CIS Methods Research Articles

Reverse Designing the Wavelength-Specific Thermally Activation Delayed Fluorescent Molecules Using a Genetic Algorithm Coupled with Cheap QM Methods.

Genetic algorithm (GA) optimization coupled with the semiempirical intermediate neglect of differential overlap (INDO)/CIS method is presented to inversely design the red thermally activation delayed fluorescent (TADF) molecules. According to the predefined donor-acceptor (DA) library to build an ADn-type TADF candidate, we utilized the chemical notation language SMILES code to generate a TADF molecule and apply the RDKit program to produce the initial 3D molecular structure. A combined fitness function is proposed to evaluate the performance of the functional-lead TADF molecule. The fitness function includes three key parameters, i.e., the emission wavelength, the energy gap (ΔEST) between the lowest singlet (S1)- and triplet (T1)-excited states, and the oscillator strengths for electron transition from S0 and S1. A cheap QM method, i.e., INDO/CIS, on the basis of an xTB-optimized molecular geometry is applied to quickly calculate the fitness function. Finally, the GA approach is utilized to globally search for the wavelength-specific TADF molecules under our predefined DA library, and the optimum 630 nm red and 660 nm deep red TADF molecules are inversely designed according to the evolution of molecular fitness functions.

Systematic review and meta-analysis of completely retroperitoneoscopic nephroureterectomy versus traditional retroperitoneoscopic nephroureterectomy in upper tract urothelial carcinoma.

This systematic review and meta-analysis aim to evaluate the efficacy and safety of completely retroperitoneoscopic nephroureterectomy (CRNU) for the treatment of upper urinary tract urothelial carcinoma (UTUC). A systematic review of PubMed and Web of Science databases was conducted to identify trials comparing the outcomes of CRNU and other surgical procedures. A total of 6 case-control studies were selected for analysis. The efficacy and safety of CRNU were evaluated using mean difference or hazard ratio (HR) with 95% CIs, employing continuous or dichotomous method with a random or fixed-effect model. Meta-analysis was performed using STATA 11.0 software. The meta-analysis indicated that CRNU in subjects with UTUC was significantly associated with a shorter operation time (standardized mean difference, -1.36; 95% CI, -1.61 to -1.11, P < .001) and lower blood loss (standardized mean difference, -0.54; 95% CI, -0.77 to -0.31, P < .001) when compared to traditionally retroperitoneoscopic nephroureterectomy (TRNU). No significant difference was observed in the occurrence of grade I & II complications (HR, 1.04; 95% CI, 0.49-2.2, P = .915) and total complications (HR, 0.69; 95% CI, 0.38-1.27, P = .238) between CRNU and TRNU. The findings suggest that CRNU is an advanced surgical technique that is safe and effective for the treatment of UTUC. We recommend that CRNU be further employed for patients with UTUC. Further randomized, multicenter trials are needed to validate these results, given the limitations of this study.

Extended pilot test of a cross-injection in situ denitrification system for pre-emptive treatment of municipal well water

Elevated groundwater nitrate concentrations have been linked to deleterious health and environmental effects. A significant source of the nitrate is nitrogen fertilizers applied to agricultural landscapes. Beneficial Management Practices (BMPs), including the optimization of fertilizer use and selective crop rotations, have proven to be effective in some cases. The city of Woodstock in southern Ontario relies on public wells for all of its municipal supply. Several of the wells have experienced chronic increases in nitrate concentrations exceeding the maximum allowable limit of 10 mg/L N-NO3−. While BMPs are established, an interim reduction plan based on enhanced in situ denitrification (Cross Injection System, CIS) in a 15 m thick zone of high nitrate mass flux within the aquifer zone was evaluated. Based in the results of preliminary acetate injection experiments, a C:N ratio of 2.35, (approximately 260 mg acetate/L), was selected to optimize the denitrification reaction. Injections were performed for six hours a day every day for a period of approximately two months. Dissolved oxygen (DO) and nitrate concentrations recorded over time indicated that reduction of both commenced within a few days of the beginning of the acetate injections and reduced levels were maintained for the remainder of the two-month injection period. Denitrification occurred throughout the profile although nitrate reduction was the highest in the lower groundwater velocity zones. An overall reduction of nitrate of 50% was achieved through the treated section of the aquifer. It is estimated that an upscaled treatment system utilizing a treatment width of only 70 m would be sufficient to reduce the nitrate concentrations to below the drinking water limit demonstrating the potential for the CIS method to functions as an interim groundwater nitrate reduction strategy.

