified with the phenanthrol ring, because the effective conjugation is reduced for compound 3 compared with HBO. The work here provides fundamental insights that may be useful for designing novel ESIPT molecules in the future.

Thermally activated delayed fluorescence (TADF) materials are an essential part of TADF-based organic light-emitting diodes (OLEDs). All the reported methods to improve the performance of TADF materials were focused on achieving a high reverse intersystem crossing rate (kRISC) and oscillator strength (f), but most of them were studies on single molecular states. In this paper, we have discovered a new dimer architecture called the "H-type" like dimer and proved that the "H-type" like dimer is another way to improve the performance of TADF materials by calculation and experiment. The calculated energy levels of excited states only provided 1.72-5.46% relative errors (RE) compare with the measured values, which indicated that the methods we chose were suitable for predicting the properties. The intermolecular interactions of the "H-type" like dimer endow it with much larger f and kRISC properties than monomer states, proving that the "H-type" like dimer could improve the performance of TADF emitters.

Quantum dots (QDs) are three-dimensional (3D) quantum confinement materials with confined size on the nanoscale. They are semiconductors, possessing a tunable energy gap in the range of visible light energy. In QDs, the 3D quantum confinements of excitons result in tunable fluorescence emission relying upon the QDs size and shape when excited by monochromatic light. Besides, the attempts to improve their outstanding optoelectronic properties, i.e. superior to those of bulk, thin-film semiconductor and organic dyes, many efforts have been conducted, in recent times, regarding sustainable QDs synthesis aiming at biocompatibility and cost reduction. Among the green synthesis routes of QDs there are two distinguished; namely inorganic QDs and carbon-based QDs. The first route is made of low-bandgap metal chalcogenide either extracted from a living being, e.g. earthworm, or capped with an organic ligand. While, the second route is made of carbon-core and passivating the surface with different functional groups, namely carboxyl, hydroxyl, in addition to amine. These functional groups are derived from coke or organic carbon reservoir, i.e. fruits and their juice, animal, vegetable, spice and waste paper. Numerous fundamental applications of QDs, such as biomedicine, sensing, catalysis, and solar cells, exploit the characteristic fluorescence emission of QDs, quantum yields and their modulation upon interaction with the external environment. In this review, two prototype QDs examples are used to highlight the route to sustainable QDs synthesis and solar cells implementation and some perspectives.

A series of functional platinum(II) complexes (Pt1-Pt3), which present high activity in four-photon absorption, in vivo imaging, and precise cancer therapy, as previously reported by the experimental work of Zhang et al. (Inorg. Chem.2021, 60, 2362-2371), are computationally investigated in the article. We find that after the complex goes through four-photon absorption to the S1 state, it undergoes intersystem crossing to the T2 state and eventually reaches the T1 state through internal conversion. On the T1 state, both radiative and nonradiative decay to S0 exit. The radiative decay forms the basis for the phosphorescence imaging in tissues as reported in the original paper. In addition, the nonradiative decay can simultaneously generate cytotoxic singlet oxygen by the excited energy transfer process, also known as triplet oxygen's quenching of triplet states. We conclude that the phosphorescence property as well as the photosensitizer character jointly bring high activity of in vivo imaging and photodynamic therapy to these complexes.

Substitutional metal doping is a powerful strategy for manipulating the emission spectra and excited state dynamics of semiconductor nanomaterials. Here, we demonstrate the synthesis of colloidal manganese (Mn

The sterically demanding carbene ITr (N,N'-bis(triphenylmethyl)imidazolylidene) was used as a ligand for the preparation of luminescent copper(I) complexes of the type [(ITr)Cu(R-pyridine/R'-quinoline)]BF4 (R = H, 4-CN, 4-CHO, 2,6-NH2, and R' = 8-Cl, 6-Me). The selective formation of linear, bis(coordinated) complexes was observed for a series of pyridine and quinoline derivatives. Only in the case of 4-cyanopyridine a one-dimensional coordination polymer was formed, in which the cyano group of the cyanopyridine ligand additionally binds to another Cu atom in a bridging manner, thus leading to a trigonal planar coordination environment. In contrast, employing sterically less demanding monotrityl-substituted carbene 3, no (NHC)Cu-pyridine complexes could be prepared. Instead, a bis-carbene complex [(3)2Cu]PF6 was obtained which showed no luminescence. All linear pyridine/quinoline coordinated complexes show weak emission in solution but intense blue to orange luminescence doped with 10% in PMMA films and in the solid state either from triplet excited states with unusually long lifetimes of up to 4.8 ms or via TADF with high radiative rate constants of up to 1.7 × 105 s-1 at room temperature. Combined density functional theory and multireference configuration interaction calculations have been performed to rationalize the involved photophysics of these complexes. They reveal a high density of low-lying electronic states with mixed MLCT, LLCT, and LC character where the electronic structures of the absorbing and emitting state are not necessarily identical.

Substituted tetralones such as 3,3,6,8-tetramethyl-1-tetralone undergo photoenolization to produce a photoenol excited state with a lifetime around ~ 3 μs, which involves the carbonyl triplet state of the ketone (τ ~ 1.9 ns), as a precursor; the excited photoenol also has biradical character and is useful for the fast synthesis of gold nanostructures. In the case of excited photoenols like this one, if metal ion trapping fails, they return to the original ketone precursor and remain available for future events that can lead to the target nanoparticles. This study includes the characterization of the photochemistry of the substituted tetralone, and the dual behavior of reaction intermediates, as biradicals and excited states, in energy and electron transfer processes.

