A Brønsted acid-mediated annulation of carbazoles with diaryl-1,2-diones has been developed for the synthesis of furo[3,2-c]carbazoles, a previously unexplored fused carbazole framework. The metal-free transformation proceeds through sequential C-C and C-O bond formation and affording the desired products in good to excellent yields. Both electron-donating and electron-withdrawing substituents on the diaryl-1,2-diones were well tolerated, and the reaction was also applicable to N-substituted as well as NH-carbazoles. The synthetic utility of the resulting furo[3,2-c]carbazoles was demonstrated through bromination, nitration, and formylation reactions. The synthesized compounds exhibited blue fluorescence with quantum yields of up to 77%, while photophysical, electrochemical, thermal, and computational studies provided insight into their electronic structures and excited-state properties.

A novel class of pyrimido[1,6-b]indazole fluorophores was synthesized via a concise condensation featuring a 6-endo-dig cyclization. The ring system displays large Stokes shifts (99-115 nm) and positive solvatochromism, suggesting an intramolecular charge transfer. Suzuki-Miyaura cross-coupling enables it-extension to derivatives with improved quantum yields and Stokes shifts exceeding 130 nm. TD-DFT calculations corroborate these trends, highlighting their potential for advanced fluorescence-based technologies.

The mechanism of thermally enhanced luminescence (TEL), such as thermally activated delayed fluorescence (TADF) and thermally stimulated delayed phosphorescence (TSDP), is of fundamental importance in the molecular design of emissive transition-metal complexes, as it can enable bright emission with enhanced radiative rate for high-performance organic light-emitting diodes (OLEDs). It is essential to resolve the excited-state landscape of complexes, including the correlation with their photophysical properties, to optimize the device efficiency. Here, we explore a series of Au(III) complexes containing asymmetric carbazolyl (Cz) motifs that regulate the co-facial distance between the electron donor and acceptor moieties. Combining with the femtosecond transient absorption (fs-TA) and in-depth density functional theory computation, we reveal rapid reverse internal upconversion to a higher-lying triplet state, T1', which is thermally accessible from the lowest triplet state, T1, at room temperature. The efficient spin-flip process from T1' to the lowest singlet state, S1, and the ground state, S0, leads to strong TEL through both TADF and TSDP pathways, substantially increasing the radiative rate to 105 s-1. The OLED devices based on the TEL Au(III) emitters reach external quantum efficiencies (eta ext) of 26.5% and 16.5% in doped and non-doped devices, respectively. The doped OLED devices exhibited an eta ext roll-off as low as 2% at a practical luminance of 1000 cd m- 2. We believe that the molecular design of highly efficient organometallic emitters of TEL character will be greatly facilitated by the mechanistic analysis and methodology presented here.

The Pt butterfly complexes, [{Pt(Cz-C∧C*im)(μ-Rpz)}2] (HC∧C* = 1-(4-(carbazolyl) phenyl)-3-methyl-1H-imidazol-2-ylidene; Rpz = pyrazolate (pz) 1; 4-fluoropyrazolate (4-Fpz) 2; 4-trifluoromethylpyrazolate (4-CF3pz) 3), with a carbazole-appended cyclometalated N-heterocyclic carbene (Cz-C∧C*im) in the wings, were prepared and characterized. DFT and TD-DFT calculations show the prevalent 1/3ILCT character of the lowest-energy absorptions and emissions of these phosphorescent complexes. In 5 wt % PMMA films, complexes 1-3 exhibit blue phosphorescence with photoluminescence quantum yield up to 0.99, even in air. The Commission Internationale de L'Eclairage (CIE) coordinates of their emission are in the blue corner, being "pure-blue" (CIEx+y < 0.3) in the case of 1. In view of these properties, these complexes were used to prepare OLEDs, with the best-performing devices achieving a maximum external quantum efficiency of 4.26% and maximum luminance of 2357.7 cd m-2 with cyan electroluminescence (CIEx,y = 0.14, 0.46).