Quantum chemical study of tautomeric equilibriums, intramolecular hydrogen bonds, and π-electron delocalization in the first singlet and triplet excited states of 2-selenoformyl-3-thioxo-propionaldehyde

In the present study, the tautomeric process, intramolecular hydrogen bonding (IMHB), and π-electron delocalization (π-ED) of 2-selenoformyl-3-thioxo-propionaldehyde (STP) in the first singlet and triplet excited states were investigated by CIS and TD-DFT methods. The relative energies of hydrogen-bonded tautomers in both excited states indicate that the thiol/enol conformers are the most/least stable forms. In this regard, a detailed analysis of various tautomeric equilibriums, different types of hydrogen bonds, and π-electron delocalization was performed. The electronic energies of different tautomers indicate the thermodynamic preference of thiol with respect to the other forms. Furthermore, the low activation energy barriers of thione⇄thiol equilibrium also show the kinetic preference of thiol. On the other hand, the estimation of different hydrogen bond energies emphasizes the stronger IMHB of enol. Moreover, the evaluation of π-ED by the structural parameter of Gilli (λ) represents the significance of electron mobility in the enol conformers. Consequently, the duality between the IMHB and π-ED with the thermodynamic stability order of tautomers indicates that the tautomeric phenomenons play a dominant role in determining the stability of the benchmark structures in both singlet and triplet excited states.

Experimental and Computational Study of Novel Pyrazole Azo Dyes as Colored Materials for Light Color Paints

This paper presents the synthesis of eight new pyrazole azo dyes using ethyl 5-amino-3-methyl-1H-pyrazole-4-carboxylate as the diazotization component and various active methylene derivatives as coupling components. These new azo dyes were characterized by spectroscopic (FT-IR, UV-VIS), and spectrometric (1H NMR, 13C NMR, MS) analyses. The dye structures were modeled by the MMFF94s force field and quantum chemical density functional theory (DFT) calculations using the B3LYP functional and the 6-311G(d,p) basis set, in the gas phase. Weak electrostatic hydrogen bonds for the azo and hydrazo dye tautomers were found in the ground state. The CIS, TD (using the B3LYP and M06-2X functionals), and ZINDO methods were used to estimate the dye UV-VIS spectra in ethanol, which were compared with the experimental ones. The anti-configuration arrangement of the π-bonds and the presence of the prevalent hydrazo dye tautomer were supported by the computed 1H NMR and 13C NMR spectra. A good accordance between the experimental and predicted absorption maxima and chemical shifts was observed. Color investigations using the CIEL*a*b* space were conducted for all dyes in powder and for their mixtures in water-based acrylic resins. The results confirm the newly synthesized dyes’ color properties and that they might be used for light color paints in the varnishes industry.

Variation in electrophilicity on electronic excitation

AbstractThe rationality of the minimum electrophilicity principle (MElP) as a companion of minimum polarizability principle and maximum hardness principle is studied for simple diatomic, triatomic, and tetratomic molecules. The applicability is further justified considering organic molecules (e.g., pyrene and acridine yellow) are known for their photophysical properties and accordingly their excited state properties. Single excitation CI (CIS) and time‐dependent density functional theory (TDDFT) are employed to study the excited state reactivity. Two types of excitations, namely vertical and adiabatic, are considered. Processes involving conservation and change in spin multiplicity are included during excitation. The general trend is that the molecules are less electrophilic in the ground state than those in the corresponding excited states. It is found that adiabatic excitation validates the principle even for the triplet ground state molecules undergoing an excitation where spin multiplicity gets altered. The TDDFT method explains the validity of the MElP augmenting the CIS method. This study echoed the MElP during molecular electronic excitation.

