Ground State Molecular Geometry Research Articles

Photosensitization of asymmetric molecular, and bimolecular aliphatic-μ-bridged-meso-phenyl porphyrin

The desired asymmetric metal-free porphyrin derivatives were prepared by condensing freshly prepared the phenyl dipyrraomethane and triphenyl tetrapyrrane building blocks with the different molar ratios of acetaldehyde ([Formula: see text]CHO), and glutaraldehyde (OHC([Formula: see text]CHO, Glu). The obtained asymmetric [3+1] ([Formula: see text]Por, [Formula: see text]Por-[Formula: see text]-([Formula: see text]Por) and [2+2] ([Formula: see text]Por, [Formula: see text]-([Formula: see text] oligomer) porphyrin derivatives were characterized by UV-Vis, FT-IR, and 1H NMR. Their photoelectric properties were investigated by examining their current density-voltage (J-V) curves in dark, and under artificial sunlight, illumination using standard bulk heterojunction cell arrangements. The [Formula: see text]-V plots show that they display photosensitive semiconducting properties in the range of ([Formula: see text] = 1.7–14.5 [Formula: see text]S/cm) with negligible photovoltaic effects. All data were compared to those of symmetric metal-free [Formula: see text]Por([Formula: see text] = 33.8 [Formula: see text]S/cm). Density functional theory (DFT) is employed to validate the ground-state molecular geometry.

Insight into electronic structure and optical properties of ZnTPP thin films for energy conversion applications: Experimental and computational study

Theoretical and experimental study of the electronic structure and optical characteristics of Zinc (II) 5,10,15,20-tetraphenyl 21 H, 23 H-porphine (ZnTPP) was reported. The ground state molecular geometry, Frontier molecular orbitals, vibrational frequency, and total energy of ZnTPP were determined using density functional theory (DFT) calculations. Homogenous ZnTPP thin films were grown on glass and fused quartz substrates using the thermal evaporation method. The ZnTPP thin film structure was described experimentally using FTIR, XRD, AFM and UV-Vis. spectroscopy. XRD results illustrate the polycrystalline structure of ZnTPP powder, whereas the pristine ZnTPP thin films have amorphous nature. The AFM results revealed that the pristine ZnTPP film has uniform elliptical crystallites dispersed throughout the whole surface. Optical parameters of the ZnTPP films were obtained from the absorbance spectra. The absorption coefficient and band gap values showed that ZnTPP can be employed in optoelectronic devices. The experimental findings are in good accord with theoretical ones. A hybrid solar cell was prepared by growing a thin film of ZnTPP on p-silicon single crystal wafers. The photovoltaic performance of the prepared solar cell were estimated as JSC = 1.556 mA/cm2, VOC = 0.366 V, FF = 0.274 and η = 3.12 %.

Comparative experimental and theoretical study on the molecular structure and spectroscopic properties of sideroxol isolated from Sideritis stricta and its electronic properties

Sideroxol, a kaurene diterpene, was obtained from the acetone extract of Sideritis stricta plant. The ground-state molecular geometry, vibrational frequencies, and NMR chemical shifts were also investigated by using various density functional theories and Pople basis sets. The computed geometries are in good conformity with the experimental data. The comparison between theory and experiments indicates that B3LYP and M06 methods with the 6-31G(d) basis set are able to provide satisfactory results for predicting vibrational and NMR properties. There seems to be no significant effect of addition of diffuse and polarization functions in the basis set used herein.

