Browsing by Author "Keskin, Selbi"

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Exploring of Indole Derivatives for Esipt Emission: a New Esipt-Based Fluorescence Skeleton and Td-Dft Calculations
(Elsevier Science Sa, 2021) Kaya, Serdal; Aydin, Hatice Gulten; Keskin, Selbi; Ekmekci, Zeynep; Menges, Nurettin
ABS T R A C T Appropriate synthesis methods gave six different indole derivatives substituted at the C-2 or C-3 position. ESIPT emission capacities of these derivatives were investigated. It was concluded that the indole derivative containing the 1,2-dicarbonyl group at the C-2 position has ESIPT emission. Although adding water to the DMSO solution of the ESIPT-based molecule (9:1) resulted in ESIPT quenching, steady-state measurements in MeOH did not occur ESIPT quenching. TD-DFT calculation for uncovering the ESIPT mechanism emerged that the ESIPT mechanism occurred as a barrierless process. The X-ray analysis and DFT conformational analysis revealed that NH and CO groups involving proton transfer mechanisms are in the cis position. A mono-exponential decay was observed in DMSO and MeOH solutions, in which lifetimes were measured as 6.1 and 5.5 ns, respectively. pH studies revealed that acidic and basic solutions of molecule 7 did not influence ESIPT emission.
Synthesis of Pyrrole-Fused C,n-Cyclic Azomethine Imines and Pyrazolopyrrolopyrazines: Analysis of Their Aromaticity Using Nucleus-Independent Chemical Shifts Values
(Amer Chemical Soc, 2016) Ozer, Merve Sinem; Menges, Nurettin; Keskin, Selbi; Sahin, Ertan; Balci, Metin
The AgOTf-catalyzed reaction of C-2 substituted pyrrole hydrazones having an N-propargyl group was studied. The selective 6-endo-dig mode of cyclization was observed, giving rise to the formation of pyrrole-fused C,N-cyclic azomethine imine derivatives. The reaction of one azomethine imine derivative with various dipolarophiles resulted in the formation of cycloadducts having a pyrazolopyrrolopyrazine skeleton. The aromaticity of C,N-cyclic azomethine imines as well as that of pyrazolopyrrolopyrazines was determined by calculating of nucleus-independent chemical shifts values.