https://hdl.handle.net/20.500.12619/1050 Mon, 13 Apr 2026 14:48:25 GMT 2026-04-13T14:48:25Z https://hdl.handle.net/20.500.12619/32379 Phosphorus-nitrogen compounds. 14. Synthesis, stereogenism, and structural investigations of novel N/O spirocyclic phosphazene derivatives Delibaş, Nagihan The reactions of hexachlorocyclotriphosphazatriene, N3P3Cl6, with N/O donor-type N-alkyl-o-hydroxybenzyl- and o-hydroxynaphthylamines result in novel mono-(3a, 4a and 4b), di- (5a and 5b), and tri- (3b, 6a, and 6b) spirocyclic phosphazene derivatives. The tetrakis-pyrrolidinophosphazene, 3b, has been obtained from the reaction of partly substituted compound 3a with the excess pyrrolidine in tetrahydrofuran. The relationship between the endocyclic NPN (alpha) and exocyclic NPO (alpha') bond angles of the analogous spirocyclic phosphazenes with the delta P shifts of NPO phosphorus atoms have been presented. It was observed that there is a linearity between alpha angles and delta P shifts, while no linear relationship has been observed for alpha' angles. In addition, we have found the correlation between Delta(P-N) and delta(NPO) shifts, which implies a linear relationship. Delta(P-N) = (a-b), where a and b are the average lengths of two adjacent P-N bonds. The structural investigations of all of the compounds have been made by elemental analyses; mass spectrometry; Fourier transform infrared spectroscopy; one-dimensional H-1, C-13, and P-31 NMR; distortionless enhancement by polarization transfer; and two-dimensional correlation spectroscopy, heteronuclear shift correlation, and heteronuclear multiple-bond correlation homo- and heteronuclear correlation techniques. The solid-state structures of 3a, 4a, 4b, and 5a have been determined by X-ray crystallographic techniques. The asymmetric units of compounds 3a and 4a contain two independent molecules, and 3a has strong intermolecular N-H center dot center dot center dot N hydrogen bonds linking three phosphazene rings. The molecular structure of 6a looks like a propeller where the chemical environment of P1 is different from that of P2 and P3. On the other hand, compounds 5a and 5b are expected to exist as cis- or trans-geometric isomers and to be in cis (meso) or trans (racemic) configurations. The crystallographic and preliminary chiral solvating agents results show that both of them are trans (racemic). In addition, 6a and 6b are also expected to exist as cis-trans-trans- and cis-cis-cis-geometric isomers; both of them are found to be in cis-trans-trans geometries. According to the two-dimensional spectroscopic data, the possible conformations of 3a and 4a in CDCl3 are the same with the solid-state structures. Mon, 01 Jan 2007 00:00:00 GMT https://hdl.handle.net/20.500.12619/32379 2007-01-01T00:00:00Z https://hdl.handle.net/20.500.12619/32377 Theoretical studies of electronic states and phonon modes on the TiC(001)(1 x 1) surface Tütüncü, Hüseyin Murat We present a comprehensive picture of structural and electronic properties of the TiC(001)(1 x 1) surface. Our investigations are based on first-principles calculations within the local-density approximation of the density-functional theory. Good agreement has been observed between our calculation and experimental data for the atomic geometry of the surface. In particular, the calculated bond lengths between the first-layer C and the second-layer Ti (d(1C)-(2Ti) = 2.188 angstrom) and between the first-layer Ti and the second-layer C (d(1Ti-2C) = 2.031 angstrom) are in good agreement with the corresponding experimental values of 2.25 angstrom and 2.14 angstrom, respectively. We have also identified surface electronic states and provided clear support for previously available photoemission measurements. We have further calculated surface phonon modes at the zone centre and at the zone-edge point X using a linear response scheme based on the ab initio pseudopotential method. Our calculated surface phonon results are in excellent agreement with electron energy loss spectroscopy results. (C) 2007 Elsevier B.V. All rights reserved. Mon, 01 Jan 2007 00:00:00 GMT https://hdl.handle.net/20.500.12619/32377 2007-01-01T00:00:00Z https://hdl.handle.net/20.500.12619/32378 Ab initio calculations of structural, electronic and dynamical properties of BeSe(110) surface Bağcı, Sadık; Tütüncü, Hüseyin Murat We use an ab initio pseudopotential method within the local-density approximation to determine the structural and electronic properties of the BeSe(1 1 0) surface. The relaxed geometry of this surface shows tilted cation-anion chains, with the anions being raised. The general pattern of the electronic structure of this surface is similar to that on other II-VI(1 1 0) surfaces. The phonon spectrum and corresponding surface density of states are also calculated using a linear response approach based on the density functional perturbation theory. In our calculations, we have found two localized phonon modes in the acoustic-optical gap region. The atomic displacement patterns of these surface phonon modes are presented and discussed. (C) 2007 Elsevier B.V. All rights reserved. Mon, 01 Jan 2007 00:00:00 GMT https://hdl.handle.net/20.500.12619/32378 2007-01-01T00:00:00Z https://hdl.handle.net/20.500.12619/32375 Diaquabis(N,N-diethylnicotinamide-kappa N)-bis(4-fluorobenzoato-kappa O)zinc(II) Delibaş, Nagihan The title compound, [Co(C7H4FO2)2(C6H6N2O)2(H2O)2], is a three-dimensional hydrogen-bonded supra­molecular com­plex. The CoII ion resides on a centre of symmetry and is in an octa­hedral coordination environment comprising two pyridyl N atoms, two carboxyl­ate O atoms and two O atoms from water mol­ecules. Inter­molecular N-H...O and O-H...O hydrogen bonds produce R32(6), R22(12) and R22(16) rings, which lead to two-dimensional chains. An extensive three-dimensional network of C-H...F, N-H...O and O-H...O hydrogen bonds and [pi]-[pi] inter­actions are responsible for crystal stabilization. Mon, 01 Jan 2007 00:00:00 GMT https://hdl.handle.net/20.500.12619/32375 2007-01-01T00:00:00Z