Papers by Athanassios Chrissanthopoulos
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The Journal of Physical Chemistry B, 2020
We report an investigation of the optical properties, structure and vibrational modes of Sb x As ... more We report an investigation of the optical properties, structure and vibrational modes of Sb x As 37-x S 48 I 15 glasses (0 at.% < x < 37 at.%). Optical parameters such as the refractive index, the absorption coefficient, and the optical band gap are correlated to the glass composition. All parameters were found to follow an almost linear dependence with the antimony content x. Both the refractive index and the absorption edge wavelength exhibit systematic increase against x. Off-resonant Raman of the glasses spectra were measured and analyzed. Structural units, representative of the glass structure, were optimized by DFT calculations providing vibrational spectra in agreement with experiments. Raman spectra were interpreted based on the harmonic frequencies and the activities of vibrational modes obtained by the DFT analysis. The results showed evidence in favor of a statistical mixing of the Iodine atoms, among the various pyramidal units; hence discarding structural models suggesting the presence of isolated pyramidal molecules of the types AsI 3 / SbI 3. Both experimental data and DFT results suggested that Iodine atoms exhibit much higher propensity to replace sulfur atoms in antimony than in arsenic-based pyramids. In addition, comparison of experimental and simulated spectra of selected clusters in mixed glasses indicate that it is more probable to find corner-sharing Sb-based pyramids than As-based ones.
Journal of Biotechnology & Biomaterials, 2015
The material of Intracorneal Rings Segments (ICRS) has seemed to be polymerized after the absorpt... more The material of Intracorneal Rings Segments (ICRS) has seemed to be polymerized after the absorption of Riboflavin and UV illumination in laboratory settings. This study aimed to assess the potential impact of in-vivo corneal crosslinking (CXL) on the chemical composition of ICRS. Within this contex, three ICRS samples (S1, S2 and S3) were extracted from patients' cornea, which formerly had undergone CXL treatment. Alterations on the chemical structure of PMMA rings were studied using Ultraviolet-Visible (UV-Vis) spectroscopy and Fourier Transform-Infrared (FT-IR) spectroscopy. An extracted ICRS from a patient who didn't underwent CXL treatment, was also used as reference (S0). UV-Vis spectroscopy didn't identify any change in the specimens S1, S2 and S3. Nevertheless, FT-IR spectroscopic analysis showed alterations in the spectra of ICRS material of samples S1, S2 and S3, mainly at the 2800 to 3200 cm-1 spectral region [modification in band intensities of CH 2 (2850 cm-1 and 2925 cm-1) and CH 3 (2950cm-1)]. In conclusion, our results suggest crosslinking reaction in ICRS material after in-vivo CXL treatment. This should be taken into consideration prior to any CXL treatment of post ICRS implanted cornea.
International Conference of Computational Methods in Sciences and Engineering 2004 (ICCMSE 2004), 2019
Chemical Communications
In this study, a simple, fast, one-pot approach for the isolation of Nanowires (NWs) in coordinat... more In this study, a simple, fast, one-pot approach for the isolation of Nanowires (NWs) in coordination chemistry is reported. Molecular compounds exhibiting the spin-crossover (SCO) behavior are motivating materials for...
The structure of the glass forming system (V20 5)x-(Na20 • P205)(1_^), (jc = 0-0.4), has been inv... more The structure of the glass forming system (V20 5)x-(Na20 • P205)(1_^), (jc = 0-0.4), has been inves tigated using Raman spectroscopy. The stretching vibrations of various phosphate groups, connected to phosphorus or vanadium atoms, have been assigned. Variation o f the composition leads to structural changes where the sodium metaphosphate-P-O-P-chains break and then reconnect with the oxovanadium units forming a-V-O-P-network structure.
Journal of Crystal Growth, 2002
Abstract The kinetics of calcium carbonate hexahydrate crystallization on polymer containing CN... more Abstract The kinetics of calcium carbonate hexahydrate crystallization on polymer containing CN, functional group was investigated by he constant composition method. The presence of the above-mentioned functional group stabilize this calcium carbonate polymorph at room temperature which transforms slowly to vaterite. The apparent order for the crystallization process was found to be 4±0.3 indicative of a surface nucleation mechanism. The number of ions forming the critical nucleus was found to be p =5. This value was confirmed by quantum mechanical calculations. The surface energy of the growing phase was 33 mJ m −2 . The formation of hexahydrate initiated through the interaction of Ca 2+ ions with the negative end of the CN bond.
Journal of Crystal Growth, 2003
Abstract The kinetics of hydroxyapatite (HAP) crystallization on polymers containing –C≡N functio... more Abstract The kinetics of hydroxyapatite (HAP) crystallization on polymers containing –C≡N functional group was investigated by the constant composition technique. The apparent order for the crystallization process was found to be 2 indicative of a surface diffusion control mechanism. Critical nucleus formation was confirmed by computational chemistry calculations using the PM3 method in the version 6.0 of MOPAC program package. The surface energy of the growing phase was 109 mJ m −2 . The HAP formation initiated through the interaction of Ca 2+ ions with the negative end of the –C≡N bond.
