A combined experimental and computational studies of 3,3,6,6-Tetramethyl-9-(4-Methoxyphenyl)3,4,6,7,9,10 hexahydroacridine-1,8-dione

ABSTRACT

In this work, we have recorded the Fourier Transform Infrared (FTIR) and Ultra-Violet Visible (UV–Vis) spectra of 3,3,6,6-Tetramethyl-9-(4-Methoxyphenyl)3,4,6,7,9,10 hexahydroacridine-1,8-dione (C₂₄H₂₉NO₃) in the spectral range 4000–400?cm^?1 and 190–1400?nm, respectively. The thermo gravimetric (TG) analysis of the compound has been performed to check the thermal stability of the compound. The molecular geometry and complete vibrational spectra in the ground state are calculated by Hartree Fock (HF) and Density Functional Theory (DFT) using6-311G(d,p) basis set. The calculated vibrational harmonic frequencies are scaled using a proper scale factor, yielding a good agreement with the experimental data. Stability of the molecule arising from hyperconjugative interactions, charge delocalisation has been studied using natural bond orbital analysis (NBO). Mulliken charges, MEP mapping and temperature dependence on the thermodynamic properties in the optimised ground state have been calculated. UV–Visible spectrum of the molecule was calculated by using TD-DFT approach and the results were compared with the experimental one. We have calculated the several molecular parameters like ionisation potential, electron affinity, global hardness, electron chemical potential, electronegativity and global electrophilicity based on HOMO and LUMO energy values calculated at B3LYP/6-311G(d,p) level of theory. The calculated optimised structural parameters and vibrational wavenumbers are found to be in good agreement with the experimental results.     

Experimental vibrational spectra (Raman,infrared) and DFT calculations on monomeric and dimeric structures of 2‐ and 6‐bromonicotinic acid

In this work, the Fourier transform infrared and Raman spectra of 2‐bromonicotinic acid and 6‐bromonicotinic acid (abbreviated as 2‐BrNA and 6‐BrNA, C₆H₄BrNO₂) have been recorded in the region 4000–400 and 3500–50 cm⁻¹. The optimum molecular geometry, normal mode wavenumbers, infrared intensities and Raman scattering activities, corresponding vibrational assignments and intermolecular hydrogen bonds were investigated with the help of B3LYP density functional theory (DFT) method using 6‐311++G(d,p) basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. From the calculations, the molecules are predicted to exist predominantly as the C1 conformer. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental (UV,NMR, IR and Raman) and theoretical spectroscopic properties of 2-chloro-6-methylaniline

In this work, the experimental and theoretical UV, NMR and vibrational spectra of 2-chloro-6-methylaniline (2-Cl-6-MA, C₇H₈NCl) were studied. The ultraviolet absorption spectra of compound that dissolved in ethanol were examined in the range of 200–400 nm. The ¹H, ¹³C and DEPT NMR spectra of the compound were recorded. FT-IR and FT-Raman spectra of 2-Cl-6-MA in the liquid phase were recorded in the region 4000–400 cm^?1 and 3500–50 cm^?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using density functional theory (DFT) employing B3LYP exchange correlation and the 6-311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies were found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital (GIAO) method. Comparison of the calculated NMR chemical shifts and absorption wavelengths with the experimental values revealed that DFT method produces good results.     

Molecular structure,spectroscopic properties (FT-IR,Micro-Raman,and UV-vis), and DFT calculations of minaprine

Molecular geometry, experimental vibrational wavenumbers, electronic properties, and quantum chemical calculations of minaprine (C₁₇H₂₂N₄O · 2HCl), (with synonym, dihydrochloride salt of N-(4-methyl-6-phenyl-3-pyridazinyl)-4-morpholineethamine) which is widely used as a psychotropic drug at medicinal treatment, in the ground state by using density functional theory (DFT/B3LYP) method with 6–31++G(d,p) basis set have been presented for the first time. The comparison of the observed fundamental vibrational frequencies were in a very good agreement with the experimental data. Furthermore, UV-vis TD-DFT calculations, the highest occupied molecular orbitals (HOMO-1, HOMO), lowest unoccupied molecular orbitals (LUMO, LUMO + 1), molecular electrostatic potential (MEP) surface, atomic charges and thermodynamic properties of minaprine molecule have been theoretically calculated and simulated at the mentioned level.     

