Browsing by Author "Turker, Lemi"

Now showing 1 - 8 of 8

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.
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.
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.
A Novel Molecular Descriptor, Tg Index, for Calculating the Detonation Properties of Explosives
(Natl inst Science Communication-niscair, 2011) Turker, Lemi; Gumus, Selcuk
A novel molecular descriptor index, viz., TG index, has been defined for modeling and estimation of detonation parameters of explosives. The index is simple to calculate, unique for each molecule and is applicable to the heteroatom containing species. The results of the correlation analyses of the TG index with the explosion data indicate that the TG index can be a very successful tool for prediction of the detonation parameters of explosives, within the limit of very small percent errors.
Substituent Effect on the Aromaticity of 1,3-Azole Systems
(de Gruyter Poland Sp Z O O, 2012) Gumus, Selcuk; Turker, Lemi
The effects of substituent type and position on the aromaticity of certain derivatives of oxazole, imidazole and thiazole have been theoretically investigated by using density functional theory at the levels of B3LYP/6-31G(d,p) and B3LYP/6-31++G(d,p) methods. The second heteroatom substitution decreases aromaticity of furan, pyrrole and thiophene. The decreased aromaticity is gained back to some extent by the substitution of strong electron withdrawing groups or atoms (NO2 and F). Nucleus-independent chemical shift (NICS) data have been considered to determine the aromaticity of the systems. The most effective substitution to enhance the aromaticity has been calculated to be at position 4. The variation of the bond lengths of the main skeleton supports the findings through NICS calculations. The frontier molecular orbital energies have also been reported to draw a general correlation between these energies and the aromaticity of the system.
Tg Index, Its Graphical Matrix Representation and Application on Polyenes
(Korean Chemical Soc, 2014) Gumus, Selcuk; Turker, Lemi
A novel topological index (TG Index) has been introduced. The graphical matrix representation of the TG index includes the use of directed subgraphs for the first time in graph theory literature. The application of the TG index on certain properties of polyenes yielded very well correlation data.
A Theoretical Study on Some (1,4)cyclophanes
(Taylor & Francis Ltd, 2009) Turker, Lemi; Gumus, Selcuk
(1, 4)cyclophanes having either two butadiene bridges, or a butadiene bridge and a cyclobutene ring or two cyclobutene rings at the bridge positions have been considered for restricted Hartree-Fock, MP2 and DFT (B3LYP/6-31G(d,p)) level type calculations. Various molecular orbital energies, thermodynamic properties, IR frequencies etc. have been obtained and discussed. Also NICS calculations for the phane decks have been performed.