Agreement of Bioluminescence Measurements and Visual Assessment in Monitoring Occlusal Surfaces of Permanent Teeth

Background: Caries lesion activity is typically assessed by visual–tactile criteria. Regular monitoring is required to detect the transition of lesions and to ensure that the initial assessment was valid. This clinical study aimed to evaluate the agreement of bioluminescence measurements (Calcivis imaging system, Cis) with visual examination to assess caries lesion activity and to monitor occlusal surfaces. Methods: The occlusal surfaces of ninety-one permanent posterior teeth were assessed for the presence or absence of active caries lesions with ICCMS criteria and Cis measurements at three visit times: baseline (t1) and six months (t2) and 12 months (t3) after baseline. Results: At the baseline visit, 70% of the included occlusal sites were assessed visually as active lesions (ICCMS codes 1 and 2). At t3, 64.8% of the sites showed signs of an active lesion. The percentage agreements between the visual and Cis methods were 87.8% (t1), 89.9% (t2) and 88.6% (t3). The corresponding κ-values were 0.71 (95% CI 0.52;0.87), 0.75 (95% CI 0.59;0.89) and 0.77 (95% CI 0.61;0.90), respectively. No significant difference between the visual and bioluminescence systems was found at any visit (p > 0.05). The results based on cluster randomization (generalized estimation equations) showed no significant differences between the visual and Cis findings for all visits (p = 0.108, Wald Χ2 with 1 df = 2.587). Conclusion: The bioluminescence system demonstrated substantial agreement for the activity assessment of occlusal lesions compared to the findings obtained by visual assessment over twelve months.

Study of the conformations and tautomerisation pathway in (Z)-4-(hydroxypropyl) isochroman-1, 3‑dione: Analysis through energy, vibrational signatures and hardness profiles

• Tautomerisation pathways in (Z)−4-(hydroxypropyl) isochroman-1, 3‑dione are identified. • Several conformers are identified for both tautomers. • The role of substituents in the tautomerisation process in AICs is explored. • Maximum hardness principle and minimum electrophilicity principles are studied extensively. • Crystal structure data and FT-IR spectra corroborate our computational results. This article thoroughly probes the interconnectivity between all the conformations/configurations and the tautomerisation pathway in ( Z )-4-(hydroxypropyl) isochroman-1, 3‑dione (PIC) both in S 0 and S 1 states. The crystal structure data corroborates our computational results done with DFT and MP2 methods utilizing various basis sets. The tautomers are separated by 2.5 ± 0.3 kcal/mole in S 0 . The comparison of potential energy curves of close analogues shows that the inertia of the substituted functional groups (here C 2 H 5 ) plays a significant role in the proton transfer process. Intrinsic Reaction Coordinate (IRC) and frequency computations locate the transitions states (TS) in S 0 .The transition region in the tautomerisation pathway is clearly marked with the evaluation of reaction force and force constants. The excited state computations with CIS and TDDFT methods show some inconsistency regarding the relative energies of the tautomers. Maximum hardness principle (MHP) and minimum electrophilicity principle (MEP) are applied in this case. The frontier molecular orbitals in both the tautomers confirms the S 0 →S 1 transition as π-π* in nature. The plot of the difference in electron densities between S 0 and S 1 states in both the tautomers hint at the photophysical processes occurring on excitation. The vibrational signatures are detected and characteristic spectral lines and their relative intensities are discussed. The strong C = O stretching vibration appearing at 1740 cm −1 in the observed FT-IR spectra is computed to be at 1757 cm −1 confirming our assertion of PIC as a minimum energy tautomer.

How to Predict Excited State Geometry by Using Empirical Parameters Obtained from Franck-Condon Analysis of Optical Spectrum.

Excited state geometries of molecules can be calculated with highly reliable wavefunction schemes. Most of such schemes, however, are applicable to small molecules and can hardly be viewed as error-free for excited state geometries. In this study, a theoretical approach is presented in which the excited state geometries of molecules can be predicted by using vibrationally resolved experimental absorption spectrum in combination with the theoretical modelling of vibrational pattern based on Franck-Condon approximation. Huang-Rhys factors have been empirically determined and used as input for revealing the structural changes occurring between the ground and the excited state geometries upon photoexcitation. Naphthalene molecule has been chosen as a test case to show the robustness of the proposed theoretical approach. Predicted 1B2u excited state geometry of the naphthalene has similar but slightly different bond length alternation pattern when compared with the geometries calculated with CIS, B3LYP, and CC2 methods. Excited state geometries of perylene and pyrene molecules are also determined with the presented theoretical approach. This powerful method can be applied to other molecules and specifically to relatively large molecules rather easily as long as vibrationally resolved experimental spectra are available to use.