A combined mechanistic and photophysical investigation of the dual-function photosensitizer DANO and its photoproduct DAPS was carried out using DFT and TDDFT approaches. DANO acts as a light-activated nitric oxide (NO) donor, with NO release proceeding via the triplet excited state through a glutathione (GSH)-assisted hydrogen transfer. The reaction is thermodynamically and kinetically favored in the triplet state, with an activation barrier of 10.4 kcal mol-1 and an overall exergonicity of -3.1 kcal mol-1. In contrast, the ground-state pathway shows a significantly higher energy barrier (32.3 kcal mol-1), confirming the photo-induced nature of the NO release. Photophysical analysis of DANO revealed that the bright state S1 efficiently undergoes intersystem crossing (ISC) to either T2 (kISC = 1.22 × 106 s-1), eventually followed by internal conversion to T1, or T1 (kISC = 3.68 × 107 s-1), the state with the most pronounced dissociative character. Upon NO dissociation, the resulting species, DAPS, functions as an efficient type II photosensitizer. Excited-state analysis of the photoproduct suggests the intersystem crossing (ISC) process occurs via the S1 → T2 channel (kISC = 1.91 × 106 s-1), followed by internal conversion to T1. The populated triplet state exhibits a calculated lifetime of ≈5 µs, suggesting sufficient persistence for energy transfer to molecular oxygen. Although this value should be interpreted qualitatively because of the reduced computational model, it is compatible with the experimentally observed singlet oxygen generation. Computational analysis confirms also the feasibility of a free radical cascade initiated by DAPS for the formation of peroxynitrite and other highly reactive species, which is likely to enhance its photodynamic efficacy. These results support the DANO/DAPS system as a promising dual-action PDT agent, combining NO delivery and ROS generation.

Organic molecular crystals have gained significant research attention in recent years due to their intriguing photophysical properties and potential applications in photovoltaic and emissive devices. This growing interest has amplified the need for accurate and robust computational protocols to investigate their photophysical behavior. In this work, we present multiscale computational strategies designed to model the shape and broadening of UV-vis absorption spectra in organic crystalline materials. These protocols enable a quantitative assessment of spectral broadening originating from various sources in typical crystalline polyacenes. Adopting an ab initio approach, we employ self-consistent microelectrostatic embedding and Ewald-based ONIOM models to incorporate structural features and environmental effects as well as contributions from static disorder, excitonic coupling, and vibronic interactions. The developed protocols successfully quantify the spectral broadening, as demonstrated for naphthalene and anthracene crystals. This framework is broadly applicable and offers a reliable foundation for the investigation of a wide range of organic molecular crystals, enabling detailed studies of diverse fluorophores and systems of photophysical relevance.

Dimethyl sulfide (DMS; CH3SCH3) is a gas produced by phytoplankton in the ocean and emitted into the atmosphere. DMS emission is the largest source of atmospheric sulfur. Hydroperoxymethyl thioformate (HPMTF) is an oxidation product of DMS in the marine atmosphere. While the formation pathways of HPMTF are well established, the atmospheric removal processes have yet to be fully characterized. Here, we study the photochemistry of HPMTF using computational methods. Our results indicate that HPMTF photolysis is efficient (high quantum yield, ϕ = 0.67), primarily proceeding via S-C bond cleavage in the thioformate (-SCHO) group. However, it is limited by the weak absorption of UV-vis solar radiation, resulting in a long photolytic lifetime (τ ≈ 30 h). Therefore, photolysis is expected to represent a minor sink for atmospheric HPMTF.

Molecular doping is a key strategy for tuning the thermoelectric (TE) properties of conjugated polymers. Yet achieving both high TE performance and long-term stability remains challenging, as counterions redistribute and microstructures reorganize under thermal and ambient exposure. Here we investigate TAB-2TFSI (TAB2+·2TFSI-), a dicationic ion-pair dopant that couples a strong oxidizing TAB motif with two weakly coordinating TFSI- counterions. Using poly(3-hexylthiophene-2,5-diyl) (P3HT) as a model polymer, we benchmark TAB-2TFSI against state-of-the-art p-doping systems and find that it delivers the highest average electrical conductivity of 290 ± 30 S cm- 1 and power factor of 40 ± 6 µW m- 1 K- 2, placing P3HT among the top high-performing isotropic doped polymer thermoelectrics ever reported. Temperature-dependent transport analysis, together with GIWAXS and AFM-IR mapping of TFSI-associated vibrational signatures, indicates morphology-induced improved transport connectivity and a more homogeneous ionic landscape than for other dopants. Consistently, TAB-2TFSI exhibits the highest stability under inert aging and accelerated thermal/oxidative stress among all the doping systems tested, evidenced by minimal spectral and structural evolution over time and the most stable TE performance. Finally, we demonstrate the wide applicability of TAB-2TFSI as a dopant across multiple popular conjugated polymers, highlighting its material-agnostic potential to boost simultaneously doping efficiency and stability.

