Ahmet Tokatlı

Quantum chemical computational studies on 5-(4-bromophenylamino)-2-methylsulfanylmethyl-2H-1,2,3-triazol-4-carboxylic acid ethyl ester

The optimized molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) (1)H and (13)C NMR shift values of 5-(4-bromophenylamino)-2-methylsulfanylmethyl-2H-1,2,3-triazol-4-carboxylic acid ethyl ester have been calculated by using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6-31G(d), 6-31G(d,p) and LANL2DZ basis sets. The optimized molecular geometric parameters were presented and compared with the data obtained from X-ray diffraction. In order to fit the calculated harmonic wavenumbers to the experimentally observed ones, scaled quantum mechanics force field (SQM FF) methodology was proceeded. Correlation factors between the experimental and calculated (1)H chemical shift values of the title compound in vacuum and in CHCl(3) solution by using the conductor-like screening continuum solvation model (COSMO) were reported. The calculated results showed that the optimized geometry well reproduces the crystal structure. The theoretical vibrational frequencies and chemical shifts are in very good agreement with the experimental data. In solvent media the energetic behavior of the title compound was also examined by using the B3LYP method with the 6-31G(d) basis set, applying the COSMO model. The obtained results indicated that the total energy of the title compound decreases with increasing polarity of the solvent. Furthermore, molecular electrostatic potential (MEP), natural bond orbital (NBO) and frontier molecular orbitals (FMOs) of the title compound were performed by the B3LYP/LANL2DZ method, and also thermodynamic parameters for the title compound were calculated at all the HF and B3LYP levels.

Aromatic character of fluorinated pyridines

Geometric structures for all the possible isomers of fluorinated pyridines were optimized at the B3LYP/6-311++G(d,p) level of theory. Aromaticities of the considered molecules were investigated using different indices included geometry-based (HOMA and Bird [I6]), magnetism-based (NICS(1) and diamagnetic susceptibility anisotropy [Δχ]), π- and σ-electron count-based (pEDA, sEDA), and recently introduced electronic-based (electric field gradient [EFG(0), EFG(0.5)] and Shannon aromaticity) indices. Moreover, we used also HOMO–LUMO gap, atomization energy (D0), and interaction energy for fluorinated pyridine complexes by water molecule as global descriptors, and the EFG values (EFGC–F(0)) on the middle points of C–F bonds and σ-electron population (Nσ) of nitrogen atom as local descriptors. All studied indices except HOMA and EFG(0.5) are well correlated to each other and to global and local descriptors.

Density Functional Theory Study on Conformers of Benzoylcholine Chloride

The optimized molecular structures and vibrational frequencies and also gauge including atomic orbital (GIAO) 1H and 13C NMR shift values of benzoylcholine chloride [(2-benzoyloxyethyl) trimethyl ammonium chloride] have been calculated using density functional theory (B3LYP) method with 6-31

Product Operator Theory for Spin‐5/2 Nuclei: Application to 2D J‐Resolved NMR Spectroscopy

Product operator theory is a simple quantum mechanical method that has often been used to analytically describe multi‐pulse NMR experiments for weakly coupled spin systems. Considering the existence of 2D‐J resolved NMR spectra of aqueous solutions containing S = 5/2 nuclear spins, the product operator formalism has been extended to the weakly coupled IS (I = 1/2, S = 5/2) spin system. The evolution of Ix, Iy, IxSz and IySz product operators under spin–spin coupling Hamiltonian are given here. The analytical results obtained are applied to the well‐known gated decoupler pulse sequence for heteronuclear 2D‐J resolved NMR spectroscopy.

Conformational, IR, NMR, and EPR analysis of ifosfamide by density functional theory calculation

The optimized molecular structure, vibrational frequencies, 1H and 13C NMR chemical shifts, and EPR hyperfine splittings of 3-(2-chloroethyl)-2-[(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine-2-oxide (ifosfamide) have been investigated using density functional theory (B3LYP) method with 6-31+G(d, p) basis set for the first time. The calculated optimized geometric parameters (bond lengths and bond angles), vibrational frequencies, NMR chemical shifts, and EPR hyperfine splittings were seen to be in a well agreement with the corresponding experimental data. The experimental EPR spectrum of the molecule was recorded after γ-irradiation. From the comparison of the calculated and experimental results the formed radical was attributed to a carbon atom-centered radical occurred upon the loss of a chlorine atom due to breakage of the weak C–Cl bonds. So we mentioned that the free electron is transferred to a carbon atom through intramolecular rearrangement while the molecular charge changes to neutral situation, giving NHĊαH2CßH2 radical.Graphical Abstract

Global Reaktiflik Parametreleri ve Bazı Spektral Sonuçlarla Polipropilenin Zincir Uzunluğuna Bağlı Kimyasal Reaktifliği