Molecular structure,spectroscopic (FTIR,FTIR gas phase,FT‐Raman) first‐order hyperpolarizability and HOMO–LUMO analysis of 4‐methoxy‐2‐methyl benzoic acid

Vibrational spectral analysis was carried out for 4‐methoxy‐2‐methyl benzoic acid (4M2MBA) by using Fourier transform infrared (FT‐IR) (solid, gas phase) and FT‐Raman spectroscopy in the range of 400–4000 and 10–3500 cm⁻¹ respectively. The effects of molecular association through O H···O hydrogen bonding have been described by the single dimer structure. The theoretical computational density functional theory (DFT) and Hatree‐Fock (HF) method were performed at 6–311++G(d,p) levels to derive the equilibrium geometry, vibrational wavenumbers, infrared intensities and Raman scattering activities. The scaled theoretical wavenumbers were also shown to be in good agreement with experimental data. The first‐order hyperpolarizability (β₀) of this novel molecular system and related properties (β, α₀ and Δα) of 4M2MBA are calculated using the B3LYP/cc‐pvdz basis set, based on the finite‐field approach. A detailed interpretation of the infrared and Raman spectra of 4M2MBA is reported. The theoretical spectrograms for FT‐IR and FT‐Raman spectra of the title molecule were also constructed and compared with the experimental one. Copyright © 2010 John Wiley & Sons, Ltd.     

FTIR and FT‐Raman spectra and density functional computations of the vibrational spectra,molecular geometry and atomic charges of the biomolecule: 5‐bromouracil

FTIR and FT‐Raman spectra of 5‐bromouracil in the powder form were recorded in the region 400–4000 cm⁻¹ and 50–4000 cm⁻¹, respectively. The observed wavenumbers were analysed and assigned to different normal modes of vibration of the molecule. Quantum chemical calculations were performed to support the assignments of the observed wavenumbers. The performance of the B3LYP hybrid density functional (DFT) method was compared with other methods. With the 6–31 G** and 6–311 + G(2d,p) basis sets, the calculated geometry, dipole moments and harmonic vibrations were determined. A comparison with the uracil molecule was made, and specific scale factors were deduced and employed in the predicted wavenumbers of 5‐bromouracil. The total atomic charges and thermodynamic parameters were calculated, and are discussed briefly. Structure and harmonic vibrations of 5‐bromouracil were also calculated in the presence of water within a simple model with one molecule. It is observed that the bromine atom at position 5 exhibits smaller inductive effects than the fluorine atom, producing a small distortion of the electrostatic potential around the ring and a reduction of the molecular dipole moment. Copyright © 2007 John Wiley & Sons, Ltd.     

Scaled Quantum Chemical Studies of the Molecular Structure and Vibrational Spectra of Minoxidil

The Fourier transform Raman and Fourier transform infrared spectra for minoxidil have been recorded in the region 4000—100 cm^?1 and 4000—450 cm^?1, respectively. The structural and spectroscopy data of the molecule in the ground state were calculated by using density functional theory methods with 6-311G (d, p) basis set. A detailed vibrational analysis of the title compound has been done using normal coordinate analysis following the scaled quantum mechanical force field methodology. The calculated molecular geometry parameters and scaled vibrational wavenumbers are well compared with the experimental data. The electronic properties, such as excitation energies, absorption wavelength, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) energies were performed by time-dependent density functional theory approach, and the results are in good agreement with experimental absorption spectrum. The charge delocalizations of these molecules have been analyzed using natural bond orbital analysis. The molecule orbital contributions are studied by density of energy states. Fukui functions, local softness, and electrophilicity indices for selected atomic sites of the title compound are determined. Finally, the thermal behaviors of the compound have been calculated by different temperature.     

Experimental and theoretical FT‐IR and FT‐Raman spectroscopic analysis of N1‐methyl‐2‐chloroaniline

In this work, the experimental and theoretical vibrational spectra of N1‐methyl‐2‐chloroaniline (C₇H₈NCl) were studied. FT‐IR and FT‐Raman spectra of the title molecule in the liquid phase were recorded in the region 4000–400 cm^?1 and 3500–50 cm^?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (B3LYP) with the 6‐311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT‐IR and FT‐Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. ¹³C and ¹H NMR chemical shifts results were compared with the experimental values. The optimized geometric parameters (bond lengths and bond angles) were given and are in agreement with the corresponding experimental values of aniline and p‐methyl aniline. Copyright © 2008 John Wiley & Sons, Ltd.     

