Synthesis,Crystal Structure and ab Initio Studies of 5-Phenylamino-3-phenylimino-3H[1, 2]dithiole-4-carboxylic acid ethyl ester

Abstract  

5-Phenylamino-3-phenylimino-3H[1, 2]dithiole-4-carboxylic acid ethyl ester, C₁₈H₁₆N₂O₂S₂, (I), has been synthesized and the structure has been solved by X–ray diffraction. The crystals are triclinic, space group P[`1] P\bar{1} , with a = 5.7127(2) ?, b = 12.1757(5) ?, c = 14.0734(5) ?, α = 112.1217(16)°, β = 97.786(2)°, γ = 100.694(2)°, Mr = 356.45, V = 868.11(6) ?³, Z = 2 and R = 0.0373. In the title compound there is an intramolecular N–H···O hydrogen bond. The crystal structure is stabilized only by weak C–H···π and π···π interactions as well as by van der Waals forces. The geometry of the isolated molecule was optimized by ab initio quantum mechanical calculations, employing both molecular orbital Hartree-Fock (HF) and density functional theory (DFT) methods. In the DFT calculation the minimum energy was achieved for a conformation very similar to that of the solid-state molecule.     

The Crystal Structures of (Z)-Ethyl 2-(4-chlorophenyl)-3-(2,4-difluorophenyl-amino)acrylate and its Analogues

Abstract  

The title compound, C₁₇H₁₄ClF₂NO₂, crystallizes in monoclinic space group P2₁/c with unit cell dimension of a = 16.276(3) ?, b = 7.5030(15) ?, c = 13.812(3) ?, α = 90°, β = 111.11(3)°, γ = 90° and Z = 4. The structure of the title compound reveals a Z configuration with respect to the C=C double bond in aminoacrylate fragment. The molecule is stabilized by intramolecular N–H···F and N–H···O hydrogen bonds. In the ethyl 2-aryl-3-arylaminoacrylates, electronic properties of the substituents in the aniline motif clearly affected the attached C–N bond length, and such effect is very little relative to Z-/E-configuration with respect to the C=C double bond.     

Crystallographic and Conformational Analysis of [(<Emphasis Type="Italic">E</Emphasis>)-2-[(3-Chlorophenylimino)methy])-4-methoxyphenol]

Abstract  The crystal structure of C₁₄H₁₂ClNO₂ was determined by X-ray analysis. It crystallizes in the triclinic space group Pc with a = 12.5346(10) ?, b = 4.5101(3) ?, c = 12.0534(11) ?, α = 90.00o, β = 113.669(6)o, γ = 90.00o, Z = 2, Dx = 1.393 mg/m³, μ (MoK_α) = 0.298 mm⁻¹. The title compound is photochromic and molecule is non-planar. It adopts a phenol–imine tautomeric form with a strong intramolecular O–H···N hydrogen bond and a strong intermolecular C–H···O hydrogen bond. Minimum energy conformations AM1 were calculated as a function of the three torsion angles θ1(C10–C9–N1–C8), θ2(C9–N1–C8–C1) and θ3(N1–C8–C1–C6), varied every 10°. As in the X-ray experiment results, molecule has an angle that makes it non-planar between two aromatic rings in AM1 optimized geometry. Graphical Abstract  Molecular and crystal structure of [(E)-2-[(3-chlorophenylimino)methy])-4-methoxyphenol], C₁₄H₁₂ClNO₂, have been determined by single crystal X-ray diffraction study, and conformational analysis of the title molecule with respect to the selected torsion angle has been achieved by AM1 semi-empirical calculations.      

Two Crystal Forms of 4-{(2<Emphasis Type="Italic">E</Emphasis>)-2-[1-(4-Methoxyphenyl)ethylidene] hydrazinyl}-8-(trifluoromethyl)quinoline

