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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Influence of soft segment structure, hydrogen bonding, and diisocyanate symmetry on morphology and properties of segmented thermoplastic polyurethanes and polyureas(Tubitak Scientific & Technological Research Council Turkey, 2023) Department of Chemistry; Yılgör, Emel; Yılgör, İskender; Department of Chemistry; College of SciencesA comprehensive review of the structure-morphology-property relations in segmented thermoplastic polyurethanes and polyureas (TPU) is provided. Special emphasis is given to the influence of the soft segment structure, polarity, and molecular weight, diisocyanate symmetry and the nature, extent, and strength of hydrogen bonding on the morphology and thermal and mechanical properties of TPUs. Experimental results obtained on composition-dependent TPU morphology and properties by various techniques were also compared by the morphology profiles generated by computational methods such as quantum mechanical calculations and molecular dynamics simulations.Publication Metadata only Exploration of novel 6,8,9-trisubstituted purine analogues: synthesis, in vitro biological evaluation, and their effect on human cancer cells(Tubitak Scientific & Technological Research Council Turkey, 2024) Polat, Muhammed Fatih; Atalay, Rengul; Tuncbilek, Meral; N/A; Şahin, İrem Durmaz; Koç University Research Center for Translational Medicine (KUTTAM); School of MedicineCancer, a leading global cause of mortality, demands continuous advancements in therapeutic strategies. This study focuses on the design and synthesis of a novel series of purine derivatives, specifically 6 -(substituted phenyl piperazine)-8-(4-phenoxyphenyl)9-cyclopentyl purine derivatives (5-11). The motivation behind this endeavor lies in addressing acquired resistance mechanisms in cancer cells, a significant hurdle in current treatment modalities. The synthesis, starting from 4,6-dichloro-5-nitropyrimidine, involves a multi -step process, resulting in seven new purine derivatives. Biological evaluation against human liver, colon, and breast cancer cells (Huh7, HCT116, and MCF7, respectively) was performed using the SRB assay. Among the synthesized analogs, compounds 5 and 6, exhibited notable cytotoxic activity, surpassing clinically used positive controls 5-Fluorouracil and Fludarabine in terms of efficacy. This research underscores the potential of purine derivatives with a phenyl group at the C-8 position as a scaffold for developing compounds with improved anticancer properties. The findings offer insights for future exploration and development of novel agents in cancer pharmaceutical research.Publication Metadata only Gas adsorption and diffusion in a highly CO2 selective metal-organic framework: molecular simulations(Taylor and Francis Ltd, 2013) N/A; Department of Chemical and Biological Engineering; Keskin, Seda; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 40548Grand canonical Monte Carlo and equilibrium molecular dynamics simulations were used to assess the performance of an rht-type metal–organic framework (MOF), Cu-TDPAT, in adsorption-based and membrane-based separation of CH4/H2, CO2/CH4 and CO2/H2 mixtures. Adsorption isotherms and self-diffusivities of pure gases and binary gas mixtures in Cu-TDPAT were computed using detailed molecular simulations. Several properties of Cu-TDPAT such as adsorption selectivity, working capacity, diffusion selectivity, gas permeability and permeation selectivity were computed and compared with well-known zeolites and MOFs. Results showed that Cu-TDPAT is a very promising adsorbent and membrane material especially for separation of CO2 and it can outperform traditional zeolites and MOFs such as DDR, MFI, CuBTC, IRMOF-1 in adsorption-based CO2/CH4 and CO2/H2 separations.Publication Metadata only FT-Raman, FT-IR and NMR spectra, vibrational assignments and density functional studies of 1,3-bis(benzimidazol-2-yl)-2-thiapropane ligand and its Zn(II) halide complexes(2008) Aghatabay, Naz Mohammed; Tulu, Metin; Yılmaz, Ayberk; Department of Chemistry; Department of Chemistry; Somer, Mehmet Suat; Haciu, Durata; Faculty Member; Teaching Faculty; Department of Chemistry; College of Sciences; College of Sciences; 178882; N/A1,3-bis(benzimidazol-2-yl)-2-thiapropane (L) ligand and its zinc halide ZnX2 (X = Cl, Br, I) complexes have been synthesized. The compounds were characterized using the elemental