Narrow Results

Two dimensional (2D) materials are widely attracting the interest of researchers due to their unique crystal structure and diverse properties. In the present work, tungsten disulfide (WS${}_2)$ nanorods were synthesized by a simple method of pulsed laser ablation in liquid (PLAL) environment. The prepared WS₂ are analyzed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and Raman spectroscopy to confirm the surface morphology, phase and structure. A possible growth mechanism of WS₂ is proposed. This study indicates new door for the preparation of 2D materials with specific morphology.

One-dimensional structures like nanotubes and nanowires are potential candidates for nanoscale sensors and actuators. Furthermore, the nanoscale cross-section of these elements introduces controllable size effects while the macroscopic length ensures good mechanical coupling to matrix materials and thus reinforcing effects in nanocomposites. Molecular dynamics simulations are employed to study the electronic and mechanical properties of smallest ZnO nanowires. It has been shown that the electronic band structure of nanowires varies with uniaxial strain and this property can be used for sensing deformation state when nanowires are embedded in a polymer matrix.

Silver nanoparticles (SNPs) have been successfully prepared using sol–gel method by annealing the sample at 550°C for 30 min. The SNPs were not confirmed by X-ray diffraction (XRD) analysis when the annealing temperature was considered at 450°C. They were also not confirmed without calcination of the sample. The physical mechanism of silver clusters formation in the densified silica matrix with respect to thermal treatment has been understood. The presence of silver metal in the silica matrix was confirmed by XRD analysis and TEM image of the samples. The average size of nanoparticles dispersed in silica matrix was determined as 10.2 nm by the XRD technique. The synthesized nanocomposites were also characterized by UV-Visible spectroscopy with a peak in the absorption spectra at around 375 nm. The distribution of particle size has been reported here in the range from 8 nm to 25 nm by TEM observations of the sample prepared at 550°C. The spherically smaller size (≈10 nm) SNPs have reported the surface plasmons resonance (SPR) peak less than or near to 400 nm due to blue-shifting and effect of local refractive index. Without annealing the silica samples the absorption spectra does not show any peak around 375 nm. The FTIR spectroscopy of the three types of samples prepared at different temperatures (room temperature, 450°C and 550°C) has also been reported. This spectra have provided the identification of different chemical groups in the prepared samples. It has been predicted that the size of SNPs by XRD, UV-Visible and TEM results have agreed well with each other. It may be concluded that formation of SNPs is a function of annealing temperature.

In the present work, a theoretical study of the geometrical structures and spectroscopic (IR, ¹H and ${}^{13}$C NMR, UV-visible) properties, and anti-cancer activity of cis-fused tetrahydrochromeno[4,3-b]quinolines have been performed. The equilibrium geometries have been optimized at the B3LYP/6-31G(d) computational level and the present study puts in evidence the stability preference of the cis stereoisomers in comparison with the trans ones as expected experimentally. The vibrational frequencies and IR spectra were calculated at the same level of theory and compared to experimental FT-IR spectra and the spectral peaks have been assigned on the basis of potential energy distribution results. UV-visible absorption bands were calculated using the TD-DFT/B3LYP/6-31G(d) method. The ${}^{13}$C nuclear magnetic resonance chemical shifts and the coupling constants were calculated at the B3LYP level using the gauge independent atomic orbital (GIAO) method in chloroform solvent. The ¹H chemical shifts were calculated using the recently proposed WP04/6-31G(d) DFT functional. The visualization of the molecular electrostatic potential (MEP) surfaces and the docking simulation show that the absence of the methyl group at 2-position of tetrahydrochromeno[4,3-b]quinoline moiety is responsible of the potential anti-cancer activity of this compound.

Lead(II) phthalocyanine (PbPc); lead(II) tetranitrophthalocyanine (PbTNP) and lead(II) tetraaminophthalocyanine (PbTAP) were synthesized in pure state by microwave irradiation and conventional heating methods. The procedures for their synthesis by the microwave technique are standardized and reported for the first time. PbPc and PbTNP were synthesized in dry conditions and PbTAP complex was synthesized in aqueous medium. All the compounds are obtained in very high yield (~90%). The synthesized complexes are characterized with respect to elemental analysis, UV-visible, IR-spectroscopy and X-ray diffraction study. The microwave methods are advantageous over the conventional method of synthesis with respect to higher yield, rapidity and simplicity.

