Norbornadiene Molecules Research Articles

The surface chemistry of norbornadiene and norbornene on Pd(111) and Pd(100): a comparative DFT study.

The interaction of norbornadiene (NBD) and norbornene (NBE) with the palladium (111) and (100) surfaces have been investigated using density functional theory (DFT). Five configurations of adsorbed NBD may be formed on Pd(111): endo-tetra-σ, endo-di-σ,π, endo-di-π, exo-di-σ, and exo-π. The NBE molecule adsorbed on Pd(111) may exist in 4 configurations: endo-di-σ, endo-π, exo-di-σ, and exo-π. On Pd(100), a smaller number adsorption configurations of NBD and NBE are formed, since the double bonds of these molecules in the endo-orientation are bound only in a di-σ mode. The adsorption energy of NBD and NBE molecules on Pd(100) is noticeably higher compared to Pd(111), which is due to the surface geometry of Pd(100). The most stable configurations on both Pd facets are endo-tetra-σ for NBD and exo-di-σ for NBE. However, due to smaller adsorption area of the exo-di-σ configuration on Pd(111), a larger number of NBD molecules may adsorbed on the same surface area. Energetically favorable endo-tetra-σ (NBD) and exo-di-σ (NBE) configurations are very mobile on Pd(111). On Pd(100), only NBE molecules can migrate, while NBD migration is hindered due to the high activation barrier. All DFT calculations were performed using the Perdew-Burke-Ernzerhof density functional (PBE) with the relativistic SBK effective core potential and TZ2P basis set in the PRIRODA program.

Preferential Solvation in Binary Liquid Mixtures with Norbornadiene

Norbornadiene has been found useful in organic and polymer synthesis and recently its mixtures have been found useful in solar energy storage. Structure factors S(0) help to identify structure and binding at microscopic level and also play a significant role in understanding and characterizing exchanges in liquid systems. Preferential solvation Parameter δij provides information about deviation from ideal behavior for the solvent. In this work structure factors S(0) and preferential solvation Parameter δij were evaluated of binary Liquid Mixtures of Norbornadiene with Benzene, Cyclohexane, Decane, and Carbon Tetrachloride using Kirkwood Buff formalism. For the said binary mixtures experimental data pertaining to the calculations were taken from literature. Obtained results indicate that molecules which tend to form dipole interactions or hydrogen bonds form favorable interactions as seen in Norbornadiene + carbon tetrachloride where the small molecule of CCl4 is not sterically hindered to approach the polar Norbornadiene molecule. Long chain and ring structure of carbon have a negative influence on hetero interactions. Studying these parameters will develop predictive techniques to determine the right composition for optimum performance of the liquid mixture.

Virtual screening of norbornadiene-based molecular solar thermal energy storage systems using a genetic algorithm.

We present a computational methodology for the screening of a chemical space of 1025 substituted norbornadiene molecules for promising kinetically stable molecular solar thermal (MOST) energy storage systems with high energy densities that absorb in the visible part of the solar spectrum. We use semiempirical tight-binding methods to construct a dataset of nearly 34000 molecules and train graph convolutional networks to predict energy densities, kinetic stability, and absorption spectra and then use the models together with a genetic algorithm to search the chemical space for promising MOST energy storage systems. We identify 15 kinetically stable molecules, five of which have energy densities greater than 0.45 MJ/kg, and the main conclusion of this study is that the largest energy density that can be obtained for a single norbornadiene moiety with the substituents considered here, while maintaining a long half-life and absorption in the visible spectrum, is around 0.55 MJ/kg.

Role of Solvent Molecules as a Trigger for the Crystal Phase Transition of Syndiotactic Polystyrene/Solvent Complex

The phase transitions occurring in the syndiotactic polystyrene−norbornadiene complex were investigated by simultaneous measurements of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). To understand the effect of norbornadiene molecules on the phase-transition behavior, the δ form samples with different contents of norbornadiene were prepared. By heating these samples, we found that the δ-to-γ transition occurred well below 100 °C in a broad temperature range, and the onset of the transition temperature depended on the content of norbornadiene included in the starting sample. The sample without norbornadiene molecules showed the δ-to-γ transition to be above 100 °C. Upon further heating, the γ form transformed into a mixture of α and β forms in the presence of norbornadiene molecules, whereas the sample without norbornadiene transformed into only the α form. In this way, it has been found that the solvent molecules, which are not completely evaporated from the sample but ...