analysis, molar conductivity, FT-Raman, FT-IR (mid i.r., far i.r.), 1H and 13C NMR spectra, and quantum chemical calculations performed with Gaussian 03 package program set. The optimized geometries and vibrational frequencies of the ligand and [Zn(L)Cl2] complex were calculated using the DFT/B3LYP method with a 6–31g(d) basis set. The geometry optimization of [Zn(L)Cl2] yields a slightly distorted tetrahedral environment around Zn ion, while the molecule clearly reveals the Cs symmetry. The molar conductivity data reveals that the complexes are neutral. The ligand is bidentate, via two of the imine nitrogen atoms in the bis-imidazole ring units, and together with the monodentate coordination of the two halides to the metal centre.Publication Metadata only Quenching vibrations of cesium dimers by He at low and ultralow temperatures: quantum dynamical calculations(Springer, 2011) Caruso, D.; Tacconi, M.; Bovino, S.; Gianturco, F. A.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129This paper analyses in detail the energy redistribution from the upper vibrational levels of Cs dimers, thought to be obtained from initial recombination processes that generate excited internal states of the triplet configuration (3) I pound (u) (+) . Their quenching is examined as they are made to further collide with (4)He buffer gas at temperatures below and around 100 mK. The relevant cross sections are computed by using a multichannel quantum dynamical approach and employ a full, ab initio potential energy surface. Due to their smallness (see Ref. [R.B. Ross, J.M. Powers, T. Atashroo, W.C. Ermler, I.A. LaJohn, P. Christiansen, J. Chem. Phys. 93, 6654 (1999)]) the fine structure effects have not been explicitly included in this study. The final, cumulative cross-sections are discussed and analyzed in terms of the overall quenching behavior shown by different initial states of the dimer and in terms of the changing ratios between collisional cooling and vibrational quenching cross sections as a function of trap temperature. The corresponding quenching rates are also computed and analysed.Publication Metadata only Structuring a quantum solvent around a weakly bound dopant: the He-Cs2((3)sigma u) complex(2009) Prosmiti, Rita; Delgado-Barrio, Gerardo; Villarreal, Pablo; Coccia, Emanuele; Gianturco, Franco A.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129The structure and energetics of 3,4HeCs2(3Σu) molecules are analyzed from first principles. Fixing the cesium dimer at its equilibrium distance, the electronic structure was determined through ab initio methods at the CCSD(T) level of theory using a large basis set to compute the interaction energies. At the T-shaped geometry, there is a shallow well with a depth of ∼2 cm−1 placed at R ∼6.75 Å, R being the distance from the center of mass of Cs2 to He. That depth gradually decreases to ∼0.75 cm−1, while R increases to about 11.5 Å at linear arrangements. A simple model of adding atom−atom Lennard-Jones potentials with well-depth and equilibrium distance parameters depending on the angular orientation was found to accurately reproduce the ab initio points. Using this analytical form, variational calculations at zero total angular momentum are performed, predicting a single bound level at ∼−0.106 (∼−0.042) cm−1 for the boson (fermion) species. Further calculations using Quantum Monte Carlo methods are carried out and found to be in good agreement with the variational ones. On the basis of the present results, such analytical expression could in turn be used to describe the structure and binding of larger complexes and therefore opens the possibility to further studies involving such aggregates.Publication Metadata only Crystal structure of tetrasodium octaeuropium(ii) [octaphosphido(3-)]-bis[diphosphido(4-)]tetraaluminate(iii),NA 4EU8[AL4P8(P2) 2](Walter de Gruyter, 1998) Carrillo-Cabrera, W.; Peters, K.; Von Schnering, H.G.; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882N/APublication Metadata only A NIR-light-driven black phosphorus based nanocomposite for combating bacteria(Wiley-V C H Verlag Gmbh, 2022) Çekçekoğlu, İlknur Aksoy; Sevgi, Fatih; Ersöz, Mustafa; Patır, İmren Hatay; Department of Chemistry; N/A; Department of Chemistry; Eroğlu, Zafer; Küçükkeçeci, Hüseyin; Metin, Önder; Researcher; Researcher; Faculty Member; Department of Chemistry; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 46962Nanocomposites of semiconducting two-dimensional (2D) materials