Fabrication of a new 2D Co(II)-organic framework tuned by semi-flexible dicarboxylate and 1,4-bis(4-pyridinylmethyl)piperazine ligands: Topology, DFT/UB3LYP calculations, Hirshfeld surface analysis and magnetic studies

A new 2D-coordination polymer, {[Co3(L−2)2(HL−)2(bpmp)](H2O)2}n (CP1) was synthesized by using a dicarboxylate ligand, H2L (5–benzylamino–isophthalic acid) and a nitrogen donor ligand 1,4-bis(4-pyridinylmethyl)piperazine (bpmp) with Co(NO3)2•6H2O under hydrothermal conditions via careful tuning the basicity of reaction conditions. Single crystal X-ray studies revealed that CP1 exist as a linear trinuclear cobalt cluster. DFT/UB3LYP/6-31G(d,p) calculations have been performed to study the ground state molecular geometry, IR spectrum, magnetic behavior by electron spin densities distribution as well as to explore various structure based molecular properties. The topological analysis of CP1 results an underlying sql net with a point symbol of {44.62}.Variable temperature magnetic susceptibility measurements of CP1 were carried out over the temperature range 2–300 K which indicates the existence of paramagnetic behavior.

Aerobic oxidation of alcohol by model complexes relevant to metal site galactose oxidase: role of copper(I) intermediate, evidence for the generation of end-on copper(II)–OOH species and catalytic promiscuity for oxidation of benzyl alcohol, catechol and o-aminophenol

Tridentate ligands having meridional NNO donor centres were designed and synthesized mimicking the copper coordination in the metal site of galactose oxidase enzyme. Mononuclear copper complexes [Cu(L1)Cl] (1) (L1H = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Cu(L2)Cl] (2) (L2H = (E)-4-methyl-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Cu(L3)Cl] (3) (L3H = (E)-1-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)naphthalen-2-ol), [Cu(L4)Cl] (4) (L4H = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Cu(L5)Cl] (5) (L5H = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), and [Cu(L6)Cl] (6) (L6H = (E)-2,4-di-tert-butyl-6-(((pyridin-2-ylmethyl)imino)methyl)phenol) were synthesized and characterized. Molecular structure of complex 3 was determined by single crystal X-ray crystallography. Phenoxyl radical complexes were generated in solution via chemical oxidation using ceric ammonium nitrate (CAN), and the radical complexes were characterized by UV–Vis–NIR spectrophotometer. DFT calculations were performed at B3LYP level to optimize the ground-state molecular geometry of the complexes. To understand the electronic properties and absorption spectra of the complexes, TD-DFT calculations were executed for phenoxyl radical complexes considering triplet as well as singlet spin states. Alcohol oxidation was examined utilizing complexes 1–6 as catalyst, and importance of stabilization of Cu(I) intermediate was scrutinized and generation of Cu(II)–OOH was examined. Catalytic promiscuity for catechol oxidase and phenoxazinone synthase activity by complexes (1–5) was investigated. Theoretical calculations and ESI–MS spectral studies were performed during oxidation chemistry of benzyl alcohol, catechol and o-amino phenol to support the proposed mechanism.

Study of the optoelectronic and piezoelectric properties of ZrO2 doped PVDF from quantum chemistry calculations

In this study, we have evaluated the optoelectronic and piezoelectric properties of doped PVDF. The electronic structures and the linear and non-linear optical properties of ZrO2-doped PVDF were calculated by adopting the LDA approximations for the exchange-correlation potential in the DFT method integrated in Gaussian 09. Optoelectronic parameters and ground state molecular geometry were calculated using B3LYP functional and LanL2DZ as the basis. We chose the calculation with the B3LYP functional because it is a relatively inexpensive and it is precise method to predict molecular structures, energies and frequencies. In this work, some optical parameters and constants such as refractive index, electrical susceptibility, dipole moment, average polarizability and hyperpolarizability, phase velocity have been calculated. Dielectric constants, ionization potentials, electronic affinities, electronegativities, hardness and flexibility were also calculated. Finally, the piezoelectric properties such as the piezoelectric coefficient and the pyroelectric coefficient are evaluated. The calculated electronic structures show that virgin PVDF, hybrid molecules PVDF/2ZrO2 and PVDF/3ZrO2 have an Egap less than 3 eV. On the other hand, the hybrid PVDF/ZrO2 molecule is a good dielectric and therefore a good piezoelectric nanocomposite because its Egap is 5.89 eV greater than 3 eV. Finally, the results show that the hybrid molecules PVDF-2ZrO2 could have potential applications not only as piezoelectric materials but also as semiconductor components, nonlinear optical materials and possible building materials for molecular electronics and photonic devices.

