Quantum Mechanics and Molecular Mechanics Studies of the Low-Energy Conformations of 9-Crown-3

Anderson, Wayne; Behm, Philip; Glennon, Timothy M.; Zerner, Michael C.

doi:10.1021/jp962172h

Cited by 17 publications

(26 citation statements)

References 42 publications

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“…In other words, inclusion of the electron correlation had a significant effect on the energy order. As was mentioned above, this is in a clear agreement to what was concluded for 12c4 22 but in contradiction to what was observed for 9c3 21 and in a previous report of 12c4. 24 It is not clear the reason of this disagreement between 12c4 and 18c6 on one hand and 9c3 on the other hand, but this may be attributed to the small number of the possible conformation of 9c3.…”

Section: Resultssupporting

confidence: 62%

“…This indicates the importance of inclusion of the electron correlation for the accurate prediction of the energy order concluded for 12c4. 22 This is in contradiction to what was reported earlier by Anderson et al 21 and Bultanic et al 24 that the electron correlation is not necessary for accurate predication of order of the relative conformational energies. Also, because of the known accuracy of the optimized geometries predicted at the B3LYP level compared to those at the HF level, according to the MP2/6-31+G*//B3LYP/6-31+G* energy order, it is reasonable to assume that conformation 115 has lower energy than the C i conformation.…”

Section: Resultsmentioning

confidence: 70%

“…Thus, because of the side chain, crown ethers are called armed crown ethers. The most important core parts are 12-crown-4 (12c4), also known as 1,4,7,10-tetraoxacyclododecane; 15-crown-5 (15c5), known also as 1,4,7,10,13-pentaoxacyclopentadecane; and 18-crown-6 (18c6), known as 1,4,7,10,13,16- Conformational analysis has been reported for 9-crown-3 (9c3), 20,21 12c4, [22][23][24] 15c5, 25 and 18c6. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] In a recent report, a full conformational search of 12c4 has been performed using the CONFLEX method.…”

Section: Introductionmentioning

confidence: 99%

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Conformational Study of the Structure of Free 18-Crown-6

2005

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A conformational search was performed for 18-crown-6 using the CONLEX method at the MM3 level. To have a more accurate energy order of the predicted conformations, the predicted conformations were geometry optimized at the HF/STO-3G level and the 198 lowest energy conformations, according to the HF/STO-3G energy order, were geometry optimized at the HF/6-31+G level. In addition, the 47 nonredundant lowest energy conformations, according to the MP2/6-31+G energy order at the HF/6-31+G optimized geometry, hereafter the MP2/6-31+G//HF/6-31+G energy order, were geometry optimized at the B3LYP/6-31+G level. According to the MP2/6-31+G//B3LYP/6-31+G energy order, three conformations had energies lower than the experimentally known Ci conformation of 18c6. At the MP2/6-31+G//B3LYP/6-31+G level, the S6 lowest energy conformation is more stable by 1.96 kcal/mol than this Ci conformation. This was confirmed by results at the MP2/6-31+G level with an energy difference of 1.84 kcal/mol. Comparison between the structure of the S6 conformation of 18c6 and the S4 lowest energy conformation of 12-crown-4, as well as other important conformations of both molecules, is made. It is concluded that the correlation energy is necessary to have an accurate energy order of the predicted conformations. A rationalization of the conformational energy order in terms of the hydrogen bonding and conformational dihedral angles is given. It is also suggested that to have a better energy order of the predicted conformations at the MM3 level, better empirical force fields corresponding to the hydrogen bond interactions are needed.

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Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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Conformational Study of the Structure of Free 18-Crown-6

2005

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“…Molar ratio method was followed to determined the M :L ratio .The results of complexes in ethanol solution, suggest that the metal to ligand ratio was (2:1) for all prepared compounds, which were comparable to those obtained from isolated solid state study, Table ( (ii)Electrostatic potential (E.P):Electron distribution governs the electrostatic potential of molecules, and describes the interaction of energy of the molecular system with a positive point charge, so it useful for finding sites of reaction in a molecule positive charged species tend to attack a molecule where the E.P is strongly negative electrophilic attach [40,41].E.P of free ligand was calculated and plotted as 2D contour to investigate the reactive sites of the molecule Fig. (3), and one can interpret the stereochemistry and rates of many reaction involving (soft) electrophiles and nucleophiles interims of the properties of frontier orbital HOMO and LUMO.…”

Section: D-solution Studysupporting

confidence: 61%

Preparation, Characterization and Theoretical Study of Some Metal Complexes of New N[4-Bis(5-Thion-1,3,4- Oxadiazole-2yl) Methane) Methyl] Dibenzyl Amine of Possible Biological Activity

