Ground State Dipole Moments Research Articles

Use of DFT Calculations as a Tool for Designing New Solvatochromic Probes for Biological Applications

The intramolecular charge transfer behavior of push–pull dyes is the origin of their sensitivity to environment. Such compounds are of interest as probes for bioimaging and as biosensors to monitor cellular dynamics and molecular interactions. Those that are solvatochromic are of particular interest in studies of lipid dynamics and heterogeneity. The development of new solvatochromic probes has been driven largely by the need to tune desirable properties such as solubility, emission wavelength, or the targeting of a particular cellular structure. DFT calculations are often used to characterize these dyes. However, if a correlation between computed (dipole moment) and experimentally measured solvatochromic behavior can be established, they can also be used as a design tool that is accessible to students. Here, we examine this correlation and include case studies of the effects of probe modifications and conformation on dipole moments within families of solvatochromic probes. Indeed, the ground state dipole moment, an easily computed parameter, is correlated with experimental solvatochromic behavior and can be used in the design of new environment-sensitive probes before committing resources to synthesis.

Designing Highly Fluorescent BenzoCoumarin‐Sesamol Conjugates for Optoelectronic Applications

AbstractIn this report we have studied, the substitutional effect on photophysical properties of newly synthesized isomeric benzocoumarin‐Sesamol conjugates using absorption, steady‐state fluorescence emission, and time‐resolved emission measurements. The structural characterization of the synthesized dyes was carried out using FT‐IR, 1H‐NMR, 13C‐NMR, and MS. The ground state dipole moment of both the molecules in the gaseous phase is estimated from ab initio computations by using Gaussian 09W software and also from solvatochromic method and the results are compared. Stoke's shift exhibits a redshift with an increase in solvent polarity for synthesized indicating a π–π* transition. The HOMO‐LUMO energy gaps computed from density functional theory and absorption threshold wavelengths are found to be in good agreement with each other. The Global chemical reactivity descriptor parameter and electrostatic potential (MESP) plots suggest that molecules have strong electrophilic and nucleophilic sites. The preliminary photophysical observations and results suggest that the fluorescent dyes can be considered as potential material for the construction of solar cells, fluorescent probes, and chemosensors.

Computational design of efficient corannulene-based Non-Fullerene acceptors for organic solar cells applications

In our study, we aimed to enhance the optoelectronic properties of corannulene through functionalization for use as a non-fullerene acceptor (NFA) in organic solar cells. To achieve this, we designed new corannulene derivatives by introducing various electron-donating and electron-withdrawing groups onto the corannulene core. Geometric, electronic, optical, and charge transport properties of newly designed molecules are analyzed using long-range corrected density functional theory methods. The potential NFA is identified by conducting extensive analysis, such as light absorption properties, ground-state dipole moments, and the energy difference between LUMO and LUMO+1 orbitals. Also, a model donor–acceptor interface is constructed by considering PTQ10 oligomer as the donor and corannulene derivatives as acceptors. Charge-transfer states and exciton dissociation processes are analyzed at the polymer chain and NFA interface. Overall, the results obtained from this study can provide useful guidance in designing high-performing NFAs.

Solvent dependent nonlinear optical properties of benzodioxol chalcone: An elucidation of spectroscopic, DFT, solvatochromism and z-scan technique

Novel push–pull chalcone derivative, 3-(1,3-Benzodioxol-5-yl)-1-phenyl-2-propen-1-one (BZDP) which can exhibit fascinating third-order nonlinear optical characteristics were probed through experimental cum theoretical simulations. The structural confirmation of the molecule is analysed via spectral studies. Studied chalcone is examined for linear and nonlinear optical studies which revealing molecule's ability as an organic NLO material. The electronic transitions are reflected in the absorption and emission spectra of the examined molecule. The fluorescence quantum yield was found to be 0.12. The experimental results were reinforced by the computational simulations executed using density functional theory method. Ground and excited state dipole moments, in addition to nonlinear optical properties were evaluated by solvatochromism. NLO studies were carried out in polar and non-polar solvent media by z-scan technique. Besides, the optical limiting ability of the compound reveals that it can be used as an optical limiter.

