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Publication Metadata only A metal nitride carbodiimide with a stuffed skutterudite-type structure: synthesis, crystal structure and ir spectra of (BA6N 5/6)2[NBN4][CN2]6(Walter de Gruyter, 2007) Reckeweg, Olaf; Disalvo, Francis J.; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882Coppery-red, transparent single crystals of (Ba6N 5/6)2[NbN4][CN2]6 [NbN4] [CN2]6 (Im3̄, no. 204, a = 1125.83(3) pm, Z = 2) are obtained by the reaction of Ba2N and ZnCN2 with the container walls of the arc-welded Nb ampoules at 1100 K. The title compound assumes a stuffed skutterudite-type structure in which edge-sharing (Ba6N5/6) octahedra form large voids which are occupied by either [NbN4] tetrahedra or by [N=C=N]2- units with symmetric C=N bond lengths of d = 121.8(6) pm but a bond angle deviating significantly from linearity (∠(N-C-N) = 175.3(9)°). The IR spectra corroborate this crystallographic result by the fact that all fundamental vibrations are visible in the IR spectrum [v1 = 1262 (symmetric stretching mode); v2 = 1957/2009 (antisymmetric stretching mode); v3 = 611/633/653 cm-1 (bending modes)], which is symmetry forbidden for [N=C=N]2- units having D∞h symmetry but expected for the C2v symmetry found in the title compound.Publication Open Access Blue TiO2 nanotube arrays as semimetallic materials with enhanced photoelectrochemical activity towards water splitting(TÜBİTAK, 2020) Department of Chemistry; Peighambardoust, Naeimeh Sadat; Aydemir, Umut; Researcher; Faculty Member; Department of Chemistry; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); College of Sciences; N/A; 58403In the past years there has been a great interest in self-doped TiO2 nanotubes (blue TiO2 nanotubes) compared to undoped ones owing to their high carrier density and conductivity. In this study, blue TiO2 nanotubes are investigated as photoanode materials for photoelectrochemical water splitting. Blue TiO2 nanotubes were fabricated with enhanced photoresponse behavior through electrochemical cathodic polarization on undoped and annealed TiO2 nanotubes. The annealing temperature of undoped TiO2 nanotubes was tuned before cathodic polarization, revealing that annealing at 500 degrees C improved the photoresponse of the nanotubes significantly. Further optimization of the blue TiO2 nanotubes was achieved by adjusting the cathodic polarization parameters. Blue TiO2 nanotubes obtained at the potential of -1.4 V (vs. SCE) with a duration of 10 min exhibited twice more photocurrent response (0.39 mA cm(-2)) compared to the undoped TiO(2 )nanotube arrays (0.19 mA cm(-2)). Oxygen vacancies formed through the cathodic polarization decreased charge recombination and enhanced charge transfer rate; therefore, a high photoelectrochemical activity under visible light irradiation could be achieved.Publication Metadata only Ca-2[BN2]H: The first nitridoborate hydride - synthesis, crystal structure, and vibrational spectra(Wiley, 2004) Reckeweg, Olaf; Protsc,Yurii; Carrillo-Cabrera, Wilder; Department of Chemistry; Department of Chemistry; Somer, Mehmet Suat; Yaren, Özlem; Faculty Member; Undergraduate Student; Department of Chemistry; College of Sciences; College of Sciences; 178882; N/ACa-2[BN2]H was synthesized from a mixture of the binary components Ca3N2, CaH2 and BN (molar ratio 1 : 1 : 2) in a sealed steel ampoule encapsulated in an evacuated silica tube at 1273 K. Ca-2[BN2]H crystallizes in the orthorhombic space group Pnma (no. 62) with a = 9.2015(8) Angstrom, b = 3.6676(2) Angstrom and c = 9.9874(12) Angstrom (Z = 4; Pearson symbol oP24). The crystal structure is a filled variant of the Co2P type and can be formulated as Co2P(square(t))(3)(square(py))(3) drop Ca-2[N-B-N]H(square(t))(2)(square(py))(3) (square(t) and square(py) = tetrahedral and square-pyramidal hole, respectively). The