Theoretical Electronic Spectra Research Articles

Synthesis and electronics of donor–accepter linear arrays comprising anthracene bisimide with butadiynylene spacers

Abstract To further explore the π-conjugated systems of anthracene bisimide (ABI) and investigate their electronic properties, we synthesized donor–accepter linear arrays. These arrays consist of an ABI unit as the accepter and a 9,10-anthrylene unit as the donor, linked by a butadiynylene spacer. We constructed these donor–accepter arrays through Hay coupling of the corresponding 9,10-diethynylABI derivative with a 9,10-diethynylanthracene derivative. Theoretical calculations and electronic spectra analysis were employed to compare the photophysical properties of these compounds with those of their acetylene analogs. Moreover, we evaluated the intramolecular electronic interactions between the ABI and anthrylene units, focusing on the effects of the butadiynylene spacer and array sequences.

Robust Optical Detection of Ga3+ by a Rhodamine- and Coumarin-Based Proficient Probe: Theoretical Investigations and Biological Applications.

The present investigation highlights a rhodamine-B- and coumarin-based efficient probe that selectively detects Ga3+ over other metal ions. The active pocket of the ligand for trapping the metal ions and the binding stoichiometry of its Ga3+ complex were discovered by single-crystal X-ray diffraction (SC-XRD) analysis. This binding stoichiometry was further confirmed in the solution state by mass spectrometry and Job's plot. The detection limit was found to be at the nanomolar level. Pyrophosphate being a well-known quencher could easily quench the fluorescence intensity of the RC in the presence of Ga3+ and reversibly recognize Ga3+ in the solution. The spiro ring opening of the ligand after Ga3+ insertion is proposed to be the principal mechanism for the turn-on fluorescence response. This ring opening was confirmed by SC-XRD data and nuclear magnetic resonance (NMR) titration experiments. Both ground- and excited-state calculations of the ligand and complex have been carried out to obtain information about their energy levels and to obtain the theoretical electronic spectra. Furthermore, the live-cell imaging of the probe only and the probe after the addition of Ga3+ have been carried out in HaCaT cells and satisfactory responses were observed. Interestingly, with the help of this probe, Ga3+ can be tracked inside the intracellular organelle such as lysosomes along with other regions of the cell. The article highlights a rhodamine-coumarin-based probe for the detection of Ga3+ over other metal ions with a nanomolar level detection limit. Structural characterization of the ligand and its Ga3+ complex was investigated by SC-XRD. Density functional theory (DFT) and time-dependent DFT (TD-DFT) studies were carried out to explore the excited-state energies and electronic spectra. The application of the probe for the detection of Ga3+ in live cells has been explored, and positive responses were observed.

Computational optimal transport for molecular spectra: The fully continuous case.

Computational optimal transport is used to analyze the difference between pairs of continuous molecular spectra. It is demonstrated that transport distances which are derived from this approach may be a more appropriate measure of the difference between two continuous spectra than more familiar measures of distance under many common circumstances. Associated with the transport distances is the transport map which provides a detailed analysis of the difference between two molecular spectra and is a key component of our study of quantitative differences between two continuous spectra. The use of optimal transport for comparing molecular spectra is developed in detail here with a set of model spectra, so that the discussion is self-contained. The difference between the transport distance and more common definitions of distance is elucidated for some well-chosen examples and it is shown where transport distances may be very useful alternatives to standard definitions of distance. The transport distance between a theoretical and experimental electronic absorption spectrum for SO2 is studied and it is shown how the theoretical spectrum can be modified to fit the experimental spectrum better adjusting the theoretical band origin and the resolution of the theoretical spectrum. This analysis includes the calculation of transport maps between the theoretical and experimental spectra suggesting future applications of the methodology.

