Spectroscopic Characterizations of Metal-Complexes of 4-Hydroxybenzoic Acid With the Ni(Ⅱ), Mn(Ⅱ), and Cu(Ⅱ) Ions

One of the phenolic acids is 4-hydroxybenzoic acid (HBA) which takes the form of a white crystalline solid with a molecular formula of C₇H₆O₃, a melting point of 214.5 ℃ and a molecular weight of 138.12 g·mol-1. It soluble in polar organic solvents like acetone and alcohols, and slightly soluble in chloroform and water. The reactions between the metal ions and the HBA were carried out under specific conditions like (molar reaction was 2∶2 (ligand to metal), reaction temperature was 60 ℃, media was neutral (pH 7), and solvent was H₂O ∶MeOH (1∶1). Under these conditions, the HBA was deprotonated to form (HOC₆H₄CO-₂; L-). The ligand L- was coordinated to the metal ions forming the metal complexation. The reaction of 4-hydroxybenzoic acid (HOC₆H₄CO₂H; HL) with the Ni(Ⅱ), Mn(Ⅱ) and Cu(Ⅱ) ions afford metal-complexes with gross formula of [Ni₂L₂(NO₃)₂(H₂O)₄], [Mn₂L₂(NO₃)₂(H₂O)₄] and [Cu₂L₂(NO₃)₂(H₂O)₄], respectively. These complexes were characterized by elemental analysis (CHN), magnetic susceptibility, UV-Vis spectra, infrared (IR), and X-ray powder diffraction (XRD) techniques. The complexes of HBA are insoluble in common solvents and hence molar conductance could not be measured, but this very insolubility indicates that the complexes are neutral. Data has demonstrated that the ligand (L-) was coordinated to the metal ion by bidentate bridging carboxylate group (COO-), with an octahedral geometry. Thus, HBA is expected to act as bidentate uninegative ions and the coordination number of the metal ions is six. XRD results showed that the complexes possess uniform and organized microstructures in the nanometer range with a main diameter in the range of 11～28 nm.     

Spectroscopic and Fluorescence Studies on the Trivalent Ce,Eu,Nd and La Metal Ions Rhodamine C Florescent Dye Complexes

The four isolates solid complexes: [La(RHC)(NO₃)₂]·3H₂O, [Nd(RHC)(NO₃)₂]·4H₂O, [Eu(RHC)(NO₃)₂]·2H₂O, and [Ce(RHC)(NO₃)₂]·5H₂O that obtained by the reaction of the nitrate salts of the Ce(Ⅲ), Eu(Ⅲ), Nd(Ⅲ) and La(Ⅲ) ions and rhodamie C (RHC) ligand were interpretative using elemental analysis (C, H and N), molar conductivity, infrared, electronic, fluorescence and 1H-NMR spectra to achieve the speculated suitable formula. The low molar conductance values of the synthesized RHC complexes concluded the non-electrolytic behavior. The infrared spectra recorded the absence of stretching vibration ν(OH) of the -COOH and presence of two new vibration bands at 1 597～1 601 and 1 383～1 399 cm-1 which were assigned to ν_as(COO-) and ν_s(COO-). The difference between them revealed that the carboxylate group acts as a bidentate ligand. 1HNMR spectra of Europium and lanthanum(Ⅲ) complexes were supported the FTIR results based on the absent of proton of the carboxylic group. Therefore, the microanalytical and spectroscopic results deduced that RHC acts as a monobasic bidentate ligand, and coordinated to the central metal(Ⅲ) ions via the two oxygen atoms of deprotonated carboxylic group. Fluorescence studies were performed on the metal complexes of Ce3+, Tb3+, Th4+, Gd3+ and La3+, that referred a quenching in the fluorescene intensity of rhodamine C in the aqueous state after complexation. The antimicrobial assessment against some kind of bacteria and fungi were also checked and recorded enhancement in case of their complexes.     