Abstract  

The Schiff base, 4-{(2E)-2-[1-(4-methoxyphenyl)ethylidene] hydrazinyl}-8-(trifluoromethyl)quinoline, crystallizes in two polymorphic forms depending on the solvent. One of these forms is monoclinic (1M), space group P2₁/c with a = 10.2906(10) ?, b = 8.9211(7) ?, c = 18.4838(15), β = 97.271(8)°, and the other is orthorhombic (1O), space group Pbca, unit-cell parameters: a = 13.6485(12) ?, b = 9.0588(9) ?, c = 27.400(2) ?. The molecules in either crystalline form have similar bond lengths and angles, but one is nearly planar while the other has a significant twist. In monoclinic form the dihedral angle between terminal ring planes is 17.26(8)° while in the orthorhombic one it is 26.11(5)°, and in this latter case the central chain is almost coplanar with the quinoline ring system while in the former these two planes are significantly twisted. The crystal structures of both forms are determined by the interplay of van der Waals forces and weak directional interactions C–H···F, π···π stacking, and—in the case of 1M—short intermolecular C–F···N contact. The crystals of 1M decomposes slowly into the powder while the other form is stable. The powder diffraction pattern of the product of decomposition of 1M is similar to that calculated for 1O. This suggests that the decomposition is a consequence of the phase transition of the less stable monoclinic into more stable orthorhombic form.     

Synthesis,Crystal Structure and Antibacterial Activity of 5-Bromonicotinic Acid [1-(4-Chlorophenyl)methylidene]hydrazide Monohydrate Methanol Solvate

Abstract  The compound 5-bromonicotinic acid [1-(4-chlorophenyl)methylidene]hydrazide monohydrate methanol solvate, derived from the condensation reaction of 5-bromonicotinic acid hydrazide with 4-chlorobenzaldehyde in a methanol solution, was synthesized and characterized by elemental analysis, IR spectrum, ¹H NMR and X-ray single crystal determination. The compound crystallizes in the triclinic space group P − 1 with unit cell dimensions a = 6.9360(14) ?, b = 10.070(2) ?, c = 12.267(3) ?, α = 84.39(3)°, β = 86.10(3)°, γ = 80.50(3)°, V = 839.8(3) Ǻ³, Z = 2, R ₁ = 0.0724, and wR ₂ = 0.1720. X-ray structure determination reveals that the compound has a trans configuration with respect to the C=N double bond or C–N single bond. In the crystal structure, molecules are linked through intermolecular O–H···N, O–H···O, and C–H···O hydrogen bonds, forming layers parallel to the ab plane. The preliminary biological tests show that the compound has excellent antibacterial activity. Index Abstract  The compound 5-bromonicotinic acid [1-(4-chlorophenyl)methylidene]hydrazide monohydrate methanol solvate, derived from the condensation reaction of 5-bromonicotinic acid hydrazide with 4-chlorobenzaldehyde in a methanol solution, was synthesized and characterized by elemental analysis, IR spectrum, ¹H NMR and X-ray single crystal determination. The molecule of the compound has a trans configuration with respect to the C=N double bond or C–N single bond. In the crystal structure, molecules are linked through intermolecular O–H···N, O–H···O, and C–H···O hydrogen bonds, forming layers parallel to the ab plane. The preliminary biological tests show that the compound has excellent antibacterial activity.      

Spectral and X-ray Diffraction Studies of <Emphasis Type="Italic">N</Emphasis>-(2-Nitrophenyl)-5-Phenyl-1,3,4-Oxadiazole-2-Amine

Abstract  

Thiosemicarbazides and their derivatives are well known for their use in biological activity and many applications in pharmaceutical and industrial fields. The cyclization of 1-benzoyl-4-(2-nitrophenyl)-3-thiosemicarbazide (BNPTSC) in dimethylformamide (DMF) medium furnished N-(2-nitrophenyl)-5-phenyl-1,3,4-oxadiazole-2-amine (NPPOA). The chemical structure of the above substituted 1,3,4-oxadiazole has been assigned by IR, mass and X-ray diffraction studies. The XRD studies reveal the presence of four types of hydrogen bonds (N–H···O, N–H···N, C–H···O, C–H···N) in the crystal packing. The crystal system was found to be orthorhombic with a space group Pca2(1) and the unit cell dimensions are: a = 26.873(3) ?, b = 6.0827(7) ?, c = 7.8502(10) ?, α = 90°, β = 90°, γ = 90° and Z = 4.     