Analytical Studies of 6-Hydroxy-5-[(2-hydroxy- 6-oxocyclohex-1-en-1-yl)(2-nitrophenyl)methyl]-1,3-dimethylpyrimidine-2,4(1H,3H)-dione

Synthesis of 6-hydroxy-5-[(2-hydroxy-6-oxocyclohex-1-en-1-yl)(2-nitrophenyl)methyl]-1,3-dimethylpyrimidine- 2,4(1H,3H)-dione in a one pot process based on barbituric acid derivatives, 1,3-cyclohexandione and 2-nitrobenzaldehyde in water media involving diethyl amine as a base. The reaction proceeds efficiently, smoothly with high yield. The synthesized compound is characterized by spectral methods and X-ray single crystal diffraction. The ground state molecular geometry of the compound has been calculated using the density functional method (DFT) with 6–311G(d,p) basis set. The calculated characteristics and electronic absorption spectra based on the TD–DFT method demonstrated good agreement with the experimental data. The electronic absorption, frontier molecular orbital analyses (HOMO–LUMO) and nonlinear optical (NLO) properties were also discussed.

Experimental and computational studies of L-tartaric acid single crystal grown at optimized pH

The good quality l-tartaric acid (LTA) single crystal of size 12 × 09 × 02 mm3 has been grown by slow solvent evaporation technique by optimizing the pH of aqueous solution. The crystallographic data and crystalline phase of grown LTA crystal has been determined using the powder X-ray diffraction study. The ground state molecular geometry of LTA molecule was optimized by means of CAM-B3LYP/6-31G* level of theory using density functional theory (DFT) approach. The qualitative and quantitative analysis of LTA crystal has been undertaken by means of energy dispersive spectroscopic technique. The UV–visible spectral analysis has been performed to determine the optical transparency of LTA crystal in the range of 190–1100 nm and the optical band gap has been evaluated using the transmittance data. The time dependent-DFT (TDDFT) was employed for calculating the absorption spectrum of the title molecule at B3LYP/6-31G*, CAM-B3LYP/6-31G*, LC-BLYP/6-31G*, M06/6-31G*, PBE1/6-31G* levels of theory. The highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) energy gap was found to be around 6.02 eV at B3LYP/6-31G* level of theory. The Kurtz-Perry powder test has been undertaken to determine the frequency doubling conversion efficiency of LTA crystal. The laser induced third order nonlinear optical (TONLO) effects occurring in LTA crystal have been evaluated by employing the Z-scan analysis at 640 nm. The phase change in refraction nonlinearity, nature of nonlinear absorption and cubic susceptibility of LTA crystal has been evaluated and their respective magnitudes have been determined. The laser damage threshold of LTA crystal has been investigated using the Nd:YAG laser operative at 1064 nm. The frequency response of dielectric constant and dielectric loss of LTA crystal has been investigated at different temperatures ranging from room temperature to 90 °C. The static dipole moment, polarizability and first hyperpolarizability has been evaluated and compared with standard urea molecule.

Thermally induced optical nonlinearity and optical power limiting action of 2,4,5-trimethoxy-4′-nitrochalcone under CW laser regime