Density Functional Theory Calculations of Electronic Properties ,IR and UV-Vis Spectrum , Dipoles Moments ,and Atomic Charge Distribution of Mg 1-X Zn XFe2O4 Ferrite

Theoretical study using (Density Functional Theory) DFT method with B3LYP functional and the 3-21G(d,p) basis set had been implemented of calculating molecular structure properties of Magnesium – Zinc spinel ferrite having the chemical formula (Mg1-xZnxFe2O4). DFT had been used to optimize molecular structure, electronic state (HOMO-LUMO) , and electronic properties ( ionization potential, electronegativity, electron affinity, electrophilic, hardness, and softness) are calculated. Theoretical electronic IR spectrum were computed and plotted . UV-Vis spectrum calculated and plotted of this molecule. Dipole, Quadrupole, and Traceless Quadrupole moments were calculated. The Mullikan and Natural Bond Orbital (NBO) distribution of Mg1-xZnxFe2O4 compound are also computed by DFT. All these properties had been calculated using Gaussian09 program with Gauss view 5.08 program by using (Density Functional Theory) DFT method with 3-21G(d,p) basis set.

Growth, crystal structure, Hirshfeld surface, spectroscopy studies and DFT calculations of an organic cocrystal of 2-amino-4-hydroxy-6-methylpyrimidine (AHMP) and 2,4-dimethylbenzoic acid (DMBA)

A newly synthesized organic cocrystal (AHMP.DMBA) of 2-amino-4‑hydroxy-6-methylpyrimidine (AHMP) and 2,4-dimethylbenzoic acid (DMBA) was successfully grown by the slow evaporation method. The current report focuses on the molecular structure, vibrational study, thermal analysis and electronic properties of the grown crystal. The crystal structure analysis of AHMP.DMBA cocrystal was done by single crystal X-ray diffraction (SCXRD) technique. The given cocrystal crystallizes in the orthorhombic system space group Pnma. 3D Hirshfeld surface map and its associated 2D fingerprint plots have been generated for understanding the noncovalent interactions which stabilized the crystal pacing. Further, FTIR spectroscopy and B3LYP-D3/6-311++G(d,p) theory have been used to examine the vibrational modes present in the synthesized complex. The observed and simulated 13C and 1H NMR spectral analyses have also supported the structural analysis. The experimental absorption spectra and optical band gap are obtained by UV–Vis absorption spectroscopy and the theoretical electronic spectrum is computed using time dependant density functional theory (TD-DFT) method. The thermal profiles of the given sample have been recorded by thermal gravimetric/differential thermal analysis (TG/DTA). Additionally, the molecular properties i.e., HOMO-LUMO, MEP and non-linear optical parameters are also discussed.

Structural, spectroscopic and computational studies of two new spirocompounds containing 2,3,4-trimethoxybenzyl group

Two new spirocompounds have been obtained by two different routes. Compound A1 was prepared in a solution of TEAF to connect the trimethoxybenzyl unit with the dioxaspirounit by a single bond. However, Compound A2 was prepared in ethanol to join the trimethoxybenzyl unit with the dioxaspirounit by a double bond. The result of X-ray single-crystal diffraction verifies the two compounds are both the monoclinic systems, space group P21/n (A1) and P21/c (A2). 1D-chained structure was formed by C(1)−H(1A)···O(4) intermolecular hydrogen bonds in A1. However, a 2D frame-work was obtained by C(8)−H(8C)···O(5) hydrogen bonds in A2. The DFT optimized geometric structures with the B3LYP/6–31 G (d, p) basis set are in accord with those crystallographic studies. The experimental and theoretical vibrational frequencies and electronic spectra of A1 and A2 have been investigated. In addition, MEP, NBO and thermodynamic properties have also been studied.