Crystal and Molecular Structure of the 1:2 Salt Formed Between 1,2-(4-Pyridyl)Ethane and 2-(4-Hydroxyphenylazo)Benzoic Acid

Abstract  Proton transfer occurred during co-crystallization of 1,2-(4-pyridyl)ethane with 2-(4-hydroxyphenylazo)benzoic acid to yield a salt comprising a 1:2 ratio of 1,2-bis(4-pyridinium)ethane dications and 2-(4-hydroxyphenylazo)benzoate anions. Centrosymmetrically related anions associate by charge-assisted O–H···O hydrogen bonds to form 24-membered {···OC₃N₂C₄OH}₂ synthons. These are connected into a supramolecular polymer via charge-assisted N–H···O hydrogen bonds involving the 1,2-bis(4-pyridinium)ethane dications. The compound crystallizes in the triclinic space group P−1 with a = 8.517(4) ?, b = 9.110(5) ?, c = 10.477(5) ?, α = 96.850(13)°, β = 94.446(12)°, γ = 104.946(10)° and Z = 1 {two anions and a dication}. Index Abstract  Supramolecular chains mediated by charge-assisted O–H···O and N–H···O hydrogen bonding are found in the salt containing a 1:2 ratio of 1,2-bis(4-pyridinium)ethane dications and 2-(4-hydroxyphenylazo)benzoate anions.      

Structures of two N-{2-([(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-halophenyl}acetamides

Abstract  

The compounds, N-{2-[(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-chlorophenyl}acetamide (1: X = Cl) and N-{2([(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-bromo-phenyl}acetamide (1: X = Br), are isostructural. The molecules are near ‘‘V’’ shaped with the angles between the two aromatic planes ca. 84° in each case. The various intermolecular interactions, namely N–H···O, N–H···N, N–H···F, and C–H···N hydrogen bonds and C–H···π, C–Cl···π and C–O···π interactions, generate 3-D arrays. Compound (1: X = Cl) crystallizes in the monoclinic space group P21/c with a = 16.9032(7) ?, 10.2193(4) ?, c = 7.5227(4) ?, β = 100.179(3)° and Z = 4. Compound (1: X = Br) crystallizes in the monoclinic space group P21/c with a = 17.2119(4) ?, 10.2167(2) ?, c = 7.5677(2) ?, β = 100.326(2)° and Z = 4.     

Structural Characterization of New Compound from the Ring-Opening Reaction of 3-(1H-1,2,4-triazol-1-yl)-1,5-Benzothiazepine with Phenylonitrile Oxide

Abstract  

The crystal structure of the product (Z)-2-((Z)-((Z)-1,3-diphenyl-2-(1H-1,2,4-triazol-1-yl)allylidene)amino)phenyl N-hydroxybenzimidothioate (4) was obtained by single crystal X-ray diffraction. The title compound, C₃₀H₂₃N₅OS (4), crystallizes in the triclinic space group, P-1, with unit cell parameters a = 8.3306(17) ?, b = 11.394(2) ?, c = 14.560(3) ?, α = 78.75(3)o, β = 89.96(3)o, γ = 70.56(3)o, Z = 2. In the crystal structure, adjacent molecules are linked by O–H···N hydrogen bonds. H-bonds and π–π stacking are the main non-bonding interactions in the molecular structure and give support to molecular packing stability. In addition, the structure is supported by a weak intermolecular C–H···Cg π-ring interaction. Detail of the synthesis, structures, and spectroscopic properties of the title compound is discussed.     

The Tetrafluoroborate Salt of 4-Methoxybenzyl N-2-(dimethylamino)ethyl-N-nitrosocarbamate: Synthesis, Crystal Structure and DFT Calculations

Abstract  

The tetrafluoroborate salt of 4-methoxybenzyl N-2-(dimethylamino)ethyl-N-nitrosocarbamate was prepared in two steps, via the corresponding carbamate. Its crystal structure is monoclinic, space group P21/c. The unit cell dimensions are: a = 19.499(8) ?, b = 5.877(3) ?, c = 15.757(7) ?, α = 90°, β = 110.019(7)°, γ = 90°, V = 1696.5(12) ?³, Z = 4. The structure exhibits an unexpected, pseudo-gauche conformation with respect to the C2–C3 bond, due to a stabilizing hydrogen bond between the carbonyl oxygen (O1) and the hydrogen atom at the trialkylammonium center (H3n), with a distance between them of 2.37 ?. DFT calculations on the cation (B3LYP/6-31 + G(d)) confirm that the hydrogen bond stabilized gauche conformation is the global minimum structure.     

