Intermediate Neglect Of Differential Overlap Research Articles

Electronic Properties of Poly(N-vinylcarbazole) Using semi-empirical oligomer extrapolation approximations

Poly(N-vinylcarbazole) has been widely used in polymer light emitting diodes due to its unique electronic properties. The electronic properties of Poly(N-vinylcarbazole) were examined using the Semi-Empirical Zerner Modified Intermediate Neglect of Differential Overlap (ZINDO) oligomer extrapolation method. In this calculation, the electronic properties of Poly(N-vinylcarbazole) were extracted from oligomer electronic properties. We identified a tendency for oligomers with large HOMO-LUMO gaps in the form of linear regression as function of reciporocal of monomeric units. The increasing number of monomers induce the interaction between energy levels of each monomer which boardening the energy levels. The localized molecular orbital and vibration spectra of the basic unit of polymer Poly(N-vinylcarbazole) also has been investigated.

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.

Semi-Empirical Calculation of Bodipy Aggregate Spectroscopic Properties through Direct Sampling of Configurational Ensembles.

Efficient prediction of the aggregation-induced callback of organic chromophores for utilization in molecular sensorics is a desirable development goal in modern computational chemistry. Dye aggregates are complicated to study when utilizing conventional quantum chemistry approaches, since they are usually composed of too many atoms to be effectively analyzed, even with high-throughput parallel systems. Here, we present a successful attempt to develop a protocol to assess the spectroscopic changes happening in BODIPY dyes upon aggregation from the first principles utilizing extended tight-binding (XTB) and Zerner’s intermediate neglect of differential overlap (ZINDO) Hamiltonians. The developed sampling technique for aggregate configurational space scanning was found to be sufficient to both reproduce peculiarities and justify experimental data on the spectroscopic behavior of chromophore aggregates. The sTDA, sTD-DFT (GFN2-XTB) and CIS (ZINDO) approaches were assessed, and then sources of errors and benefits were outlined. Importantly, our goal was to keep any of the mentioned calculations within a computational cost feasible for a single workstation, whereas scaling was possible at any point in time. Finally, several aggregate structures were investigated in the external field to try to achieve distributions similar to the ones observed in the electrostatic potential of the air–water interface to assess the borderlines of practical applicability of the suggested scheme.

Advances, challenges and perspectives of quantum chemical approaches in molecular spectroscopy of the condensed phase.

The purpose of this review is to demonstrate advances, challenges and perspectives of quantum chemical approaches in molecular spectroscopy of the condensed phase. Molecular spectroscopy, particularly vibrational spectroscopy and electronic spectroscopy, has been used extensively for a wide range of areas of chemical sciences and materials science as well as nano- and biosciences because it provides valuable information about structure, functions, and reactions of molecules. In the meantime, quantum chemical approaches play crucial roles in the spectral analysis. They also yield important knowledge about molecular and electronic structures as well as electronic transitions. The combination of spectroscopic approaches and quantum chemical calculations is a powerful tool for science, in general. Thus, our article, which treats various spectroscopy and quantum chemical approaches, should have strong implications in the wider scientific community. This review covers a wide area of molecular spectroscopy from far-ultraviolet (FUV, 120-200 nm) to far-infrared (FIR, 400-10 cm-1)/terahertz and Raman spectroscopy. As quantum chemical approaches, we introduce several anharmonic approaches such as vibrational self-consistent field (VSCF) and the combination of periodic harmonic calculations with anharmonic corrections based on finite models, grid-based techniques like the Numerov approach, the Cartesian coordinate tensor transfer (CCT) method, Symmetry-Adapted Cluster Configuration-Interaction (SAC-CI), and the ZINDO (Semi-empirical calculations at Zerner's Intermediate Neglect of Differential Overlap). One can use anharmonic approaches and grid-based approaches for both infrared (IR) and near-infrared (NIR) spectroscopy, while CCT methods are employed for Raman, Raman optical activity (ROA), FIR/terahertz and low-frequency Raman spectroscopy. Therefore, this review overviews cross relations between molecular spectroscopy and quantum chemical approaches, and provides various kinds of close-reality advanced spectral simulation for condensed phases.