Higher-lying excited states beyond S1 and T1 are widely recognized in many photophysical systems, including thermally activated delayed fluorescence (TADF). However, their explicit and quantitative impact on photophysical observables such as photoluminescence quantum yields (PLQY) and lifetimes is difficult to be attained experimentally and it has not been systematically assessed within a fully ab initio kinetic modeling framework. To address this gap, we developed KinLuv, a multistate excited state kinetic model that includes higher-lying excited states (S2, T2) and all possible monomolecular interconversion processes between all the electronic states, whose rate constants were computed using Fermi's golden rule (FGR) explicitly including the Herzberg-Teller (HT) vibronic coupling effect. We applied KinLuv to prototypical multi-resonance TADF (MR-TADF) emitters and their derivatives, as well as other representative organic chromophores, demonstrating its broad applicability across diverse photophysical playgrounds beyond TADF. The resulting simulations quantitatively reproduce key experimental observables, including PLQY and prompt/delayed fluorescence lifetimes. Beyond its predictive power, the present results establish clear criteria for identifying when higher-lying excited states influence the excited-state decay and when simplified models remain adequate. This framework enables rational selection of minimal kinetic models that balance physical insight with numerical robustness, with direct implications for the in silico design of high-performance organic emitters.

8-Hydroxyquinoline-based tetracoordinate boron complexes have been observed to exhibit pronounced luminescence and light-activated reactive oxygen species (ROS) generation, while their copper(II) analogs demonstrate significant cytotoxic effects in cancer cells. Nevertheless, both types of complexes are hindered by their inherent hydrophilicity, thereby limiting their efficacy in biological applications. Thus, we developed heavy-metal-free photosensitizers (PSs) based on 8-quinolinolato boron complexes, which exhibit light-activated fluorescence emission and ROS generation upon aggregation. The PSs effectively localize within lipid droplets and exhibit immediate and sustained ROS production upon exposure to light, even under hypoxic conditions, leading to lipid droplet-specific peroxidation, which is in accordance with the intracellular location, leading to ferroptosis-like cell death. Moreover, their fluorescence emission is quenched in the presence of Cu2+ ions, and the produced complexes enhance cytotoxicity instead. The photophysical properties of the complexes were comprehensively studied by a combination of experimental measurements, quantum mechanical (QM) and hybrid QM/molecular mechanics (MM) simulations. Thus, this investigation offers insights into new molecular design approaches for multifunctional probes with potential applications in photodynamic therapy and chemotherapy for cancer treatment.

We perform an in-depth computational study of degradation processes occurring during OLED operation for three commonly used emissive-layer host molecules: TBSO (4-(mtolylsulfonyl)-1,1-biphenyl), DPPCarba (9-(3,5-diphenylphenyl)carbazole), and DPPTriphen (2-(3,5diphenylphenyl)triphenylene). The investigation is carried out from both static and dynamic viewpoints. In the static framework, we evaluate thermodynamic descriptors that allow us to analyze possible chemical degradation pathways in the ground state, charged states, first excited states, and after exciton–polaron annihilation (EPA) and exciton–exciton annihilation (EEA). In the dynamic framework, non-adiabatic molecular dynamics (NAMD) simulations are used to follow degradation starting from both the first excited state and a higher-lying excited state representative of an EEA process. Furthermore, machine-learning-accelerated NAMD (ML-NAMD) simulations are employed to enhance the sampling of degradation pathways in TBSO. Combining static descriptors with direct and ML-accelerated dynamics provides molecular-level insight into chemical degradation mechanisms in OLED host materials and highlights the importance of going beyond static stability criteria when assessing degradation. These findings can support the rational design of more stable host materials for next-generation OLEDs.