A novel series of nitrone-substituted, metal phthalocyanine complexes (the central metal ion being Co, Ni and Cu, respectively) were synthesized for the first time in pure state with quantitative yield. These complexes were characterized using elemental analysis, UV-visible, IR-spectroscopy, magnetic susceptibility, X-ray crystallography, and thermogravimetry. All three complexes had a monoclinic structure with different crystal lattice constants. Horowitz-Metzger, Coats-Redfern and Broido's relations were employed to calculate the kinetic and activation parameters associated with the thermal decomposition of the above complexes. Electrical conductivity studies were undertaken for all three complexes using a two-probe technique in the temperature range 30-200°C. They showed an improvement of 10³-10⁵ times the electrical conductivity at room temperature, compared to the corresponding unsubstituted metal phthalocyanines.

This paper has scrutinized, both experimentally and theoretically, the conformation of an olefinic substituent on the pyrrole β-carbon of tetraphenylporphyrin. Compelling evidences collected from linear optical absorption and NOESY ¹H NMR experiment strongly suggest that, in solution, it is highly possible for the olefinic acceptor on pyrrole β-carbon to have a coplanar or near coplanar conformation with the pyrrole of the porphyrin core. This conformation ensures effective π-conjugation between the pyrrole ring and its olefinic substituent which is reflected in the linear absorption spectroscopy as the red-shifting of both Soret and Q-bands and possibly the splitting of the absorption Soret band. The intensified long wavelength absorption Q-band of the porphyrin is also consistent with the proposed π-conjugation. Regarding nonlinear optical absorption, an active nonlinear optical (NLO) response has been observed for these porphyrins, indicative of efficient electronic coupling (resonance interaction) between the electronic acceptor and porphyrin macrocyclic ring, compatible with a coplanar or near coplanar conformation in order to achieve π-conjugation. Such conformation of the peripherally appended olefinic acceptor has been further confirmed by INDO/1 Hamiltonian in the ZINDO computational calculations. The INDO/S electron density calculation further reveals that the range of intramolecular charge-transfer (ICT) does not encompass the whole porphyrin core but is mostly confined to the pyrrole ring attached to the olefin-linked acceptor. Furthermore, ICT characteristics were found to be more heavily involved in the Soret absorption band than Q-band. Our analysis of the porphyrin π-conjugation is consistent with modest solvatochromic behavior and the moderate NLO activity of the porphyrins compared with NLO chromophores with many less π-electrons.

The synthesis and physicochemical properties of the Zn^II complexes, [Py₈QxPzZn](Py₈QxPz = tetra-2,3-[6,7-di(2-pyridyl)quinoxalino]porphyrazinato dianion), the corresponding octacation [(2-Mepy)₈QxPzZn]⁸⁺ (neutralized by I^- ions), and the heteropentanuclear complex [(PdCl₂)₄Py₈QxPzZn] are presented and discussed. According to their UV-visible spectral data in non aqueous solvents (CHCl₃, pyridine, dimethyl sulfoxide, dimethylformamide), the species exhibit intense absorptions in the Q-band region at 750–770 nm, in line with parallel spectral data observed for the free base [Py₈QxPzH₂], also reported, and the previously investigated Mg^II complex [Py₈QxPzMg(H₂O)]. The observed Q-band position for this series of "quinoxalinoporphyrazine" macrocycles is about 100 nm to the red with respect to the position of the same absorption for the series of the already reported "pyrazinoporphyrazine" analogs. The spectral effects induced by the peripherally appended methyl-pyridinium groups in the octacation [(2-Mepy)₈QxPzZn]⁸⁺ or by exocyclic coordination in the complex [(PdCl₂)₄Py₈QxPzZn] are also considered. Of the investigated Zn^II complexes, [Py₈QxPzZn] and the related octacation [(2-Mepy)₈QxPzZn]⁸⁺ are active in dimethylformamide solution as singlet oxygen photosensitizers, which is of interest for applications in the photodynamic therapy (PDT) of cancer.