Synthesis,Structural,Spectroscopic Characterization and Biological Properties of the Zn(Ⅱ),Cu(Ⅱ),Ni(Ⅱ),Co(Ⅱ),and Mn(Ⅱ) Complexes With the Widely Used Herbicide 2,4-Dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acid (2,4-D) is a board-leaf selective herbicide and globally used in agricultural activities. Complexation mode, spectroscopic investigations and biological properties of complexes formed between 2,4-D (C₆H₃Cl₂OCH₂·COOH; HL) with Zn(Ⅱ), Cu(Ⅱ), Ni(Ⅱ), Co(Ⅱ), and Mn(Ⅱ) metal ions were investigated. To characterize the binding mode between 2,4-D and the metal ions, many physicochemical approaches were employed. The complexes obtained are characterized quantitatively and qualitatively by using micro elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, 1H-NMR, and magnetic susceptibility measurements. Results of these approaches suggested that the gross formula of the complexes obtained with the metal ions were [ZnL₂](2H₂O (1), [CuL₂(H₂O)₂] (2), [NiL₂](3H₂O (3), [CoL₂(H₂O)₂] (4), and [MnL₂(H₂O)₂] (5). In all complexes, two L- anion were coordinated the metal ion by their bidentate carboxylate groups. From the spectral study, all the complexes obtained as monomeric structure and the metals center moieties are six-coordinated with octahedral geometry except Ni(Ⅱ) and Zn(Ⅱ) complexes which existed as a tetrahedral and square pyramidal geometry respectively. The complexes were screened in vitro against several microbes (fungi and bacteria) using Kirby-Bauer disc diffusion method, and data has demonstrated that complex 3 showed excellent antifungal activity.     

Preparations and Spectroscopic Studies on the Three New Strontium(Ⅱ), Barium(Ⅱ), and Lead(Ⅱ) Carbocysteine Complexes

Carbocisteine, also known as carbocysteine, is a mucolytic that reduces the viscosity of sputum and thus can be used to help relieve symptoms of chronic obstructive pulmonary disorder and bronchiectasis by allowing the sufferer to expel sputum more easily. A total of three new metal complexes of carbocysteine, HCcy with the metal ions Sr(Ⅱ), Ba(Ⅱ), and Pb(Ⅱ) have been successfully prepared in alkaline medium in situ H₂O/CH₃OH (50/50 w/w). The complexes obtained are characterized quantitatively and qualitatively by using micro elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, X-ray powder diffraction spectroscopy, 1H-NMR, and conductivity measurements. From the spectral study, all the synthesized Ccy complexes obtained as monomeric structure and the metals center moieties are six-coordinated except lead(Ⅱ) complex which existed as a four-coordinated respectively, suggesting formulas [Sr(Ccy)(H₂O)₂], [Ba(Ccy)(H₂O)₂] and [Pb(Ccy)] in neutral form. Beside, regarding both Sr(Ⅱ) and Ba(Ⅱ) complexes, the aquo groups are existed inside the coordination sphere. The infrared assignments reveal that HCcy ligand act as a bidentate ligand with the metal ions through oxygens of the deprotonated carboxylic COOH group. The 1H-NMR spectrum of the [Ba(Ccy)(H₂O)₂] complex has an absent of the proton of -COOH groups upon the deprotonated of carboxylic group.     

Spectroscopic Investigations for the Six New Synthesized Complexes of Fluoroquinolones and Quinolones Drugs With Nickel(Ⅱ) Metal Ion: Infrared and Electronic Spectroscopy

Quinolone has a broad spectrum of synthetic antibiotics with a strong therapeutic effect and quinolone is a term used for chemical treatments used to treat a powerful bacteria. Quinolones are divided into 4 generations according to the bacterial spectrum, the majority of quinolones used clinically belong to the sub fluoroquinolones group, which has a fluorine atom linked to the central ring system, usually on its carbon atom 6 or 7. Herein in this article, six new nickel(Ⅱ) complexes (Ⅰ-Ⅵ) have been synthesized in aqueous alkaline media at pH ranged 8-9, the chemical reactions take place between levofloxacin (HLEV), lomefloxacin (HLOM), nalidixic acid (HNLA), oxolonic acid (HOXO), pipemidic acid (HPIP), and pefloxacin mesylate (HPEF) with nickel(Ⅱ) nitrate hexahydrate. The microanalytical (percentage of carbon, hydrogen and nitrogen), molar conductance (Λ_m), Infrared (FTIR) spectra, electronic (UV-Vis) spectra, and effective magnetic moment instrumentals were used to identify the suggested structures and their surface morphology. According the analytical and spectroscopic analyses, the stoichiometry between nickel(Ⅱ) metal ion and drug ligands was found to be 1∶2 with general formula as [Ni(L)₂(H₂O)₂]·xH₂O (L=LEV (Ⅰ), LOM (Ⅱ), NAL (Ⅲ), OXO (Ⅳ), PIP (V), and PEF (Ⅵ); x=2 or 4). By the comparison between FTIR spectra of quinolone drugs and their complexes, it can be deduced that all the drug ligands act as a bidentate chelates through oxygen atoms of pyridine ring and carboxylate group. The electronic configuration of all synthesized nickel(Ⅱ) complexes were octahedral geometry which confirmed based on the values of magnetic susceptibility and the electronic transition bands.     