Four new mono-, di-, tri-, and tetra-nuclear boron complexes (BPA1-4) were synthesized from triphenylborane (BPh3) and characterized by elemental analysis, ESI-MS, IR, and H-1 NMR spectroscopy. The single-crystal X-ray diffraction of BPA1 and BPA2 confirmed that in the complexes, the central boron atom exhibits a coordination number of four, coordinating with the ligands through the nitrogen atom of the imine group and the oxygen atom of the phenolic OH group, while two phenyl groups occupy the remaining two coordination sites. The photophysical studies showed that the emission peaks of complexes BPA2-4 shifted to longer wavelengths compared to the free ligand in the examined solvents (524 to 614 nm for the complexes and 510 to 598 nm for the corresponding ligand in ACN), except for complex BPA1. While the quantum yield of complex BPA2 increased with solvent polarity, the quantum yields of the other complexes (except for BPA1) decreased. Among them, the BPA2 complex has the highest quantum yield in all examined solvents, including Tol (66.8%), THF (68.5%) and ACN (72.3%). In the solid state, the quantum yield of the complexes increases in the order BPA4 (0.3%) < BPA3 (3.4%) < BPA2 (9.9%) < BPA1 (11.6%). In addition, the solid-state complexes of BPA2 (0.52 ns) and BPA4 (0.57 ns) exhibited longer lifetimes compared to their corresponding ligands PA2 (0.23 ns) and PA4 (0.22 ns). We also applied DFT and TD-DFT calculations to analyze and clarify the trends in the variation of optical properties across the series of ligands and complexes. Interestingly, PA1's anomalously low-energy emission and unusually small oscillator strength are rationalized by an excited-state intramolecular proton-transfer (ESIPT) pathway that generates a keto* tautomer prior to radiative decay. Finally, the solution structures of PA1-4 in TFA/ACN were examined and assigned on the basis of computed protonation energetics and validated against the experimental spectra.

Intersystem crossing (ISC) is a nonradiative process in which a molecule transitions between electronic states of different spin multiplicities. We modeled ISC rate constants of BODIPY derivatives (BDPDs) using a path-integral approach incorporating Franck-Condon and Herzberg-Teller effects. The main ISC channels were identified and their corresponding spin-orbit coupling matrix elements (SOCME) were calculated. Among the studied BDPDs, we evaluated the effect of combining n-electron-containing groups and heavy-atoms, i.e., bromine. Some designed BDPDs show promise as metal-free photosensitizers. Remarkably, the alpha,beta-disubstituted BDPD (BDP11) exhibited an ISC rate constant ca. 3 order of magnitude larger than the parent BODIPY.

BOPAM exhibits high fluorescence quantum yields, along with exceptional photostability, rendering it a promising platform for applications as fluorescence sensors. However, the development of BOPAM-based fluorophores with extended emission wavelengths remains limited, and the underlying mechanisms of fluorescence quenching via the population of dark twisted intramolecular charge transfer (1TICT) excited states are not yet fully understood. To address these gaps, we synthesized a series of BOPAM derivatives by incorporating electron-donating groups at the boron atoms and the phenyl rings of the BOPAM core. The introduction of bromide, phenyl, and naphthyl groups preserved the intrinsic locally excited (1LE) emission of BOPAM. In contrast, the incorporation of diphenylamine (BP-DA) and triphenylamine (BP-TA) moieties resulted in a red-shifted emission, attributed to an enhanced intramolecular charge transfer (ICT) process. Notably, in acetonitrile, BP-DA exhibited weak fluorescence originating from a 1TICT state, which was populated via the S2 → 1TICT transition. Furthermore, the emission observed from BP-TA was associated with a higher-lying excited state, likely the initially populated S2 state possessing a 1LE character. These findings not only introduce novel red-emissive BOPAM-based fluorophores, but also offer valuable insights into the role of the S2 state in governing fluorescence quenching mechanisms in BOPAM derivatives.

