Browsing by Author "Gumus, Selcuk"

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1,3-Dipolar Cycloaddition Reactions of 1-Methyl Betaine With C70-A Theoretical Study
(Amer Scientific Publishers, 2009) Turker, Lemi; Gumus, Selcuk
In the present study, the molecular orbital properties of 1,3-dipolar cycloaddition products of 1-methyl-3-oxidopyridinium betaine with C-70 have been investigated theoretically at the level of PM3 (RHF) type semi empirical quantum chemical calculations and then single point DFT calculations were performed for the energies. The betaine acts as a 4 pi-component across its 2,6-positions and certain C=C bonds of C-70 act as 2 pi-component in the 1,3-dipolar cycloadditions considered presently. Various cycloadducts are structurally possible because C-70 structure possesses 8 different 2 pi-components, therefore 8 different pairs of reaction termini exist. The results indicate that, the cycloadducts (including regioisomers) formed with [6, 6]-type double bond are more stable and less endothermic than adducts formed with the [5, 6]-type with some exceptions. Some structural, spectral and physicochemical properties of these cycloadducts have also been studied.
The Aromaticity of Substituted Diazanaphthalenes
(Elsevier, 2011) Gumus, Selcuk
Substituted (F, Cl, OH) diazanaphthalene derivatives have been considered theoretically to obtain information about their stabilities and aromaticities. The expected decrease of aromaticity of naphthalene itself by double aza substitution has been compensated by substitution of one of the hydrogens of the system by an electronegative atom. The position of the substituent has been proved to be strongly effective on the aromaticity of the structure such that, the aromaticity is enhanced when the susbtituent is closer to the aza points. (C) 2010 Elsevier B.V. All rights reserved.
A Computational Study on A Series of Phenanthrene and Phenanthroline Based Potential Organic Photovoltaics
(Soc Chemists Technologists Madeconia, 2017) Gumus, Aysegul; Gumus, Selcuk
A series of phenanthrene and phenanthroline derivatives were considered computationally by the application of Density Functional Theory at the B3LYP/6-31++G(d,p) level to investigate their potential usage as organic solar cell components, thermally activated delayed fluorescence and nonlinear optic compounds. The structures were constructed as a D-pi-A motif in order to increase the ability to achieve intramolecular charge transfer enabling them to act as organic semiconductors. The inter-frontier energy gap of all compounds was found to be in the range of semiconductors. The thermally activated delayed fluorescence (TADF) properties of the compounds were also discussed in relation to the results obtained by TD-DFT calculations. Some of them possessed very narrow triplet-singlet transition energy leading to future TADF applications. Moreover, the nonlinear optic characteristics of all compounds were investigated through calculations of the total molecular dipole moment (mu(tot)), linear polarizability (alpha(tot)) and hyperpolarizability (beta(tot)). The results indicate the potential nonlinear optic property of all of the systems.
A Computational Study on Azaazulenes
(de Gruyter Poland Sp Z O O, 2013) Gumus, Selcuk
All possible aza analogs of azulene, containing from one to three nitrogen atoms in the five-membered ring or from one to five nitrogen atoms in the seven-membered ring, have been theoretically considered to obtain information about their stabilities and aromaticities. Total electronic energy and nucleus independent chemical shift (NICS) data have been used to evaluate stability and aromaticity, respectively. The stabilities of the structures are strongly affected by the positions of the nitrogen atoms. Calculations of azaazulenes show that stability is decreased with close proximity of the nitrogen atoms. When nitrogen in the five-membered ring is adjacent to a ring junction, aromaticity of the cyclopentadienyl anion is reduced and that of the tropylium cation is increased. The number of nitrogen atoms affects the aromaticity of the system.