In electron-transfer initiated photosensitization processes, molecular oxygen (O2 ) is not involved in the first bimolecular event, but almost always participates in subsequent steps giving rise to oxygenated products. An exception to this general behavior is the photosensitized dimerization of tyrosine (Tyr), where O2 does not participate as a reactant in any step of the pathway yielding Tyr dimers (Tyr2 ). In the pterin (Ptr) photosensitized oxidation of Tyr, O2 does not directly participate in the formation of Tyr2 and quenches the triplet excited state of Ptr, the reactive species that initiates the process. However, O2 is necessary for the dimerization, phenomenon that we have named as the oxygen paradox. Here, we review the literature on the photosensitized formation of Tyr2 and present results of steady-state and time resolved experiments, in search of a mechanistic model to explain the contradictory role of O2 in this photochemical reaction system.

Electron transfer dissociation (ETD) is an analytically useful tool for primary structure interrogation of intact proteins, but its utility is limited by higher-order reactions with the products. To inhibit these higher-order reactions, first-generation fragment ions are kinetically excited by applying an experimentally tailored parallel ion parking waveform during ETD (ETD-PIP). In combination with subsequent ion/ion proton transfer reactions, precursor-to-product conversion was maximized as evidenced by the consumption of more than 90% of the 21 kDa Protein G precursor to form ETD product ions. The employment of ETD-PIP increased sequence coverage to 90% from 80% with standard ETD. Additionally, the inhibition of sequential electron transfers was reflected in the high number of complementary ion pairs from ETD-PIP (90%) compared to standard ETD (39%).

Three anionic luminescent metal-organic frameworks (LMOFs; [M(tcbpe)(CH3)2NH2]·H2O; M = In3+, Eu3+, Gd3+; tcbpe = 4',4‴,4‴″,4‴‴'-(ethene-1,1,2,2-tetrayl)tetrakis[(1,1'-biphenyl)-4-carboxylic acid]) are synthesized by employing the tetraphenylethene core ligand H4tcbpe with M3+ ions. They stack in the similarly 4-fold-interpenetrated three-dimensional porous structure. All give blue emission when excited at 365 nm, with fluorescence quantum yields of 34.8% (MOF-In), 7.1% (MOF-Eu), and 28.1% (MOF-Gd). Somewhat surprisingly, these three complexes are extremely stable both in various solvents and across a broad pH range: MOF-In is stable between pH = 0 and 14, and MOF-Eu and MOF-Gd are stable between pH = 0 and 13. Additionally, they also show good proton conductivities of 2.29 × 10-5 S·cm-1 (MOF-In), 2.02 × 10-4 S·cm-1 (MOF-Eu), and 1.24 × 10-4 S·cm-1 (MOF-Gd) at high temperature under 98% relative humidity. To the best of our knowledge, this is the first reported LMOF series combining aggregation-induced emission behavior with good proton conductivities.

Integrating multiple photosensitive properties into an “all-in-one” photosensitizer (PS) shows great promise for the treatment of cancers owing to synergistic effect among them. However, the development of such PSs, especially those that need a single laser source, remains a challenge. Herein, we report an orchestration of electron donors and acceptors in a propeller-like pentad, PBI-4Cz, where four carbazole (Cz) units are covalently linked to the ortho-positions of the perylene bisimide (PBI) core. Strong intramolecular donor-acceptor interaction significantly quenches the luminescence and largely extends the absorption spectra to near-infrared region. Excited-state dynamics investigated via femto- and nano-second transient absorption spectroscopy revealed exclusive charge separation of the PBI-4Cz within initial 0.5 ps when photoexcited regardless of which intermediate is involved. Energy dissipation of the resulting charge-separated state (PBI•−-4Cz•−) is subjected to the toggle between intersystem-crossing toward excited triplet states and charge recombination toward ground states. Relative importance of the two pathways can be tuned by micro-environmental polarity, which endows PBI-4Cz remarkable performances of singlet-oxygen generation (>90.0%) in toluene and photothermal conversion (∼28.6%) in DMSO. Harnessing intrinsic photostability and excited-state processes of heavy-atom-free PBI derivatives not only holds a promise for multifunctional phototheranostics, but also provides a prototype for designing high-performance PSs with tunable photoconversion pathways.

Strategic incorporation of a meta dimethylamino (-NMe2 ) group on the conformationally locked green fluorescent protein (GFP) model chromophore (m-NMe2 -LpHBDI) has drastically altered molecular electronic properties, counterintuitively enhancing fluorescence of only the neutral and cationic chromophores in aqueous solution. A ~200-fold decrease in fluorescence quantum yield of m-NMe2 -LpHBDI in alcohols (e.g., MeOH, EtOH, and 2-PrOH) supports this GFP-derived compound as a fluorescence turn-on water sensor, with large fluorescence intensity differences between H2 O and ROH emissions in various H2 O/ROH binary mixtures. A combination of steady-state electronic spectroscopy, femtosecond transient absorption, ground-state femtosecond stimulated Raman spectroscopy (FSRS), and quantum calculations elucidates an intermolecular hydrogen-bonding chain between a solvent -OH group and the chromophore phenolic ring -NMe2 and -OH functional groups, wherein fluorescence differences arise from an extended hydrogen-bonding network beyond the first solvation shell, as opposed to fluorescence quenching via a dark twisted intramolecular charge transfer state. The absence of a meta-NMe2 group twisting coordinate upon electronic excitation was corroborated by experiments on control samples without the meta-NMe2 group or with both meta-NMe2 and para-OH groups locked in a six-membered ring. These deep mechanistic insights stemming from GFP chromophore scaffold will enable rational design of organic, compact, and environmentally friendly water sensors.