Vibrational Spectroscopy, 2008
Bioinorganic chemistry and applications, 2017
In this work we present a structural and spectroscopic analysis of a copper(II) N-acetyl-5-arylid... more In this work we present a structural and spectroscopic analysis of a copper(II) N-acetyl-5-arylidene tetramic acid by using both experimental and computational techniques. The crystal structure of the Cu(II) complex was determined by single crystal X-ray diffraction and shows that the copper ion lies on a centre of symmetry, with each ligand ion coordinated to two copper ions, forming a 2D sheet. Moreover, the EPR spectroscopic properties of the Cu(II) tetramic acid complex were also explored and discussed. Finally, a computational approach was performed in order to obtain a detailed and precise insight of product structures and properties. It is hoped that this study can enrich the field of functional supramolecular systems, giving place to the formation of coordination-driven self-assembly architectures.
Vibrational Spectroscopy, 2008
Bioorganic Chemistry, 2016
Two new series of nortopsentin analogues, in which the imidazole ring of the natural product was ... more Two new series of nortopsentin analogues, in which the imidazole ring of the natural product was replaced by thiazole and indole units were both substituted by 7-azaindole moieties or one indole unit was replaced by a 6-azaindole portion, were efficiently synthesized. Compounds belonging to both series inhibited the growth of HCT-116 colorectal cancer cells at low micromolar concentrations, whereas they did not affect the viability of normal-like intestinal cells. A compound of the former series induced apoptosis, evident as externalization of plasma membrane phosphatidylserine (PS), and changes of mitochondrial trans-membrane potential, while blocking the cell cycle in G2/M phase. In contrast, a derivative of the latter series elicited distinct responses in accordance with the dose. Thus, low concentrations (GI30) induced morphological changes characteristic of autophagic death with massive formation of cytoplasmic acid vacuoles without apparent loss of nuclear material, and with arrest of cell cycle at the G1 phase, whereas higher concentrations (GI70) induced apoptosis with arrest of cell cycle at the G1 phase.
Journal of Molecular Structure, 2007
Electronic absorption spectroscopy is used in the temperature range 850-1300 K, to study the vapo... more Electronic absorption spectroscopy is used in the temperature range 850-1300 K, to study the vapor species over molten HoI 3-CsI (1:1), molten CsI and solid HoI 3. Quantitative absorbance measurements are used to calculate the following enthalpies of transition: Δ Hsubl(HoI 3) = 271 ± 3 kJ mol -1, Δ Hvap. (CsHoI 4) = 155 ± 2 kJ mol -1 and Δ Hvap. (CsI) = 151 ± 2 kJ mol -1. The ligand field components of the 5G 6 ← 5I 8 hypersensitive transition of Ho(III) for the three different, all iodide, coordination geometries of HoI 3(g), CsHoI 4(g) and HoI 63- (in molten CsI) have been examined in detail. The molar absorptivities ( ɛ) and oscillator strengths ( f) increase as the coordination decreases from the "octahedral" HoI 63- ( ɛ = 65 L mol -1 cm -1; f = 99 × 10 -6) to the distorted tetrahedral HoI 4- ( ɛ = 235 L mol -1 cm -1; f = 290 × 10 -6) to the trigonal HoI 3 ( ɛ = 390 L mol -1 cm -1; f = 500 × 10 -6). The main factors affecting the hypersensitive transition intensities are the coordination number and symmetry and the ligand polarizability as well as the Boltzmann population effects on the ground state levels which are responsible for the appearance of "hot" bands in the spectra. A C2v symmetry is anticipated for the CsHoI 4(g) with the HoI 4- "tetrahedra" distorted towards a square planar symmetry leading to a structure with a pseudo-like inversion center.
Vibrational Spectroscopy, Sep 1, 2008
In this work we report on a vibrational spectroscopic study on the structural aspects of the bina... more In this work we report on a vibrational spectroscopic study on the structural aspects of the binary xCaOÁ(100 À x)SiO 2 , xMgOÁ(100 À x)SiO 2 and ternary xCaOÁyMgO (100 À x À y)SiO 2 systems for various x values up to 50%. Raman and IR spectroscopies have revealed the degradation of the silica network with the addition of the oxide modifiers. The main differences in the spectra of the alkaline earth modified sol-gel glasses are located in the region 900-1200 cm À1 where vibrations of SiO 4 tetrahedra with a variable number of non-bridging oxygen atoms are located. A comparison between the structural modifications of bulk (melt-quenched) and porous glasses is also advanced revealing particular differences in the network modification of the two types of glasses. CaO is more drastic than MgO in depolymerizing silica's network and both of them cause more significant structure modifications in the sol-gel glasses. The depolymerization structural units offer the appropriate sites in the glass network that are responsible for the facilitation of Ca/Mg dissolution, which is an important step for bioactivity. Furthermore, to support the conclusions drawn from the experimental data, preliminary molecular structure simulations using semiempirical molecular orbital theory are also presented. #
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Papers by Athanassios Chrissanthopoulos