A Computational Study on Substituted and Unsubstituted Mono and Diazaanthracenes
(Taylor & Francis Ltd, 2013) Gumus, Selcuk; Akbay, Murat
Substituted (F, Cl, OH, and NO2) diazaanthracene derivatives have been considered theoretically to obtain information about their stabilities and aromaticities. The expected decrease of aromaticity of parent anthracene by mono or diaza substitution has been compensated by substitution of one of the hydrogens of the system by an electronegative atom. The position of the substituent has been proved to be strongly effective on the aromaticity of the structure such that, the aromaticity is enhanced when the susbtituent is closer to the aza points.
A Computational Study on Substituted Diazabenzenes
(Tubitak Scientific & Technological Research Council Turkey, 2011) Gumus, Selcuk
The results of computational calculations on the aromaticity of the monosubstituted diazabenzenes (pyridazine, pyrimidine, and pyrazine) are reported herein. The aromaticity of the parent heterocycle was enhanced by substitution of strong electron-withdrawing groups. The effects of the position of the substituent on the aromaticity and the stability of the system were also investigated by studying all possible derivatives of the systems.
Design, Stereoselective Synthesis and Computational Calculations of Novel Hybrid Compounds Via Pauson-Khand Reactions
(Pergamon-elsevier Science Ltd, 2017) Gumus, Selcuk; Aslan, Nezir; Buyukadali, Nalan Nuriye; Gumus, Aysegul
A series of novel chiral hybrid compounds between benzofuran and bicyclic cyclopentenone and also benzothiophene and bicyclic cyclopentenone have been designed and synthesized. Chiral enynes derived from enantiomerically enriched homoallyl and homopropargyl alcohols were converted into bicyclic cyclopentenone structures by intramolecular Pauson-Khand reactions. This strategy provides a facile access to various bicyclic cyclopentenones substituted with benzofuran or benzothiophene ring systems in good yields. In addition to the experimental work, the ground state geometries of the hybrid compounds were optimized using Density Functional Theory applications at the B3LYP/6-31G(d,p) level in order to obtain information about the 3D geometries and electronic structure. (C) 2017 Elsevier Ltd. All rights reserved.
Effects of Asymmetric Acceptor and Donor Positioning in Deep Blue Pyridyl-Sulfonyl Based Tadf Emitters
(Elsevier Sci Ltd, 2021) Haykir, Gulcin; Aydemir, Murat; Danos, Andrew; Gumus, Selcuk; Hizal, Gurkan; Monkman, Andrew P.; Turksoy, Figen
In this work, we report synthesis and photophysical properties of deep-blue emitting donor-acceptor (D-A) and donor-acceptor-donor (D-A-D) thermally activated delayed fluorescence (TADF) molecules, where the molecules designed using carbazole as a donor (D) and a pyridyl (a)-sulfonyl (A) based bifunctional group as an acceptor. The work reveals how structural changes favor reverse intersystem crossing (rISC) by forming emissive charge transfer (CT) state, which is thoroughly investigated in different donor and asymmetric acceptor positions. Three comparison sets of regioisomers are investigated. 2,5-substituted pyridine derivatives in Set-1, are D-Aa, D-aA and D-Aa-D structures with asymmetric acceptor systems, revealing that the donor nearer to the pyridine group substantially controls the TADF properties In Set-2, modified the D-Aa-D structures reveal how ortho and meta positioned a relative to A (keeping the carbazole at meta to the A) affects the emission properties, deactivating TADF and promotion triplet-triplet annihilation. In the final set, 2,4-substituted pyridyl-sulfonyl derivatives show that the positioning of the donor far from the pyridine group has minimal influence. This final set of molecules show superior optical and physical properties though, indicating the importance of correct positioning between D, a, and A.
Efficient Transfer Hydrogenation Reactions With Quinazoline-Based Ruthenium Complexes
(Pergamon-elsevier Science Ltd, 2015) Karabuga, Semistan; Bars, Songul; Karakaya, Idris; Gumus, Selcuk
(4-Phenylquinazolin-2-yl)methanamine was synthesized in high yield by starting from naturally and commercially available glycine in a few steps. The ligand was reacted with RuCl2(PPh3)(3) and RuCl2(PPh3) dppb to obtain N-heterocyclic ruthenium(II) complexes. We have examined these catalysts in transfer hydrogenation of acetophenone derivatives and excellent conversions of up to 99% and high TOF values of up to 118,800 h(-1) using 0.1 mol % of catalyst were achieved. (C) 2014 Elsevier Ltd. All rights reserved.