Crystal Structures of 1,7-Bis(furyl)-4-(1,3-dithiolan-2-ylidene)-1,6-heptadiene-3,5-dione and 1,7-bis(thienyl)-4-(1,3-dithiolan-2-ylidene)-1,6-heptadiene-3,5-dione

Abstract  

The title compounds (bis(alkenoyl) ketene dithioacetals) were prepared starting from the cyclic acyl ketene dithioacetal and aromatic aldehydes. These compounds were characterized by IR, ¹H NMR, mass spectral studies and X-ray crystal structure analysis. The bis(furyl) ketene dithioacetal crystallized in the space group P[`\text1] P{\bar{\text{1}}} with unit cell dimensions a = 7.7626(12) ?, b = 9.0217(13) ?, c = 26.827(5) ?, α = 86.271(14)°, β = 87.643(14)°, γ = 66.286(11)° and the structure was refined to an R-factor of 0.0528 while bis(thienyl) ketene dithioacetal crystallized in the space group P2₁/c with unit cell dimensions a = 10.2433(9) ?, b = 10.4142(6) ?, c = 18.0973(18) ?, β = 106.0° and the structure was refined to an R-factor of 0.0446. The ketenedithioacetal functionality present between the carbonyl groups prevents the possibility of keto-enol tautomerization in these compounds. In both the crystal structures, the crystal packing is stabilized by C–H···O hydrogen bonds as well as van der Waals interactions.     

Structural Consequences of Anomeric Effect in 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecan-1-ium pentachlorophenolate monohydrate

Abstract  

The asymmetric unit of the crystal structure contains one molecule of the title compound and one molecule of water. X-ray diffraction spectrum of the ammonium salt of title compound exhibits deviations from the ideal molecular geometry which is explained on the basis of anomeric effect. This conclusion is consistent with the natural bond orbital analysis at the B3LYP/6-311+G** level of the anomeric effect. The molecules are linked via N–H···O hydrogen bonds. This compound crystallizes in monoclinic symmetry, in space group P2 _1/n , with lattice constants: a = 12.3850(2) ?, b = 6.8123(1) ?, c = 19.6208(4) ?, α = 90°, β = 94.864(2)°, γ = 90°, V = 1649.45(5) ?³, Z = 4, F(000) = 896, R ₁ = 3.3%, wR ₂ = 10.6%.     

Synthesis and Crystal Structures of Two New Schiff Base Hydrazones Derived from Biphenyl-4-Carbohydrazide

Abstract  

The crystal structures of two novel Schiff base hydrazones have been determined by means of the X-ray diffraction. These compounds: N′-[(E)-(2,5-dimethoxyphenyl)methylidene]biphenyl-4-carbohydrazide, C₂₂H₂₀N₂O₃ (1) and N′-[(E)-(4-fluorophenyl)methylidene]biphenyl-4-carbohydrazide, C₂₀H₁₅FN₂O (2), are the first structurally characterized biphenyl derivatives of phenylmethylidene-carbohydrazide. Both compounds crystallize in the monoclinic space groups, 1 in P2₁/c space group with a = 13.987(2) ?, b = 16.426(3) ?, c = 8.214(2) ?, β = 98.12(2)°, and 2 in C2/c with a = 37.163(5) ?, b = 10.696(2) ?, c = 8.098(2) ?, β = 101.18(2)°. Both molecules have very similar bond lengths and angles pattern, even in the differently substituted phenyl ring. However, the conformations of the molecules differ significantly, the more crowded molecule 1 is much more folded than 2. The dihedral angle between the terminal ring planes is 56.17(6)° in 1 while in 2 it is as small as 2.83(14)°. In both structures relatively short and linear N–H···O hydrogen bonds (created by the best available hydrogen bond donor and acceptor) connect molecules into the chains along the unit cell parameter of ca. 8 ? in length. The next stage of the crystal architecture determination, the secondary interactions, are however quite different: in 1 there are almost solely dispersion van der Waals interactions while in 2 some more specific C–H···F and C–H···π interactions are also involved in the crystal packing.     