Moiré band structures of twisted phosphorene bilayers

We report on the theoretical electronic spectra of twisted phosphorene bilayers exhibiting moir\'e patterns, as computed by means of a continuous approximation to the moir\'e superlattice Hamiltonian. Our model is constructed by interpolating between effective $\Gamma$-point conduction- and valence-band Hamiltonians for the different stacking configurations approximately realized across the moir\'e supercell, formulated on symmetry grounds. We predict the realization of three distinct regimes for $\Gamma$-point electrons and holes at different twist angle ranges: a Hubbard regime for small twist angles $\theta < 2^\circ$, where the electronic states form arrays of quantum-dot-like states, one per moir\'e supercell; a Tomonaga-Luttinger regime at intermediate twist angles $2^\circ < \theta \lesssim 10^\circ$, characterized by the appearance of arrays of quasi-1D states; and finally, a ballistic regime at large twist angles $\theta \gtrsim 10^\circ$, where the band-edge states are delocalized, with dispersion anisotropies modulated by the twist angle. Our method correctly reproduces recent results based on large-scale ab initio calculations at a much lower computational cost, and with fewer restrictions on the twist angles considered.

A new tetradentate Schiff base of N, N’-bis (3, 5 - diiodosalicylidene)-1,2-phenylenediamine: Spectral aspects, Hirshfield surfaces, DFT computations and molecular docking

We reported a new tetradentate Schiff base, 6,6′-(1,2-phenylenebis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2,4-diiodophenol) (PMDP) and its binding with the bovine serum albumin which was comprehensively investigated with the aid of UV–Vis, fluorescence spectroscopy and molecular docking. The molecular structure of the ligand was optimized by DFT/B3LYP/LANL2DZ levels of theory were found in good agreement with the experimental data. Based on the optimized structure, the theoretical frequency and electronic absorption spectrum of the compound were computed to elucidate the vibrational and electronic transition assignments. 1H and 13C NMR was computed using SCF-GIAO method to assess the chemical structure. Natural bond orbital (NBO), molecular electrostatic potential (MEP), Mulliken atomic charge and HOMO-LUMO energies were calculated using the same level of theory. Fukui functions and global reactivity parameters were also performed. Hirshfield surface analysis exactly revealed each significant interaction and the influence of contacts involving hydrogen such as I···H, H···H, C···H on their molecular properties. The combination of BSA and Schiff base induced conformational changes in the microenvironment around the fluorophores of BSA were studied using synchronous and three dimensional fluorescence measurements. Molecular docking studies supported the interactions involved and its minimum binding energy conformer to be revealed.

Computational, spectroscopic and molecular docking investigation on a bioactive anti-cancer drug: 2-Methyl-8-nitro quinoline

2-Methyl-8-nitroquinoline (2M8NQ) is optimized using density functional theory with B3LYP/6-311++G(d,p) basis set. The vibrational (FT-IR, FT-Raman) frequencies with potential energy distribution (PED) and the geometrical parameters of headline molecule is obtained and compared with the experimental data. Multiwave-functions like Reduced gradient density (RDG), Electron localisation function (ELF), Localised orbital locator (LOL) is computed. HOMO-LUMO energy gap is analysed for different orbital level. HOMO-LUMO energy gab for the molecule in various solvent has studied and are correlated with theoretical electronic spectra. The reactivity of the examined molecule is analysed with DFT methods such as Molecular electrostatic potential (MEP), Local reactivity descriptors are understood. Natural bond orbital (NBO) and Nonlinear optical behaviour (NLO) are also analysed. Furthermore, biological parameters from Molinspiration-preADME and GUSAR such as drug-likeness, ADME, Toxicity properties are studied. Ramachandran plot are drawn to understood the stability of anticancer proteins. Docking analysis reveals that the molecule is a potent anti-cancer drug.

Computational Investigations of a Novel Charge Transfer Complex for Potential Application in Dye-Sensitized Solar Cells