In the present work, we report the results of thermally induced third-order nonlinear optical (NLO) properties of 2,4,5-trimethoxy-4[Formula: see text]-nitrochalcone (abbreviated as 2,4,5TMNC) investigated by [Formula: see text]-scan technique using continuous wave (CW) Argon ion laser at a wavelength of 488[Formula: see text]nm with adjusted power ranging from 2.5[Formula: see text]mW to 20[Formula: see text]mW. The experiments were performed by varying the concentration of the molecules in solution. The sample demonstrated strong reverse saturable absorption (RSA) and self-defocusing effect (negative nonlinear refractive index). The estimated values of the NLO absorption coefficient ([Formula: see text], nonlinear refraction ([Formula: see text] and absolute nonlinear susceptibility [Formula: see text] are found to be of the order of 10[Formula: see text][Formula: see text]m/W, 10[Formula: see text][Formula: see text]m2/W and 10[Formula: see text][Formula: see text]esu, respectively. The magnitude of the nonlinear absorption coefficient ([Formula: see text] was found to increase with concentration. The linear absorption spectrum of 2,4,5TMNC was measured using UV–Vis–NIR spectrometer. The optical band gap (Eg) value of title chalcone is obtained from the tauc’s plot of ([Formula: see text] versus [Formula: see text]. The optical limiting performance of 2,4,5TMNC is also investigated for device application. In addition to the above, the computation studies are also carried out to attain the ground state molecular geometry which is found in close to experimental results. Time-Dependent- Density Function Theory (TD-DFT) was used to determine the UV–Vis spectrum at B3LYP/6-31G* level of theory and found to be comparable with experimental data. The HOMO–LUMO energy gap was also determined and discussed. The results promote this chalcone derivative as a promising candidate for optical limiting and optical switching applications.

A first principles study of key electronic, optical, second and third order nonlinear optical properties of 3-(4-chlorophenyl)-1-(pyridin-3-yl) prop-2-en-1-one: a novel D- $$\pi $$ π -A type chalcone derivative

In this work we assess the significant electrooptic properties of a novel chalcone derivative 3-(4-chlorophenyl)-1-(pyridin-3-yl) prop-2-en-1-one using a computational approach. The ground-state molecular geometry was optimized, and geometrical parameters and vibrational modes are established and found to be in strong correlation with experimental results. The excitation energy is observed to be 326 nm (3.8 eV), calculated at the TD/B3LYP/6-31G level (stands for time dependent/Becke’s three Lee-Yang-Parr/basis set). Additionally, a unique insight was gained on a number of properties of the molecular levels such as the HOMO-LUMO gap (i.e. $${\sim } 4\,\hbox {eV}$$ ) and electrostatic potential maps. The potential applications of the 3-(4-chlorophenyl)-1-(pyridin-3-yl)prop-2-en-1-one (CPP) molecule in nonlinear optics are confirmed by second and third harmonic generation studies at five different characteristic wavelengths. The static and dynamic polarizability are found to be many-fold higher than that of urea. The second and third harmonic generation values of the titled molecule are found to be 56 and 158 times higher than standard urea molecule, respectively, computed at same wavelength (i.e. 1064.13 nm). From these studies it is clear that the material possesses superior properties and could be applied in optoelectronic device fabrications.

Key functions analysis of a novel nonlinear optical D-π-A bridge type (2E)-3-(4-Methylphenyl)-1-(3-nitrophenyl) prop-2-en-1-one chalcone: An experimental and theoretical approach

In the current work a new third-order nonlinear optical organic single crystal of (2E)-3-(4-Methylphenyl)-1-(3-nitrophenyl) prop-2-en-1-one (ML3NC) has been grown with well-defined morphology using the slow evaporation solution growth technique. X-ray diffraction technique was used to confirm the crystal system. The presence of functional groups in the molecular structure was identified by robust FT-IR and FT-Raman spectra by experimental and theoretical analysis. The ultraviolet-visible-near infrared and photoluminescence studies shows that the grown crystals possess excellent transparency window and green emission band (∼560 nm) confirms their use in green OLEDs. The third-order nonlinear and optical limiting studies have been performed using femtosecond (fs) Z-scan technique. The third-order nonlinear optical susceptibility (χ(3)), second-order hyperpolarizability (γ), nonlinear refractive index (n2) and limiting threshold values are found to be 4.03 × 10−12 esu, 14.2 × 10−32 esu, −4.33 × 10−14 cm2/W and 2.41 mJ/cm2, respectively. Furthermore, the quantum chemical studies were carried out to achieve the ground state molecular geometry and correlate with experimental results. The experimental value of absorption wavelength (λabs = 328 nm) is found to be in excellent accord with the theoretical value (λabs = 328 nm) at TD-DFT/B3LYP/6-31G* level of theory. To understand the static and dynamic NLO behavior, the polarizability (α) and second hyperpolarizability (γ) values were determined using TD-HF method. The computed second hyperpolarizability γ(-3ω; ω,ω,ω) at 800 nm wavelength was found to be 0.499 × 10−32 esu which is in good agreement with experimental value at the same wavelength. These results confirms the applied nature of title molecule in optoelectronic and nonlinear optical devices.

