فهرس المقالات Chemical shielding

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  1 - Theoretical investigation of the implicit effects water molecules and resonance interactions on structural stability and NMR tensors of hallucinogenic harmine by density functional calculations
  neda ahmadinejad arezoo tahan Mostafa Talebi Tari1
  Abstractl Density functional theory (DFT) was used to investigate the effects of intra-moecular interactions and implicit water molecules on the relative stability and the NMR shielding tensors of hallucinogenic harmine in the monomeric and dimeric states. Results repre أکثر

  Abstractl Density functional theory (DFT) was used to investigate the effects of intra-moecular interactions and implicit water molecules on the relative stability and the NMR shielding tensors of hallucinogenic harmine in the monomeric and dimeric states. Results represented that the relative stability and the NMR shielding tensors are dependent on the resonance interactions and chemical environment However, their values are obviously different in the considered states and the media. The energetic data demonstrated that dimeric and monomeric states of harmine in water medium are more stable than they are in the gaseous form. Based on NBO interpretation and NMR calculations it can also be concluded that by increasing lone pair electrons contribution of nitrogen atoms in resonance interactions and aromaticity development in the monomeric dimeric states, the values of NMR chemical shielding around them increase. Keywords: Harmine, NMR chemical shielding, NBO interpretation, monomer, dimer β-Carboline derivatives (H-pyrido [3, 4-b] indol derivatives) (BC) make up a group of drug-binding alkaloids, widely distributed in nature. Harmine [C13H12N2O] (MeO-1-1Me-9H-7pyrido [3,4-b]-indole ) is a well known member of the β-caroline alkaloid family تفاصيل المقالة
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  2 - Computation of the NMR Parameters of H-Capped (10,0) and (5,5) Single-Walled SiC Nanotubes
  Goudarz M. Rouzbehani Temer S. Ahmadi Ahmed Seif
  Geometrical structure, nuclear magnetic resonance (N1,1It) chemical shielding tensors, and chemical shiftsof silicon and carbon nucler are investigated for twn infinite size zigzag and armchair single-walled siliconcarbide nanotabes (SiCNTs). Geometrical structures of S أکثر

  Geometrical structure, nuclear magnetic resonance (N1,1It) chemical shielding tensors, and chemical shiftsof silicon and carbon nucler are investigated for twn infinite size zigzag and armchair single-walled siliconcarbide nanotabes (SiCNTs). Geometrical structures of SieNTs, Sit bonds and bond angles of St and Cvertices in both zigzag and armchair nanotubes, Indicate that bond lengths are approximately constant inthe armchair model but vary in the zigzag model. The NAIR parameters of C nuclei change more in thezigzag model as compared to the armchair model in agreement with geometrical structure changea. Thecalculations were performed with H3LYR OFT method and 6-310 (d) standard basis sets using theGaussian 03 package.Gaussian 03 package. تفاصيل المقالة
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  3 - Ab Initio Quantum Chemical Studies of 15N and 13C NMR Shielding Tensors in Serine and Complexes of Serine- nH2O: Investigation on Strength of the CαH…O Hydrogen bonding in the Amino Acid Residue.
  M. Monajjemi T. Karimkeshteh F. Mollaamin
  In this paper, the hydrogen bonding (HB) effects on the NMR chemical shifts of selected atoms in serineand serine-nH2O complexes (from one to ten water molecules) have been investigated with quantummechanical calculations of the 15N and 13C tensors. Interaction with wat أکثر

