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In this study, firstly the minimum energy structure of the title compound was determined by a result of the scanning of the potential energy surface at DFT(B3LYP)/6-31 G (d, p) from -180o to -180o at 20o steps at a dihedral angle. Then, the ground state optimized structure and spectral results of the molecule were calculated by using DFT(B3LYP) method at 6-311++G(d,p) level of theory. Its optimized structure parameters (bond lengths, bond angles and torsion angles), vibrational frequencies and chemical shift values were listed and, compared with the corresponding experimental results.

© 2022, TUBITAK. All rights reserved.In the present study, we have theoretically obtained the enthalpies and activation energies of several gas reactions by Intrinsic Reaction Coordinate (IRC) calculations. Being a first time, the approximate transition states used in the IRC calculations were obtained from the saddle points on the two dimensional Potential Energy Surface (PES) scans trucking the pathway of the reactions. In all the calculations, the Density Functional Theory (DFT/B3LYP) with 6-31 G (d, p) level was used. The saddle points on the PES graphs of the reactions were used one by one as an approximate transition state (TS) in the IRC calculations until the appropriate reaction path was obtained. The obtained TS’s from the IRC calculations were tested for having only one imaginary frequency. The energy diagram schemes showing the reactants, products, and transition states of all the reactions were drawn, and their enthalpies and activation energies were determined. From the enthalpy values it was decided whether the reactions are endothermic or exothermic. The calculated activation energies were compared with the ones in the literature.

Bu çalışmada bazı gaz reaksiyonlarının İçsel Reaksiyon Koordinat (IRC) hesaplamaları ile entalpileri ve aktivasyon enerjileri teorik olarak elde edildi. İlk kez olarak IRC hesaplamalarında kullanılan yaklaşık geçiş halleri, reaksiyon aşamalarını takip eden iki boyutlu Potansiyel Enerji Yüzey (PES) taramalarındaki merdiven noktalar olarak kullanıldı. Bütün hesaplamalarda, 6-31 G(d,p) seviyede Yoğunluk Fonksiyonel Teori (DFT/B3LYP) kullanıldı. Reaksiyonların PES grafiklerindeki merdiven noktalar, IRC hesaplamalarında uygun reaksiyon eğrisi bulununcaya kadar birer birer yaklaşık Geçiş Hali (TS) olarak alındı. IRC hesaplamaları ile elde edilen TS’ler tek bir negatif (imejiner) frekans için test edildi. Bütün reaksiyonların, reaktant, ürün ve geçiş hallerini gösteren enerji diyagram şemaları çizildi ve onların entalpileri ve aktivasyon enerjileri elde edildi. Entalpi değerlerinden reaksiyonların, endotermik veya ekzotermik olduğu tespit edildi. Hesaplanan aktivasyon enerjileri literatürdeki değerlerle karşılaştırıldı., In the present study, we have theoretically obtained the enthalpies and activation energies of several gas reactions by Intrinsic Reaction Coordinate (IRC) calculations. Being a first time, the approximate transition states used in the IRC calculations were obtained from the saddle points on the two dimensional Potential Energy Surface (PES) scans trucking the pathway of the reactions. In all the calculations, the Density Functional Theory (DFT/B3LYP) with 6-31 G (d, p) level was used. The saddle points on the PES graphs of the reactions were used one by one as an approximate transition state (TS) in the IRC calculations until the appropriate reaction path was obtained. The obtained TS’s from the IRC calculations were tested for having only one imaginary frequency. The energy diagram schemes showing the reactants, products and transition states of all the reactions were drawn, and their enthalpies and activation energies were determined. From the enthalpy values it was decided whether the reactions are endothermic or exothermic. The calculated activation energies were compared with the ones in the literature.

The aim of this work is to explore the stable hydrogenated forms of carbazole and 9-methylcarbazole molecules by using M06-2X density functional as computational method. Binding energies per hydrogen atom in these hydrogenated forms were calculated by the counterpoise correction procedure. Relative energies, complexation and binding energies for the conformers of dodecahydrocarbazole were also calculated. Stabilities of all the hydrogenated forms were discussed by the analysis of the frontier molecular orbitals.

