Nontemplate synthesis, characterization and theoretical study of tetraazamacrocycles

2012 ◽  
Vol 23 (1) ◽  
pp. 121-127
Author(s):  
İbrahim Șen ◽  
Cem Burak Yildiz ◽  
Akın Azizoğlu
Keyword(s):  
Density Functional ◽  
Basis Sets ◽  
Frontier Molecular Orbital ◽  
Spectroscopic Techniques ◽  
Functional Theory ◽  
Hartree Fock ◽  
H Nmr ◽  
Ft Ir ◽  
Molecular Electrostatic Potential Maps ◽  
C Nmr

Abstract The syntheses of new tetraaza macrocyclic compounds of variable ring sizes by non-template methods and their characterization with the help of elemental analysis and spectroscopic techniques (FT-IR, 1H-NMR, and 13C-NMR) have been reported in detail. The vibrational frequencies determined experimentally are compared with those obtained theoretically from density functional theory (DFT) and Hartree-Fock (HF) calculations. The comparisons between the experimental and theoretical results indicate that B3LYP level with both the 3-21G(d) and 6-31G+(d,p) basis sets is able to provide satisfactory results for predicting IR properties. The frontier molecular orbital diagrams and molecular electrostatic potential maps of title compounds have been also calculated and visualized at the B3LYP/6-31G+(d,p) level of theory.

scholarly journals Scaled quantum chemical studies of the structural and vibrational spectra of acetyl coumarin

2006 ◽  
Vol 4 (4) ◽  
Author(s):  
Khaled Bahgat
Keyword(s):  
Density Functional ◽  
Solid Phase ◽  
Normal Modes ◽  
Basis Sets ◽  
Functional Theory ◽  
Hartree Fock ◽  
Full Structure ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Ft Ir

AbstractThe solid phase FT-IR and FR-Raman spectra of acetyl coumarin have been recorded in the regions 4000–50 cm−1. The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculations based on density functional theory (DFT) and Hartree-Fock (HF) at 6–31G* and 6–311++G** basis sets. The resulting force fields were transformed to internal coordinates, the calculated vibrational frequencies and normal modes were utilized in the assignment of the observed vibrational fundamentals. The measured spectral data were used to refine the vibrational force constants by means of a small number of scaling factors.

THE ORIGIN OF THE ROTATIONAL BARRIER IN DIMETHYL ETHER AND DIMETHYL SULFIDE: A THEORETICAL STUDY

2007 ◽  
Vol 06 (03) ◽  
pp. 421-434 ◽  
Author(s):  
JÍMENEZ-FABIAN ◽  
A. F. JALBOUT
Keyword(s):  
Dimethyl Ether ◽  
Density Functional ◽  
Dimethyl Sulfide ◽  
Nbo Analysis ◽  
Rotational Barrier ◽  
Basis Sets ◽  
Functional Theory ◽  
Hartree Fock ◽  
Torsional Potential ◽  
Methyl Rotation

The torsional potential function for methyl rotation in dimethyl ether (DME) and dimethyl sulfide (DMS) has been determined by utilizing ab initio (Hartree–Fock and MP2) and density functional theory (B3LYP, B3P86, and B3PW91) methods along with several basis sets. Natural bond orbital (NBO) analysis was also applied to investigate the origin of the rotational barrier.

scholarly journals Synthesis, antioxidant activity, and density functional theory study of catechin derivatives

RSC Advances ◽  
2017 ◽  
Vol 7 (85) ◽  
pp. 54136-54141 ◽  
Author(s):  
Jing Wang ◽  
Han Tang ◽  
Bo Hou ◽  
Pan Zhang ◽  
Qi Wang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Density Functional Theory ◽  
Antioxidant Activity ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
H Nmr ◽  
C Nmr

Catechin derivatives were synthesized, and their structures were characterized by 1H-NMR, 13C-NMR, and mass spectrometry.

scholarly journals NMR and Theoretical Studies on the Conformational Preferences of Some Non-metal Coordinated N-Enoyl Systems Attached to Common Chiral Auxilaries

2017 ◽  
Vol 58 (2) ◽  
Author(s):  
Rosmarbel Morales-Nava ◽  
Alejandro Ramírez-Solís ◽  
Mario Fernández-Zertuche
Keyword(s):  
Density Functional ◽  
Vibrational Analysis ◽  
Basis Sets ◽  
Chiral Auxiliaries ◽  
Nmr Studies ◽  
Stable Conformation ◽  
Functional Theory ◽  
Exchange Correlation ◽  
H Nmr ◽  
Conformational Preferences

<p>We report a systematic study of a series of N-enoyl systems attached to common oxazolidin-2-ones, oxazolidine-2-thiones and thiazolidine-2-thiones chiral auxiliaries in order to determine the most stable conformation of these compounds. <sup>1</sup>H NMR studies show an <em>anti</em>-<em>s</em>-<em>cis</em> structure as the most stable conformation for these series of compounds. Density Functional Theory geometry optimizations and vibrational analysis using the b3lyp exchange-correlation functional with the standard 6-31g** basis sets were done, including solvent effects (chloroform and toluene). Gibbs free energy differences show that the <em>anti</em>-<em>s</em>-<em>cis</em> structures are the most stable conformers lying, on average, ca. 6 kcal/mol lower in energy than the <em>syn</em>-<em>s</em>-<em>cis</em> conformers, widely used to explain the structure and reactivity of <em>N</em>-enoyl systems.</p>

scholarly journals A Statistically Supported Antioxidant Activity DFT Benchmark—The Effects of Hartree–Fock Exchange and Basis Set Selection on Accuracy and Resources Uptake