Composite performance indicators for helmet and seat-belt enforcement as imprecise data

Objectives Composite road safety performance indicators (RSPIs) are useful tools in regional road safety planning. Among the indicators and data calculated by the World Health Organization (WHO), information on the effectiveness of law enforcement on various risk factors for road casualties were provided, which can be considered as qualitative indicators. The purpose of this study is to analyze the performance indicators related to the percentage of helmet and seat-belt use versus the qualitative enforcement scores attributed by WHO. Methods This analysis was performed for 30 member states of WHO and will show how and with what degree of efficiency the qualitative output of the enforcement score acts versus the input percentage of seat-belt and helmet use. The qualitative nature of the output index has led us to depart the traditional analysis of crisp numerical indicators related to road safety performance and to consider data as imprecise or fuzzy indices. In this study we used two methods including imprecise DEA-based CIs and fuzzy DEA-based CIs, respectively. Results Results show that the clear score achieved by the Imprecise DEA-based CI model is easy to interpret and use. Whereas, in the Fuzzy DEA-based CI model, the fuzzy indicator scores obtained based on the level of several probabilities are strong in capturing the uncertainties related to human behavior. Conclusions Both RSPIs are applicable with slight differences that were in the order of countries and the ease of reading the results. We also found that each method has different strengths and that the FDEA-based CIs method is more accurate and more in line with the inputs than the IDEA-based CIs method.

Peri-Acenoacene molecules: tuning of the singlet and triplet excitation energies by modifying their radical character.

The energy difference between singlet and triplet excitons, or ΔEST, is a key parameter for novel light-emission mechanisms (i.e., TADF or thermally activated delayed fluorescence) or other photoactivated processes. We have studied a set of conjugated molecules (peri-acenoacenes and their heteroatom-doped analogues) to observe the evolution of their excited-state properties upon increasing the system size with and without substitution with a pair of N atoms. Since these molecules exhibit a (ground-state) diradicaloid character, together with marked correlation effects influencing the excited-states formed, we have applied a variety of theoretical methods (FT-DFT, TD-DFT, SF-TD-DFT, CIS, CIS(D), SCS-CC2, SA-CASSCF, and SC-NEVPT2) to bracket the accuracy of the results while concomitantly providing insights into electronic structure. The results show how this chemical strategy (N-doping) largely modifies not only the excited-state energies but also the oscillator strengths and the ΔEST values, constituting versatile platforms for fine-tuned photophysical applications.

Synthesis, spectral characterization, and theoretical investigations of a new azo-stilbene dye for acrylic resins

This paper presents the synthesis of a new symmetrical disazo direct dye with good coloring properties for acrylic resins and several theoretical approaches to choose the best simulation method of the dye structure and spectra. The synthesized dye contains 4,4′-diaminostilbene-2,2′-disulfonic acid, as middle component and 2,7-dihydroxynaphthalene, as coupling component. It was analyzed by thin-layer chromatography (TLC), FT/IR, UV/VIS, 1H NMR, 13C NMR spectroscopy, and HRMS spectrometry. The molecular dye structure was investigated using molecular mechanics and the Density Functional Theory (DFT) approach at the B3LYP/6-31G(d,p), B3LYP/6-31+G(d,p) and B3PW91/6-311G(d,p) levels. Theoretical vibrational frequencies and structural parameters were calculated and the dye UV/VIS spectrum was simulated using the CIS, TD and ZINDO methods and compared with the experimental data. The ZINDO approach gave better maximum absorption predicted values compared to the CIS and TD methods. A generally good agreement between the experimental and theoretical computed absorption maxima and excellent correspondences between the experimental and calculated vibrational frequencies and chemical shifts were found. The experimental and simulated vibrational, UV/VIS and 13C NMR spectra confirmed the trans-configuration form of the π-bonds of the investigated dye. The CIEL∗a∗b∗ color space was used in all color measurements for the dye in powder and its mixtures with a water-based acrylic resin and confirmed the color properties of the newly synthesized dye.