FT‐Raman,FT‐IR spectra and DFT calculations on monomeric and dimeric structures of 5‐fluoro‐ and 5‐chloro‐salicylic acid

The experimental and theoretical study on the structures and vibrations of 5‐fluoro‐salicylic acid and 5‐chloro‐salicylic acid (5‐FSA and 5‐ClSA, C₇H₅FO₃ and C₇H₅ClO₃) is presented. The Fourier transform infrared spectra (4000–400 cm⁻¹) and the Fourier transform Raman spectra (4000–50 cm⁻¹) of the title molecules in the solid phase were recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman intensities and Raman scattering activities were calculated for a pair of molecules linked by the intermolecular O H···O hydrogen bond. The geometrical parameters and energies of 5‐FSA and 5ClSA were obtained for all eight conformers/isomers from density functional theory (DFT) (B3LYP) with 6‐311++G(d,p) basis set calculations. The computational results identified the most stable conformer of 5‐FSA and 5‐ClSA as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The spectroscopic and theoretical results were compared with the corresponding properties for 5‐FSA and 5‐ClSA monomers and dimer of C1 conformer. The optimized bond lengths, bond angles and calculated wavenumbers showed the best agreement with the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular structure and vibrational spectra of alpha-benzoinoxime by density functional method

In the present study, an exhaustive conformational search of the Alpha-benzoinoxime has been performed. The FT-IR spectrum of this compound was recorded in the region 4000–400 cm^?1. The FT-Raman spectrum was also recorded in the region 3500–50 cm^?1. Vibrational frequences of the title compound were calculated by B3LYP method using 6–311++G(d, p) basis set. The calculated vibrational frequences were analysed and compared with experimental results.     

Vibrational Spectroscopic Investigation,First Hyper Polarizability and Homo–Lumo Analysis of Tetrahydroxy-1,4Quinone Hydrate Using Density Functional Theory and Hartree-Fock Method

The FTIR and FT-Raman spectra of tetrahydroxy-1,4quinone hydrate have been recorded in the regions 4000–400 and 3500–50 cm^–1 respectively. Using the observed Fourier-transform infrared spectroscopy (FTIR) and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound has been carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by the density functional theory (DFT/B3LYP) and Hartree–Fock (HF) method with 6-311+G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamental vibrations is very small. A detailed interpretation of the infrared and Raman spectra of tetrahydroxy-1,4quinone hydrate is also reported. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.     

Sensitive and Selective PET-Based π-expanded Phenanthrimidazole Luminophore for Zn2+ Ion

The novel photoinduced electron transfer (PET) chemosensor, 1-(1-(4-methoxyphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)naphthalen-2-ol [MPPN] and its zinc complex were synthesised and characterized by electronic spectral and Frontier molecular orbital energy analysis. MPPN becomes efficient fluorescent chemosensor upon binding with metal ions and shows a strong preference toward Zn²⁺ ion. Density Functional theory (DFT) calculations reveal that luminescence of free MPPN originates from its orbital structure in which two π-orbitals (HOMO and HOMO-1) of the imidazole ring are situated between two π-orbitals (HOMO-2 and LUMO) of the naphthyl fragment. Therefore the absorption and emission processes occur between the two π- orbitals (HOMO-2 and LUMO). The two higher energy imidazole orbitals (HOMO and HOMO-1 ) serve as quenchers for the excited state of the molecule through nonradiative processes. Upon binding with Zn²⁺ ion, MPPN becomes a highly luminescent with λ_emi???421 nm. The significant enhancement of luminescence upon binding with Zn²⁺ ion is attributed to the stabilization of HOMO-2 and HOMO-1 π-orbitals of imidazole ring upon their engagement in new bonds with Zn²⁺ ion. The affinity of MPPN to zinc ion is found to be very high [K?=?6?×?10⁶ M^?1] when compared with other metals ions. The nonlinear absorption coefficient γ for MPPN is 1.9?×?10^?12 m/W and 3.9?×?10^?11 m/W for MPPN-Zn complex.     