Electronic Spectra and Photolysis of Bisphenol A in Water

A quantum chemical study of the spectral and luminescent properties of the BPA + 2H2O complex was carried out. Calculations were performed by the semi-empirical method of intermediate neglect of differential overlap using a program complex and a special parameterization. The spectral behavior of BPA in water was modeled by a complex with water molecules in the ratio 1: 2 forming the hydrogen bond. The calculated data were compared with the results of investigation of the isolated BPA molecule. The nonplanar BPA structure leads to the strong mixing of the π- and σ-type atomic wave functions. The main reason for the low quantum yield of the BPA fluorescence is the efficient process of singlet-triplet conversion in the S1(ππ*) ≳ Tn(πσ*) channel of the BPA molecule and its complex with water. A study of the photolysis of the isolated BPA molecule upon exposure to solar radiation, the short-wavelength boundary of which on the Earth’s surface is located at ~290 nm (~34480 cm–1), showed that the energy of the photodissociative state localized on the O–H bond is much higher than this value for BPA. The binding curve is characteristic of the S1(ππ*) state, while the singlet and triplet states of the πσ* type, localized on the single C–C bonds of the central fragment of the molecule, are repulsion curves with a barrier. From our point of view, the low efficiency of the BPA degradation under the influence of solar radiation is due to the presence of a significant potential barrier to the photolysis in the singlet or triplet state. The mechanisms of bond breaking in the BPA + 2H2O complex are different for the singlet and triplet states, namely, for the S3(πσ*) state, the break occurs by the predissociation mechanism, and for the Tn(πσ*) state, due to its population through the singlet-triplet conversion in the S1(ππ*) → Тn(πσ*) channel.

A semiempirical effective Hamiltonian based approach for analyzing excited state wave functions and computing excited state absorption spectra using real-time dynamics.

We describe a new approach to extract information about an excited state wave function using a reduced orbital space molecular orbital decomposition approach for time-dependent density obtained from real-time dynamics. We also show how this information about the excited state wave function can be used to accelerate the convergence of real-time spectra and model excited state electron dynamics. We have combined this approach with our recent implementation of the real-time intermediate neglect of differential overlap for spectroscopy (INDO/S) to study the solvatochromic shift of Nile Red in acetone, ethanol, toluene and n-hexane solvents, and, for the first time, the excited state absorption spectra of coronene, 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP), zinc phthalocyanine, and nickel TPyP using a semiempirical Hamiltonian.

Nature of Electronically Excited States of Furocoumarins

A comprehensive study of spectral-luminescent and photophysical properties of coumarin sensitizers is performed using the methods of quantum chemistry, electron spectroscopy, and fluorescence. A comparative study of photophysical processes occurring in 8-methoxypsoralen (8-MOP) and 4,9-dimethoxy-7-methylfuro [3,2-g][1] benzofuran-5-1 (khellin) is performed using the quantum-chemical software package based on the semi-empirical method of intermediate neglect of differential overlap with original spectroscopic parameterization. The dependences of the fluorescent properties and reactivity of the compounds on the geometry and composition of the solvation shell of molecules are established. It is shown that incorporation of additional methoxy groups in the structure of molecules has the strongest effect on the spectral-luminescent characteristics of khellin compared with 8-MOP.

Structural, electrochemical and optical properties of 4′-n-alkyl-4-cyanobiphenyl (nCB) – A computational approach

ABSTRACTThe structures of nCB (n = 6 & 7 where n is the number of carbon atoms in the alkyl chain) have been optimized using the Becke3-Lee-Yang-Parr (B3LYP) hybrid functional with 6–31G+(d) basis set using the crystallographic geometry as input. The electronic structures of the dimer molecules have been computed using the optimized geometries. The spectra of the dimer molecules have been calculated by employing the DFT method. The features of electronic transitions and excited states have been calculated via configuration interaction singles (CIS) with the semiempirical Hamiltonian Zerner intermediate neglect of differential overlap (ZINDO). The photo sensitivity of liquid crystalline alkyl cyanobiphenyl has been presented on ultraviolet (UV) absorption based approach through Density functional theory (DFT) calculations. The structural and electrochemical properties such as HOMO (H), LUMO (L), and energy gap (Eg = EL – EH) have been investigated. A comparison of dimers during the different modes of interactions suggests an absorption maxima at longer wavelength for 7CB, indicating the high photo sensitivity. Further, the 6CB dimers exhibit a lower band gap; hence its conductivity is high in comparison with the 7CB dimers.