d(B-N) bond lengths and bond angle for the linear [N-B-N](3-) anion are: d(B-N1) = 1.324(3) Angstrom, d(B-N2) = 1.350(2) Angstrom and angleN-B-N = 177.2(2)degrees. The vibrational spectra of Ca-2[BN2]H confirm the presence of [N-B-N](3-) groups deviating only slightly from the ideal D-infinityh symmetry. The vibrational frequencies and the f(B-N) force constants are discussed and compared with those of the isotypic compound Ca-2[BN2]F.Publication Open Access CO2 absorption into primary and secondary amine aqueous solutions with and without copper ions in a bubble column(TÜBİTAK, 2022) Güler, Cansu; Uzunlar, Erdal; Department of Chemical and Biological Engineering; Erkey, Can; Yousefzadeh, Hamed; Faculty Member; Researcher; Department of Chemical and Biological Engineering; College of Engineering; 29633; N/AChemical absorption of CO2 into aqueous amine solutions using a nonstirred bubble column was experimentally investigated. The performance of CO2 absorption of four different primary and secondary amines including monoethanolamine (MEA), piperazine (PZ), 2-piperidineethanol (2PE), and homopiperazine (HPZ) were compared. The effects of initial concentration of amine, the inlet mole fraction of CO2, and solution temperature on the rate of CO2 absorption and CO2 loading (mol CO2/mol amine) were studied in the range of 0.02–1 M, 0.10–0.15, and 25–40 °C, respectively. The effect of the presence of copper ions in the amine solution on CO2 loading was also studied. By comparison of the breakthrough curves of the amines at different operational conditions, it was revealed that the shortest and longest time for the appearance of the breakthrough point was observed for MEA and HPZ solutions, respectively. CO2 loading of MEA, 2PE, PZ, and HPZ aqueous solutions at 25 °C, 0.2 M of initial concentration of amine, and 0.15 of inlet mole fraction of CO2 were 1.06, 1.14, 1.13, and 1.18 mol CO2/mol amine, respectively. By decreasing the inlet mole fraction of CO2 from 0.15 to 0.10, CO2 loading slightly decreased. As the initial concentration of amine and temperature decreased, CO2 loading increased. Also, the presence of copper ions in the absorbent solution resulted in a decrease in the CO2 loading of MEA and HPZ aqueous solutions. In case of PZ and 2PE amines, adding copper ions led to precipitation even at low copper ion concentrations.Publication Metadata only Comparative analysis of hypervascular microcystic serous cystadenoma with MRI and immunohisto-chemistry(Edizioni Luigi Pozzi, 2019) Erkan, Burcu; Doctor; Koç University HospitalPURPOSE: Cystic tumors of the pancreas are increasingly common lesions. Unlike mucinous cystic tumors, serous cystadenomas are benign lesions and do not pose a risk of cancer. Often seen in women in the 6th and 8th decades, they are rarely seen in younger women or in male patients. Serous cystadenomas do not require surgical treatment unless they produce symptoms due to compression. Sometimes they may be misdiagnosed as cystic neuroendocrine tumors and resec-ted because of the contrast enhancement on contrast enhanced cross-sectional studies. The purpose of this article is a translational analysis of why a cystic tumor enhances. MATERIAL and METHODS: The preoperative T2 HASTE, fat-suppressed T2 Turbo Spin Echo sequences, magnetic resonance cholangiopancreatography, diffusion weighted images, ex-vivo high-resolution T2 HASTE images of the post-ope-rative pathologic specimen and immunohistochemical analysis with vascular marker CD31 were compared in a 58-year-old male patient with a pancreatic corpus microcystic serous cystadenoma. RESULTS: The nodular lesion is observed as fluid signal in T2 weighted sequences and enhancing in postcontrast series. Ex-vivo high-resolution MRI has also revealed cysts with millimetric different sizes and septations within the lesion. Evaluation with the