  In this paper, the hydrogen bonding (HB) effects on the NMR chemical shifts of selected atoms in serineand serine-nH2O complexes (from one to ten water molecules) have been investigated with quantummechanical calculations of the 15N and 13C tensors. Interaction with water molecules causes importantchanges in geometry and electronic structure of serine.For the compound studied, the most important intermolecular interaction between serine and watermolecules employ different geometrical models of numerous N…H and C-H…O bonds in the crystallinestructures. These interactions have been approximated by explicitly adding the nearest neighbors into thecalculations.At present, quantum chemistry is almost universally applicable to the interpretation of physical andchemical properties of various compoundsChemical shift calculations, geometry optimization and energies have been performed with ab initiomethod at HF/6-31G* and HF/6-31G** levels with GIAO methods.There is strong evidence that intermolecular effects are important in determining the 15N chemical shiftsof free amino acid residue to assign principal axes of the tensors and some systematic trends appear fromthe analysis of the calculated values.Formation of each interaction (in ten orientations) results in a shift of the bridging hydrogen's chemicalshifts of N…H bond that indicate the most stabilized compound.The CαH…O bond plays an important role in the interactions of amino acids residue upon the structureand function of a protein.Despite the finding of numerous CαH…O contacts in proteins, major questions remain about theirimportance. Thus it is the strength of this binding that is of most importance in understanding the possiblefactor that the CαH…O H-bond may play in the folding of proteins.This paper represents comparison between theoretical and experimental values of NMR resonances, andcalculations of HF/6-31G** level produce results in better agreement with the experimental data. تفاصيل المقالة
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  4 - Relationship between 13C NMR Parameters and Antimalarial activity of Cryptolepine Isosteres
  Mohamad Reza Talei Bavil Olyai Hadi Behzadi Payman Roonasi
  Density functional theory calculations were applied to investigate13C Chemical Shielding (CS) tensors in cryptolepine (1) and its sulfur (2) and oxygen (3) isosteres. The results showed that the CS of carbon nuclei in these compounds may be divided into three types. F أکثر

  Density functional theory calculations were applied to investigate13C Chemical Shielding (CS) tensors in cryptolepine (1) and its sulfur (2) and oxygen (3) isosteres. The results showed that the CS of carbon nuclei in these compounds may be divided into three types. First, carbons type α,are those directly bonded to X (X= NH, S, O) and σ33shielding component of these carbons are deshielded in O isostere compared to N and S isosteres. The second group of carbons (β-carbons) is attached to α-carbons, in which σ11 components of S isostere differs from O and N isosteres. The third carbon group, γ-carbons are positioned at a distance of three interatomic bonds or greater away from X. The replacement of N by O or S in cryptolepine isosteres has negligible influence on all components of the later carbon type. The variations of CS components could be related to the inactivity of O isostere and broad spectrum activity of S isostere. تفاصيل المقالة
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  5 - Study on Sunitinib Adsorption on Graphene Surface as an Anticancer Drug
  Sepideh Tanreh Abolghasem Shameli Ebrahim Balali
  In recent years, Nano technology and its application have moved to discovering chemicaltherapy drugs. Research, development for finding new targets in tumors, targeting methodsand stabilizing the nano particle in targeted cells is based on drug delivery and its cruciale أکثر

  In recent years, Nano technology and its application have moved to discovering chemicaltherapy drugs. Research, development for finding new targets in tumors, targeting methodsand stabilizing the nano particle in targeted cells is based on drug delivery and its crucialeffect. Examining the computational controlled drug delivery by graphene sheets has becomevery significant due to numerous side effects of this drug especially on nervous system as aresult of direct injection. In this work, adsorption of Sunitinib on Si and Al or nitrogen dopedgraphene has been studied using density functional theory. Doping Si or Al significantlyaffects the adsorption of Sunitinib over graphenes. Still, not much impact of doping Ni ongraphene is observed. Interaction energy, estimated using the super molecular approachranges from 54.97 KJ mol−1 to 63.95 KJ mol−1 in the gas phase. Furthermore, the calculateddensity of states (DOS) shows the existing of noteworthy orbital hybridization betweenSunitinib and Si or Al doped graphene during the adsorption process which is trying out tostrong interaction while there is no evidence for hybridization between the those moleculesand the pristine graphene. 11C and 1H chemical shielding correlate noticeably with thederivatives graphene. 11C, 27Al and 2H nuclear quadrupole coupling constants, CQ, andasymmetry parameter, η, reveal the remarkable effect of Sunitinib adsorption on electronicstructure of the graphene. تفاصيل المقالة
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  6 - مقایسه تانسورهای NMR - NQR و واکنش پذیری شیمیایی آنالوگ های میرتازاپین و نورمیرتازاپین با استفاده از روش های مکانیک کوانتومی
  آرزو طحان مهیا خجندی
  روش های نظریه تابعیت چگالی (DFT) برای بررسی و مقایسه طیف های NMR - NQR و واکنش پذیری شیمیایی دو ترکیب ضدافسردگی میرتازاپین و نورمیرتازاپین مورد استفاده قرار گرفتند. نتایج بدست آمده در سطح محاسباتی B3LYP/6-311++G** نشان دادند که مقادیر پوشیدگی شیمیایی NMR و تانسورهای NQR أکثر