A quantum-chemical study of conformational and electronic properties of ter-anthrylene-ethynylene derivatives in neutral and ionized states

ABSTRACTThe density functional theory (DFT) calculations are applied to the series of 9,10-ter-anthrylene-ethynylene derivatives being in neutral, cationic and anionic charge states to gain insight into their conformational properties, frontier orbitals, ionization potentials (IP), electron affinity (EA) and reorganizations energies. The evolution of intramolecular transfer integrals are investigated within the energy-splitting in dimer (ESD) model using the intermediate neglect of differential overlap (INDO) semi-empirical method, the oscillating behavior is observed both for electrons and holes charge carriers. The computed results are reasonably consistent with data of available experimental and theoretical studies.

Structural and optical properties of novel nematogens based on DFT and semiempirical method—A comparative picture

ABSTRACTA comparative picture of structural, and optical properties of nematogens, viz., bis(4-propyloxyphenyl) 1,12-dicarba-closo-dodecaborane-1,12-dicarboxylate (Nematic1), and bis(4-butoxyphenyl) 1,10-dicarba-closo-decaborane-1,10-dicarboxylate (Nematic2) have been studied in ultraviolet (UV) and visible (Vis) regions. The structure of nematogens have been optimized using the Density functional B3LYP with 6–31+G (d) basis set using crystallographic geometry as input. The electronic structure of the molecules has been evaluated using the DFT, and semiempirical methods, namely; CNDO/S (complete neglect of differential overlap/ spectroscopy) and INDO/S (intermediate neglect of differential overlap/ spectroscopy). The HOMO (Highest Occupied Molecular Orbital)/LUMO (Lowest Unoccupied Molecular Orbital) energies, and oscillator strength (f) have also been reported using these methods. The electronic absorption spectra of the molecules have been simulated by employing the DFT method, semiempirical parameterizations. Molecular charge distribution and phase stability of these nematogens have been analyzed based on Mulliken and Loewdin population analysis. It has been observed that Nematic2 molecule shows the much flexibility for electronic transitions over a long wavelength region that leads to high photosensitivity.

Properties of the Triplet State of Coumarin Substituted Compounds

The absorption spectra of the triplet excited state of coumarin sensitizers are investigated both theoretically and experimentally. The most intense triplet-triplet (TT) absorption bands are determined. The experimental spectra of the T-T absorption are compared with the theoretical T-T transitions. The phosphorescence spectra of five compounds are measured at a temperature of 77 K. The quantum phosphorescence yield is determined by the method of comparison with an etalon (8-methoxypsoralen). The phosphorescence lifetime is determined for the examined molecules at a temperature of 77 K. For 3,4-phenyl-4',5'-cyclohexylpsoralen, 4'-methyl-3,4-cycloheptylpsoralen, and 4'5'-dimethyl-3,4-cyclohexylpsoralen compounds, this time is equal to 1.1, 1.25, and 2.5 s, respectively. The main energy deactivation channel for all examined compounds is the phosphorescence. The positions of the lower excited triplet states, calculated by the quantum-chemical method of intermediate neglect of differential overlap with spectroscopic parameterization (INDO/S), are confirmed by the available experimental data.

Effect of Molecular Interactions and Homologue Number on UV Absorption Spectra of Liquid Crystalline Alkyl Cyanobiphenyl Dimers: DFT Calculations

The ultraviolet (UV) absorption spectra of the liquid crystalline dimer complexes of 4′-n-alkyl-4-cyanobiphenyls (nCB: n = 3, 4, 5 where n is the number of carbon atoms in the alkyl chain) have been presented. The nCB structures have been optimized using the density functional Becke3-Lee-Yang-Parr (B3LYP) hybrid functional with 6-31+G (d) basis set using the crystallographic geometry as input. The electronic structures of the dimer molecules have been computed using the optimized geometries. The spectra of the dimer molecules have been calculated by employing the density functional theory (DFT). The features of electronic transitions and excited states have been calculated via configuration interaction singles (CIS) with the semiempirical Hamiltonian Zerner intermediate neglect of differential overlap (ZINDO). The various modes of molecular interactions and the homologue number are found to be structural parameters affecting the formation of mesophases, UV absorption spectral characteristics, and photo stability of the compounds. These results offer a hint for the calculations involving the different modes of molecular interactions, and separations between dimers, to model photo stability or in tuning the absorbing chromophore to match the wavelength of desired application.

