scholarly journals 2-Substituted agelasine analogs: Synthesis and biological activity, and structure and reactivity of synthetic intermediates

2011 ◽  
Vol 83 (3) ◽  
pp. 645-653 ◽  
Author(s):  
Heidi Roggen ◽  
Lars Bohlin ◽  
Robert Burman ◽  
Colin Charnock ◽  
Jenny Felth ◽  
...  
Keyword(s):  
Significant Variation ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Atomic Charges ◽  
Functional Theory ◽  
Methyl Group ◽  
H Nmr ◽  
Nmr Techniques ◽  
Synthetic Intermediates

2-Substituted N-methoxy-9-methyl-9H-purin-6-amines were synthesized either from their corresponding 6-chloro-9-methyl-9H-purines or 2-chloro-N-methoxy-9-methyl-9H-purin-6-amine. Great diversity in the amino/imino tautomeric ratios was observed and calculated based on 1H NMR. The tautomers were identified by 1D and 2D 1H, 13C, and 15N NMR techniques, and showed significant variation both in 13C and 15N shift values. Comparison of the tautomeric ratios with Hammett F values revealed that as the field/inductive withdrawing abilities of the 2-substituent increased, the ratio of amino:imino tautomers was shifted toward the amino tautomer. Computational chemistry exposed the significance of hydrogen bonding between solvent and the compound in question to reach accurate predictions for tautomeric ratios. B3LYP/def2-TZVP density functional theory (DFT) calculations resulted in quantitatively more accurate predictions than when employing the less expensive BP86 functional. N-7-Alkylation of the 2-substituted N-methoxy-9-methyl-9H-purin-6-amines showed that when the field/inductive withdrawing ability of the 2-substituent reached a certain point the reactivity drastically dropped. This correlated with the atomic charges on N-7 calculated using a natural bond orbital (NBO) analysis. Biological screening of the final 2-substituted agelasine analogs indicated that the introduction of a methyl group in the 2-position is advantageous for antimycobacterial and antiprotozoal activity, and that an amino function may improve activity against several cancer cell lines.

scholarly journals Tipping the balance: theoretical interrogation of divergent extended heterolytic fragmentations

2020 ◽  
Vol 11 (8) ◽  
pp. 2231-2242 ◽  
Author(s):  
Croix J. Laconsay ◽  
Ka Yi Tsui ◽  
Dean J. Tantillo
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Electric Field ◽  
Ab Initio ◽  
External Electric Field ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Functional Theory

We interrogate a type of heterolytic fragmentation called a ‘divergent fragmentation’ using density functional theory (DFT), natural bond orbital (NBO) analysis, ab initio molecular dynamics (AIMD), and external electric field (EEF) calculations.

Theoretical investigation of some N-nitrosodiphenylamine biological molecules — A natural bond orbital (NBO) study

2011 ◽  
Vol 89 (10) ◽  
pp. 1230-1235
Author(s):  
Xiao-Hong Li ◽  
Rui-Zhou Zhang ◽  
Xian-Zhou Zhang
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Biological Molecules ◽  
Basis Set ◽  
Natural Hybrid ◽  
Functional Theory ◽  
Molecular Stability ◽  
Hybrid Orbitals

Theoretical study of several N-nitrosodiphenylamine biological molecules has been performed using quantum computational ab initio RHF and density functional B3LYP and B3PW91 methods with 6–311G++(d,p) basis set. Geometries obtained from density functional theory (DFT) calculations were used to perform Natural bond orbital (NBO) analysis. The p characters of two nitrogen natural hybrid orbitals (NHOs) σN3−N2 increase with increasing σp values of the substituents on the benzene, which results in a lengthening of the N3–N2 bond. The p characters of oxygen NHO σO1−N2 and nitrogen NHO σO1−N2 bond orbitals decrease with increasing σp values of the substituents on the benzene, which results in a shortening of the N2=O1 bond. It is also noted that decreased occupancy of the localized σN3−N2 orbital in the idealized Lewis structure, or increased occupancy of [Formula: see text]of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are also related to the resulting p character of the corresponding nitrogen NHO of σN3−N2 bond orbital.

scholarly journals A binuclear Cd(II) complex containing bridging pyrimidine-based ligands

2020 ◽  
Vol 75 (3) ◽  
pp. 287-293
Author(s):  
Samireh Hosseini ◽  
Zahra Mardani ◽  
Keyvan Moeini ◽  
Cameron Carpenter-Warren ◽  
Alexandra M.Z. Slawin ◽  
...  
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Distribution Patterns ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
H Nmr ◽  
Crystal Network ◽  
Ft Ir ◽  
Orbital Analysis