An experimental and theoretical study on a novel donor-π-acceptor bridge type 2, 4, 5-trimethoxy-4′-chlorochalcone for optoelectronic applications: A dual approach

In this article the authors aim is to investigate and analyze the various key parameters of an organic D-π-A type novel nonlinear optical material 2, 4, 5-trimethoxy-4′-chlorochalcone (2,4,5TMCC) through experimental and quantum chemical studies. The Claisen–Schmidt condensation reaction mechanism was applied to synthesize the 2,4,5TMCC compound and its single crystal was grown by a slow evaporation solution growth (low cost) technique. The crystal structure was confirmed by powder X-ray diffraction analysis. The robust vibrational study has been done using FT-IR and FT-Raman spectra and its NLO activity was discussed. The factor group analysis was also performed. The optical absorption spectrum was recorded and the band gap was calculated to be 2.8eV. In photoluminescence spectrum, an intense emission band at ~540nm has been observed which shows that the grown crystals can be used in green organic light emitting diodes and laser applications. To achieve the stable ground state molecular geometry of 2,4,5TMCC, the computational techniques were applied at different levels of theory using 6-31G* basis set. The calculated geometrical parameters and vibrational spectra are found to be in good agreement with the experimental results. To probe the optical properties of the title compound the time dependent density functional theory was applied. The excitation wavelength was observed at ~398.63nm calculated at B3LYP/6-31G* level of theory and found close to experimental value (i.e. 396nm). The static first hyperpolarizability value is found to be 136 times higher than prototype urea molecule. Additionally, the molecular level approach was attained as HOMO–LUMO gap and electrostatic potential maps. The DSC study reveals that the titled material is stable up to 149°C. The photophysical and nonlinear optical properties suggest that the titled material could be a better choice for the fabrication of optoelectronic devices.

Shedding light on molecular structure, spectroscopic, nonlinear optical and dielectric properties of bis(thiourea) silver(I) nitrate single crystal: A dual approach

The current work is to spotlight the key structure-property features of a novel thiourea complex bis(thiourea) silver(I) nitrate (BTSN) for future applications in nonlinear optical devices through dual approach involving experimental and theoretical techniques. The synthesis and growth of good quality single crystals of a relatively new material BTSN have been done. The crystal structure, quantitative and qualitative, vibrational, optical and dielectric analysis of the grown single crystals was carried out. The optical transparency of the grown crystals is found to be more than 80% confirms its colorless nature and applications in optoelectronic devices. Further, the state-of-art computational methods have been applied to obtain the ground state molecular geometry at B3LYP/6-31G∗, MP2/6-31G∗ and M06/6-31G∗ levels of theory. Various key electro-optical properties (complementary to experimental results) such as IR, Raman, and polarizabilities have been determined at the same levels of theory. The static and dynamic polarizability and first hyperpolarizability both were calculated to comprehend the potential applications of BTSN in nonlinear optics. In addition to the above, numerous novel molecular level insights have been achieved in the form of total and partial density of states, HOMO-LUMO gap and molecular electrostatic potential map. The calculated values of static and frequency dependent dynamic first hyperpolarizability are found to be 8.46×10−30 and 2.30×10−30esu which are about 23 times and 13 times greater than those of prototype urea molecule, respectively, calculated at the same B3LYP/6-31G∗ level of theory. From the analyzed results it is clear that the titled compound possesses excellent electro-optic properties that make it a decent contestant for photonic devices.