Donor-π-Acceptor Porphyrin-Assisted Bifunctional Defect Passivation for Enhanced Temporal Domain-/Wavelength-Dependent Nonlinear Absorption Properties in Perovskite Films.

Perovskite layer defects are a primary inhibiting factor for their optical nonlinearity, which restricts their use in nonlinear photonics devices. Nevertheless, due to the variety of defect types, the passivation and repair of these defects remain challenging. Herein, a novel bifunctional passivation strategy was proposed, and the porphyrin with a donor-π-acceptor structure was designed to bifunctionally repair perovskite defects by linking different types of functional groups via acetylenic π-conjugated linkage bridges on both sides, thus improving the nonlinear optical (NLO) absorption properties of porphyrin-perovskite hybrid materials. Research results indicate that the amino and carboxyl groups of porphyrins endow the ability to bifunctionally passivate charged defects via effective coordination interactions. The nonlinear absorption properties of all porphyrin-passivated MAPbI3 films were remarkably enhanced compared to that of the MAPbI3 film across multiple wavelengths and temporal domains. Particularly, the Por3-passivated perovskite film (MAPbI3/Por3) exhibited optimized strongest NLO performance, including reverse saturable absorption (RSA) under 800 nm femtosecond (fs) and 1064 nm nanosecond (ns) laser irradiations, as well as saturable absorption (SA) with 515 and 532 nm ns laser excitations. The value of the NLO absorption coefficient (β = 266.23 cm GW-1) is 1 order of magnitude higher than that of the pristine perovskite film (β = 12.93 cm GW-1), also outperforming other porphyrin-passivated perovskite films and some reported materials. The bifunctional passivation mechanism of porphyrin not only intensifies the perovskite's photoinduced ground-state dipole moment in the two-photon absorption (TPA) process and the free carrier absorption ability to deepen the RSA properties under 800 nm fs and 1064 nm ns lasers, respectively, but also enables the improvement of SA responses under 515 nm fs and 532 nm ns lasers by expediting the Pauli blocking effect of perovskite. Our study offers a viable paradigm, which aims at exploiting high-performance NLO perovskite materials across wide spectral regions and time scales.

Determination of the ground and excited state dipole moments of ferulic and sinapic acids by solvatochromic effects and density function theory method

Ferulic acid (FA) and sinapic acid (SA) are groups of phenolic acids that belong to the class of hydroxycinnamic acid. Due to their molecular structure and functional groups, these compounds exhibit a wide range of biological activities. In this research, we have determined the dipole moments of these compounds in gas and solvent phases using spectroscopic and computational methods. The change in the dipole moments of FA and SA was calculated by Bakhshiev’s, Kawski–Chamma–Viallet’s, Lippert–Mataga’s, and microscopic solvent polarity functions. The results show that the change in the dipole moment calculated using Lippert–Mataga’s method is higher than that using other methods. This is due to the fact that this method ignores the specific interactions of the solute and solvent as well as the polarizability of the solute molecule. Similarly, the ground and excited-state dipole moments were determined by theoretical quantum chemical calculations using density functional theory (DFT); the results are found to be similar to the experimental ones. In both approaches, the excited dipole moment is greater than the ground state, indicating a significant redistribution of electron densities and being more sensitive to the solvent in the excited state for both molecules. The HOMO-LUMO energy bandgaps calculated in the gas phase for FA and SA are 4.001 and 4.055 eV, respectively. In addition, electron charge density maps, UV–Vis absorption spectra, and oscillator strengths were calculated using the DFT method to obtain general information about the compounds.