The synthesis and physicochemical characterization of a new class of water soluble homo/heteropentanuclear porphyrazine complexes are described. The investigated compounds, prepared from the previously reported mononuclear species [LM]⋅xH₂O (L = tetrakis-2,3-[5,6-di(2-pyridyl) pyrazino]porphyrazinato dianion; M = Mg^II(H₂O), Zn^II, Cu^II, Co^II, Pd^II, Pt^II; x = 3–8) in DMSO under mild experimental conditions, are represented as [{Pd(OAc)₂}₄LM]⋅xH₂O (x = 11–22) and bear four Pd(OAc)₂ units, each externally coordinated at the vicinal pyridine N atoms of a single dipyridinopyrazine fragment of the porphyrazine macrocycle (py–py coordination). The newly synthesized compounds were examined by IR and magnetic susceptibility measurements in the solid state. Solution UV-visible spectral studies on all of the species were conducted in the low-donor organic solvents pyridine, dimethyl sulfoxide and dimethylformamide and in the water medium, whereas electrochemical measurements were performed in these media in the presence of tetrabutylammonium perchlorate (organic solvents) and KCl or NaOAc (water). Data on the photosensitizing activity for the generation of singlet oxygen, ¹O₂, of interest in photodynamic therapy, were also obtained in dimethylformammide solution on the compounds [{Pd(OAc)₂}₄LM](M = Mg^II(H₂O), Zn^II, Pd^II, Pt^II) and the measured Φ_Δ values are presented and discussed. NMR spectral data on the complex [{Pd(OAc)₂}₄LZn] are also included and discussed.

The synthesis and physicochemical characterization of a new class of low-symmetry water soluble heteropentanuclear porphyrazine complexes are described. The investigated compounds, represented as [{Pd(OAc)${}_{\mathrm{\text{2}}}$}${}_{\mathrm{\text{3}}}$(PtCl${}_{\mathrm{\text{2}}})$LM] •xH${}_{\mathrm{\text{2}}}$O where L $=$ tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato dianion, M $=$ Mg${}^{\mathrm{\text{II}}}$(H${}_{\mathrm{\text{2}}}$O), Zn${}^{\mathrm{\text{II}}}$ or Pd${}^{\mathrm{\text{II}}}$ and $x=$ 3–8, were prepared under mild experimental conditions from the previously described heterobimetallic compounds [(PtCl${}_{\mathrm{\text{2}}})$LM]. Peripheral binding of one PtCl${}_{\mathrm{\text{2}}}$and three Pd(OAc)${}_{\mathrm{\text{2}}}$units in the new series of compounds occurs at the vicinal pyridine N atoms of each dipyridinopyrazine fragment via a “py–py” coordination. The newly synthesized porphyrazines were characterized by IR measurements in the solid state and UV-visible absorption spectroscopy in the polar nonaqueous solvents pyridine, dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) as well as in water, the enhanced solubility in this medium being due to the presence of the external Pd(OAc)${}_{\mathrm{\text{2}}}$ moieties. Data on the photosensitizing activity of the compounds for the generation of singlet oxygen, ${}^{\mathrm{\text{1}}}$O${}_{\mathrm{\text{2,}}}$ were also obtained in DMF and should be of interest to researchers in the area of photodynamic therapy.

Two dimensional (2D) materials are widely attracting the interest of researchers due to their unique crystal structure and diverse properties. In the present work, tungsten disulfide (WS₂) nanorods were synthesized by a simple method of pulsed laser ablation in liquid (PLAL) environment. The prepared WS₂ are analyzed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and Raman spectroscopy to confirm the surface morphology, phase and structure. A possible growth mechanism of WS₂ is proposed. This study indicates new door for the preparation of 2D materials with specific morphology.