Electrochemistry and spectroelectrochemistry of 5,10,15,20-tetrakis(1,3-benzodioxole) porphyrin and its manganese and iron complexes

Cyclic voltammetry and thin-layer spectroelectrochemical properties of the free base 5,10,15,20-tetrakis(1,3-benzodioxole)porphyrin ( H 2 P ), and its manganese and iron complexes ( MnP and FeP , respectively) were studied in dichloromethane with tetra-butyl ammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. The free base undergoes two monoelectronic oxidations at +0.71 and +0.96 V vs.  Ag / Ag +, corresponding to the formations of the π-cation radical and dication. Two reductions were observed at -1.53 and -1.87 V corresponding to the formation of π-anion and dianion species. The cyclic voltammograms of the Mn III and Fe III complexes also showed a reversible process centered in the metal ion with E1/2 values at -0.61 and -0.59 V, respectively. In a typical experiment, in situ spectroelectrochemical response showed a decrease of the Soret band at 422 nm, a red shift of the Q-bands, and the new low intensity bands between 800–950 nm range. Structural features and spectroscopic assignments were proposed and discussed based on semi-empirical (molecular mechanics MMFF and ZINDO/S (Zerner method of intermediate neglect of differential overlap for spectroscopy) calculations.

Effect of molecular interactions and end chain length on ultraviolet absorption behavior and photo stability of alkoxycinnamic acids: Theoretical models of liquid crystal

The ultraviolet (UV) absorption spectra of the liquid crystalline dimer complexes of 4-n-alkoxycinnamic acids (nOCNA: n=4, 6, 8, where n is the number of carbon atoms in the alkoxy chain) have been presented. The nOCNA structures have been optimized using the density functional Becke3–Lee–Yang–Parr (B3LYP) hybrid functional with 6-31+G (d) basis set using the crystallographic geometry as input. The electronic structures of the dimer molecules have been evaluated using the optimized geometries. The spectra of the dimer molecules have been calculated by employing the density functional theory (DFT), semiempirical complete neglect of differential overlap/spectroscopy (CNDO/S), and intermediate neglect of differential overlap/spectroscopy (INDO/S) parameterizations. The features of electronic transitions and excited states have been calculated via configuration interaction singles (CIS) with the semiempirical Hamiltonian Zerner intermediate neglect of differential overlap (ZINDO). The effect of molecular interactions and the end chain length may be reasonably useful for the progress and efforts in developing the photo-addressed color displays.

Theoretical study of two-photon absorption properties of a series of platinum (II) acetylide complexes

Transition metal acetylide compounds have attracted enormous attention because of the extraordinary photophysical properties arising from the electronic interaction between the transition metal and the organic molecular fragment. In this study, the geometrical structure, electronic structure, one-photon absorption (OPA) and two-photon absorption (TPA) properties of a series of D–π′–A–π–[Pt]–π–A–π′–D type and A′–π′–A–π–[Pt]–π–A–π′–A′ type platinum(II) acetylides were studied theoretically by using density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods for getting TPA materials possessing large TPA cross-section. Our analysis suggests that intramolecular charge transfer between center metal and π-conjugated organic fragment dominates in TPA transitions, in which metal center increases conjugation length in the direction of long ligand. This contribution provides detailed theoretical analysis of one- and two-photon absorption property of Platinum (II) acetylide compounds and an effective way for designing of platinum (II)/nickel (II) acetylide compounds possessing large TPA cross-section.

Role of molecular interactions and end chain length on the photosensitivity of liquid crystalline alkyl cyanobiphenyl dimers – UV absorption-based approach through DFT calculations

In this paper, the photosensitivity of liquid crystalline alkyl cyanobiphenyl (nCB: n = 6, 7; n is the number of carbon atoms in the alkyl chain) dimers has been presented through density functional theory (DFT) calculations. The nCB structures have been optimized using the Becke, three-parameter, Lee–Yang–Parr hybrid functional with the 6-31+G (d) basis set using the crystallographic geometry as input. The electronic structures of the dimer molecules have been computed using the optimized geometries. The spectra of the dimer molecules have been calculated by employing the DFT method. The excited states have been calculated via configuration interaction singles with the semi-empirical Hamiltonian Zerner intermediate neglect of differential overlap. The influence of molecular interactions and the end chain length on ultraviolet absorption spectral characteristics and the photosensitivity of the compounds has been discussed. These results offer a hint for the protection of various optical devices from the intense light induced damages, and to model photosensitivity.