Systematic photophysical investigation on pyrromethene 650 laser dye: Experimental and DFT approach

In the current study, we have chosen a highly fluorescent laser dye called pyrromethene 650 (PM-650) to investigate its photophysical properties using theoretical and experimental methods. We measured the absorption and emission spectra of PM-650 in polar protic and polar aprotic solvents at ambient temperature. Bathochromic and hypsochromic shifts were observed in the absorption and fluorescence spectra of the laser dye, confirming the presence of transitions between π → π* and n → π* states. We further estimated the ground and excited state dipole moments of PM-650 through experimental (solvatochromic correlations) and theoretical (ab initio) techniques, and compared the results. Interestingly, the PM-650 displayed an increased excited state dipole moment when contrasted with its ground state. Furthermore, using the B3LYP/6-311G++(d, p) approach, we estimated the natural bond orbital and molecular electrostatic potential map of PM-650 and discussed the results. Additionally, we theoretically determined the HOMO-LUMO energy band gap of PM-650 in different solvents with varying polarities, and found good agreement with the experimentally obtained values. To assess the reactivity and softness of PM-650, we calculated global chemical reactive descriptor values based on the theoretically estimated HOMO-LUMO. Our results suggest that PM-650 is highly reactive and possesses a soft nature.

Unveiling Solvation Dynamics of Excited and Ground States via Ultrafast Pump-Dump-Probe Spectroscopy.

The conventional ultrafast pump-probe spectroscopy has primarily focused on examining the formation and decay of the excited state intermediates, but it is very difficult to detect those intermediates while the formation is slow and dissipation is much fast because of the limited concentration during the intrinsic photocycle. To address this issue, a multipulse ultrafast pump-dump-probe spectroscopy was employed to generate and probe the short-lived ground state intermediates (GSIs) in an electronic push-pull pyrene derivative (EPP). This particular derivative undergoes planarized intramolecular charge transfer (PICT) in the excited state upon initial femtosecond pulse excitation. After applying the dump pulse once the PICT was formed, the blue-shifted transient absorption GSIs with the ground state dynamics of the structure recovery was directly observed. It is found that GSIs undergo slower reorganization than the PICT formation in the excited state of EPP due to the solvation effect with different dipole moments of ground states and excited states. These findings provide a comprehensive understanding of the full photocycle dynamics of both the ground and excited states, shedding light on the presence of hidden ground state behaviors.

Systematic Photophysical Interaction Studies Between Newly Synthesised Oxazole Derivatives and Silver Nanoparticles: Experimental and DFT Approach.

In this study, the photophysical properties of oxazole derivatives such as 5-(furan-2-yl) -4-tosyloxazole (OX-1) and 5-(2-bromothiazol-4-yl)-4-tosyloxazoles (OX-2) were investigated using theoretical and experimental techniques. The ground and excited state dipole moments were empirically obtained utilising the solvatochromic shift technique and several solvatochromic correlations such as Lippert's, Bakhshiev's, KawskiChamma- Viallet's, and solvent polarity equations. The ground state dipole moments, HOMO-LUMO and molecule electrostatic potential map were also computed using ab initio calculations and evaluated using Gaussian 09 W software. Furthermore, spectroscopic interactions between newly synthesised dyes (OX-1 and OX-2) and freshly synthesised silver nanoparticles (size 40nm) were studied. Increased absorbance and widening of absorption spectra for both dyes in the presence of varied quantities of silver nanoparticles show the potential of dye-nanoparticle interactions. Fluorescence quenching has been detected for both dyes in the presence of colloidal silver nanoparticles, indicating dynamic quenching, and a significant overlap between the absorption and emission spectra of the silver nanoparticle reveals that fluorescence quenching is also due to energy transfer.

Understanding the Role of Triplet‐Triplet Annihilation in Non‐Fullerene Acceptor Organic Solar Cells

AbstractNon‐fullerene acceptors (NFAs) have enabled power conversion efficiencies exceeding 19% in organic solar cells (OSCs). However, the open‐circuit voltage of OSCs remains low relative to their optical gap due to excessive non‐radiative recombination, and this now limits performance. Here, an important aspect of OSC design is considered, namely management of the triplet exciton population formed after non‐geminate charge recombination. By comparing the blends PM6:Y11 and PM6:Y6, it is shown that the greater crystallinity of the NFA domains in PM6:Y11 leads to a higher rate of triplet‐triplet annihilation (TTA). This is attributed to the four times larger ground state dipole moment of Y11 versus Y6, which improves the long range NFA out‐of‐plane ordering. Since TTA converts a fraction of the non‐emissive triplet states into bright singlet states, it has the potential to reduce non‐radiative voltage losses. Through a kinetic analysis of the recombination processes under 1‐Sun illumination, a framework is provided for determining the conditions under which TTA may improve OSC performance. If these could be satisfied, TTA has the potential to reduce non‐radiative voltage losses by up to several tens of millivolts.