AbstractIn this work, a pyrimidine-based ligand, N′-(amino(pyrimidin-2-yl)methylene)pyrimidine-2-carbohydrazonamide hydrate (APPH · H2O), and its binuclear complex of cadmium, [Cd(μ-APPH)Br]2, 1, were prepared and identified by elemental analysis, FT-IR, 1H NMR spectroscopy as well as single-crystal X-ray diffraction. X-ray structure analysis of 1 revealed octahedrally coordinated cadmium centers with a CdN4Br2 environment containing two bridging APPH ligands; each APPH ligand acts as an N4-donor (N2-donor toward each cadmium atom) and forms two five-membered chelate rings that are approximately perpendicular to each other. In the network of 1, the N–H · · · Br hydrogen bonds form motifs such as ${\rm{R}}_{\rm{2}}^{\rm{2}}(12,{\rm{ }}14),{\rm{ R}}_{\rm{6}}^{\rm{6}}(24,{\rm{ }}26,{\rm{ }} \ldots ,{\rm{ }}46).$ The crystal network is further stabilized by π-π stacking interactions between pyrimidine rings. The optimized structures of the ligand and complex were investigated along with their charge distribution patterns by density functional theory and natural bond orbital analysis, respectively.

scholarly journals DFT Study on the Substituent Effect of Anticancer Picoline-Diazido-Pt(IV) Compounds

2022 ◽  
Vol 11 ◽  
Author(s):  
Meilin Mu ◽  
Hongwei Gao
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Intramolecular Interactions ◽  
Bending Vibrations ◽  
Functional Theory ◽  
Energy Gaps ◽  
Frequency Calculation ◽  
Calculation Results ◽  
Homo Lumo

The geometric structure of azido Pt(IV) compounds containing picoline was calculated by using density functional theory(DFT) at the LSDA/SDD level. The ESP distribution shows the possible reaction sites of the compounds. In addition, the frequency calculation results assigned the infrared spectra of these compounds, and specified important stretching and bending vibrations. The HOMO-LUMO energy gaps of these compounds are also calculated to explain the charge transfer of the molecules. The distribution of Mulliken charges and natural atomic charges of these atoms is also calculated. Natural bond orbital(NBO) analysis explains the intramolecular interactions and their electron density.

Stereoelectronic interaction effects on the conformational properties of 5-methyl-5-aza-1,3-dithiacyclohexane and its analogous containing N, P, O, and Se atoms — A hybrid density functional theory (DFT), ab initio study, and natural bond orbital (NBO) analysis

2010 ◽  
Vol 88 (7) ◽  
pp. 579-587 ◽  
Author(s):  
Davood Nori-Shargh ◽  
Neda Hassanzadeh ◽  
Meisam Kosari ◽  
Parvin Rabieikarahroudi ◽  
Hooriye Yahyaei ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Hybrid Density Functional Theory ◽  
Functional Theory ◽  
Dipole Interactions ◽  
Conformational Properties ◽  
Hybrid Density Functional

Natural bond orbital (NBO) analysis, hybrid density functional theory (hybrid DFT: B3LYP/6-311+G**//B3LYP/6-311+G**), and ab initio molecular orbital (MO: MP2/6-311+G**//B3LYP/6-311+G**) based methods were used to study the electronic delocalization energy (DE), dipole–dipole interactions, and steric repulsions on the conformational properties of 5-methyl-5-aza-1,3-dioxacyclohexane (1) (-phospha- (2), -arsena- (3)), 5-methyl-5-aza-1,3-dithiacyclohexane (4) (-phospha- (5), -arsena- (6)), and 5-methyl-5-aza-1,3-diselenacyclohexane (7) (-phospha- (8), -arsena- (9)). The MP2/6-311+G**//B3LYP/6-311+G** and B3LYP/6-311+G**//B3LYP/6-311+G** results revealed that the axial stereoisomers of compounds 1–9 are more stable than their equatorial stereoisomers. In this regard, the obtained results showed an egregious axial preference for compounds 1, 4, and 7. Importantly, the results showed that the energy differences between the axial and equatorial stereoisomers decrease from compounds 1 → 3, 4 → 6, and also, 7 → 9. The NBO analysis of donor–acceptor interactions revealed that the calculated DE for compounds 1–3 are –21.50, –7.84, and –4.38 kcal mol–1, respectively. The decrease of the calculated DE values from compound 1 to compound 3 could reasonably explain the decrease of the energy differences between the axial and equatorial stereoisomers from compound 1 to compound 3. The correlation between the DE, dipole–dipole interactions, structural parameters, and conformational behaviors of compounds 1–9 has been investigated.

scholarly journals NBO, nonlinear optical and thermodynamic properties of 10-Acetyl-10H-phenothiazine 5-oxide

BIBECHANA ◽  
2017 ◽  
Vol 15 ◽  
pp. 131-139
Author(s):  
Bhawani Datt Joshi ◽  
Manoj Kumar Chaudhary
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Thermodynamic Properties ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Basis Set ◽  
Functional Theory ◽  
Density Functional Theory Level