Specific features of photoprocesses in molecules with a styryl group

Rate constants of photophysical processes are calculated for molecules with a styryl group (stilbene (styrylbenzene), 4-trans-styrylbiphenyl, 4-trans-styrylterphenyl, and 1,4-distyrylbenzene) using an original method based on the theory of nonradiative transitions. The values for calculations are obtained using a software package based on the method of intermediate neglect of differential overlap with spectroscopic parametrization. The results make it possible to numerically estimate the molecular parameters and effect of substituents. Torsional and twist rotations are simulated in the fluorescence structure of trans-stilbene, and the effect of these rotations on the rates of photoprocesses is analyzed. The results additionally contribute to the interpretation of excitation-energy relaxation and photoisomerization of stilbene.

Semi-empirical ZINDO/S description of the electronic structure and the spectral features of methyl orange and its products of oxidation. A study of relationship between molecular geometry and spectroscopic properties

Molecular modelling and a detailed spectroscopic characterization have been made of 4-(4-sulfophenylazo)-N-N-dimethylaniline (methyl orange) and its products of oxidation at the azo group and at the dimethylamino group. Correlations between structural and spectroscopic features are discussed and assignments were proposed on the basis of semi-empirical (molecular mechanics MMFF and ZINDO/S (Zerner method of intermediate neglect of differential overlap for spectroscopy) calculations. Our findings are consistent with the H2O2/manganese complex catalyzed oxidation of methyl orange with the formation of the azo bond oxidized derivative.

One- and two-photon absorption of fluorescein dianion in water: A study using S-QM/MM methodology and ZINDO method

One- and two-photon absorption (1PA and 2PA) of fluorescein dianion (FSD) in water were studied using a combined and sequential Quantum Mechanics/Molecular Dynamics methodology. Different sets of 250 statistically relevant (uncorrelated) configurations composed by the solute and several solvent molecules were sampled from the classical simulation. On these configurations, the electronic properties were calculated a posteriori using the Zerner’s intermediate neglect of differential overlap (ZINDO) method. The linear and nonlinear absorption of FSD in water were calculated using discrete and explicit solvent models. In the largest case, the relevant configurations are composed by FSD and 47 explicit water molecules embedded in the electrostatic field of all remaining water molecules. Both INDO/CIS and INDO/CISD calculations were performed to study the absorption processes of FSD and the Sum-Over-States (SOS) model was used to describe the 2PA process. A semi-classical method for spectrum simulations was employed to simulate the 1PA and 2PA cross-section spectra of FSD in water. For comparison purposes, in the case of the 2PA process two approaches, the “full expression” and “resonant expression” methods, were employed to simulate the nonlinear spectrum. The last method assumes resonant conditions and on the computation point of view it represents an interesting option to study the 2PA process. The INDO/CI calculations give a satisfactory description of the 1PA spectrum of FSD and properly describe the unusual blue-shift of its first π→π* transition in water. In the case of 2PA, the introduction of doubly excited configuration interactions (INDO/CISD) has proven to be essential for an appropriate description of the process at the higher energy spectral region. It was observed that the solvent effects do not drastically change the cross-sections of both processes. The simulated 2PA cross-section spectrum provided by the “full expression” method presents a better definition of the bands which appear along the experimental spectrum than the one provided by the “resonant expression” method. However, both approaches provide similar description for the effect of the solvent environment on the 2PA process of FSD in water.

A Benchmark of Excitonic Couplings Derived from Atomic Transition Charges

In this report we benchmark Coulombic excitonic couplings between various pairs of chromophores calculated using transition charges localized on the atoms of each monomer chromophore, as derived from a Mulliken population analysis of the monomeric transition densities. The systems studied are dimers of 1-methylthymine, 1-methylcytosine, 2-amino-9-methylpurine, all-trans-1,3,5-hexatriene, all-trans-1,3,5,7-octatetraene, trans-stilbene, naphthalene, perylenediimide, and dithia-anthracenophane. Transition densities are taken from different single-reference electronic structure excited state methods: time-dependent density functional theory (TDDFT), configuration-interaction singles (CIS), and semiempirical methods based on intermediate neglect of differential overlap. Comparisons of these results with full ab initio calculations of the electronic couplings using a supersystem are made, as are comparisons with experimental data. Results show that the transition charges do a good job of reproducing the supersystem couplings for dimers with moderate to long-range interchromophore separation. It is also found that CIS supermolecular couplings tend to overestimate the couplings, and often the transition charges approach may be better, due to fortuitous cancellation of errors.