Electroluminescent Properties of Certain Polyaromatic Compounds: Part 1-Characteristics of Oled Devices Based on Fluorescent Polyaromatic Dopants
(Taylor & Francis Ltd, 2009) Turker, Lemi; Tapan, Alper; Gumus, Selcuk
Organic electroluminescent devices recently have been focus of attention. Since the first demonstrations in this field, rapid developments have occurred in the usage of organic polyaromatic compounds and their derivatives for the purpose of multi-layer structures, multi-color, and full-color organic light-emitting diode displays. In the part-1 of the present short review, recent technical developments in the preparation and structure of organic light emitting diodes with special attention to organic emitters involving polyaromatic kernels have been considered.
Electroluminescent Properties of Certain Polyaromatic Compounds: Part 2-Organic Emitters
(Taylor & Francis Ltd, 2009) Turker, Lemi; Tapan, Alper; Gumus, Selcuk
This review is based on the electroluminescent and optical properties of certain polyaromatics in OLEDs with special attention to their specific function in the emitting layer, performance and emissive color. DAD and TDAD dopants depending on their concentration in the emitting layer exhibit good efficiencies and color purity for blue emission. When copolyethers with diphenylanthracene emitting segments are used in a single layer diode, visible pure blue light (440 nm maximum) around 15-20V can be achieved. J-Aggregates including anthracene moieties contribute to the efficient IR electroluminescence. Blue, white, yellow and orange electroluminescent devices can be obtained by ADNor ADN-doped with rubrene at ultra low concentrations. Pyrene derivatives (P1, P2) linked to fluorene exhibit high thermal stability, bright blue emission and improved hole injection ability. Aminobenzanthrone derivatives as host emitters emit orange-to-red light with high brightness (25000 cd. m(-2)), current efficiency (3.52 cd. A(-1)) and power efficiency. Due to its bipolar transport property, when doped in Alq3 or NPB, tetraphenylnaphtacene shows excellent yellow electroluminescence. Multiple quantum well (MQW) structures including rubrene are helpful in narrower and tunable spectral emission, as well as higher emission efficiency. Perylene derivatives such as copolymer+PVK blend show sharp red emission peaks, photochemical and thermal stability. Pentacene derivatives, DPP, 1-DNP and 2-DNP can be used to obtain highly pure purple color. An increase in the doping concentration of DPP enhances photoluminescent peak intensity. New blue-green emitting dopants like coronene, decacylene and conjugated ladder systems based on phthalocyanines are centers of attraction for electroluminescence in recent years.
Hydroxyl Group Effect in Novel Nnn Type Pyridine Based Ruthenium (Ii) Complex for the Transfer Hydrogenation of Ketones
(Elsevier, 2016) Sahin, Irfan; Emir, Sedat; Ispir, Esin; Karakaya, Idris; Gumus, Selcuk; Ulusoy, Mahmut; Karabuga, Semistan
The new NNN type pyridine ligands were prepared by using low cost and readily available starting materials and metalated with RuCl2(PPh3)(3) to obtain ruthenium(II) complexes. All structures were illuminated by NMR, HRMS, and FT-IR spectroscopy. The complexes exhibited good catalytic activity in transfer hydrogen reaction of ketones and it was found that a hydroxyl group on beta-position of the pyridine ring had a dramatic effect on the catalyst efficiency. (C) 2016 Elsevier B.V. All rights reserved.