Synthesis,Spectroscopic Characterization,Thermogravimetric and Biological Activity Evaluation of Te(Ⅳ),Se(Ⅳ),V(Ⅲ),Nb(Ⅴ),Ta(Ⅴ)Complexes With Indole-3-Acetic Acid Plant Hormone Ligand

Te(Ⅳ), Se(Ⅳ), V(Ⅲ), Nb(Ⅴ) and Ta(Ⅴ) complexes of indole-3-acetic acid (IAAH) ligand were synthesized, characterized by elemental analysis and various spectroscopic techniques like, IR, 1H-NMR, X-ray powder diffraction, UV-Visible, thermogravimetry analysis, magnetic measurements, molar conductance and surface morphology using SEM. All the synthesized complexes of IAAH ligand have 1∶2 stoichiometry of the types [Te(IAA)₂(NH₃)₂]·2Cl (Ⅰ), [Se(IAA)₂(NH₃)₂]·2Cl (Ⅱ), [V(IAA)₂(NH₃)(Cl)] (Ⅲ), [Nb(IAA)₂(Cl)₃] (Ⅳ), and [Ta(IAA)₂(Cl)₃] (Ⅴ). Spectral analysis indicates octahedral geometry for the Te(Ⅳ), Se(Ⅳ) and V(Ⅲ) complexes, whereas both Nb(Ⅴ) and Ta(Ⅴ) have a seven-coordination. The bonding sites are the oxygen atoms of carboxylate group for the deprotonated indole-3-acetic acid (IAA) ligand. The thermogravimetry analysis studies gave evidence for the presence of other coordinated molecules (Cl or NH₃) in the composition of IAA complexes, which were further supported by IR and micro analytical measurements. The higher molar conductance data of tellurium and selenium (Ⅳ) complexes reveal that these chelates are electrolytes, while low conductivity values for the vanadium(Ⅲ), niobium and tantalum(Ⅴ) chelates indicated a non-electrolytes. To test the antibacterial property of the five complexes in this study, four bacterial strains Klebsiella (G-), Escherichia coli (G-), Staphylococcus aureus (G+) and Staphylococcus epidermidis (G+) were used in the investigation. The effects of the five complexes in the cytotoxicity of Caco-2 and Mcf-7 human cancer cell lines were studied Neutral red uptake assay for the estimation of cell viability/cytotoxicity protocol.     

Fabrication of Semiconductor Polymer Membranes Combined with a Colored Charge Transfer Complexes Used in the Manufacture of Solar Cells as a Source of Alternative Energy

The main task of this article was to prepared of new pigment model in situ solar cells accordance to charge-transfer complexes of rhodamine C (RhC) donor as dye laser gain media with iodine (σ-acceptor) and chloranilic acid, CLA (π-acceptor). The synthesis stoichiometry of these complexes were of 1∶2 (donor∶acceptor) with general formulas [(RhC)]I·I₃ and [(RhC)(CLA)₂]. The discussed data of elemental analysis, conductivity measurements, FT-IR, UV-Vis spectroscopy and photometric titration data visualized the stoichiometry, formula and complexity of the complexes. The physicochemical and spectroscopic analyses obtained suggested that the electron transfer occurred through nitrogen atom in a tertiary amine -N(C₂H₅)₂ of RhC donor with acceptor. The synthesized solid complexes were under go to thermogravimetric analyses to investigate their thermal stability and decomposition steps. The molar conductance measurements revealed that RhC complexes have an electrolytic statement. The thermal stability of rhodamine C complexes was enhanced in comparable with RhC itself. The polymer membranes of poly-methyl methacrylate) (PMMA) combined with the RhC charge(transfer complexes in chloroform solvent have been prepared and characterized by (infrared & electronic) spectroscopy and scanning electron microscopy (SEM) morphological examination. The photo-stability properties of the RhC complexes have been investigated.     