CD31 vascular marker showed that fibrous septa between the cysts were dense vascular and stained. CONCLUSION: We show here that microcystic serous cystadenomas have intense vascularity of their septations that enhance in cross-sectional studies, especially when the cyst diameter is smaller. © 2019, Edizioni Luigi Pozzi. All rights reserved.Publication Metadata only Competitive hydrogen bonding in aspirin-aspirin and aspirin-leucine interactions(Scientific Technical Research Council Turkey-Tubitak, 2012) Department of Chemistry; Department of Chemical and Biological Engineering; Department of Chemistry; Yurtsever, Zeynep; Erman, Burak; Yurtsever, İsmail Ersin; Undergraduate Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; College of Sciences; College of Engineering; College of Sciences; N/A; 179997; 7129Aspirin-aspirin and aspirin-leucine interactions are studied by the density functional theory (DFT) and high level ab initio calculations with second order Moller-Plesset perturbation theory (MP2). The rotational isomers of aspirin are identified by their relative stability both in gaseous phase and in water using the polarizable continuum method (PCM). Local minima of aspirin monomers in water are found to be all highly populated compared to the gas phase behavior. Homodimers of aspirin form hydrogen bonds with bond energies of 10 kcal/mol. Weak hydrogen bonds utilizing phenyl and methyl groups are also found. The interaction between aspirin and leucine is stronger with relatively short bond lengths compared to homodimeric aspirin interactions. The potential energy surface has several minima with comparable stability. This study shows the significance of diverse bonding schemes, which are important for understanding complete interaction mechanisms of aspirin.Publication Metadata only Crystal structure of bis[μ2-(3-benzimidazol-2-yl)-2- ethanethiolato-N,S,S-chloro-palladium(II)], [(C6H4N 2HCCH2CH2S)PdCl]2 · C 2H5OH(Walter de Gruyter GmbH, 2005) Agh-Atabay, N.M.; Borrmann, H.; 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/AC20H24Cl2N4OPd 2S2, triclinic, P1̄ (no. 2), a = 8.796(1) Å, b = 9.844(1) Ä, c = 14.718(2) Ä, α = 94.330(6)°, β = 98.546(6)°, γ = 99.258(7)°, V = 1237.3 Å3, Z = 2, Rgt(F) = 0.068, wRref(F2) = 0.142, T = 295 K.Publication Metadata only Crystal structure of bis[µ2-(3-benzimidazol-2-yl)-2-ethanethiolato-N,S,S)- chloro-palladium(II)], [(C6H4N2HCCH2CH2S)PdCl]2 C2H5OH(Walter de Gruyter GmbH, 2005) Agh-Atabay, N.M.; Borrmann, H.; 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/AC20H24Cl2N4OPd2S2, triclinic, P1 (no. 2), a = 8,796(1) Å, b = 9.844(1) Å, c = 14.718(2) A, α = 94.330(6)°, β = 98.546(6)°,γ = 99.258(7)°, V= 1237.3 Å3, Z= 2, Rgt(F) = 0.068, wRref(F2)= 0.142, T= 295 K.Publication Metadata only Crystal structure of diaqua(magnesium, cobalt) bis(hydroxyboro)bis- phosphate monohydrate, Mg1-xCox(H2O) 2[B2P2O8(OH)2] · H2O (x ≈ 0.25)(Walter de Gruyter GmbH, 2005) Ewald, B.; Prots, Y.; Kniep, R.; Department of Chemistry; Öztan, Yiğit; Undergraduate Student; Department of Chemistry; College of Sciences; N/AB2Co0.23H8Mg0.77O 13P2, monoclinic, P121/c1 (no. 14), a = 7.7591(5) Å, b = 14.654(1) Å, c = 8.2382(5) Å, β = 90.26(1) °, V = 936.7 Å3, Z = 4, Rgt(F) = 0.040, wRref(F2) = 0.098, T = 293 K.Publication Metadata only Crystal structure of diaqua(magnesium, cobalt) bis(hydroxyboro)bisphosphate monohydrate, Mg1-xCox(H2O)2[B2P2O8(OH)2] • H2O (x ≈ 0.25)(Walter de Gruyter GmbH, 2005) Ewald, B.; Prots, Y.; Kniep, R.; Department of Chemistry; Öztan, Yiğit; Undergraduate Student; Department of Chemistry; College of Sciences; N/AB2Co0.23H8Mg0.77O13P2, monoclinic, P121/cl (no. 14), a = 7.7591(5) Å, b = 14.654(1) Å, c = 8.2382(5) Å, β = 90.26(1)°, V = 936.7 Å3, Z = 4, Rgt(F) = 0.040, wRref(F2) = 0.098, T= 293 K. 2005, Oldenbourg Wissenschaftsverlag GmbH, Rosenheimer Str. 145, 81671 München.