  روش های نظریه تابعیت چگالی (DFT) برای بررسی و مقایسه طیف های NMR - NQR و واکنش پذیری شیمیایی دو ترکیب ضدافسردگی میرتازاپین و نورمیرتازاپین مورد استفاده قرار گرفتند. نتایج بدست آمده در سطح محاسباتی B3LYP/6-311++G** نشان دادند که مقادیر پوشیدگی شیمیایی NMR و تانسورهای NQR هسته های نیتروژن دو آنالوگ تحت تاثیر محیط شیمیایی، ساختار مولکولی و برهمکنش های رزونانسی قرار می گیرند، طوری که مقادیر پارامترهای NMR-NQR اتم های نیتروژن با موقعیت هندسی مشابه با یکدیگر در دو آنالوگ تقریبا یکسان بوده و در هر مولکول مقادیر این پارامترها برای هر یک از نیترو ژن ها متفاوت از دیگری است . در این حال، آنالیز NBO نیز نشان می دهد که جفت الکترون های N10 حلقه آزپین بیشترین مقدار انرژی رزونانس مربوط به برهمکنش های LP(1) N10→ 𝛔* or π* را در بین نیتروژن های هر دو ساختار دارا می باشند. براساس تحلیل NBO و محاسبات NMR-NQRمی توان نتیجه گیری نمود که در ساختار نورمیرتازاپین با افزایش سهم الکترون های جفت تنهای اتم های نیتروژن در برهمکنش های رزو نانسی و توسعه آروماتیسیته، مقادیر پارامتر های NQR اطراف آنها افزایش می یابند در حالی که در ساختار میرتازاپین با افزایش بار منفی بر روی اتم های نیتروژن مقدار پارامترهای NMR و NQR اطراف آنها افزایش می یابند. مقایسه شاخص های واکنش پذیری دو آنالوگ بررسی شده با ابزار NBO نیز نشان داد که تفاوت ساختاری این دو آنالوگ اثر قابل توجهی بر روی واکنش پذیری شیمیایی این دو ترکیب ندارد. تفاصيل المقالة
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  7 - بررسی تانسورهای NMRو NQR در آنالوگ های دارویی متیل فنیدات
  آرزو طحان مهیا خجندی
  در این مطالعه، اثرات جایگزینی چهار استخلاف در دو موقعیت مختلف ساختار داروی متیل فنیدات (MPH )، بر روی تانسورهای NMR و NQR هسته های کربن، نیتروژن و اکسیژن بررسی شدند. نتایج بدست آمده با استفاده از محاسبات تحلیل اوربیتال های پیوندی طبیعی(NBO) و بر پایه ساختار اتمی تفسیر ش أکثر