Synthesis and Spectroscopic Investigations of Four New Y(Ⅲ), Ge(Ⅳ), W(Ⅵ) and Si(Ⅳ) Penicillin Antibiotic Drug Complexes

A four new penicillinate complexes were prepared through the chemical interactions of penicillin potassium salt (Pin) with YCl₃, GeCl₄, WCl₆ and SiCl₄ metal ions. These metal complexes were characterized using spectroscopic techniques (e.g. 1H-NMR, infrared, electronic UV-Vis) as well as elemental, conductivity, and magnetic measurements. The molar conductance values were highly, showing their electrolytic nature. The magnetic and electronic study strongly recommends the octahedral geometry of all penicillinate complexes. A monomeric structures of Pin complexes are proposed with octahedral coordinated metals ions. The metal ions are coordinated toward Pin as tridentate ligand through the amide and β-lactam carbonyls and a carboxylate group from penicillin. The in vitro antimicrobial activity of all the complexes, at concentrations in μg·mL-1, was screened against four bacterial pathogens, namely, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, and two kinds of fungi Aspergillus flavus and Candida albicans showed better activity compared to parent drug and control drug. The anti-cancer inhibition of the tungsten(Ⅵ) complex was assessed against the human hepato cellular carcinoma (HepG-2) tumor cell line with IC50 value is 646 μg·mL-1.     

PHOTO- AND ELECTRO-LUMINESCENCE FROM HYDROGENATED AMORPHOUS SILICON CARBIDE FILMS PREPARED BY USING ORGANIC CARBON SOURCE

Hydrogenated amorphous silicon carbide (a-SiC:H) films were grown by using an organic source, xylene (C₈H₁₀), instead of methane (CH₄) in a conventional plasma enhanced chemical vapor deposition system. The optical band gap of these samples was increased gradually by changing the gas ratio of C₈H₁₀ to SiH₄. The film with high optical band gap was soft and polymer-like and intense photoluminescence were obtained. Room temperature electro-luminescence was also achieved with peak energy at 2.05 eV (600 nm) for the a-SiC:H film with optical band gap of 3.2 eV.     

Microstructured hydroxyl environments and Raman spectroscopy in selected basic transition-metal halides

Raman vibrational spectra of the selected basic (hydroxyl OH and deuteroxyl OD) transition-metal halides, geometrically frustrated material series α-, β-, γ-Cu₂(OH)₃Cl, α-Cu₂(OH)₃Br, β-Ni₂(OH)₃Cl, β-Co₂(OH)₃Cl, β-Co₂(OH)₃Br, γ-Cu₂(OD)₃Cl, and β-Co₂(OD)₃Cl are measured at room temperature and analysed to investigate the relationship between the microstructured OH environments and their respective Raman spectra. Among these selected samples, the last two are used to determine the OH stretching vibration region (3600 cm^-1—3300 cm^-1) and OH bending vibration region (1000 cm^-1—600 cm^-1) of OH systems in the spectra. Through the comparative analysis of the distances d(metal—O), d(O—halogen), and d(OH), the strong metal—O interaction and trimeric hydrogen bond (C_3v, C_s or C₁ symmetry) are found in every material, but both determine simultaneously an ultimate d(OH), and therefore an OH stretching vibration frequency. According to the approximately linear relationship between the OH stretching vibration frequency and d(OH), some unavailable d(OH) are guessed and some doubtful d(OH) are suggested to be corrected. In addition, it is demonstrated in brief that the OH bending vibration frequency is also of importance to check the more detailed crystal microstructure relating to the OH group.     

Synthesis and Spectroscopic Characterizations on the Complexation of Three Different Metal Ions Ba(Ⅱ), Ni(Ⅱ), and Ce(Ⅲ) with Atenolol Drug Chelate

Three types of metal ions barium(Ⅱ), nickel(Ⅱ) and cerium(Ⅲ) complexity of ATN drug have been prepared and characterized using molar conductance method, FT-IR, electronic, and ~1H-NMR analysis measurements. The chemical and physical results for all atenolol complexes are agreement with the speculated structures. For the divalent(Ba Ni) and trivalent(Ce) metal atenolol a molar ratio 1∶2 was established. Qualitative chemical analysis showed that for the divalent metal complexes, the chloride ions are not involved in the complexes, suggesting that all of these complexes, [Ba(ATN)_2]·2 H_2O and [Ni(ATN)_2(H_2O)_2]·4 H_2O are neutral. However, for the cerium(Ⅲ) complex, [Ce(ATN)_2(NO_3)]·3 H_2O, the nitrate group is existed inside the coordination sphere. ATN make astable metal complexity with barium(Ⅱ), nickel(Ⅱ) and cerium(Ⅲ) ions. Electronic absorption analysis of Atenolol give two fundamental peaks at 225 nm and 274 nm refers to variation in transition electrons of ligand, UV spectral analysis of the three complexity obtained give asymmetric broad band in the range 200～400 nm, the reults are convenient with the suggestion of metal-nitrogen and metal-oxygen bonds. The infrared analysis data proved that ATN act as bidentate ligand through the N atom of the —NH group and O atom of the deprotonated alcoholic OH group. Nickel(Ⅱ) and cerium(Ⅲ) complexity make six-coordinate geometry, whereas the barium(Ⅱ) complex exhibit four-coordinate geometry. Ni(Ⅱ)-ATN complex has an effective magnetic moment equal 3.12 B.M, that is assigned to octahedral structure. The ~1H-NMR spectral results of Ba(Ⅱ)-ATN complexity give strong signal at ～4.00 ppm due to protons of —CH_2 that influenced by low degree due to complexity. These results confirm the position of chelation through the N atom of the —NH group and O atom of the deprotonated alcoholic OH group.     