Estimation of dipole moments by Solvatochromic shift method, spectroscopic analysis of UV–Visible, HOMO-LUMO, ESP map, Mulliken atomic charges, NBO and NLO properties of benzofuran derivative

Solvatochromic shift method has been used to estimate ground state (μg) and excited state (μe) dipole moments of benzofuran derivative (5NFMOT) at room temperature indifferent solvents. This method involves Lippert, Bakhshiev and Kawski-Chamma-Viallet equations. Reichardt microscopic solvent polarity parameter was used to calculate the change in dipole moment. Effect of solvents on absorption and fluorescence spectra was investigated using Kamlet and Catalan's MLR approach. Computational studies of benzofuran derivative were carried out using Gaussian 16. Geometry optimization was performed using DFT method at 6–311++G (d, p)/B3LYP basis set. UV–Visible spectra have been studied by using TD-DFT method for the same basis set. The μg was obtained from DFT method, whereas μe from TD-DFT method. It has been observed that both from experimentally and theoretically the ground state dipole moment is higher than the excited state dipole moment. HOMO-LUMO surfaces and Mulliken atomic charges have been studied in gas phase and solution. Furthermore, 3D plots of electrostatic potential map are used to identify reactive centers such as electrophilic and nucleophilic sites. NBO analysis is helpful to obtain stability and charge delocalization of the title molecule. Polarizablity, and hyper polarizability values were used to study the NLO properties.

Ground and Excited State Dipole Moments of Metformin Hydrochloride using Solvatochromic Effects and Density Functional Theory.

In this research, the ground (µg) and excited (µe) state dipole moments of metformin hydrochlorides were determined using Lippert-Mataga, Bakhshiev's, Kawski-Chamma-Viallet, and Reichardt models from fluorescence emission and UV-Vis absorption spectra in various solvents.From solvatochromic effects the calculated excited (µe) dipole moment of metformin hydrochloride were, 8.55 D, 8.34 D, 6.08 D, and 6.40 D using the Lippert-Mataga, Bakhshiev's, Kawski-Chamma-Viallet and Reichardt models respectively.The results also indicated that the dipole momentat the ground state is smaller than the excited state. This is due to solvent polarity having a stronger effect on fluorescence emission than absorption spectra.Similarly, from density functional theory, the calculated ground and excited states dipole moments of metformin hydrochloride using (DFT-B3LYP- 3-21+G*(μg= 10.02 D and μe= 11.94 D), DFT-B3LYP- 6-31+G (d, p) (μg= 8.44 D and μe= 10.87 D), and DFT-B3LYP- 6-311+G (d, p) (μg= 8.24 D and μe= 18.74 D)) analyzed by Gaussian 09W. From the optimized geometry of the molecule, the HOMO-LUMO energy band gap of metformin hydrochloride were computed using DFT [DFT-B3LYP- 3-21+G*(5.51 eV), DFT-B3LYP- 6-31+G (d, p) (5.66 eV), and DFT-B3LYP- 6-311+G (d, p) (5.70 eV)] respectively.

Benchmarking of different optimizers in the variational quantum algorithms for applications in quantum chemistry.