A Theoretical Study on Structural, Spectroscopic, Electronic and Nonlinear Optical Properties of 1-[(E)-{[4-(Morpholin-4-Yl)Phenyl]Imino}Methyl]Naphthalen-2-Ol

Density functional theory calculations on ground state molecular geometry, stable conformers, and vibrational wavenumbers for 1-[(E)-{[4-(morpholin-4-yl)phenyl]imino}methyl]naphthalen-2-ol (MPIMN) molecule were performed by using B3LYP and B3PW91 functionals for the exchange-correlation energy with the 6-311++G(d,p) basis set. The detailed assignments of vibrational wavenumbers were carried out on the basis of potential energy distribution (PED) analysis. Nonlinear optical (NLO) behavior of MPIMN was investigated by the determining of electric dipole moment (μ), polarizability (α), and first hyperpolarizability (β) by using B3LYP and B3PW91 functionals. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was analyzed using natural bond orbital (NBO) analysis. The frontier molecular orbitals (HOMO and LUMO) were simulated, and the obtained relatively small energy gap confirmed that charge transfer occurs within MPIMN. Finally, molecular electrostatic potential (MEP) surface was simulated to demonstrate reactive sites for the title molecule.

Synthesis, computational and spectroscopic analysis on (E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-3-methyl-2,6-diphenylpiperidine-1-yl)(phenyl)methanone using DFT approach

(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-3-methyl-2,6-diphenylpiperidin-1-yl)(phenyl)methanone [EPHDPM] and its derivatives were synthesized and characterized by FT-IR, 1H NMR, 13C NMR and elemental analysis. The target compound [EPHDPM] was computed using density functional theory (DFT) method. The ground-state molecular geometry and vibrational frequencies were calculated by using B3LYP/6-31G (d,p) level of theory. The experimentally observed FT-IR and FT-Raman bands were assigned to different normal modes of the molecule. The stability and charge delocalization of the molecule were also studied by natural bond orbital (NBO) analysis. The HOMO–LUMO energies describe the charge transfer takes place within the molecule. Molecular electrostatic potential has been analyzed. The reported EPHDPM molecule used as a potential NLO material since it has high μβ0 value. Thermodynamic parameter like entropy and enthalpy are calculated and these values are increased with increasing the temperature due to the enhancement of vibrational intensities.

Molecular structure, vibrational spectra, AIM, HOMO-LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree-Fock and density functional theory.

In this work, the molecular structure, harmonic vibrational frequencies, UV, NBO and AIM of 3-thiophenecarboxilic acid (abbreviated as 3-TCA) monomer and dimer has been investigated. The FT-IR and FT-Raman spectra were recorded. The ground-state molecular geometry and vibrational frequencies have been calculated by using the Hartree-Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d,p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with VEDA program. Comparison of the observed fundamental vibrational frequencies of 3-TCA with calculated results by HF and DFT methods indicates that B3LYP is better to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title compound have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, frontier molecular orbitals (HOMO-LUMO), molecular electrostatic potential (MEP) and thermodynamic properties have been performed. The electric dipole moment (μ) and the first hyperpolarizability (β) values of the investigated molecule have been also computed.