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 5058
Author(s):  
Maciej Spiegel ◽  
Andrzej Gamian ◽  
Zbigniew Sroka
Keyword(s):  
Density Functional ◽  
Optimal Level ◽  
Basis Set ◽  
Basis Sets ◽  
Linear Regression Models ◽  
Functional Theory ◽  
Hartree Fock ◽  
Diffuse Function ◽  
Vertical Electron Affinity ◽  
High Level

Polyphenolic compounds are now widely studied using computational chemistry approaches, the most popular of which is Density Functional Theory. To ease this process, it is critical to identify the optimal level of theory in terms of both accuracy and resource usage—a challenge we tackle in this study. Eleven DFT functionals with varied Hartree–Fock exchange values, both global and range-separated hybrids, were combined with 14 differently augmented basis sets to calculate the reactivity indices of caffeic acid, a phenolic acid representative, and compare them to experimental data or a high-level of theory outcome. Aside from the main course, a validation of the widely used Janak’s theorem in the establishment of vertical ionization potential and vertical electron affinity was evaluated. To investigate what influences the values of the properties under consideration, linear regression models were developed and thoroughly discussed. The results were utilized to compute the scores, which let us determine the best and worst combinations and make broad suggestions on the final option. The study demonstrates that M06–2X/6–311G(d,p) is the best fit for such research, and, curiously, it is not necessarily essential to include a diffuse function to produce satisfactory results.

scholarly journals Synthesis, Characterization and DFT Study of 4,4′-Oxydianiline Imines as Precursors of Tetrahalo-1,3-oxazepine-1,5-dione

2017 ◽  
Vol 17 (2) ◽  
pp. 330
Author(s):  
Abdullah Hussein Kshash ◽  
Mohammed Ghannam Mokhlef
Keyword(s):  
Schiff Bases ◽  
Phthalic Anhydride ◽  
Density Functional ◽  
Spectroscopic Techniques ◽  
Functional Theory ◽  
Homo And Lumo ◽  
Ft Ir ◽  
Gaussian Program ◽  
Theoretical Results ◽  
Direct Condensation

This work presents four Schiff bases derived from 4,4′-Oxydianiline, distinguished by the para substituted halogen of benzaldehyde. These bases were used to synthesize eight compounds of di-1,3-oxazepine by direct condensation with tetrachloro phthalic anhydride and tetrabromo phthalic anhydride. The reactions were monitored with TLC and all structures were characterized using spectroscopic techniques such as FT-IR, 1H-NMR, 13C-NMR and C, H, N techniques. On the other hand, a theoretical study by Density Functional Theory (DFT) for the electronic structures was intended to study the effects of para-substituted halogen of benzaldehyde on the electronic structure of synthesized Schiff bases by using the Gaussian program. Theoretical results indicate that there is no effect of halogen atoms except for bromine on HOMO and LUMO energies of the synthesized compounds.

Synthesis and Characterization of Imidazo[1,2-a]Pyrimidine

2015 ◽  
Vol 52 ◽  
pp. 1-4
Author(s):  
A.M. Shah ◽  
A.J. Rojivadiya
Keyword(s):  
Mass Spectroscopy ◽  
Synthesis And Characterization ◽  
Spectroscopic Techniques ◽  
One Pot ◽  
H Nmr ◽  
Ft Ir ◽  
C Nmr

An efficient protocol for the synthesis of imidazo [1,2-a] pyrimidine was developed by using three component one-pot Biginelli synthesis. The synthesized compounds were characterized by spectroscopic techniques like FT-IR, 1H NMR, 13C NMR, and mass spectroscopy.

scholarly journals Experimental and theoretical study of a novel naphthoquinone Schiff base

2018 ◽  
Vol 16 (1) ◽  
pp. 1115-1121
Author(s):  
Güvenç Görgülü
Keyword(s):  
Density Functional Theory ◽  
Schiff Base ◽  
Density Functional ◽  
Active Agent ◽  
Theoretical Data ◽  
Basis Set ◽  
Magnetic Data ◽  
Functional Theory ◽  
Ft Ir ◽  
C Nmr

AbstractA novel Schiff base was synthesized and characterized by spectroscopic and theoretical methods. A potentially active agent 4-(2-hydroxy-5-methylphenylimino)naphthalen-1(4H)-one (PINQ) was designed and synthesized. The synthesis was carried out by a condensation reaction of 1-4-naphthoquinone and 2-amino-4-methyl phenol. The spectral and structural properties of the PINQ molecule were investigated by elemental analysis, 1H- and 13C-NMR, FT-IR and Uv-vis spectroscopies. The energetic, atomic, electronic, molecular, vibrational and magnetic data were theoretically obtained using density functional theory (DFT) at B3LYP level with 6-311++G(d,p) basis set. Chemical shifts were calculated using gauge-invariant atomic orbital (GIAO) method. UV-vis spectrum for the title compound was also obtained by time-dependent density functional theory (TD-DFT). The theoretical and experimental results were compared and interpreted. The theoretical data obtained from 1H- and 13C-NMR, FT-IR and Uv-vis spectroscopies were quite compatible with experimental ones.

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.

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