The computational study of a novel charge-transfer complex as a photoactive blend for potential application in dye-sensitized solar cells was carried out using the semi-empirical method. The adsorption of two natural dyes, 1S,3R,4R,5R-3-(3,4-dihydroxyphenyl)acryloyloxy)-1,4,5-trihydroxycyclohexane carboxylic acid (DHTH) and 2-Phenyl-4H-chromen-4-one (PCO) was achieved independently on to 1×1×1 TiO2 crystal to form TiO2-DHTH and TiO2-PCO adsorption complexes. Semiempirical calculations were performed on the optimized molecules, as well as on the adsorption complexes, to obtain the total energies and EHOMO/ELUMO values, manifesting a flow of electrons from DHTH/PCO to TiO2. The theoretical electronic absorption spectra calculated via ZINDO/s method revealed a large bathochromic shift to 810 nm and 526 nm for TiO2-DHTH and TiO2-PCO, respectively, indicating the formation of a charge-transfer complex. Subsequently, the co-adsorption of PCO and DHTH on TiO2 was accomplished with the aim to minimize the possible charge recombination in the photoactive blend. The semiempirical PM3 calculations evidenced the high stability of the co-adsorption complex, TiO2-PCO-DHTH, with the total energy of -200678.578 kcal/mol. The positions of HOMO and LUMO orbitals as obtained from single-point energy calculations, coincided accurately with our proposition of electron flow in a cascade manner from DHTH to PCO and finally to TiO2. The theoretical electronic absorption spectrum ofTiO2-PCO-DHTH evinced absorption range of 351.8-800 nm demonstrating the high potential of TiO2-PCO-DHTH to be used as a photoactive blend for solar cells.

Sensing of fluoride anion based on desilylation and intramolecular charge transfer of 2‐[2‐(tert‐butyl‐diphenyl‐silanyloxy)‐phenyl]‐4,5‐diphenyl‐1H‐imidazole

AbstractIn view of the tremendous potential for fluorescent chemosensors, more and more people pay attention to design and synthesize high‐efficiency sensors. Given the importance of fluorescence response mechanism, in the present work, the specific sensing mechanism of a novel fluoride anion chemosensor 2‐[2‐(tert‐butyl‐diphenyl‐silanyloxy)‐phenyl]‐4,5‐diphenyl‐1H‐imidazole (abbreviated as TBDI) has been investigated based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Our theoretical electronic spectra (vertical excitation energies and fluorescence emission peaks) reproduced previous experimental results (Sensor Actuat B‐Chem. 2016, 232, 175), which confirms the rationality of our theoretical level adopted in this work. The constructed potential energy curve about fluoride‐triggered desilylation reaction suggests that the low barrier could be responsible for the rapid response to fluoride anion. Analyses about binding energies demonstrate that only fluoride anion could be detected for TBDI chemosensor in dimethyl sulfoxide (DMSO) solvent. In view of the vertical excitation process, the strong intramolecular charge transfer (ICT) process between the S0‐state and S1‐state transition explains the redshift of absorption peak for TBDI sensor with the addition of fluoride anion. This work not only presents a straightforward sensing mechanism of fluoride anion for TBDI sensor but also plays important roles in synthesizing and designing fluorescent chemosensors in future.

Theoretical and experimental electronic spectra of neutral, monoprotonated and diprotonated dapsone

Dapsone has been receiving growing interest due to it use as a new class of corrosion inhibitors, forming copolymers with aniline, pyrrole, diphenylamine and 4-aminodiphenylamine. The present work focuses on characterizing the theoretical and experimental electronic spectra of the neutral, monoprotonated and diprotonated dapsone. The theoretical electronic spectrum was obtained through the excited state characterization via time-dependent DFT theory. NBO analysis was carried out to identify the molecular orbitals involved in the detected experimental UV bands. The detected absorption wavelength values for the neutral dapsone were 292 and 258 nm (experiment), and 286.9 and 251.7 nm (theoretical). Concerning the protonated dapsone species, it was observed that the absorbance values were strongly dependent on pH, especially at pH between 1.0 and 4.0. As the pH of the solution decreases, the experimental band at 292 nm slowly decreases and shifts to 290 nm, while the absorption at 258 nm decreases until it disappears, and a new absorption band arises at 240 nm. While, when the basicity increases, the absorption spectra of dapsone do not change, but a regular red shift is noticed, and it is continued even up to pH 14.0. The red-shifted spectra may be due to the formation of a monoanion and/or dianion, but the isosbestic points were not constant.