The Investigation of Sky-Blue Emitting Anthracene-Carbazole Derivatives: Synthesis, Photophysics and Oled Applications
(Elsevier, 2018) Haykir, Gulcin; Aydemir, Murat; Han, Si Hyun; Gumus, Selcuk; Hizal, Gurkan; Lee, Jun Yeob; Turksoy, Figen
New well-defined structurally different 9,10-bis(9-hexyl-6-((E)-styryl)-9H-carbazol-3-yl)anthracene derivatives, shortly named "6a, 6b and 6c", with side groups having electron donating and withdrawing were systematically synthesized using Suzuki cross-coupling and Vilsmeier-Haack reactions. The impact of electron donating and withdrawing groups and their influence on the molecules photophysical properties has been investigated. The materials showed sky-blue emissions with high internal quantum efficiencies. Based on photophysical investigations the most promising molecule (6a) has been selected and high efficiency OLEDs with external quantum efficiency at very low current efficiency (similar to 1 mA/cm(2)) reaching 5% (doped) were obtained.
Investigation of Tadf Properties of Novel Donor-Acceptor Type Pyrazine Derivatives
(Soc Chilena Quimica, 2019) Irak, Zeynep Turhan; Gumus, Aysegul; Gumus, Selcuk
In this study 2,3-dicyanopyrazine based acceptor was combined with donors to obtain Donor-Acceptor type potential thermally activated delayed fluorescence (TADF) emitters (1-10). All molecules' structural and electronic properties were computed theoretically at the level of Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT) with the application of three different hybrid functionals. Most of the designed structures have been found to possess the potential to be TADF compounds because they have very narrow energy gap between their first excited singlet and triplet states. As a result, 6-10 molecular pyrazine derivative has been calculated as the best candidate for the purpose. Moreover, having 0.90 eV interfrontier molecular orbital energy band gap, compound 6 has a very strong potential to serve as an efficient OLED material.
Investigation of the Aromaticity of Mono, Di, Tri and Tetraazaphenanthrene Derivatives
(Walter de Gruyter Gmbh, 2020) Ozturk, Erhan; Irak, Zeynep Turhan; Karakoyun, Necdet; Gumus, Aysegul; Gumus, Selcuk
In this chapter mono, di, tri and tetraaza substituted phenanthrene derivatives have been investigated computationally with B3LYP/6-31 + G(d,p) level of theory. Substitution of carbon atom of the main structure with nitrogen obviously disturbs the aromaticity, indeed it decreases it. Thus, the idea of regaining of the aromaticity back by using electron withdrawing groups came across. As a result of the computational calculations, energetically most unfavored structures have been found to be those where aza substitutiona are vicinal. Secondly, the aromaticities of the present species depend on the position of the centric substituent. In addition, the effect position of the side substituent has been considered. The system becomes more aromatic (possess greater negative NICS values or smaller HOMA value) when the electron withdrawing atoms or groups are adjacent to the centrically substituted heteroatoms.
Isomeric Structures of Furoxan-Fused [2,2]paracyclophane-A Dft Study
(Taylor & Francis Ltd, 2012) Turker, Lemi; Gumus, Selcuk
The present study theoretically deals with furoxan-fused [2,2]paracyclophane systems and some structures possibly involved in their isomerization processes. These intermediate structures are certain di- and tetra-nitroso derivatives and systems having dioxadiazatidine ring(s). Computationally, B3LYP/6-31G(d,p) level of density functional theory has been employed. Certain properties of the systems, such as geometries, energies, and aromaticity of the benzenoid rings, are harvested and discussed.
Isoquinoline-Substituted Hybrid Compounds: Synthesis and Computational Studies
(Mdpi, 2016) Gumus, Aysegul; Gumus, Selcuk; Yenidede, Duygu
The one-pot synthesis of novel 1,4-disubstituted 1,2,3-triazoles from isoquinoline-substituted homopropargyl alcohol backbone is described (42-88% yields). A ring closing metathesis (RCM) reaction and an intramolecular Pauson-Khand reaction (PKR) of enyne system derived from a homopropargyl alcohol backbone to afford the corresponding isoquinoline-substituted dihydropyran and cyclopentenone-pyran, respectively, are also described (54% and 78% yields). Information about the structural, electronic and physico-chemical properties of the novel compounds, obtained by density functional theory application, is also reported.
