Vibrational Spectra of 2,6-Diphenyl Pyridine, 2,2′:6′,2″-Terpyridine and Meta-terphenyl

The Raman and infrared spectra of 2,6-diphenyl pyridine, m-terphenyl and 2,2′:6′,2″-1erpyridine have been analysed as metadisubstituted benzene or pyridine molecules. Complete vibrational assignment shows that some modes in the case of internal vibrations of substituents appear in pairs. The splitting of these modes have been attributed to the in-and out-of-phase motions arising out of interaction between phenyl or pyridine rings, as the case may be. In the case of meta terphenyl and terpyridine, two probable cases of Fermi resonance have been observed.     

Synthesis and plant growth regulatory activities of 2′,3′-PhABA and iso-2′,3′-PhABA esters

Molecular Diversity - Methyl and phenyl esters of 2′,3′-PhABA and iso-2′,3′-PhABA were prepared for the biological investigation and development of practical applications....     

Non-doped,blue-emitting,color-stable,organic light-emitting diode based on 2,2′:6′,2″-ternaphthalene

A novel non-doped blue-emitting material, 2,2′:6′,2″-ternaphthalene (NNN), which is based on three naphthalene units forming a rodlike molecule, has been synthesized and characterized. Organic light-emitting diodes based on NNN as emitter exhibit blue emission with Commission Internationale de l’Eclairage color coordinates of x = 0.18 and y = 0.11. In addition, the morphology and crystallographic structure of the NNN thin films has been investigated. NNN deposited on poly[3,4-(ethylenedioxy) thiophene]:poly (styrene sulfonate) on Indium Tin Oxide-covered glass forms crystalline structures of high crystallographic quality. The molecules are aligned almost perpendicular to the substrate surface and exhibit a tilt angle of 23 $^{\circ }$ .     

Preparation and Photophysics of 2-(1-Pyrenyl)acrylic Acid and Its Methyl and 2′,2′,6′,6′-Tetramethyl-4′-Piperidyl Esters

Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO^.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form –COO⁻. Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form –COOH and the cationic form –COOH₂⁺. The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1′-oxo-2′,2′,6′,6′-tetramethyl-4′-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO^.).     

Assignments of the 13C NMR Spectra of Enhydrin and 2′,3′-Dehydromelnerin A and the Molecular Structure of Enhydrin

Abstract

Two melampolide-type sesquiterpene lactones, enhydrin and 2,′ 3′-dehydromelnerin A, were isolated from a Louisiana population of Polymnia uvedalia. Their ¹³C NMR spectra were assigned using ¹³C-¹H correlation, DEPT and COLOC experiments. The molecular structure of enhydrin was established by single crystal X-ray diffraction.     

Vibrational Spectra of 2,2′-Pyridil and 2,2′-Pyridil-18O and Assignment of Infrared and Raman Bands

Abstract

Vibrational spectra of 2,2′-pyridil and 2,2′-pyridil-¹⁸O in the solid state and in solutions have been measured in the Raman (4000–50 cm^?1) and infrared (4000–100 cm^?1). The assignment of the bands observed is performed using the group vibrational concept and isotopic shifts data of the normal modes. The presence of synand anti-phase vibrations of both pyridyl rings is discussed. The results are compared to the corresponding data for some similar molecules.     

Orange Fluorescent Ru(III) Complexes Based on 4′-Aryl Substituted 2,2′:6′,2″-Terpyridine for OLEDs Application

A series of ruthenium (III) complexes of the formulae [Ru(4-Mephtpy)₂]Cl₃(1) [Ru(L ₁ )], [Ru(3,4,5-tmphtpy)₂]Cl₃(2) [Ru(L ₂ )], and [Ru(4-thptpy)₂]Cl₃(3) [Ru(L ₃ )], (where L?=?terpy?=?2.2′:6′2″ terpyridine ligands) are synthesized. The complexes were characterized by elemental analyses, spectroscopic and electrochemical data. The density functional theory (DFT) outlines the geometric optimisation and electronic charge transition of these complexes. Photophysical studies describe that the luminescence of Ru(III) complexes is due to electronic transition between the energy levels of singly unoccupied molecular orbitals (SUMO) and singly occupied molecular orbitals (SOMO). It also exhibits the potential charge transfer to π–π* and n–π* states due to MLCT and ILCT processes of the complexes. The observed bands centered at 591 and 620 nm demonstrate that these emissions originated from the transition of SUMO to SOMO energy levels, that is, from the radiative decay from the doublet exciton. Due to the heavy metal effect of Ru(III) ions the photophysical behaviour depends on the MLCT process. In conclusion, that the all three Ru(L ₁ -L ₃ ) complexes are fallen orange emission.     