Classical optimizers play a crucial role in determining the accuracy and convergence of variational quantum algorithms; leading algorithms use a near-term quantum computer to solve the ground state properties of molecules, simulate dynamics of different quantum systems, and so on. In the literature, many optimizers, each having its own architecture, have been employed expediently for different applications. In this work, we consider a few popular and efficacious optimizers and assess their performance in variational quantum algorithms for applications in quantum chemistry in a realistic noisy setting. We benchmark the optimizers with critical analysis based on quantum simulations of simple molecules, such as hydrogen, lithium hydride, beryllium hydride, water, and hydrogen fluoride. The errors in the ground state energy, dissociation energy, and dipole moment are the parameters used as yardsticks. All the simulations were carried out with an ideal quantum circuit simulator, a noisy quantum circuit simulator, and finally a noisy simulator with noise embedded from the IBM Cairo quantum device to understand the performance of the classical optimizers in ideal and realistic quantum environments. We used the standard unitary coupled cluster ansatz for simulations, and the number of qubits varied from two starting from the hydrogen molecule to ten qubits in hydrogen fluoride. Based on the performance of these optimizers in the ideal quantum circuits, the conjugate gradient, limited-memory Broyden-Fletcher-Goldfarb-Shanno bound, and sequential least squares programming optimizers are found to be the best-performing gradient-based optimizers. While constrained optimization by linear approximation (COBYLA) and Powell's conjugate direction algorithm for unconstrained optimization (POWELL) perform most efficiently among the gradient-free methods, in noisy quantum circuit conditions, simultaneous perturbation stochastic approximation, POWELL, and COBYLA are among the best-performing optimizers.

Synthesis, characterization, TD‐DFT, molecular docking, biological applications, and solvatochromic studies of some new metal complexes derived from semicarbazone of pyrano[3,2‐c]quinoline‐3‐carboxaldehyde

New Zn(II), Cd(II), VO(IV), and UO2(VI) solvatochromic complexes derived from 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde‐semicarbazone ligand (H2L) were synthesized and established by elemental analyses, spectral (IR, UV, NMR, mass spectra), molar conductivity measurements, magnetic susceptibility, and thermal gravimetric analysis (TGA). The ligand coordinates with metal ions through ONO chelating sites, forming an octahedral geometry arrangement, except UO2(VI) that showed pentagonal bipyramidal geometry. Using Coats–Redfern methodology, the kinetic parameters (Ea, A, ΔH, ΔS, and ΔG) of the thermal decomposition steps were calculated and discussed. The complexes showed solvatochromic behavior that used to estimate the ground and excited state dipole moments. Optimization and structural parameters were carried out by density function theory (DFT) at B3LYP/GENECP method at 6‐311G(d,p) basis set for C, H, N, and O atoms and SDD (Stuttgart/Dresden) basis set for the metal atoms and interrelated with the experimental results. The complexes were tested for antimicrobial efficiency against Gram‐positive bacteria, Gram‐negative bacteria, yeast, and fungi. Also, antitumor activity was investigated against HepG‐2 cell line. Finally, the new synthesized complexes upon subjecting to molecular docking and distinguishable results showed outstanding inhibition results of VEGFR‐2 via achieving a high stabilization level inside the largest pocket of 1YWN protein.

Tetrachromophoric Derivatives of Dibenzoylmethanatoboron Difluoride Based on Stereoregular Cyclotetrasiloxanes: Synthesis and Properties.

A series of new tetrachromophoric systems based on stereoregular tetracyclosiloxanes and dibenzoylmethanatoboron difluoride derivatives have been synthesized and characterized by a complex of physicochemical methods. The photophysical properties of the synthesized compounds are studied by electronic absorption, steady-state, and time-resolved fluorescence spectroscopy. In the synthesized compounds, four dibenzoylmethanatoboron difluoride (DBMBF2)-based fluorophores are in an all-cis arrangement with respect to a cyclotetrasiloxane scaffold. DFT calculations predict that they can form H-type dimers, trimers, or tetramers with an antiparallel orientation of their ground-state dipole moments. Under UV excitation, solutions of these compounds in polar and nonpolar solvents exhibit complex fluorescence consisting of monomer- and excimer-like emissions with different lifetimes. Global fitting analysis reveals the presence of at least four kinetically distinguishable species in the excited state. The studied compounds in solutions have CIE chromaticity coordinates very close to the white color point and are promising objects for the development of next-generation single-emission materials for white illumination.