2 + 2] Dimerization of norbornadiene and its derivatives in the presence of nickel complexes and zinc metal

Norbornadiene undergoes [2 + 2] reaction in THF in the presence of NiX 2 and zinc metal powder to give an exo- trans-exo dimer and an exo- trans-exo- trans-exo trimer. In these products, the norbornadiene molecules are linked to each other by forming cyclobutane rings with all cyclobutane carbons occupying exo positions relative to the bridging carbons on the two norbornadiene fragments. Polymerization of norbornadiene occurs if the catalyst NiX 2 is replaced by Ni(PPh 3) 2Cl 2. 1,4-Dihydro-1,4-epoxynaphthalene, 5,8-dimethoxy-1,4-dihydro-1,4-epoxynaphthalene, 5-methoxy-1,4-dihydro-1,4-epoxynaphathalene and methyl 1,4-dihydro-1,4-iminonaphthalene-9-carboxylate also dimerize to give exo- trans-exo products in excellent yields in toluene in the presence of Ni(PPh 3) 2Cl 2 and Zn powder. For the dimerization products of 5-methoxy-1,4-dihydro-1–4-epoxynaphthalene, cis and trans isomers with respect to the orientation of methoxy groups in about 1 : 1 ratio were oberved. Under similar reaction conditions for the dimerization of norbornadiene, norbornene undergoes reductive dimerization to afford a product which consists of two norbornyl groups. The structure of this product is also exo- trans-exo.

Microstructure of ring-opened polymers and copolymers of norbornadiene

A variety of homopolymers of norbornadiene and copolymers with norbornene have been synthesized using a range of olefin metathesis catalysts. By employing hex-1-ene as chain-transfer agent, the molecular weight of these materials has been regulated to levels that permit high solubilities in suitable solvents. As a result, high-quality 13C and 1H NMR spectra of these poly(norbornadienes) have been obtained of a quality hitherto observed only for analogous poly(norbornenes). These spectra have been fully assigned and the detailed microstructure of the homopolymers and copolymers established. One of the most significant observations is that OsCl 3 as catalyst affords essentially all- cis polymers of norbornadiene, in contrast to norbornene, where the cis content is <50%. Furthermore, the copolymer of the monoene and diene is also high- cis and compositionally random, a result which indicates that the metallacarbene propagating complex holds one norbornadiene molecule as a diendo chelating ligand, which remains intact as a spectator species throughout the reaction. The steric bulk of this extra ligand then constrains the incoming monoene or diene monomer to form metallacyclobutanes in the cis mode. In some cases, for example RuCl 3, this chelating effect is so dramatic that it effectively renders the catalyst almost inert.

The evidence for a metastable phase in norbornadiene: X-ray and quasi-elastic neutron scattering studies

The dynamics of the norbornadiene molecule is studied over the temperature range 190-265 K. Measurements below T=202 K and above T=254 K correspond to the ordered phase and to the liquid state, respectively. In the range 202-254 K, two plastic phases can exist, depending on the cooling conditions. On the timescale accessible to time-of-flight neutron spectroscopy (10-11-10-12 s), an elastic incoherent structure factor is extracted in the different phases. From its analysis, quasi-elastic spectra are described on the basis of a model associating 60 degrees jump rotations with a displacement of the centre of mass of the molecules. The same model holds for the two plastic phases, no difference in the dynamics of the molecules being evident. The temperature dependence of the broadening yields a unique Arrhenius law with a rather small value of the activation energy. In the liquid state, in addition to this rotational motion, a long-range diffusion by a jump mechanism was evidenced.

Vinyliden-Metallkomplexe aus Norbornadien: Isolierung eines Metallacyclus als Zwischenstufe

The iridium compound [Ir(C 7H 8Cl] x ( 6), which is obtained from [(C 8H 14) 2Ir-Cl] 2 and norbornadiene, reacts with triisopropylphosphine in benzene at 50°C to give the square-planar vinylidene complex trans-[IrCl(CCHC 7H 9)(P-i-Pr 3) 2] ( 10) almost quantitatively. At lower temperatures, a polycyclic intermediate 8 can be isolated in which iridium, together with two norbornadiene molecules forms a metallacyclic ring. 8 reacts smoothly at 35°C in chloroform to give 10 and cyclopentadiene. Similar di-t-butylmethylphosphine derivatives have been prepared analogously.