Synthesis,Redetermination and Molecular Conformation Analysis of the Structure of 2,2′-Diaminodiphenyl Disulfide

A new synthesis and the crystal structure of C₁₂H₁₂N₂S₂ have been described and redetermined. In order to optimize the geometry of the molecule, the semi empirical methods MNDO, AMI and PM3 were used. The conformation of the energy profile showed that the minimum energy conformation has the torsion angle θ [Cl-Sl-Sl′-Cl′] near 90°. The energy barrier at 0° attributed to the lone pair repulsion of sulphur atoms and interactions between NH…S and H(C6)…S non-bonded atoms.     

Electrochemical behavior and DNA-binding properties of binuclear copper(II) complex containing mixed ligands of N-hydroxyethylaminoethyl oxamido and 2,2′-bipyridine

The electrochemical property of dinuclear copper(II) complex containing mixed ligands of N-hydroxyethylaminoethyl oxamido and 2,2′-bipyridine [Cu₂(bpy)₂(HAO) ₂ ²⁺ ] was studied with cyclic voltammetry. Cu₂(bpy)₂(HAO) ₂ ²⁺ had irreversible oxidation peaks in 0.1 mol/L NaCl solution at the stearic acid-modified carbon paste electrode. Cyclic voltammetry and absorption spectra measurements were used to study the interaction between Cu₂(bpy)₂(HAO) ₂ ²⁺ and herring fish sperm DNA. All the experimental results showed that Cu₂(bpy)₂(HAO) ₂ ²⁺ interacted with DNA mainly through electrostatic affinity to make tiny difference between Cu₂(bpy)₂(HAO) ₂ ²⁺ –ssDNA and Cu₂(bpy)₂(HAO) ₂ ²⁺ –dsDNA. The binding ratio and the binding constant of DNA–Cu₂(bpy)₂(HAO) ₂ ²⁺ were calculated as 1:1 and 6.41?×?10⁴, respectively. The redox peak current of Cu₂(bpy)₂(HAO) ₂ ²⁺ decreased markedly after its interaction with DNA. This was used to detect the concentration of DNA quantitatively.     

Synthesis and characterization of binaphthalene-2,2′-diamine-functionalized gold nanoparticles

Gold nanoparticles 1.7 and 54 nm in diameters have been synthesized and functionalized successfully with their surfaces engineered using two atropisomeric capping ligands, 2,2′-bis(diphenylphosphino)-1,1′-binaphthalene (BINAP) and 1,1′-binaphthalene-2,2′-diamine (DABN), respectively. A systematic study to compare the two different gold nanoparticles is presented using multiple material characterization techniques. It was found that the two systems show different capping mechanism and hence differ in their intrinsic core and surface properties. The compound BINAP plays only surface capping agent and stabilizes the gold nanoparticles, resulting in small particle size and suppressed surface plasmon resonance absorption at 520 nm. The DABN capping ligand is different from BINAP and acts as both reducing and capping agent, causing the reduction of Au (III) to Au (0). The nucleation growth of the gold core occurs in accordance with the polymerization-passivation process by DABN, resulting in a big particle size of 20 nm. A strong surface plasmon resonance band shows a maximum peak at 564 nm, consistent with the Au core size. The simultaneous oxidative polymerization of DABN and the induced metal reduction process lead to the formation of gold nanoparticles encapsulated by a mixture of DABN oligomers or polymers.

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Thermal behavior and X-ray study of the new double salt hydrate SrCd2Cl6 · 8H2O

The double salt hydrate SrCd₂Cl₆?·?8H₂O undergoes a phase transition at T?=?318?K (phase I?–?(T?=?318)?→phase II). The structural characteristics, Raman scattering and dielectric measurements have been investigated. Phase II exhibits monoclinic symmetry (a?=?17.102(6), b?=?21.716(9), c?=?8.582(5)?Å and β?=?91.58(13)°).     

Structure of spin polarons in the t-t′ -t″ -Jz model

We calculate the Green function in the t-t '-t ”-J^z model and analyze the deformation of the quantum Néel state in the presence of a moving hole. Solving the problem in a self-consistent Born approximation and using Reiter's wave function we have found various spin correlation functions. We show that the different sign of hopping elements between the hole- and electron-doped system of high- cuprates is responsible for the sharp difference of the polaron structure between the two systems with antiferromagnetism stabilized in the electron-doped case by carriers moving mainly on one sublattice. Received 11 January 2000     

A study of morphological and compositional evolution of nanoprecipitates in the Zr–Nb system and their transformational behavior

The metastable transformational behavior (both martensitic and omega) along with compositional and morphological evolution of bcc β precipitates, dispersed in the hcp α matrix of a Zr–1 wt% Nb alloy, were studied as a function of temperature and time. The evolution of the chemical composition of the β phase suggested preference towards metastable compositions having Nb content higher than the equilibrium value. Thermodynamic analysis showed that the metastable chemical compositions are the driving force for the nucleation of such β precipitates. The β to martensite transformation was observed to be possible only if β precipitate size exceeded a critical value of 160?nm. Micromechanical modeling was performed to estimate the critical size of β precipitate required to induce martensite transformation and the model predictions were in close agreement with the experimental observations. The omega transformation, on the other hand, showed less size dependence.     

