Benzopiran kumarinleri doğal bitkilerden sentezlenen ve pek çok özellik gösteren önemli bileşiklerdir. Bu moleküller, kromofor özelliklerinden dolayı en çok boya kimyasında kullanılmaktadırlar. Kuvvetli oksijen köprüleri içeren bu makro halkalı bileşikler, alkali ve toprak alkali metaller ile (+) yüklü kompleksler oluşturmaktadırlar. Pedersen, yüksek seçiciliği olan taç eter moleküllerin keşfi ve kullanımı ile ilgili olarak yaptığı çalışmalardan ötürü 1987 Nobel Kimya ödülünü almıştır. Kumarin türevlerinin optik özellikleri ile makro halkalı taç eterlerin katyon bağlama özelliklerini bir araya getirerek uygulama alanlarını genişletmek üzere Tiftikçi ve Erk tarafından bir seri molekül sentezlenmiştir (Tiftikçi ve Erk,2004). Literatüre son yıllarda kazandırılan bu moleküllerin elektronik ve optik özelliklerinin bilinmesi daha sonra yapılacak olan sentezlere de ışık tutacaktır. Bu özelliklerin teorik yöntemlerle anlaşılmasına yönelik yapılan bu çalışmada ayrıca kumarin halkasının makro halkaya bağlanma pozisyonuna, kumarin halkası üzerindeki sübstitüsyona, makro halka büyüklüğüne ve katyonun büyüklüğüne bağlı olarak moleküllerin UV soğurma spektrumlarındaki ve katyon bağlama enerjilerindeki değişiklikler de incelenmiştir. Bağlanma enerjileri ya da moleküllerin iyon seçiciliği Li+, Na+, ve K+ iyonları için Yoğunluk Fonksiyoneli Teorisi (YFT) yöntemiyle B3LYP/6-31g(d) seviyesinde gaz fazında, su ve asetonitril için ortamın dielektrik sabiti değiştirilerek çözücü ortamında hesaplanmıştır. Elde edilen sonuçlar mevcut olan deneysel sonuçlarla karşılaştırılmıştır. Katyonlu ve katyonsuz moleküllerin 0 Kelvin’deki gaz fazı ve çözücüye göre düzeltilmiş elektronik enerjileri, sıfır enerjisi göz önüne alınarak hesaplanmıştır. Katyon bağlama reaksiyonunun entalpisi ve serbest enerjisi ise baz fonksiyonundan gelen hatalara göre düzeltilerek rapor edilmiştir. Bağlanma enerjilerinin daha yüksek bazda tekrarlanan hesaplarla baz fonksiyonuna bağlı olarak nasıl değiştiği incelenmiştir. Anahtar Kelimeler: Kumarin, Taç Eterler, DFT, BSSE.The coumarins of benzopyran are important compounds which are synthesized from natural plants and have a good number of features. These molecules are mostly used at dye chemistry-because of their chromophoric features. Macrocyclic ether molecules which are known as good cation binding compounds, are first discovered in 1967 by Charles J. Pedersen who won 1/3 of the Chemistry Nobel Prize for the development and use of molecules with structure-specific interactions of high selectivity These molecules contain strong oxygen bridges and have a tendency to form positively charged complexes with alkaline and soil alkaline metals in solution. Being aware of the electronic and optical features of these molecules, which have been shown recent literatures, will illuminate the forthcoming syntheses. To bring optical features of the coumarin derivatives and the cation binding features of macrocyclic crown ethers together, a series of new molecules are synthesized by Tiftikçi and Erk to expand the application areas of both type of molecules (Tiftikçi; Erk, 2004). In this study which is done to understand these features with theoretical methods, the binding position of the coumarin to the macrocyclic, the substitution on the coumarin, the magnitude of macrocyclic and according to the magnitude of the cation, the changes on the UV absorption spectrums of molecules and the cation binding energy are also analyzed. The energy of binding or the ion selectivity of the molecules are calculated with the following methods; for Li+, Na+, ve K+ ions with the method of DFT (Density Functional Theory) at the B3LYP/6-31g(d) level at gas phase, for water and asetonitril, by changing the constant dielectric at the solvent medium. The outcomes which are yield are compared with the existing experimental outcomes. The gas phase at the 0 Kelvin of the molecules with and without cations and their corrected electronic energy according to the solvent are calculated by regarding the zero energy. Also, the enthalpies and free energy of the cation binding reaction are reported by correcting according to the errors coming from the base function (BSSE). Depending on the base function, how the binding energies change with repeated calculations at a higher base is examined. In this study cationic recognition of the computerized form of crown ethers, which were synthesized before, has been investigated. For that reason optimization of the molecules has been carried out. Geometries of the studied molecules optimized using Density Functional Theory method (Devlin vd, 1994,1996) B3LYP (Becke 3 Parameter Lee-Yang-Parr) functional (Lee vd, 1998), and 6-31g(d) bases functional. Using optimized molecules with Time Dependent Density Functional Theory methods Exited states were optimized. Using exited states values which were computed by TDDFT method, UV graphics drawn with a computer software written in Fortran. The attained values are normalized to 1 and graphs are plotted according to wave lengths. UV spectra peaks are analyzed to find source and reasons of the peak it could happen is investigated (Erk vd., 1998). To investigate interactions with Na+ cation, BSSE correlation energy method used for calculation of reaction energies. To investigate effect of solvent water and asetonitril used as solvent. Reaction energies of water and asetonitril were also calculated. Attained results are compared with the experimental results. To confirm optimized geometries, experimental X-ray results of 18crown6 Na+ molecules compared with results of the study. There is a concordant between experimental X-Ray data and theoretical optimized geometry. So the method applied in this study has been chosen correctly for those molecules?. For studies carried out in asetonitril, when UV peaks are compared with experimental data, it has been understood that there is accommodation between them. With comparing experimental and theoretical data It has been tried to proof the correctness of the applied methods. These evidences could be used in further studies as basis. The UV absorption is shifted to visible region when coumarin ring is added to alone crown ethers. For that reason the optical properties of crown ethers can be investigated. Moreover if coumarin rings are added to aromatic groups like phenyl, the maximum UV peaks are shifted to red region. If more functional groups are added to the crown ether ring, the cation binding energy of the crown ether will decrease. For that reason cation binding also decreases. Keywords: Coumarin, Crown Ethers, DFT, COMPASS, BSSE