Conformers of 1,2,3,4 –tetrahydroisoquinoline in S0 and S1: An analysis through potential energy surface, hardness principles and vibrational spectroscopy

The conformational search for 1, 2, 3, 4-tetrahydroisoquinoline (THIQ) yields a number of conformers in S0 and S1 states. DFT calculations with different functionals along with ab-initio calculations indicate that the structure of the global minima in S0 strongly depends on basis sets and methods of calculation. The two close lying low energy conformers are the twisted ones with i) the axial position of NH and ii) equatorial position of NH. Their energy differs by 60 ± 30 cm−1 over all possible variations. The computed potential energy surfaces (PES) show three inequivalent minima in S0 and two in S1. Three transition states are found in S0 and two in S1. The twisted conformer with axial hydrogen (TA) is found to be the global minima in S1. The twisting angle for the optimized TA conformer is ∼31° in S0 and ∼32° in S1. The excited state is probed through CIS and TDDFT methods. The characteristic low-frequency vibrations appear at 93 cm−1 and 146 cm−1 in S0. The observed FT-IR spectra and the earlier observations in molecular beam experiments corroborate well with our calculated spectra. Frontier molecular orbital calculations associated with the electron density plots clearly identify the changes on the density on excitation. The calculated UV–Vis absorption spectra are explained with the help of these orbitals. Molecular electrostatic potential is calculated and the sites of eletrophilic interactions are noted. Hardnesses and electrophilicities are calculated for all the conformers to check their relative stability. The maximum hardness principle (MHP) is obeyed by the lowest energy conformer in DFT calculations with different functionals, but minimum electrophilicity principles (MEP) are not obeyed.

Evidence of Skewness and Sub-Gaussian Character in Temperature-Dependent Distributions of One Million Electronic Excitation Energies in PbS Quantum Dots.

Obtaining statistical distributions by sampling a large number of conformations is vital for an accurate description of temperature-dependent properties of chemical systems. However, constructing distributions with 105-106 samples is computationally challenging because of the prohibitively high computational cost of performing first-principles quantum mechanical calculations. In this work, we present a new technique called the effective stochastic potential configuration interaction singles (ESP-CIS) method to obtain excitation energies. The ESP-CIS method uses random matrix theory for the construction of an effective stochastic representation of the Fock operator and combines it with the CIS method. Excited-state energies of PbS quantum dots (0.75-1.75 nm) at temperatures of 10-400 K were calculated using the ESP-CIS method. Results from a total of 27 million excitation energy calculations revealed the distributions to be sub-Gaussian in nature with negative skewness, which progressively became red-shifted with increasing temperature. This study demonstrates the efficacy of the ESP-CIS method as a general-purpose method for efficient excited-state calculations.

A corrected CIS(D∞) method for valence and Rydberg excitation energies

CIS(D∞) method provides reasonable valence excitation energies, but fails for Rydberg states. A corrected CIS(D∞) method is proposed where excitation energies are calculated based on the energy expression in EOM-CCSD(2) using wavefunctions from CIS(D∞). Its performance on singlet and triplet valence and Rydberg excitation energies is investigated by comparing with CC3 results. Excitation energies with this method are always overcorrected. On the other hand, reasonable valence and Rydberg excitation energies will be achieved when the energy correction is halved. This method has a non-iterative N6 scaling and can serve as an economical method in studying both valence and Rydberg excitations.

Excited States of Weak Interacting Complexes of Formaldehyde and Alkali Metal Ions

The electronically excited states of formaldehyde and its complexes with alkali metal ions are investigated with the time-dependent density functional theory (TD DFT) method. Vertical transition energies for several singlet and triplet excited states, adiabatic transition energies for the first singlet and triplet excited states S1 and T1, the adiabatic geometries and vibrational frequencies of the ground state S0 and the first singlet and triplet excited states S1 and T1 for formaldehyde and its complexes are calculated. Better agreement with the experiment than that of the CIS method is obtained for CH2O at the TD DFT level. The nonlinear C=O⋯M+ interaction in the excited states S1 and T1 is weaker than the linear interaction in the ground state. In the S0 and S1 states, the C=O bond is elongated by cation complexation and its stretching frequency is red-shifted, but in the T1 state the C=O bond is shortened and its frequency is blue-shifted.