The groundstate optimized structures of some radical adducts of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in water and benzenesolutions have been determined by using Density Functional Theory (DFT/B3LYP, DFT/B3PW91 ve DFT/PBEPBE)ve Hartree Fock (HF) methods with 6-31G (d,p), 6-311++G (d,p),LanL2DZ, LanL2MB and SDD levels. As trapped radicals, H, OH, O(CH2)(CH3)and OC(CH3)3 have been used. The calculated isotropichyperfine coupling constants of all the trapped radicals have been seen to beagree with the corresponding experimental data. The hyperfine coupling constantdue to the β proton of nitroxideradical is concluded to be effected with the opposite spin density of oxygennucleus bonded to the nitrogen. From all the calculated data it was obtainedthat on the hyperfine calculations the DFT (B3LYP) LANL2MB level is superiorrelative to the other levels for the used radicals. Also, the study has beenenriched by the computational of the geometrical parameters, binding energies,atomic spin densities and hyper conjugative interaction energies for all theradical adducts., Su ve benzen çözeltilerinde5,5-dimetil-1-pirolin N-oksit(DMPO)’nun bazı radikal ürünlerinin temel hal optimize yapıları, 6-31G (d,p),6-311++G (d,p), LanL2DZ, LanL2MB ve SDD setlerinde Yoğunluk Fonksiyon Teori (DFT/B3LYP,DFT/B3PW91 ve DFT/PBEPBE) ve Hartree Fock (HF) metotları kullanılarakhesaplandı. Tuzaklanmış radikaller olarak, H, OH, O(CH2)(CH3) ve OC(CH3)3 kullanıldı.Tuzaklanan radikallerin hesaplanan izotropik ince yapı çiftlenim sabitlerinin,deneysel veriler uyum içinde olduğu görüldü. Azot radikalinin β protonundan kaynaklı aşırı ince yapıçiftlenim sabitinin, azota bağlı oksijen çekirdeğindeki zıt spin yoğunluğundanetkilendiği görüldü. Elde edilen bütün teorik sonuçlardan, kullanılan radikalleriçin ince yapı hesaplamalarında, DFT(B3LYP)/LANL2MB setinin diğer setlere kıyasladeneysel veriler ile daha uyumlu sonuçlar verdiği tespit edildi. Ayrıcaçalışma, bütün radikal ürünleri için teorik geometrik parametreler, bağlanmaenerjileri, atomik spin yoğunlukları ve hiper konjugatif etkileşim enerjileriile zenginleştirildi.

The vibrational frequencies and 1H and 13C chemical shifts of choline halides have been calculated using density functional theory (B3LYP) method with 6-311++G(d, p) and 6-31 G(d, p) basis set level in Gaussian 03 and Parallel Quantum Solutions (PQS) ab initio packages programs, respectively. The calculated optimized geometric parameters, vibrational frequencies and chemical shifts were seen to be a very good agreement with the experimental data. The electronegativity influence of the halogen substitutions on the vibrational frequencies and chemical shifts have also been investigated. It was observed that the chemical shifts for H nucleus, especially the most near nucleus to the halogen atom decrease while it increases for C nucleus. The roughly linear variation of the chemical shift with the electronegativity of the halogen, whatever the shielding for C nucleus or deshielding for H nucleus is, has been commented that the local electron density near the halogen atom is affected. Key words: Choline halides, vibrational spectroscopy, chemical shift, B3LYP, Gaussian, PQS Kolin Halidlerin (F, Cl, Br) Kimyasal Kaymalarının ve Titreşim Frekanslarının Teorik Çalışması Taban setleri 6-311++G(d,p) ve 6-31G(d,p) olan yoğunluk fonksiyon kuramı (B3LYP) yöntemi kullanılarak kolin halojenlerinin (F, Cl, Br), Gaussian 03 programında titreşim frekansları ve Paralel Quantum Solutions (PQS) programında ise, 1H ve 13C çekirdeklerinin kimyasal kaymaları hesaplandı. Hesaplanan optimize geometrik yapı parametreleri, titreşim frekansları ve kimyasal kaymalar, deneysel verilerle çok iyi uyuşmaktadırlar. Kimyasal kaymalara ve titreşim frekanslarına, halojen katkılanmalarının, yani elektronegatifliğin etkileri incelendi. Kimyasal kaymaların, H çekirdeği için özellikle halojen atomuna en yakın çekirdekler olmak üzere azalırken, C çekirdeği için aynı sıralamayla arttığını gözledik. Halojenin elektronegatifliği ile kimyasal kaymanın kabaca çizgisel değişimi, C çekirdeği için ekranlanma ya da H çekirdeği için ekranlanmama ne olursa olsun, halojen atomu yakınındaki yerel elektron yoğunluğunun değişimin olarak yorumlandı. Anahtar kelimeler: Kolin halidleri, titreşim spektroskopisi; kimyasal kayma; B3LYP, Gaussian, PQS