Preparation and Spectroscopic of Vanadyl(Ⅱ) Vitamin D_3 Amino Acid Mixed Complexes as Insulin Mimetic Drug

A new six intraperitoneal injection insulin-mimetic vanadyl(Ⅱ) compounds [(VD-1₃)(VO+2)(AA-1_n)] (where (n=1～6); AA₁=isoleucine, AA₂=threonine, AA₃=proline, AA₄=phenylalanine, AA₅=lysine and AA₆=glutamine) were synthesized by the chemical reactions between vitamin D₃ (VD₃), VOSO₄ and amino acids (AA_n) with equal molar ratio 1∶1∶1 in neutralized media. The structures of these complexes were elucidated by spectroscopic methods like, infrared and solid reflectance spectroscopes. Magnetic moments and electronic spectra reveal square pyramid geometrical structure of the complexes. The infrared spectra assignments of these complexes revealed that the chelation towards vanadyl(Ⅳ) ions existed via deprotonation of the hydroxyl group of VD₃ drug ligand and so amino acids act as bidentate ligand via N-amino and O-carboxylate groups. The anti-diabetic efficiency of these complexes were evaluated against streptozotocin induced diabetic male albino rats.     

Ultrafast dynamics of cationic electronic states of vinyl bromide by strong-field ionization-photofragmentation

Strong field ionization-photofragmentation(SFI-PF)with ultrafast pump–probe scheme is a powerful approach to study the dynamics of molecular cationic electronic states.Here we carry out a SFI-PF study on the cationic electronic states of vinyl bromide,C₂H₃Br.The yields of the parent C₂H₃Br₊and the formation of the fragment(Br⁺,C₂H⁺2 and C₂H⁺3)ions have been measured at different pump–probe delay time.Analysis provides experimental evidence of A²A'–X²A' internal conversion of vinyl bromide cations which occurs in a time of about 220 fs,and the time of C₂H₃⁺ formation induced by the dissociation of the A²A' state around 300 fs.The study would add our knowledge of the behavior of electronic excited states of complex molecular cations.     

Synthesis and Spectroscopic Characterizations of New Mercury(Ⅱ), Cerium(Ⅲ), and Thorium(Ⅳ) Captopril Drug Complexes

In this article, three types of metal ions with different oxidation state as mercury(Ⅱ), cerium(Ⅲ) thorium(Ⅳ) have been reacted with captopril drug(CAP). The isolated solid complexes were explained using elemental analysis, conductance measurements, infrared and ~1H-NMR spectroscopy as well as the thermo gravimetric(TG/DTG) analysis. The micro analytical and spectroscopic results for all CAP complexes were agreement with the speculated structures. The stoichiometry for divalent Hg~(2+), trivalent Ce~(3+) and tetravalent Th~(4+) metal ions with CAP ligand was established with 1∶2(M~(n+):CAP) molar ratio. The qualitative analysis showed that in case of the mercury(Ⅱ) complex, the chloride ions didn't involved in the complexity, suggesting formula [Hg(CAP)_2] in neutral form. However, regarding both Ce(Ⅲ) and Th(Ⅳ) complexes as [Ce(CAP)_2(NO_3)]·3 H_2O and [Th(CAP)_2(NO_3)_2(H_2O)]·3 H_2O formulas, the nitrate group is existed inside the coordination sphere. The infrared analysis data proved that CAP drug act as a bidentate ligand with the metal ions of Ce(Ⅲ) and Th(Ⅳ) through oxygen carbonyl group ■ and oxygen of the deprotonated carboxylic COOH group, while for the Hg(Ⅱ) complex, the CAP acts as a bidentate ligand through oxygen of ■ group and sulfur atom of the deprotonated —SH group. Thorium(Ⅵ) complex has a nine-coordinate geometry, while Hg(Ⅱ) and Ce(Ⅲ) have a four and six-coordination behaviors respectively. The ~1H-NMR data of the CAP compound has a singlet sharp signal at 1.90 ppm due to the proton of —SH group, this peak absent in the spectrum of the Hg(Ⅱ) CAP complex upon the deprotonated of thiol group.     