Concerted-asynchronous reaction path of the excited-state double proton transfer in the 7-azaindole homodimer and 6H-indolo[2,3-b]quinoline/7-azaindole heterodimer

Reaction path of the excited-state double proton transfer (ESDPT) in the homodimer of 7-azaindole (7AI2 homodimer) and heterodimer of 6H-indolo[2,3-b]quinoline and 7-azaindole (6HIQ-7AI heterodimer) is computationally studied by means of intrinsic reaction coordinate (IRC) calculations. The IRC path determined at the TDDFT level predicts the concerted-asynchronous mechanism for the ESDPT in 6HIQ-7AI as well as in 7AI2, where the N–H⋯N hydrogen bonds exhibit asymmetric structures along the reaction path with a single energy barrier. The IRC calculations at the CIS level, however, exhibits a local minimum for single-proton-transferred intermediate, suggesting the stepwise mechanism. Single-point energy calculations at the RI-CC2 level reproduce the TDDFT results, but do not the CIS results. On the basis of potential-energy profiles calculated against intermolecular distance, the discrepancy between the TDDFT and CIS methods is likely attributed to the underestimation of intermolecular interaction energy in the latter method due to the lack of dynamical electron correlation.

Assessment of TDDFT- and CIS-based methods for calculating fluorescence spectra of (dibenzoylmethanato)boron difluoride exciplexes with aromatic hydrocarbons.

The applicabilities of various CIS- and TDDFT-based procedures to the calculation of the fluorescence spectra of DBMBF2 exciplexes with aromatic hydrocarbons are analyzed. It is shown that a reasonable agreement between the calculated and experimental fluorescence spectra is obtained when a combined procedure is used. In this combined procedure, the geometries of the exciplexes are optimized beforehand using the CIS method with an empirical dispersion correction, while the exciplex transition energies are calculated at the optimized geometries using the CIS(D) method or the TDDFT approach with double-hybrid B2PLYP and mPW2PLYP functionals.

TD-DFT benchmark: Excited states of atoms and atomic ions

Time-Dependent Density Functional Theory (TD-DFT) calculations in their conventional form, starting from the ground, low-spin state of atoms and atomic ions, have been carried out to examination the precision of excitation energy predictions. Results obtained for several functionals and basis sets have been compared with experimental data and include valence low- and high-spin states.All DFT methods achieve basis sets limits extremely quickly, but produce results that are far from the experimental values. A simple scaling procedure, analogous to that used for IR frequency calculations, is difficult to find. In principle, one can assume that the excitation energy is underestimated. The CIS method is less precise than most of the global hybrid DFT functionals. It also turns out that CIS(D) and TD-DFT methods can give results of similar precision. Consideration of diffusion functions is strongly recommended, even in the case of valence low-spin states. The adiabatic linear response scheme currently used by TD-DFT is a source of problems in the calculation of triplet states.

Synthesis and photophysical properties of halogenated derivatives of (dibenzoylmethanato)boron difluoride

A series of (dibenzoylmethanato)boron difluoride (BF2DBM) derivatives with a halogen atom in one of the phenyl rings at the para-position were synthesized and used to elucidate the effects of changing the attached halogen atom on the photophysical properties of BF2DBM. The room-temperature absorption and fluorescence maxima of fluoro-, chloro-, bromo- and iodo-substituted derivatives of BF2DBM in THF are red-shifted by about 2–10nm relative to the corresponding peaks of the parent BF2DBM. The fluorescence quantum yields of the halogenated BF2DBMs (except the iodinated derivative) are larger than that of the unsubstituted BF2DBM. All the synthesized compounds are able to form fluorescent exciplexes with benzene and toluene (emission maxima at λem=433 and 445nm, respectively). The conformational structure and electronic spectral properties of halogenated BF2DBMs have been modeled by DFT/TDDFT calculations at the PBE0/SVP level of theory. The structure and fluorescence spectra of exciplexes were calculated using the CIS method with empirical dispersion correction.