Toward strong nonlinear optical absorption properties of perovskite films via porphyrin axial passivation

Defects within perovskite layers are considered to be a primary factor that inhibits nonlinear optical (NLO) performance, and mitigating or eliminating them is indispensable for the implementation of high-performance perovskite-based photonic and energy devices. Herein, we propose a novel defect modulation strategy through binding the functional groups at the axial positions of porphyrins with the defects of perovskites. Two axially-coordinated porphyrin molecules (TiOPr and SnOHPr) were utilized as effective functional additives to passivate the defects and control perovskite crystallization, while the role of axial functional groups of porphyrins has been systematically studied. Z-scan measurement results demonstrate that porphyrin-treated perovskite films exhibit prominently enhanced optical absorption nonlinearities under ultrafast femtosecond (fs) laser excitation at 800 nm in comparison to the MAPbI3 perovskite film, the NLO absorption coefficient (β) values for the modified films are approximately one or two orders of magnitudes superior to that of the pristine film. This significant improvement in NLO performance likely stems from the increased photoinduced ground-state dipole moment of the perovskite film treated by porphyrin during the process of two-photon absorption (TPA), and their photoinduced charge/energy transfer between perovskite and porphyrin. Particularly, the MAPbI3/SnOHPr film displays the largest β values (636.92–6621.42 cm GW−1) among all measured samples at different irradiation energies and a low optical limiting threshold of 5 mJ cm−2, which may profit from the dual-functional passivation effect of SnOHPr onto perovskite, suggesting its great potential as optical limiters. These observations strongly indicate that porphyrin-axial passivated perovskite films are outstanding material candidates for optical limiting applications towards ultrafast fs laser pulses in the near-infrared region. Our work affords a feasible paradigm for constructing high-performance NLO perovskite materials through porphyrin-axial passivation of defects.

Push–pull octaphenylporphyrins with mixed substituents pattern: Synthesis, redox, ultrafast dynamics and nonlinear optical studies

A new family of β-functionalized octaphenylporphyrins, MOPP(NO2)Br3 (M = 2H, ZnII, NiII, or CuII, and OPP = octaphenylporphyrin) has been synthesized possessing unsymmetrical substitutions of bromo and nitro groups and the effect of asymmetrical substitutions on the redox, spectral, ultrafast dynamics, and nonlinear optical properties of the porphyrin macrocycles are investigated. Routes for the mixed functionalized OPPs begin with the bromination of NiOPP(NO2), leading to the formation of NiOPP(NO2)Br3 and H2OPPBr4. These ‘push–pull’ OPPs exhibited nonplanar conformation, red-shift in absorption spectra, tunable redox properties, and very high ground state dipole moments due to nonplanarity and asymmetric β-substitutions. All synthesized porphyrins exhibited a bathochromic shift (λmax = 23–38 nm) in the B band and λmax = 21–83 nm in the last Q band in comparison to MOPP due to attachment of the bromo and nitro groups on its peripheral positions. In the cyclic voltammograms, the first oxidation and reduction potential showed an anodic shift compared to its parent porphyrins due to the presence of strong electron acceptor bromo and nitro groups, which are present on the porphyrin periphery. These β-functionalized octaphenylporphyrins have shown excellent nonlinear optical response. The observed structure-dependent nonlinear refractive index (n2) values are in the range of ∼ 0.37–1.68 × 10−19 m2 W−1, and two-photon absorption coefficient (β) values are in the range of ∼ 0.19–4.56 × 10−12 m W−1. The transient absorption studies reveal that the decay dynamics of ZnOPP(NO2)Br3 exhibited long-lived τ1 component, while NiOPP(NO2)Br3 exhibited long-lived τ2 component than other OPP derivatives.