Hassan¹,

Abdul-Hameed²,

Alias³

2008

JNUS

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A new Mannich base N[4-bis(5-thion-1,3,4-oxadiazole-2yl)methane)methyl] dibenzyl amine (L), have been prepared and characterized by (FTIR) spectroscopy. (L) has been used as a chelating ligand to prepare a number of metal complexes were isolated and characterized by (FTIR) (UV-Vis) spectroscopy, and Flame atomic absorption technique,in addition to magnetic susceptibility, and conductivity measurement. The study of the nature of the complexes formed in ethanolic solution following the mole ratio method, gave results which were compared successfully with those obtained from isolated solid state studies .The antibacterial activity for the ligand and their metal complexes were studied against two selected micro-organisms, pseudomonas aeruginosa and Bacillus subtilis, the antibiotics Ampicillin has been chosen to compare their activity with those of the new compounds. Theoretical treatment of the formation of the complexes in the gas phase, this was done using the HyperChem-6 program for the semi-empirical and molecular mechanics calculations. The heat of formation (ΔHf o ) and binding energy (ΔE b ) at 298K for the free ligand and their complexes were calculated by PM3 and AMBER. Furthermore the electrostatic potential of the free ligand was calculated to investigate the reactive sites of the molecule.PM3 was used to evaluate the vibrational spectra of the base(L) and compare the theoretically calculated wave number with the experimental values by using bis (5-thion-1,3,4-oxadiazole-2yl) methane, as authonetic compound. The theoretically obtained frequencies a gree with those values experimentally found, in addition, the calculation helped to assign unambiguously the most diagnostic bands.

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“…(1) and (2). ** Electrostatic potentials (E.P) :Electron distrib-ution governs the electrostatic potential of mole-cules,and describes the interaction of energy of the molecular system with a positive point charge, so it is useful for finding sites of reaction in a molecule positive charged species tend to attack a molecule where the E.P is strongly negative electrophilic attack [31,32]. E.P of free ligand was calculated and plotted as 2D contour to investig-ate the reactive sites of the molecule Fig.…”

Section: D-theoretical Study Of Mannich Basementioning

confidence: 99%

Synthesis and Characterization of Some New Metal Complexes With Bis[4-Phenyl-2-Dibutyl Aminomethyl-1,2,4- Triazole-3-Thion-5yl]methane and Theoretical Study

Alias¹

2007

JNUS

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A new Mannich base bis[4-phenyl-2-dibutyl aminomethyl-1,2,4-triazole-3-thion-5yl]methane , formed by the condensation of formaldehyde and appropriate dibutyl amine,with bis triazole ,and its complexes (Cu II ,Co II ,VO IV ,Pd II , Pt IV ( have been synthesized . Their structures have been elucidated on the basis of analytical, magnetic susceptibility, electrical conductivity and spectra study as well as metal analysis.Structural geometries of complexes were suggested in solid state and in gas phase by using theoretical treatments,using the hyperchem-6program for the molecular mechanics and semiempirical calculations.The heat of forma-tion(ΔHf o )and binding energy(ΔE b )for the free ligand and its metal complexes were calculated by PM3,ZINDOandAMBERmethods,PM3was used to evaluate the vibration spectra of Mannich base and to compare the theoretically calculated wave numbers with experimental values by using bis (4-phenyl-3-thio-1,2,4-triazole-5yl) methane as authentic compound. The theoretically obtained frequencies a greed calculation helped to assign unambiguously the most diagnostic bands. IntroductionThe biological activity of many aromatic triazoles and their derivatives especially of 3-thio-1,2,4-triazole is now fairly documented [1,2].These compounds were described with variety of pharmacological actions,as fungicidal ,bactericidal and hypoglycemic agents [1,3].In a previous work [4,5], the synthesis and characterization of Mannich bases derived from 2-thio-1,3,4-oxadiazole and 3-thio-1,2,4-triazole with different cyclic aliphatic amines were described along with a number of their transition metal complexes.The elements of medical important Pd,Pt, Cu,Co and Au offer the potential for design of novel therapeutic and diagnostic agents [6]. Recent reviews [6,7]cover the current states of metal therapeutic drugs,where a wide applications involving metal complexes ,which either used or close to being used clinically as antitumer drugs especially Platinium are scribed .Some drugs have increased activeity when administrated as metal complexes,this attributed to the synergetic effect between the metal and the ligand [8].The present paper describes the preparation of new Mannich base,in an attempt to introdu-ce the methylamine moiety

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Quantum Mechanics and Molecular Mechanics Studies of the Low-Energy Conformations of 9-Crown-3

Cited by 17 publications

References 42 publications

Conformational Study of the Structure of Free 18-Crown-6

Conformational Study of the Structure of Free 18-Crown-6

Preparation, Characterization and Theoretical Study of Some Metal Complexes of New N[4-Bis(5-Thion-1,3,4- Oxadiazole-2yl) Methane) Methyl] Dibenzyl Amine of Possible Biological Activity

Synthesis and Characterization of Some New Metal Complexes With Bis[4-Phenyl-2-Dibutyl Aminomethyl-1,2,4- Triazole-3-Thion-5yl]methane and Theoretical Study

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