Three-dimensional potential energy surface for fission of 236U within covariant density functional theory

We calculate the three-dimensional potential energy surface(PES) for the fission of the compound nucleus ²³⁶U using covariant density functional theory with constraints on the axial quadrupole and octupole deformations(β₂, β₃)coexistence of the elongated and compact fission modes is predicted for comes shallow across a large range of quadrupole and octupole deformations for small scission line in the(β₂, β₃)plane extends to a shallow band, l...     

Strong spin frustration and magnetism in kagomé antiferromagnets LnCu3(OH)6Br3(Ln = Nd,Sm, and Eu)

To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties,we grew high-quality single crystals of LnCu₃(OH)₆Br₃(Ln=Nd,Sm,and Eu) by hydrothermal method and studied their crystal structures and magnetic properties.The refinements of the crystal structure referred to the powder x-ray diffraction data show that LnCu₃(OH)₆Br₃ adopt a Kapellasite-type layer structure,which is...     

Structural and magnetic properties of LiNi0.5Mn1.5O4 and LiNi0.5Mn1.5O4-δ spinels： A first-principles study

<正>Structural and magnetic properties of LiNi_0.5Mn_1.5O₄ and LiNi_0.5Mn_1.5O_4-δ are investigated using densityfunctional theory calculations.Results indicate that nonstoichiometric LiNi_0.5Mn_1.5O_4-δ and stoichiometric LiNi_0.5Mn_1.5O₄ exhibit two different structures,i.e.,the face-centred cubic（Fd-3m） and primitive,or simple,cubic （P4₃32） space groups,respectively.It is found that the magnetic ground state of LiNi_0.5Mn_1.5O₄（P4₃32 and Fd-3m） is a ferrimagnetic state in which the Ni and Mn sublattices are ferromagnetically ordered along the[110]direction whereas they are antiferromagnetic with respect to each other.We demonstrate that it is the presence of an O-vacancy in LiNi_0.5Mn_1.5O_4-δ with the Fd-3m space group that results in its superior electronic conductivity compared with LiNi_0.5Mn_1.5O₄ with the P4₃32 space group.     

MULTIPHOTON IONIZATION MASS SPECTRA OF n-C3H7I AND i-C3H7I AT 532 nm

Multiphoton Ionization (MP) Mass Spectra of n-C₃H₇I AND i-C₃H₇I are obtained using a time-offlight mass spectrometer at 532 nm. No parentions are observed in MPI of both isomers. N-propyl cation dissociates more extensively than isopropyl cation. The C₂H⁺₅(M/Z=29) ion is observed instead of C₂H⁺₄(M/Z=28) ion in MPI of n-C₃H₇I, in contrast to i-C₃H₇I. It is found that parent molecules are first two-photon resonantly excited to A-band, then go through dissociation. Fragment ions are produced by ionization and dissociation of neutral fragments. We present directly the diss ociation pathways of n-propyl cation according to the results proposed by Levine using maximum entropy formalism. Moreover, those of isopropyl cation are discussed in this paper through branching ratio analyses.     

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp³ s^* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε₂ (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε₂(ω) spectrum. The two components of the ε₂(ω) (i. e. ε_2xy(ω) and ε_2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.     

Structural Evolution of D5h（1）-C90 under High Pressure:A Mediate Allotrope of Nanocarbon from Zero-Dimensional Fullerene to One-Dimensional Nanotube

The hybridization of fullerene and nanotube structures in newly isolated C₉₀ with the D_{5 h} symmetric group(D_{5 h}（1）-C₉₀) provides an ideal model as a mediating allotrope of nanocarbon from zero-dimensional（OD） fullerene to one-dimensional nanotube.Raman and infrared spectroscopy combined with classical molecular dynamics simulation were used to investigate the structural evolution of D_{5 h}（1）-C₉₀ at ambient and high pressure up to35...