The design of organic emitters with inverted singlet-triplet (INVEST) gaps presents a promising route to enhance triplet harvesting in optoelectronic applications, yet reliable descriptors for predicting this phenomenon remain scarce. Here, we introduce a wave function-based descriptor, Qat, derived from the transition density matrix, to quantify the short-range charge transfer (SRCT) character and transition charges localization on atomic-sites, critical for singlet-triplet inversion. Through a systematic computational study of N-triangulenes, extended π-systems, and nonalternant hydrocarbons, we demonstrate that Qat correlates with negative singlet-triplet gap values computed at the SCS-CC2 level. The trend in the Qat values is also found at the TDA-DFT level, offering a reliable and universal metric for inversion prediction and enabling efficient screening with a cost-effective procedure. Our findings underscore Qat is a versatile tool for INVEST design, bypassing the need for high-level correlated methods while providing insights into the relationship between electronic structure and inversion. We further analyze the excited state decay kinetics of INVEST dyes by computing their fluorescence (kf), intersystem crossing (kISC), and reverse intersystem crossing (kRISC) rate constants, revealing that Herzberg-Teller effects dominate the spin conversion processes. For the investigated INVEST dyes, larger kRISC values are systematically calculated with respect to the kISC values with several dyes exhibit kRISC values exceeding 106 s-1, indicating promising potential for efficient delayed fluorescence. This work advances both the theoretical framework of excited-state dynamics in INVEST systems and the design of efficient organic emitters.

Higher lying excited states beyond S1 and T1 are widely recognized in many photophysical systems, including thermally activated delayed fluorescence (TADF). However, their explicit and quantitative impact on photophysical observables such as photoluminescence quantum yields (PLQY) and lifetimes is difficult to be attained experimentally and it has not been systematically assessed within a fully ab initio kinetic modeling framework. To address this gap, we developed KinLuv, a multistate excited state kinetic model that includes higher lying excited states (S2, T2) and all possible monomolecular interconversion processes between all the electronic states, whose rate constants were computed using Fermi golden rule explicitly including the Herzberg Teller (HT) vibronic coupling effect. We applied KinLuv to prototypical multi resonance TADF (MRTADF) emitters and their derivatives, as well as other representative organic chromophores, demonstrating its broad applicability across diverse photophysical playgrounds beyond TADF. The resulting simulations quantitatively reproduce key experimental observables, including PLQY and prompt and delayed fluorescence lifetimes. Beyond its predictive power, the present results establish clear criteria for identifying when higher lying excited states influence the excited state decay and when simplified models remain adequate. This framework enables rational selection of minimal kinetic models that balance physical insight with numerical robustness, with direct implications for the in silico design of high performance organic emitters.

Noble metal-based photoactive complexes have applications in photodynamic therapy (PDT), but their toxicity and high cost drive interest in sustainable and cheaper alternatives like iron-based compounds. In this paper, quantum chemistry and classical molecular dynamics were employed to characterize the photophysical properties and non-covalent interactions with DNA of two Fe(III) complexes. We explained the absorption of IR wavelength by bright ligand-to-metal transitions and showed that the complexes exhibit persistent, albeit modest, interaction with DNA. Building on these traditional simulation methods, we propose a conceptual ML-driven optimization module designed to refine the structure of iron complexes and enhance their photophysical features. While the framework is not yet implemented, we demonstrate that key properties relevant for PDT can be computationally evaluated, providing a foundation for future iterative optimization. The ML module integrates 3D molecular structures, simulation results, and quantum chemical insights to suggest modifications aimed at shifting the absorption spectrum more favorably into the visible range, improving their suitability for phototherapies.

Transition-metal-containing molecules and materials present significant computational challenges, requiring careful benchmarking to determine which quantum chemical methods provide the most accurate estimates. In this work, we assess the performance of the GW approximation and equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) theory for computing ionization potentials (IP) and electron-attachment (EA) energies across a comprehensive benchmark set of open-shell 3d transition-metal systems, including 10 atoms and 44 molecules. As a reference, we use the ΔCCSD(T) (coupled-cluster singles and doubles plus perturbative triples) approach. Our results show that the single-shot GW (G0W0) approximation achieves an accuracy comparable to that of higher-level wave function methods. The mean absolute errors range from 0.19 to 0.33 eV for EOM-CCSD and from 0.30 to 0.47 eV for G0W0, when using the PBE0 functional as the starting point. EOM-CCSD is, on average, only 0.13 eV more accurate than G0W0@PBE0 relative to ΔCCSD(T). While eigenvalue (evGW) or quasi-particle (qpGW) self-consistent GW calculations reduce the dependence on the starting point, they come with a higher computational cost and offer no significant improvement in the agreement with ΔCCSD(T). Both G0W0 and the CC-based methods yield mean absolute errors relative to experiments below 0.6 eV, further underscoring their reliability for this class of systems. However, G0W0 is significantly more computationally efficient than ΔCCSD(T) and EOM-CCSD, making it a compelling alternative for extended open-shell transition-metal systems.