Isoquinoline-Substituted Triazole and Pyran Derivatives: Synthesis and Computational Studies
(Tubitak Scientific & Technological Research Council Turkey, 2016) Yenidede, Duygu; Gumus, Selcuk; Gumus, Aysegul
The one-pot synthesis of novel 1,4-disubstituted 1,2,3-triazoles from isoquinoline-substituted homopropargyl alcohol backbone is described (42%-88% yields). A ring closing metathesis reaction and an intramolecular Pauson-Khand reaction of enyne system derived from a homopropargyl alcohol backbone to afford the corresponding isoquinoline-substituted dihydropyran and cyclopentenone-pyran, respectively, are also described (54% and 78% yields). Information about the structural, electronic, and physico-chemical properties of the novel compounds, obtained by density functional theory application, is also reported.
Metallo and Metal Free Phthalocyanines Bearing (4-(1(4 Substituents: Synthesis, Characterization, Aggregation Behavior, Electronic, Antioxidant and Antibacterial Properties
(Elsevier Science Sa, 2014) Agirtas, M. Salih; Guven, M. Emin; Gumus, Selcuk; Ozdemir, Sadin; Dundar, Abdurrahman
As starting material the phthalonitrile derivative bearing (4-(1(4-phenoxyphenyl)-1-phenylethyl)phenol substituents at peripheral position was prepared by a nucleophilic displacement reaction. Cyclotetramerization of 4-(4-(1-(4-hydroxyyphenyl)-1-phenylethyl)phenoxy)phthalonitrile derivative in the presence of corresponding metal salts gave the new metallophthalocyanines. Metal free phthalocyanine was obtained from the reaction of 4-(4-(1-(4-hydroxyyphenyl)-1-phenylethyl)phenoxy)phthalonitrile units. The novel compounds have been characterized by using various spectroscopic data. The aggregation investigations carried out in different concentrations indicate that 4-(4-(1-(4-hydroxyyphenyl)-1-phenylethyl)phenoxy)phthalocyanine compounds do not have any aggregation behavior for the concentration range of 10(-4)-10(-5) M in tetrahydrofuran. The antioxidant activities of novel compounds were analyzed through radical scavenging ability of 1,1-dipheny1-2-picrylhydrazyl, chelating ability to ferrous ions and reducing power. In addition to these, the antibacterial activities of compounds were investigated. Moreover, the ground-state geometries of the complexes were optimized using B3LYP/6-31G(d,p) level of density functional theory in order to predict the three-dimensional geometries and electronic structure. (C) 2014 Elsevier B.V. All rights reserved.
Metallo Phthalocyanines Bearing 2-Isopropyl Substituents: Synthesis, Characterization, Aggregation Behavior, Antioxidant and Antibacterial Activity, and Electronic Properties
(Wiley-v C H verlag Gmbh, 2014) Agirtas, M. Salih; Dede, Emrah; Gumus, Selcuk; Dundar, Abdurrahman; Okumus, Veysi
A novel phthalonitrile derivative bearing 2-isopropyl-6-methylpyrimidin-4-yloxy substituents at peripheral positions was synthesized by a nucleophilic substitution reaction. Metallophthalocyanines were obtained from the reaction of the novel phthalonitrile with metal Zn, Cu, Co, and Ni salts. The characterization of the compounds was performed using elemental analysis as well as UV/Vis, FT-IR, and H-1-NMR spectroscopy. The aggregation behaviors of phthalocyanine complexes were also investigated. These metallophthalocyanines do not show any aggregation behavior between 10 (4)-10 (6) M concentration range in THF. The antioxidant activities of the synthesized compounds were evaluated using three different tests: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, metal chelating activity, and reducing power assays. All the compounds exhibited various antioxidant activities. In addition, antimicrobial activity of the compounds was tested over four gram positive and two gram negative bacteria. Moreover, the ground-state geometries of the complexes were optimized using density functional theory (DFT) methods at B3LYP/6-31G(d,p) level in order to obtain information about the 3D arrangements and electronic structure.