Conformational Analysis of Ethylene Oxide and Ethylene Imine Oligomers by Quantum Chemical Calculation

Kobayashi, Minoru; Sato, Hisaya

doi:10.1295/polymj.pj2007140

Cited by 8 publications

(6 citation statements)

References 23 publications

(37 reference statements)

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“…Every dihedral angle was independently assigned along the skeletal chains. As reported in our previous paper, 20 both energies and pseudoasymmetries (racemo or meso, due to a nitrogen inversion) of EI conformers (1-11 mers) in gaseous phase opitimized using QCC (RHF/ 6-31+G(d,p)) were affected by the designation values for the trans conformation. And all the most stable conformers, in which the pseudoasymmetries of (ttt) x conformers were racemo, were obtained by using the designation values for the trans conformation as follow: n = nþ1 = nþ2 was À175 /À175 /180 (partially restricted system).…”

Section: Quantum Chemical Calculations (Qcc)supporting

confidence: 62%

“…20 The hydrate effects on the energy of each conformer were examined. The hydrate energy, Á h (kcal/m.u.…”

Section: Hydrate Effects On the Energy Of Each Conformermentioning

confidence: 99%

“…20 j Transferred from the designated (g þ g þ g þ ) 1 to the (tg þ t) 1 conformer by optimization in gaseous phase. 20 effects (by hydrogen bonding, and so on) contribute to the stabilities of the conformers, and such effects are diluted with increasing monomer units. In our previous paper, 21 in which the conformational analyses for the solutions of EI oligomers (1-4 mers) were carried out by QCC (RHF/ 6-31+G(d,p) or B3LYP/6-31G(d)==SCRF/IPCM) using the permittivities of solvents (IPCM method 22 ), the energy of each conformer decreased with increasing values of the permittivities: " (" ¼ 0{80:1 of water), and such effects seemed to relate to the electrostatic interaction with solvents.…”

Section: Hydrate Effects On the Energy Of Each Conformermentioning

confidence: 99%

“…We have reported the conformational analyses of EI oligomers, as a model of PEI, in the gaseous 20 and liquid phases 21 using QCC. In the case of liquid phases, 21 the conformational energies of 1-$4-mers were estimated by IPCM method 22 using the permittivity: " (" ¼ 0{80:1: water) of solvents, and the results were in good agreement with those obtained by NMR analysis.…”

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Conformational Analysis for Hydrated Ethylene Imine Oligomer Models by Quantum Chemical Calculations

2009

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Hydrate effects on the conformations of ethylene imine oligomers (EI-x, x ¼ 1{8 mers) were examined using quantum chemical calculations. Models were constructed by locating a water molecule to each nitrogen atom in the structures optimized for non-hydrate oligomers. Hydrate ratio, h (h = H 2 O mol /N mol ), was set from 0 to 1. Six type conformations with repeated units of N-C, C-C and C-N bonds were examined. Conformational energies (E c ) were calculated as differences between energies of oligomers with water molecules and those of non-hydrogen and/or hydrogen bonding water molecules. Hydrate energies for each conformer (Á h , based on E c in non-hydrate state) were negative and linearly decreased with increase of h, and all conformers were stabilized by electrostatic effect with hydration. All (tg þ t) x conformers with h < 1, and the (ttt) x conformers over 3 mers with h ¼ 1, were the most stable. Each result corresponded to results observed for nonhydrated and hydrated linear PEI crystals, respectively, and seemed to be related with hydrogen bonding between water molecules. Lengths of conformers having gauche structure significantly decreased with increasing h. Such contractions by hydrations, however, were independent of gauche preference energy (ÁE c(g) ) of each conformer.KEY WORDS: Conformation / Poly(ethylene imine) / Oligomer / Hydrate Effect / Quantum Chemical Calculation / Poly(ethylene imine) (PEI) has unique properties because it possesses electron-releasing heteroatom (N) in the skeletal chain, similar to heteroatom (O) in poly(ethylene oxide) (PEO). Such properties, including specific affinity to substrate and solubility of inorganic salt, have been employed in the advancement of solid polymer electrolytes, 1 gene delivery polymers, 2 etc. These properties are often affected by conformational characteristics such as trans/gauche preferences, which depend on environmental factors such as temperature, solvent, etc. The conformational analyses of these polymers, therefore, are essential in the molecular design towards various applications.X-Ray diffraction (XRD) 3-5 and other analyses 6 have confirmed that the structure of a linear non-hydrated PEI crystal is a 5/1 double stranded helix, with a repeating tgt conformation for the N-C, C-C, and C-N bonds. In the hydrate state, the structure transforms to the planar zigzag ttt conformation. Unlike the PEO solutions, the trans-fractions of the C-C bonds of the PEI solutions increase with increase of permittivity (") of solvents, based on NMR analyses of N,N 0 -dimethylethylenediamine (di-MEDA) as a model of PEI. 7 The conformation of PEI, in this manner, specifically depends on environmental factors. Unfortunately, detailed understandings of these environmental effects have yet to be clarified because of the complexity in these effects.To complement the experimental observations in the conformational analyses of PEO or PEI, computational chemistry is employed. Pioneering works on PEO, involving a rotational isomeric state model (RIS), was reported by M...

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Section: Quantum Chemical Calculations (Qcc)supporting

confidence: 62%

“…20 The hydrate effects on the energy of each conformer were examined. The hydrate energy, Á h (kcal/m.u.…”

Section: Hydrate Effects On the Energy Of Each Conformermentioning

confidence: 99%

Section: Hydrate Effects On the Energy Of Each Conformermentioning

confidence: 99%

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Conformational Analysis for Hydrated Ethylene Imine Oligomer Models by Quantum Chemical Calculations

2009

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“…The reports concerning an analysis using hydrate model of PEI, however, seem to be little [10]. We have investigated the conformation analyses for EI oligomer models by QCC [11][12]. Most recently, for the hydrate models with various conformations ((ttt) x , (ttg + ) x , (tg + t) x , (tg + g + ) x , (tg + g -) x , and (g + g + g + ) x , x: monomer units number; x = 1 -8) of EI oligomers, we reported [13] that the (tg + t) x and (ttt) x conformers are the most stable in anhydrate and hydrate (hydrate ratio: h (H 2 O/N (mol) = 1), respectively, and the stabilities of conformers seemed to be related with hydrogen bonding between water molecules.…”

Section: Introductionmentioning

confidence: 99%

Structure Analysis for Hydrate Models of Ethyleneimine Oligomer by Quantum Chemical Calculation

Kobayashi¹,

Sato²

2010

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Structure analyses for hydrate models of ethyleneimine oligomer (5-mer as model of PEI) were investigated by quantum chemical calculations. Conformation energies and structures optimized for hydrate models of (ttt)5 and (tgt)5 conformers were examined. Hydrate ratio, h [h = H2O/N (mol)], was set from 0.5 to 2. In anhydrates, (tg+t)5 conformer was more stable (?1.8 kcal/m.u.) than (ttt)5. In hydrates, (ttt)5 conformers were more stable (?0.7 - ?4.3) than (tg+t)5. These results corresponded to experimental results that anhydrous linear PEI crystal changes from double helical to single planar chain in hydration process. Structures calculated for (ttt)5 agreed in those observed for hydrates of PEI. In all (tg+t)5 conformers, O???H bonds between waters were found with the decreases of N???H bonds between imino group and water. The O???H bonds in (tg+t)5 conformer resulted in its high chain torsion, and strongly related with instability and structure change (large swelling)

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