Synthesis,Crystal Structure and Thermal Properties of <Emphasis Type="Italic">N</Emphasis>-Acetyl-3-(2-furyl)-5-ferrocenyl-2-pyrazoline and <Emphasis Type="Italic">N</Emphasis>-Acetyl-3-(2-thienyl)-5-ferrocenyl-2-pyrazoline

Abstract  

Two novel ferrocenyl substituted N-acetyl-2-pyrazolines, N-acetyl-3-(2-furyl)-5-ferrocenyl-2-pyrazoline (3) and N-acetyl-3-(2-thienyl)-5-ferrocenyl-2-pyrazoline (4), have been synthesized and characterized by FTIR, ¹H-NMR, ¹³C-NMR techniques, elemental analysis and X-ray structure analysis. Thermal properties of these compounds have been determined by TGA, DTA and DSC analysis. Compound 3 (C₁₉H₁₈N₂O₂Fe) crystallizes in the monoclinic space group P21/c and Z = 4, with a = 8.6970(4) ?, b = 18.4725(9) ?, c = 11.0041(5) ?, β = 110.942(3)°. Compound 4 (C₁₉H₁₈N₂OSFe) crystallizes in the orthorhombic space group Fdd2 and Z = 16, with a = 84.242(2) ?, b = 13.5416(5) ?, c = 5.9405(2) ?, β = 90°. In terms of crystal packing, each compound shows different molecular arrangement, which are stabilized by C–H···O intermolecular weak hydrogen bonds, and/or C–H···π interactions.     

Crystal Structure,Conformation and Vibrational Analysis of a Mannich Base: 2-[(phenylamino) methyl]-isoindole-1,3-dione

Abstract  

The crystal structure of 2-[(phenylamino) methyl]-isoindole-1,3-dione, C₁₅H₁₂N₂O₂, crystallizes in the triclinic space group Pī with cell parameters of a = 7.1176 (2) ?, b = 8.5533 (3) ?, c = 10.9163 (4) ?, α = 95.937 (2)°, β = 102.975 (2)°, γ = 108.474 (2)°, V = 603.18 (4) ?³ and Z = 2. This indole derivative is a Mannich base in which a methyl group bridges the molecules of phthalimide and aniline molecules. The dihedral angle between the phthalimide and aniline is 75.47 (3)°. The molecules of the title compound forms a centrosymmetric hydrogen-bonded dimer through a pair of N–H···O hydrogen bonds. C–H···π and an extensive π···π interactions, in addition, stabilize the molecular structure. The compound presented here is V-shaped, the angle at the methyl bridge [N–C–N] being 115.04 (12)°. Present study reports the conformation and hydrogen bonding interactions which play an important role in biological functions. Vibration analysis complement the structure analysed.     

Spectroscopic Studies and Crystal Structure of 1-[(2,5-dioxopyrrolidin-1-yl)(phenyl) methyl] Thiourea

Abstract  A new mannich base 1-[(2,5-dioxopyrrolidin-1-yl)(phenyl)methyl] thiourea formed by the direct condensation of thiourea, succinimide and benzaldehyde has been synthesized. The structure of this mannich base has been elucidated on the basis of micro elemental analysis, IR, ¹H NMR, ¹³C NMR, Mass and UV–Visible Techniques. The crystal structure of the title compound C₁₂ H₁₃ N₃ O₂ S was determined. It crystallizes in the monoclinic system, space group P2₁/c with a = 10.8234 (7) ?, b = 6.0355 (5) ?, c = 19.3692 (14) ?, β = 100.540(3)°, Z = 4 and V = 1243.94 (16) ?³. The structure was solved by the full-matrix least squares on F ² and had a refined R value of 0.0465 for 1,964 observed reflections. The crystal structure is stabilized by strong intramolecular C–H···O, C–H···S interactions and inter molecular N–H···O and S···S interactions. Graphical Abstract  This paper describes the spectroscopic and crystallographic studies of the title compound which is essential in ascertaining the structure of this new compound.      