Self-assembled structures of 4′-([2,2′:6′,2″-terpyridine]-4′-yl)-[1,1′-phenyl]-4-carboxylic acid molecules induced by metal atoms on ag(111) surface

The self-assembled supramolecular structures of 4′-([2,2′:6′,2″-terpyridine]-4′-yl)-[1,1′-phenyl]-4-carboxylic acid (Y) molecules on Ag(111) surface induced by metal elements have been studied by scanning tunneling microscopy. After annealing, the as-deposited monolayer of Y molecules shows four kinds of well-ordered structures due to the competition between dipole interaction, hydrogen bonding and Van der Waals interaction. Introduced Cu atoms drive ordered monolayer into a self-assembled supramolecular structure with bright spots. Deposited Ag atoms cause the monolayer change to a windmill shape self-assembled supramolecular structure. Though the Cu and Ag are in the same group of the periodic table, a Cu atom connects two COOH groups and an Ag atom trends to bind to three COOH groups during the formation of metal-organic bonding within both induced structures. Such result suggests that the self-assembled structures formed by metal-organic coordination bonding can be controlled by choosing the number of metal-organic coordination bonds, which can be helpful to design metal-organic molecular architectures comprising functional building blocks.     

Experimental and theoretical study of the IR spectrum and barriers to internal rotation of 4-hydroxypropyl-4′-cyanobiphenyl

The IR absorption spectrum of polycrystalline 4-hydroxypropyl-4′-cyanobiphenyl is measured in a KBr pellet over the range 400–4000 cm^?1. The structure of the molecule and the frequencies and the intensities of the bands in the spectrum are calculated in the approximation of the B3LYP hybrid density functional with the 6-31 G(d) and 6-31+G(d) basis sets. The normal vibrations are reliably assigned by the method of linear scaling of frequencies, which made it possible to reproduce the experimental IR spectrum with high accuracy. The barriers to internal rotation of phenyl rings and three barriers for the hydroxypropyl radical are calculated.     

The adiabatic calorimetry study of the polymorphism of solid 4,4′-Di-n-Butyloxyazoxybenzene

Specific heat measurements for 4-OAOB using adiabatic calorimetry are presented in the temperature range 290 K to 380 K. In the solid state three anomalies are found in the specific heat curve, at 315.5 K, 323.3 K and 360.5 K. A new solid phase is found in addition to those previously reported. Some observations concerning the kinetics of the phase transitions are also presented.     

4′-[4-（3吡-啶基）苯基]-2,2′：6′,2″联三吡啶及其金属配合物的光谱

合成了多齿配体4′-[4-（3吡-啶基）苯基]-2,2′：6′,2″-联三吡啶（L）,研究了L与过渡金属（Zn^2＋,Cu^2＋,Co^2＋）形成配合物的紫外可见光谱和荧光发射光谱。结果表明：在95%乙醇溶液中,L的最大吸收峰位于295nm,形成配合物后,在330nm附近出现了新的吸收峰;与L相比,Zn^2＋使L的荧光增强并红移,而Cu^2＋和Co^2＋能够完全猝灭L的荧光。由此可见,L不仅能够与金属离子构建组装体,也可以作为具有潜在应用价值的荧光材料。     

4′-(对-胺苯基)-2,2′:6′,2′′-三联吡啶光物理性质

用稳态吸收和荧光光谱技术研究4′-(对-胺苯基)取代的三联吡啶配体(APT)分子在不同极性溶剂中的光谱和光物理性质. 在极性溶剂中APT分子存在着双荧光现象,它分别对应于局域激发态和分子内电荷转移态. APT分子的胺基N原子与醇类溶剂之间的氢键作用使该分子在质子性与非质子性溶剂中具有不同的线性关系. 此外,APT分子的三联吡啶部分与锌离子络合以及三联吡啶N4—N8—N14与甲醇分子形成氢键后,在低能区域出现新的吸收光谱带与荧光光谱带,表明在基态和激发态均形成了新的络合物. 时间分辨单光子计数技术测量的APT分子的荧光衰减过程,证明了APT分子的分子内电荷转移机制符合〝两态〞模型.