Theoretical and experimental characterization of Cu-doped amorphous silicate glass

The coordinative environment of Cu2+ ions incorporated in oxide glasses has been intensively studied for glasses doped with copper ions by melting or ion exchange. Much less is known about their coordination in a sol-gel derived silicate glass. Mesoporous silicate glasses doped with copper (II) ions coming from four different salts were synthesized by the acid-catalyzed sol-gel method. The electronic and structural states of copper sites were probed by optical and X-ray spectroscopies. The experimental observations were confronted with the results of quantum-chemical calculations. The theoretical models consisted of four- and five-coordinated Cu2+-complexes, where water ligands were sequently replaced with the SiO44‒ tetrahedra. The best agreement between the experimental and theoretical electronic spectra has been reached for the four-coordinated Cu2+-complex with a water molecule and three or four SiO44‒ tetrahedra. The energy band gap intervals of 4.21–4.61 eV and 4.09–4.23 eV were estimated graphically by the TAUC plot method and from quantum-chemical modelling, respectively.

Quantum mechanical and photovoltaic studies on the cocrystals of hydrochlorothiazide with isonazid and malonamide

Theoretical calculations were done using density functional theory in order to determine vibrational frequencies, infrared and Raman intensities, MEP, NLO and NBO properties of the Hydrochlorothiazide-isoniazid (HCTA-IN) and Hydrochlorothiazide-malonamide (HCTA-MA) cocrystals. Electron donor-acceptor due to charge transfer mechanism has been scrutinized by the NBO investigation. First order hyperpolarizability of HCTA-IN and HCTA-MA are 19.86 and 7.80 times that of urea. The downshift of NH2, NH and CO modes are due to strong hyper conjugative interactions are indicated in NBO analysis. TD-DFT analysis was used to generate the theoretical electronic spectra, which shows a charge transfer process between the thiazide and isoniazid in HCTA-IN complex. Light harvesting efficiency studies reveal efficient photosensitization potential and photochemical modeling proves the efficiency of the cocrystal to be used in dye sensitized solar cells. Title compounds are docked with glucocorticoid receptor (1NHZ) and peroxidase manganese-dependent I (1YYD).

Synthesis, characterization, investigation of biological activity, docking studies, and spectroscopic properties of hydrazone compounds containing different substituents

To assess electronic absorption spectra, molecular docking, and antibacterial activity, 12 new hydrazone compounds that have different substituents and in different positions were synthesized and characterized. HOMO–LUMO energies and theoretical electronic spectra of synthesized compounds were computed via Gaussian 09 software. Global reactivity descriptors were computed from HOMO–LUMO energies. In addition, 1JXA protein was used for molecular docking studies structure. Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 (as negative bacteria), Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853 (as gram positive) was selected. Compound 3 was observed to be the most effective against propagations of E. Coli. Similarly, compounds 7 and 9 were found to be the most effective against the reproduction of P. aeroginosa. The most powerful compound against the growth of E. faecalis was ascertained to be compound 7.

Resonance Raman and UV–vis characterization of charge transfer complexes of TCNQ and aromatic amines

Although the molecular charge transfer complexes formed by 7,7,8,8-tetracyanoquinodimethane (TCNQ) and several different donors have been widely investigated in the past, in this paper it is shown for the first time the vibrational spectroscopic characterization of the complexes formed by TCNQ and the simplest series of substituted anilines in solution. The UV–vis spectra indicate the formation of TCNQ complexes stabilized by two aromatic amines in a sandwich π type complex. It was observed that the charge transfer transition energies of the complexes follow a linear correlation with the ionization potential of the amines. The resonance Raman spectra revealed, by the analysis of the ν(CC) and ν(CN) stretching modes of TCNQ, that the complexes keep their neutral character in the ground electronic state, and not as a TCNQ2− dianion species as reported before. The observed enhancement of the TCNQ bands as the amine donor capacity increases, confirmed the charge transfer nature of the electronic transitions. The DFT and TDDFT results were obtained and the theoretical Raman and electronic spectra data supported the experimental findings. The results of the model systems presented herein can contribute to a deep understanding of the photoinduced charge transfer process in complexes of TCNQ, which is a key step in the designing of organic molecular devices.