Ozet: Bu calismada polipropilenin zincir uzunluguna (n) bagli olarak kimyasal reaktifligi ya da kararliligi, global reaktiflik parametreleri ve bazi spektral sonuclar yardimiyla arastirildi. Bu maksatla, molekulun optimizasyonlari (n=1-12) B3LYP/6–311++G(d,p) seviyesinde yapildiktan sonra global reaktiflik parametreleri yani; E HOMO , E LUMO, E LUMO - E HOMO enerji farki, iyonlasma enerjisi, elektron ilgisi, kimyasal potansiyel, elektronegatiflik, sertlik, yumusaklik, elektrofilisiti ve nukleofilisiti indeks degerleri ve spektral sonuclar yani; IR, 1 H NMR ve 13 C NMR spektrumlari hesaplanarak yorumlandi. Molekulun reaktifliginin zincir uzunluguna bagli olarak artigi fakat n=10’dan sonra hemen hemen sabit kaldigi goruldu. Bulunmus bu zincir uzunlugunun bu molekulun kimyasal ozelliklerinin teorik olarak arastirmada yeterli oldugu kanaatine varildi. Abstract: In the present study, the chemical reactivity or stability of polypropylene depending on the number of chain (n) were investigated via global reactivity parameters and some spectral results. In this context, after the geometry optimizations of the molecule (n=1-12) were carried out at B3LYP/6–311++G(d,p) level, the global reactivity parameters such as; E HOMO , E LUMO , energy gap between E LUMO and E HOMO , ionization enerjisi, electron affinity, chemical potential, electronegativity, hardness, softness, electrophilicity index and nucleophilicity index, and the spectral results such as; IR, 1 H NMR and 13 C NMR have been calculated and commented. It was seen that its reactivity increases with increasing chain number but, become nearly constant after n=10. We have concluded this found chain number is enough to investigate its chemical properties as theoretical.

Aromatization of triafulvene and its exocyclic Si, Ge, and Sn derivations by complexation with halogen atoms

GRAPHICAL ABSTRACT ABSTRACT The geometries of triafulvene (TF) and its exocyclic Si, Ge, and Sn analogues complexes with F, Cl, Br, and I halogen atoms (TF(X)···Y, X═C, Si, Ge, and Sn; Y═F, Cl, Br, and I) were studied. The complexes were optimized at DFT(B3LYP)/6–311+G(d,p) level of theory. To assess the aromaticity of the considered complexes the geometry-based (HOMA), magnetism-based (NICS), and recently introduced electronic-based (electric field gradient (EFG(0); Shannon aromaticity (SA)) aromaticity indices were employed. The increasing tendency of aromaticity in each complex species was noted as the series of TF(X)···F > TF(X)···Cl > TF(X)···Br > TF((X)···I. Then, the binding energies corrected by basis set super position error (BSSE) were calculated by single point energy calculations at M06-2X/6-311+G(d,p) level. Natural bond orbital (NBO) analysis confirmed that the charge transfer takes place from TF(X) to the halogen atoms. Some topological parameters, within the framework of the quantum theory of atoms in molecules (QTAIM), were also calculated to estimate the aromaticity of the complexes. It was seen that there are some important correlations between the topological parameters and aromaticity indices. In addition the most striking finding was that all the TF(X) molecules are connected with the halogen atoms through Y···C1═C2 (π) noncovalent interaction. This interaction was also investigated through noncovalent interaction (NCI) analysis.

Product operator descriptions of the 2D DEPT J-resolved NMR experiment for weakly coupled ISn (, ; n=1, 2, 3) spin systems

There are a variety of multi-pulse nuclear magnetic resonance (NMR) experiments for spectral assignment of complex molecules in a solution. The two-dimensional (2D) distortionless enhancement by polarization transfer (DEPT) J-resolved NMR experiment is a 13C-detected, spectral editing polarization transfer technique. The product operator theory is widely used for an analytical description of the multi-pulse NMR experiment for weakly coupled spin systems. In this study, analytical descriptions of the 2D DEPT J-resolved NMR experiment for weakly coupled ISn (, ; n=1, 2, 3) spin systems using the product operator theory have been introduced for the first time. The calculated intensities and positions of the observable signals are simulated for molecules containing [13C , 81Br )] nuclei by using a MAPLE program on a computer. Finally, we present a theoretical discussion and experimental suggestions.

2B-SEMUT ÇMR Spektroskopisi

Bu calismada, ilk defa zayif ciftlenimli ISn (I=1/2, S=1/2; n=0,1,2,3) spin sistemleri icin carpim operator kurami kullanilarak 2B-SEMUT (Coklu kuantum oyunlariyla alt spektrumlara ayristirma) CMR deneyinin analitik tanimlamasi yapilmistir. Gozlenebilir sinyallerin siddet ve pozisyonlari icin hesaplanmis sonuclar, *Maple programi kullanilarak {13C (I=1/2), 1H (S=1/2)} cekirdeklerini iceren molekul icin benzetisim spektrumlari elde edilmistir. Benzetisim spektrumlari, estrone 3-metil ether (C19H24O2) icin 2BSEMUT CMR deneyinden elde edilen deneysel spektrumla iyi bir uyusum icinde oldugu gorulmustur.