provide advantageous for combating bacterial infections to overcome antibiotic resistance. In this study, the nanocomposites of 2D black phoshorus (BP) and silver nanoparticles (NPs) were prepared by anchoring as-synthesized Ag NPs on few-layer BP nanosheets via liquid self-assembly method and used as a NIR-light-driven antibacterial agent against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and Gram-positive bacteria (Enterococcus faecalis and Bacillus cereus). The BP/Ag nanocomposites showed excellent photothermal effect and oxidative stress ability to inhibit the initial logarithmic growth phase of E. faecalis and B. cereus. According to the bacterial growth curve, agar plate assay and live/dead viability test, as-synthesized BP/Ag nanocomposites were found to be more effective antibacterial agent for Gram-positive bacteria than Gram-negative bacteria. The presented NIR-light-driven BP-based nanoplatform can open a new avenue for avoiding bacterial resistance and combating pathogenic bacteria and also broad-spectrum disinfection applications.Publication Metadata only Synthesis, crystal structure, and vibrational spectra of compounds with the linear dipnictidoborate (3-) anions [P-B-P]3-, [As-B-As]3- and [P-B-As]3-(Wiley-VCH Verlag, 2000) Carrillo-Cabrera, Wilder; Peters, Karl; Von Schnering, Hans Georg; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882The alkali metal boron compounds M3[BX2] with X = P, As are synthesized from the alkali metals M and the binary components MX or M4X6 and BX in sealed steel ampoules (phosphides) or niobium ampoules (arsenides) at 1000 K. The compounds are obtained as bright yellow prisms (M3[BP2]) or plates (K2Na[BP2]) and yellow-red prismatic crystals (M3[BAs2], Cs3[BPAs]) which are very sensitive against oxidation and hydrolysis. Three different structure types are formed, namely K2Na[BP2] (C2/m (No. 12); Z = 4; a new mC24 structure type); Na3[BP2] (P21/c (No. 14); Z = 4, β-Li3[BN2] type), M3[BX2] with M = K, Rb, Cs and X = P, As and Cs3[P-B-As] (C2/c, (No. 15); Z = 4, K3[BP2] type). The bond lengths of the linear [BX2]3- anions are hardly changed and correspond to a Pauling bond order PBO = 1.9 (d(B-P) = 176.7-177.1 pm; d(B-As) = 186.5-188.0 pm). The vibrational spectra confirm the existence of unmixed and mixed units [P-B-P]3-, [As-B-As]3- and [P-B-As]3- with D∞h and C∞v symmetry, respectively. The valence force constants f(B-X) and the corresponding Siebert bond orders, calculated from the frequencies, are discussed and compared with those of the isoelectronic anions and molecules.Publication Metadata only Surfactant-free synthesis of CdS nanorods for efficient reduction of carcinogenic Cr(VI)(Taylor and Francis Ltd, 2021) Butler, Ian S.; Rehman, Zia Ur; N/A; N/A; Department of Chemistry; Ullah, Haseeb; Balkan, Timuçin; Kaya, Sarp; Researcher; Other; Faculty Member; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); N/A; N/A; College of Sciences; N/A; N/A; 116541Hexavalent chromium, Cr(VI), is a toxic, mutagenic and carcinogenic species. We report here the semiconductor-based, photocatalytic reduction of Cr(VI) to trivalent chromium, Cr(III), using CdS nanorods (NRs) as the photocatalyst under visible light illumination. The CdS NRs were synthesized by a facile and scalable solvothermal method in which ethylenediamine acts as solvent and morphology controller. The CdS NRs produced were studied by PXRD, Raman, FESEM, EDX, XPS, PL, UV-visible DRS and BET techniques in order to investigate their structural, morphological and optical properties, as well as their porosity. The photoreduction of Cr(VI) to Cr(III) under visible light illumination was performed under a variety of conditions, i.e., varying the irradiation time, pH, substrate concentration, and the amount of photocatalyst. The maximum photoreduction of Cr(VI) to Cr(III) (99%) was achieved using 60 min of irradiation under acidic conditions (pH 4). The excellent photoreduction ability of the CdS NRs can be attributed to their rod-like structure together with their small particle size, large surface area, and clean surfaces. These properties enhanced separation of the photo-generated electron-hole pairs, which was confirmed by the XRD, BET, and PL measurements. In addition, the results of a kinetic study indicated that the photoreduction of Cr(VI) to Cr(III) follows a pseudo-first-order kinetic model. A possible mechanism for the photocatalytic reduction of Cr(VI) to Cr(III) is also proposed in this paper.