Theoretical study of structure and analytic potential energy function for the ground state of PO2 molecule

In this paper, the energy, the equilibrium geometry, and the harmonic frequency of the ground electronic state of PO₂ are computed using B3LYP, B3P86, CCSD(T), and QCISD(T) methods in conjunction with 6-311++G(3df, 3pd) and cc-pVTZ basis sets. A comparison between the computational results and the experimental values indicates that the B3P86/6-311++G(3df, 3pd) method can give better energy calculation results for the PO₂ molecule. It is shown that the ground state of the PO₂ molecule has C_2v symmetry and its ground electronic state is X²A₁. The equilibrium parameters of the structure are R_P-O=0.1465 nm, d=19.218 eV. The bent vibrational frequency ν₁=386 cm^-1, the symmetric stretching frequency ν₂=1095 cm^-1, and the asymmetric stretching frequency ν₃=1333 cm^-1 are obtained. On the basis of atomic and molecular reaction statics, the reasonable dissociation limit for the ground state of the PO₂ molecule is determined. Then the analytic potential energy function of the PO₂ molecule is first derived by using the many-body expansion theory. The potential curves correctly reproduce the configurations and the dissociation energy for the PO₂ molecule.     

Vibrational investigation of 1-cyclopentylpiperazine: A combined experimental and theoretical study

FT-IR and Raman spectra of 1-cyclopentylpiperazine(1cppp)have been experimentally examined in the region of 4000–200cm-1.The optimized geometric parameters,conformational equilibria,normal mode frequencies and corresponding vibrational assignments of 1cppp(C9H18N2)are theoretically examined by means of B3LYP hybrid density functional theory(DFT)method together with 6-31++G(d,p)basis set.On the basis of potential energy distribution(PED)reliable vibrational assignments have been made and the thermodynamics functions,highest occupied and lowest unoccupied molecular orbitals(HOMO and LUMO)of 1cppp have been predicted.Calculations are employed for four different conformations in C1 and Cs point groups of 1cppp in gas phase.Comparison between the experimental and theoretical results indicates that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and the structural parameters,vibrational frequencies and assignments.Furthermore,C1(equatorial-axial)point group has been found as the most stable conformer of 1cppp.     

A combined experimental and theoretical study on 8-hydroxy-2-quinolinecarboxylic acid

The mid-IR and Raman spectra of 8-hydroxy-2-quinolinecarboxylic acid (8HQC) were recorded. These spectra were interpreted with the help of B3LYP/6–311 ++G(d,p) calculations and potential energy distribution (PED) analysis. As a result of the calculations, seven tautomers were determined among many stable conformations. The experimental spectra were concordant with the theoretical data of one tautomer. In the functional group region overtone and combination bands were detected and assigned. In addition, because of several peaks in the IR spectrum, it was proposed that the 8HQC exhibits dimerization in condensed phase. Possible dimeric forms of 8HQC were evaluated at the same level of theory, and it has been seen that the calculation results confirm the above proposal. ¹H and ¹³C NMR chemical shifts of 8HQC have been calculated, and compared with the experimental data. The frontier molecular orbital properties and the atomic charges were also theoretically obtained and presented.     

Conformational stability and vibrational study of phenylacetyl chloride

The Fourier transform infrared spectroscopy and Fourier transform Raman spectra of phenylacetyl chloride were recorded and analyzed in the range 3500–400 and 3500–200 cm^?1 at room temperature, respectively. In order to obtain the structural information and conformational stabilities, a potential energy surface scan for internal rotation was carried out at the B3LYP/6‐31G(d) level. The potential energy surface reveals that the title compound has two minimal conformers (A and B). The optimized geometries, structural parameters, stabilities, energies, thermodynamic parameters, vibrational wavenumbers, infrared intensities, and Raman activities for the two conformers (A and B) have been obtained by employing B3LYP and MP2 calculations with 6‐311++G (d, p) basis sets. The conformational energy difference between A and B is very small, indicating that the B conformer coexists with the A conformer. The detailed vibrational assignments of vibrational spectra of each conformer have been made on the basis of the potential energy distributions analysis. The highest occupied molecular orbital –lowest unoccupied molecular orbital energy gap and molecular electrostatic potential of the two conformers have been also calculated for comparison of their chemical activities. Copyright © 2015 John Wiley & Sons, Ltd.     