  در این مطالعه، اثرات جایگزینی چهار استخلاف در دو موقعیت مختلف ساختار داروی متیل فنیدات (MPH )، بر روی تانسورهای NMR و NQR هسته های کربن، نیتروژن و اکسیژن بررسی شدند. نتایج بدست آمده با استفاده از محاسبات تحلیل اوربیتال های پیوندی طبیعی(NBO) و بر پایه ساختار اتمی تفسیر شدند. یافته ها بیان کردند که با افزایش مشارکت استخلاف های جایگزین شده در برهمکنش های درون مولکولی، اثرگذاری آنها بر روی تانسورهای NMR و NQR هسته های بررسی شده افزایش می یابد. بنابراین، استخلافات الکترون کشنده در موقعیت های R7 و R9 ساختار MPH، با بیشترین مشارکت در برهمکنش های درون مولکولی، بیشترین افزایش را در برهمکنش های رزونانسی حلقه بنزن ایجاد نمودند و باعث کاهش بار منفی بر روی اتم های مجاور و کربن های حلقه بنزن شده و مقادیر تانسورهای NQR و پوشیدگی شیمیایی اطراف هسته های مجاور و کل حلقه بنزن را کاهش دادند. تفاصيل المقالة
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  8 - Calixarene Drug deleivery invistegation of Calixarene compounds with conection by histidine L and D stereochemistry
  Hooriye Yahyaei Neda Hasanzadeh
  In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatur أکثر

  In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatures. According to these theoretical results of IR, we extracted thermo chemical parameters such as enthalpy (∆H Kcal/mol), Gibbs free energy (∆G Kcal/mol) and entropy (∆S cal/molK). Important relationship have been found between solvent effect and structure of Calixarens with histidine L and D stereochemistry. Also, nuclear shielding parameters of Calixarene, such as chemical shift isotropic value (σiso) and the anisotropy shielding (σaniso, ∆σ), have been taken into account using GIAO method at the HF method with the 6-31+G* basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and in different solvents such as water, DMSO, methanol, ethanol and dichloromethane. The results were revealed that the NMR chemical shielding parameters are strongly affected by inducing different solvent media. According to these theoretical results,it can be drastically concluded that the dielectric permittivity of the solvent is a key factor that determines the chemical behavior of Calixarene with histidine L and D stereochemistry in solution. Also the natural bond orbital (NBO) analysis has been performed at the six levels in the gas phase and different solvent media which show some important atomic and structural features. تفاصيل المقالة
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  9 - Solvent Effects on Medicinal Structure and 15N NMR Shielding of Medazepam
  Arezoo Tahan Fatemeh Alimohammadi
  10.22034/jchr.2020.1892885.1102
  The Density Functional Theory (DFT) and Tomasi’s Polarized Continuum Model (PCM) were used to investigate the effects of solvent dielectric constant on the structural stability and 15N NMR tensors of Medazepam (MDZ) drug. The results revealed that the structural s أکثر

  The Density Functional Theory (DFT) and Tomasi’s Polarized Continuum Model (PCM) were used to investigate the effects of solvent dielectric constant on the structural stability and 15N NMR tensors of Medazepam (MDZ) drug. The results revealed that the structural stability of MDZ in polar protic solvents was higher than that in the polar aprotic and non-polar solvents; and its value depended on the solvent dielectric constant and its structure. so that in most cases, relative stability increased by increasing the solvent dielectric constant and the most stable structures were observed in water media at DFT level and in methanol at MP2 level. In this regard, natural bond orbital (NBO) interpretation showed that the tetravalent N1 nucleus of diazepine ring in the MDZ structure had the highest value of negative charge and the resonance energy related to LP (1) N1 → σ* and π* delocalizations among heteroatoms of MDZ structure in the tested solvents. The findings reported that with an increase in the solvent dielectric constant, the resonance energy related to LP (1) N1 → σ* and π* delocalizations increased and the highest value of resonance energy was observed in water media. Furthermore, NMR results represented that the N1 nucleus had a higher value of chemical shielding than the trivalent N4 nucleus in all of the tested media. However, it may be concluded that by increasing the accumulation of negative charge and lone pair electrons participation of nitrogen nuclei in the resonance delocalizations, isotropic chemical shielding around them increase. تفاصيل المقالة