Dipole Moments and Transition Dipole Moments Calculated by Pair-Density Functional Theory with State Interaction

We develop response-function algorithms for dipole moments and transition dipole moments for compressed multistate pair-density functional theory (CMS-PDFT). We use the method of undetermined Lagrange multipliers to derive analytical expressions and validate them using numerical differentiation. We test the accuracy of the magnitudes of predicted ground-state and excited-state dipole moments, the orientations of these dipole moments, and the orientation of transition dipole moments by comparison to experimental data. We show that CMS-PDFT has good accuracy for these quantities, and we also show that, unlike methods that neglect state interaction, CMS-PDFT yields correct behavior for the dipole moment curves in the vicinity of conical intersections. This work, therefore, opens the door to molecular dynamic simulations in strong electric fields, and we envision that CMS-PDFT can now be used to discover chemical reactions that can be controlled by an oriented external electric field upon photoexcitation of the reactants.

Fine Tuning of Donor‐Acceptor Structures in Fused‐Carbazole Containing Thermally Activated Delayed Fluorescence Materials towards High‐Efficiency OLEDs

Comprehensive SummaryConjugated fused‐ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited‐state relaxation and non‐radiative decay, and further to enhance the luminance efficiency for emissive materials. Herein, we develop a series of donor‐acceptor type thermally activated delayed fluorescence (TADF) emitters by introducing fused‐ring 5H‐benzofuro[3,2‐c]carbazole (32BFCz) as electron donating unit. Through optimizing the numbers and structure of donor and acceptor moieties, three compounds named 32BFCzA, mCF3BFCzOXD and dCF3BFCzOXD are designed, which are composed by mono‐32BFCz/trifluoromethylpicolinonitrile, penta‐BFCz/3‐(trifluoromethyl)phenyl)‐1,3,4‐oxadiazol‐2‐yl)benzene and penta‐32BFCz/3,5‐bis(trifluoromethyl)phenyl)‐1,3,4‐oxadiazol‐2‐yl)benzene as donor/acceptor groups, respectively. They all exhibited green emission with peak value ranging from 532 to 540 nm. Through rationally tuning the donor/acceptor properties to reduce the distance between positive and negative charges, the ground state dipole moments decline from 8.93, 6.18 to 5.30 Debye, which further induced sequentially reduced singlet‐triplet energy splits (ΔESTs), increased photoluminescence quantum yields (PLQYs), enhanced reverse intersystem crossing rate (kRISCs) and diminished delayed fluorescence lifetime from 32BFCzA, mCF3BFCzOXD to dCF3BFCzOXD. Therefore, gradually increased external quantum efficiency (EQE) is accordingly achieved when employing them as emitters for TADF OLEDs. dCF3BFCzOXD with the mostly optimized donor/acceptor structures demonstrates the highest efficiency with maximum EQE to 21.4%. Our work provides guidelines on the design of high‐efficiency D‐A type TADF materials.

Automated Active Space Selection with Dipole Moments.

Multireference calculations can provide accurate information of systems with strong correlation, which have increasing importance in the development of new molecules and materials. However, selecting a suitable active space for multireference calculations is nontrivial, and the selection of an unsuitable active space can sometimes lead to results that are not physically meaningful. Active space selection often requires significant human input, and the selection that leads to reasonable results often goes beyond chemical intuition. In this work, we have developed and evaluated two protocols for automated selection of the active space for multireference calculations based on a simple physical observable, the dipole moment, for molecules with nonzero ground-state dipole moments. One protocol is based on the ground-state dipole moment, and the other is based on the excited-state dipole moments. To evaluate the protocols, we constructed a dataset of 1275 active spaces from 25 molecules, each with 51 active space sizes considered, and have mapped out the relationship between the active space, dipole moments, and vertical excitation energies. We have demonstrated that, within this dataset, our protocols allow one to choose among a number of accessible active spaces one that is likely to give reasonable vertical excitation energies, especially for the first three excitations, with no parameters manually decided by the user. We show that, with large active spaces removed from consideration, the accuracy is similar and the time-to-solution can be reduced by more than 10 fold. We also show that the protocols can be applied to potential energy surface scans and determining the spin states of transition metal oxides.