FT‐Raman spectroscopic spectra on 3‐phenylpropylamine inclusion compounds

Some new Hofmann‐3‐phenylpropylamine‐type clathrates with chemical formulae of M(3‐phenylpropylamine)₂ Ni(CN)₄. 2G (MNi or Co, G = 1,2‐dichlorobenzene or 1,3‐dichlorobenzene) have been prepared and their Fourier transform infrared(FT‐IR; 4000–400 cm⁻¹), far‐infrared (600–100 cm⁻¹) and FT‐Raman (4000–60 cm⁻¹) spectra are reported. The ligand molecule, guest molecules, polymeric sheet and metal‐ligand bands of the clathrates are assigned in detail. The compounds are also characterized by thermal gravimetric analysis (TGA), differential thermal analysis (DTA), elemental analysis and magnetic susceptibility measurements. From the results, the monodentate 3‐phenylpropylamine ligand molecule bonds to the metal atom of |M‐Ni(CN)₄ | _∞ polymeric layers in the trans‐gauche‐gauche (TGG) form, and 1,2‐dichlorobenzene or 1,3‐dichlorobenzene molecules are guested by this structure revealing the inclusion ability of the host complexes. Copyright © 2010 John Wiley & Sons, Ltd.     

Magnetic shielding tensors of carbon nuclei in 3,5-dichlorophenylacetylene,a theoretical ab initio and experimental study

Ab initio GIAO-CHF and DFT(B3LYP) molecular geometry optimization and magnetic shielding tensor calculations of carbon nuclei of 3,5-dichlorophenylacetylene have been performed using 6–311G?? and 6–311+G(2d,p) basis sets. The isotropic ¹³C chemical shifts, needed for comparison, have been measured in C₆D₁₂ solution. The principal elements of the shielding tensor of the carbon nuclei in the investigated molecule in the solid state have been determined from an intensity analysis of the spinning sidebands in ¹H-¹³C CP/MAS NMR spectra. Shielding anisotropy parameters of the acetylenic carbons have been independently determined using the method based on proton-coupled ¹³C nematic phase spectra as well as from the interpretation of the ¹³C longitudinal relaxation rates. The latter data have been analysed assuming the molecular reorientation to be the rotational diffusion of an asymmetrical top, which has provided, apart from the diffusion coefficients, an additional check on the reliability of the theoretical calculation of the shielding tensors. In general, satisfactory agreement between the theoretical and experimental results has been achieved.     

Zn2+-Schiff’s Base Complex as an “On–Off-On” Molecular Switch and a Fluorescence Probe for Cu2+ and Ag+ Ions

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff’s base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H₂L) and its metal complexes with Zn²⁺, Cu²⁺ and Ag⁺ ions. This study aims to investigate the behavior of H₂L and the binuclear Zn²⁺ complex (1) as fluorescent probes for the detection of metal ions (Zn²⁺, Cu²⁺ and Ag⁺) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the H₂L ligand were optimized using the B3LYP/6–311?+??+?G** level of theory, while the L^?2-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6–311?+??+?G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of the E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6–311?+??+?G** basis set for C, O, N and H atoms and a LANL2DZ basis set for the metal ions (Zn²⁺, Cu²⁺ and Ag⁺). The computational results of the B3LYP functional were in excellent agreement with the experimental results. Hence, it was adopted for performing the emission calculations. The results indicated that metal complex (1) can act as a fluorescent chemosensor for the detection of Ag⁺ and Cu²⁺ ions through the mechanism of intermolecular charge transfer (ICT) and as a molecular switch “On–Off-On” via the replacement of Cu²⁺ by Ag⁺ ions, as proved experimentally.

     

Density functional theory calculations and vibrational spectra of p‐bromonitrobenzene

FT‐IR and FT‐Raman spectra of p‐bromonitrobenzene (p‐BNB) have been recorded in the region 4000–400 cm⁻¹ and 4000–50 cm⁻¹, respectively. The molecular structure, geometry optimization, vibrational wavenumbers have been investigated. The spectra were interpreted with the aid of normal coordinate analysis based on the density functional theory (DFT) using the standard B3LYP/6‐31G method and basis set combination and was scaled using multiple scale factors yielding good agreement between observed and calculated wavenumbers. The results of the calculations are applied to simulate infrared and Raman spectra of the title compound which showed reasonable agreement with the observed spectra. Copyright © 2009 John Wiley & Sons, Ltd.