In this paper, natural bond orbital (NBO) analysis, nonlinear optical and the thermodynamic properties of 10-Acetyl-10H-phenothiazine 5-oxide have been analyzed by employing density functional theory level employing 6-311++G(d,p) basis set. NBO analysis reveals that the intra- intermolecular charge transfer occurs within the molecule leading to the stabilization. The predicted nonlinear optical properties (NLO) like; polarizability and first hyperpolarizabiliy support that the molecule could attract the interests for future investigation.BIBECHANA 15 (2018) 131-139

A novel nitrogen-containing compound with D-π-A structure: theoretical and experimental study

2014 ◽  
Vol 92 (5) ◽  
pp. 411-416 ◽  
Author(s):  
Xiaoting Gong ◽  
Ziyan Zhou ◽  
Shuguang Zhang ◽  
Shuping Zhuo ◽  
Xiurong Huang ◽  
...  
Keyword(s):  
Density Functional ◽  
Fluorescence Spectra ◽  
Density Functional Theory Calculations ◽  
Absorption And Fluorescence Spectra ◽  
Functional Theory ◽  
H Nmr ◽  
Measured Absorption ◽  
Nmr Techniques ◽  
Good Agreement ◽  
C Nmr

2-(2-Hydroxy-styryl)-4,6-dimethyl-1,3,5-triazine (P1), a novel compound with D-π-A structure, possesses a variety of isomers. Density functional theory calculations were employed to explore the isomerization mechanisms of its various isomers at the 6-311+G** level. The calculated results show that the phenol configurations of compound P1 are more stable than the quinoid configurations, whether they exist as monomers, complexes, with methanol or dimers. The most stable structure of compound P1 was used to calculate the UV-vis and fluorescence spectra. To validate the calculated results, the title compound was synthesized and characterized by 1H NMR and 13C NMR techniques. The measured absorption and fluorescence spectra of P1 in methanol and N,N-dimethylformamide are in good agreement with the calculated ones.

scholarly journals DFT Study of Molecular and Electronic Structure of Ca(II) and Zn(II) Complexes with Porphyrazine and tetrakis(1,2,5-thiadiazole)porphyrazine

2020 ◽  
Vol 21 (8) ◽  
pp. 2923 ◽  
Author(s):  
Arseniy A. Otlyotov ◽  
Igor V. Ryzhov ◽  
Ilya A. Kuzmin ◽  
Yuriy A. Zhabanov ◽  
Maxim S. Mikhailov ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Absorption ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Electronic Absorption Spectra ◽  
Bathochromic Shift ◽  
Nbo Analysis ◽  
Functional Theory ◽  
Use Of Time ◽  
Molecular And Electronic Structure

Electronic and geometric structures of Ca(II) and Zn(II) complexes with porphyrazine (Pz) and tetrakis(1,2,5-thiadiazole)porphyrazine (TTDPz) were investigated by density functional theory (DFT) calculations and compared. The perimeter of the coordination cavity was found to be practically independent on the nature of a metal and a ligand. According to the results of the natural bond orbital (NBO) analysis and quantum theory of atoms in molecules (QTAIM) calculations, Ca–N bonds possess larger ionic contributions as compared to Zn–N. The model electronic absorption spectra obtained with the use of time-dependent density functional theory (TDDFT) calculations indicate a strong bathochromic shift (~70 nm) of the Q-band with a change of Pz ligand by TTDPz for both Ca and Zn complexes. Additionally, CaTTDPz was synthesized and its electronic absorption spectrum was recorded in pyridine and acetone.

scholarly journals Investigation of hydrogen bonding between nitrosamine and sulfuric acid using Density Functional Theory

2014 ◽  
Vol 25 (1) ◽  
pp. 5-10
Author(s):  
Sadeghali Bavafa ◽  
Mona Mahboubi
Keyword(s):  
Hydrogen Bonding ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Basis Sets ◽  
Stable Complex ◽  
Antibonding Orbital ◽  
Functional Theory ◽  
Hydrogen Bonding Interactions ◽  
Density Transfer

Abstract DFT calculations were performed to analyze those interactions; B3LYP and B3PW91 methods were applied and the following basis sets were used: 6-311++G(2d, 2p), 6-311++G(3df, 3pd) and aug-cc-pVDZ. The natural bond orbital (NBO) analysis and atom in molecules (AIM) theory were applied to understand the nature of the interactions. The most stable complex NS1 with an eight-membered cyclic structure contains two O- H· ··O and N-H·· ·O hydrogen bonding interactions. From the values of r(r) at O·· ·H critical points, it can be concluded that the H-boding in eight-membered cyclic NS1 is stronger than other. The elongation of the O-H bond length is caused by the electron-density transfer to the O-H antibonding orbital.

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