Synthesis and Crystal Structure of a Fe(III) Complex with an Isonicotinyl Hydrazone Ligand, [Fe(N-Isonicotinamidosalicylaldimine)Cl<Subscript>2</Subscript>]

Abstract  

A new complex [Fe(N-isonicotinamidosalicylaldimine)Cl₂] has been synthesized by template reaction at room temperature and structurally characterized by X-ray single-crystal analysis. The complex crystallizes in triclinic crystal system, Pī space group, a = 7.273(6) ?, b = 10.015(8) ?, c = 10.479(8) ?, α = 71.067(10)°, β = 89.964(11)°, γ = 75.528(10)°, V = 696.4(9) ?³ and Z = 2. The coordination geometry around the Fe(III) ion is a distorted trigonal bipyramid with a O₂N₁Cl₂ donor set. In the crystal structure, N–H···Cl, C–H···O and C–H···Cl hydrogen bonds and π···π stacking interactions involving aromatic and unclosed π-systems link the molecules to form supramolecular double layers.     

Experimental and Semi-Empirical and DFT Calculational Studies on (<Emphasis Type="Italic">E</Emphasis>)-2-[(2,4-Dichlorophenylimino) methyl]-<Emphasis Type="Italic">p</Emphasis>-cresol

Abstract  

The molecular and crystal structure of the title compound, C₁₄H₁₁Cl₂NO, has been determined by X-ray single crystal diffraction technique. The compound crystallizes in the orthorhombic, space group Pbca with unit cell dimensions a = 7.5537(10) ?, b = 11.5518(13) ?, c = 29.760(4) ?, M _r  = 280.14, V = 2596.8(6) ?³, Z = 8, R ₁ = 0.065 and wR ₂ = 0.191. The title compound exists in the enol–imine tautomeric form with a strong intramolecular O–H···N hydrogen bond. The dihedral angle between the two benzene rings is 37.66(15)°. The asymmetric unit in the crystal structure contains only one neutral molecule. Calculational studies were performed by using AM1, PM3, PM6 semi-empirical and DFT methods. Geometry optimizations of compound have been carried out by using three semi-empirical methods and DFT method and bond lengths, bond and torsion angles of title compound have been determined. Dipole moments (Debye) and the energy parameters of compound (kcal/mol) were calculated by using above mentioned calculation methods. Atomic charge distribution has been obtained from AM1, PM3, PM6 and DFT. In order to determine conformational flexibility on the molecule, molecular energy profile of the title compound was obtained with respect to the selected torsion angle T(N1–C7–C1–C2), which is varied from −180° to +180° in every 10 via PM3 semi-empirical method.     

Crystal Structure?4-(2,4-Dihydroxybenzylideneamino)-5-methyl-2H-1,2,4-triazol-3(4H)-one

Abstract  

The title compound (I), 4-(2,4-dihydroxybenzlideneamino)-5-methyl-2H-1,2,4-triazol-3(4H)-one was characterized by single crystal X-ray diffraction. This crystal is monoclinic, space group P2₁/c with a = 10.1447(7) ?, b = 7.0972(3) ?, c = 14.6726(10) ?, β = 98107(5)°, V = 1045.85(11) ?³, Z = 4, D _c = 1.487 g/cm³, F ₀₀ = 488, R = 0.039 and wR = 0.1025, S = 1.003, T = 293 (2) K. The title molecule is planar: the angle between the triazole ring and benzene ring is 179.1(1)°. The crystal structure contains two intramolecular (O–H···N and C–H···O) and three intermolecular interaction (O–H···N, N–H···O, and C–H···O). In addition, there is also π–π interactions.     

Synthesis, Crystal Structure and Density Functional Theory Study of (2-(2-Hydroxyphenyl)benzimidazolate-based Al(III) Complex Cocrystallized by DMF Solvate and Neutral (2-(2-Hydroxyphenyl)benzimidazole

Abstract  

The aluminium(III) complex with 2-(2-hydroxyphenyl)benzimidazole, namely [Al₂(μ-OH)₂L₄)]·6DMF·2HL (1·6DMF·2HL) (HL = 2-(2-hydroxyphenyl)benzimidazole), has been synthesized and characterized by X-ray crystallography. It crystallizes in monoclinic space group C2/c with cell parameters a = 23.6752(13) ?, b = 20.8253(12) ?, c = 18.1645(10) ?, α = 90°, β = 91.929(1)°, γ = 90°, Z = 4, V = 8950.8(9) ?³. The dimeric structure of 1, featuring [Al₂(μ-OH)₂] core has been studied with the density functional theory level (DFT) calculation and molecular orbital analyses.