Theoretical Treatment, Microwave Synthesis and Spectroscopic Analysis of New Schiff Bases Derived from 4-Aminoantipyrene

The new Schiff base was obtained compounds (I, II, III, IV) derived from 4-aminoantipyrene were synthesized by using microwave technique. And these Schiff bases were verified by some spectral data (IR, UV). HyperChem release 8.0 program was used to calculate the heat of formation (ΔH0f) binding energy (ΔEb) and dipole moment (μ) for all compounds, also theoretical vibration frequencies and electronic spectra of compounds were calculated.

The sensing mechanism of fluoride anion for a novel molecule D2: Desilylation and intramolecular charge transfer

In this work, the sensing mechanism of a new fluoride chemosensor 12‐([tert‐butyldiphenylsilyl]oxy)‐8a,13a‐dihydro‐7H‐benzo[de]benzo[4,5]imidazo[2,1‐a]‐isoquinolin‐7‐one (abbreviated as D2) is investigated using density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. The theoretical electronic spectra (vertical excitation energies and fluorescence peak) reproduced previous experimental results (D. Li et al., Spectrochim. Acta A Mol. Biomol. Spectrosc. 2017, 185, 173), which confirms the rationality of the theoretical level used in this work. The constructed potential energy curve of the desilylation process suggests that the low barrier could be responsible for the rapid response to fluoride anions. Analyses of the binding energies show that only fluoride anion can be detected by D2 chemosensor in dimethylsulfoxide (DMSO). In view of the excitation process, the strong intramolecular charge transfer (ICT) process of the S0 → S1 transition explains the red shift of the absorption peak of the D2 sensor with the addition of fluoride anions. This work not only presents a straightforward sensing mechanism of sensing of the fluoride anion by the D2 chemosensor but should also play an important role in the synthesis and design of fluorescent sensors in future.

Vibrational (FT-IR and FT-Raman), electronic (UV–vis) and quantum chemical investigations on pyrogallol: A study on benzenetriol dimers

Pyrogallol was identified for the first time from the natural extract of Abrus precatorius Linn seeds using GC–MS technique. The vibrational analysis of pyrogallol was investigated in solid phase by FT-IR and FT-Raman spectroscopic techniques in the region 4000–400 cm−1 and 4000–40 cm−1, respectively. The optimized molecular geometry, wave number and intensity of the vibrational bands of pyrogallol and its isomers were obtained by DFT method with different basis sets. The electronic transition energy and intensities, HOMO-LUMO energy gap have been computed with the ZINDO, CIS, TDDFT theory for isomers and the differences were compared with UV–vis absorption spectra. The observed wave numbers in FT-IR, FT-Raman and UV–vis spectra were analyzed and assigned to various fundamental modes of vibration in the molecules. Experimentally observed vibrational frequencies and electronic transitions were assigned with the help of theoretical vibrational and electronic spectra, respectively. The differences between observed and calculated wave number values of most of the fundamental modes are very small. The calculated parameters were found to be in best agreement with experimental findings, thereby confirming the monomer and dimer structure of the identified molecule as well as its isomers.

DFT study of electron absorption and emission spectra of pyramidal LnPc(OAc) complexes of some lanthanide ions in the solid state

The electron absorption and emission spectra were measured for the pyramidal LnPc(OAc) complexes in the solid state and co-doped in silica glass, where Ln=Er, Eu and Ho. The theoretical electron spectra were determined from the quantum chemical DFT calculation using four approximations CAM-B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ, B3LYP/LANL2DZ and B3LYP/CC-PVDZ. It was shown that the best agreement between the calculated and experimental structural parameters and spectroscopic data was reached for the CAM-B3LYP/LANL2DZ model. The emission spectra were measured using the excitations both in the ligand and lanthanide absorption ranges. The possibility of energy transfer between the phthalocyanine ligand and excited states of lanthanide ions was discussed. It was shown that the back energy transfer from metal states to phthalocyanine state is responsible for the observed emission of the studied complexes both in the polycrystalline state and silica glass.