Spectroscopic (FT-IR, FT-Raman) and quantum mechanical studies of 3t-pentyl-2r,6c-diphenylpiperidin-4-one thiosemicarbazone

In this study, the molecular structure and vibrational spectra of 3t-pentyl2r,6c-diphenylpiperidin-4-one thiosemicarbazone (PDPOTSC) were studied. The ground-state molecular geometry was ascertained by using the density functional theory (DFT)/B3LYP method using 6-31++G(d,p) as a basis set. The vibrational (FT-IR and FT-Raman) spectra of PDPOTSC were computed using DFT/B3LYP and HF methods with 6-31++G(d,p) basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED⩾10%) of the vibrational modes, calculated with scaled quantum mechanics (SQM) methods PQS program. The electrical dipole moment (μ) and first hyperpolarizability (βo) values have been computed using DFT/B3LYP and HF methods. The calculated result (βo) shows that the title molecule might have nonlinear optical (NLO) behavior. Atomic charges of C, N, S and molecular electrostatic potential (MEP) were calculated using B3LYP/6-31G++(d,p). The HOMO–LUMO energies were calculated and natural bonding orbital (NBO) analysis has also been carried out.

Spectroscopic (FT-IR, FT-Raman and NMR) and computational studies on 3-methoxyaniline

In this work, the molecular structure, vibrational, UV and NMR spectra of 3-methoxyaniline (abbreviated as 3MOA, C7H9NO) were studied. The FT-IR and FT-Raman spectra were recorded. The ground-state molecular geometry and vibrational frequencies were calculated by using the Hartree–Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d,p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Comparison of the observed fundamental vibrational frequencies of 3MOA with calculated results by HF and DFT methods indicates that B3LYP is superior to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, Frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed and compared with methoxybenzene and aniline. The electric dipole moment (μ) and the first hyperpolarizability (β) values of the investigated molecule were computed using ab initio quantum mechanical calculations. The calculated results also show that the 3MOA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. The 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.

Molecular structure and solvent effects on the dipole moments and polarizabilities of some aniline derivatives

This work presents the quantum chemical studies of the effects of substituents and solvents on the ground state molecular geometry, dipole moments, polarizabilities and frontier orbital energies of aniline (A), N-methylaniline (NMA), N-ethylaniline (NEA), N,N-dimethylaniline (DMA) and N,N-diethylaniline (DEA) towards understanding their structure–property relationship. The ground state molecular geometry, dipole moments, polarizabilities and frontier orbital energies of A, NMA, NEA, DMA and DEA were computed by use of the ab initio restricted HF–DFT self-consistent field method (B3LYP) with 6-31G* basis set in vacuum, ethanol and tetrahydrofuran. The results of the B3LYP/6-31G* calculations revealed that these properties are enhanced upon successive substitution with size and number of alkyl groups at the amino group of the molecules, and as the dielectric constant of the solvents decrease. It was also found that for all the molecules, the enhanced ground state molecular geometry, dipole moments and polarizabilities upon substitution or solvent effect are associated with a decrease in the EHOMO−ELUMO (optical) gap. The lower optical gap, higher dipole moments and polarizabilities with increased size and planarity illustrates increased reactivity and ground state electro-optic (non-linear optical) activity of the molecules upon substitution, and as the dielectric constant of the solvents decreased. Of the studied molecules, DEA was found to exhibit the most electro-optic activity and reactivity.

Theoretical Study of the Structure and Bonding in ThC2 and UC2

The electronic structure and various molecular properties of the actinide (An) dicarbides ThC(2) and UC(2) were investigated by relativistic quantum chemical calculations. We probe five possible geometrical arrangements: two triangular structures including an acetylide (C(2)) moiety, as well as the linear AnCC, CAnC, and bent CAnC geometries. Our calculations at various levels of theory indicate that the triangular species are energetically more favorable, while the latter three arrangements proved to be higher-energy structures. Our SO-CASPT2 calculations give the ground-state molecular geometry for both ThC(2) and UC(2) as the symmetric (C(2v)) triangular structure. The similar and, also very close in energy, asymmetric (C(s)) triangular geometry belongs to a different electronic state. DFT and single-determinant ab initio methods failed to distinguish between these two similar electronic states demonstrating the power of multiconfiguration ab initio methods to deal with such subtle and delicate problems. We report detailed data on the electronic structure and bonding properties of the most relevant structures.