Diolefin cationic rhodium complexes with sulfur donors. X-ray structure of [Rh(NBD) 2(SEt 2)]CIO 4

The preparation and properties of cationic rhodium complexes of the type [Rh(diolefin)L 2]ClO 4 (diolefin  COD, NBD; L  sulfur donor ligand) are described. Pentacoordinated complexes of general formula [Rh(NBD) 2L]ClO 4 (L  SMe 2, SEt 2, tetrahydrothiophen or trimethylene sulfide) are also reported. The crystal structure of [Rh(NBD) 2(Set 2)]ClO 4 has been determined by X-ray methods. The crystals are rhombohedral, space group R3 c, with a 14.530(7) Å and α 77.86(5)° ( Z = 6). The structure was solved from diffractometer data by direct and Fourier methods and refined by full-matrix least-squares to R = 0.054 for 937 independent observed reflections. In the cationic [Rh(NBD) 2(SEt 2)] + complex the Rh atom is pentacoordinated, the geometry about the metal being a square pyramid whose base is defined by the midpoints of the olefin bonds from two norbornadiene molecules and the apex is occupied by a sulfur atom of the thioether ligand at a rather long distance [Rh−S 2.500(4) Å].

Photobehavior of copper(I) compounds. Role of copper(I)-phosphine compounds in the photosensitized valence isomerization of norbornadiene

The valence isomerization of norbornadiene to quadricyclene can be photosensitized with high quantum efficiency by certain copper(I)-phosphine compounds. Sensitization yields in the presence of Cu(PPh/sub 3/)/sub 2/BH/sub 4/ and Cu(PPh/sub 2/Me)/sub 3/BH/sub 4/ attain limiting values of 0.76 and 0.54, respectively, at high norbornadiene concentrations. In contrast, Cu(diphos)BH/sub 4/ (diphos is 1,2-bis(diphenylphosphino)ethane), which contains a bidentate phosphine ligand, is decidely less effective. The mechanism of sensitization by these copper(I)-phosphine compounds is fundamentally different from that exhibited by simple cuprous salts in that no ground-state coordination to the metal center occurs. A pathway involving the bimolecular interaction of the photoexcited Cu(I) compound with a ground-state norbornadiene molecule is better able to accommodate the available data. Electronic absorption and emission studies reveal some interesting differences between the spectral properties of effective vs. noneffective sensitizers.

Reacktivität von metall-metall-bindugen: Katalytisch aktive komplexe mit Fe-Fe-, Fe-Co- und Mn-Co-bindungen

Several dinuclear arsenic bridged carbonyl complexes with FeFe, MnCo, and mainly feCo bonds catalyse the dimerization of norbornadiene. The reactions can be directed exclusively to the exo-trans-exo or the Binor-S dimer. In two cases catalytically active intermediates could be isolated. Of these (CO) 4Fe-AsMe 2-Co(CO) 2C 7H 8 was characterized by an X-ray crystal structure analysis which showed that the norbornadiene molecule has opened the metal metal bond. The catalysts are inactive towards other olefinic substrates.

Catalytic role of copper(I) in the photoassisted valence isomerization of norbornadiene

A detailed investigation of the photoassisted valence isomerization of norbornadiene (NBD) to quadricyclene (Q) in the presence of copper(I) salts is reported. In the prototypal cuprous chloride-norbornadiene system, spectral evidence indicates that a 1 : 1 ClCu-NBD ..pi.. complex is present in solution and is, in fact, the photoactive species. Quantum yield data obtained in several solvents and at different initial NBD concentrations support this premise. The photoreaction is thought to originate via population of an olefin-metal charge-transfer state of the complex. Possible pathways by which this excited state yields Q are considered. The absence of NBD photodimerization products suggests that Cu(I) salts containing strongly binding anions have little tendency to coordinate more than one NBD molecule.

Vibrational spectra of complexes of norbornadiene with transition metals

1. The IR spectra of norbornadiene in three aggregated states and the Raman spectra of the liquid were investigated. 2. An assignment was proposed for the basic vibrations of the norbornadiene molecule. 3. It is suggested that the diagonal force constant of the C=C bond lies below the usual value of 14.2·106 cm−2.

The refinement of the crystal structure of norbornadiene palladium chloride

Abstract : The crystal structure of norbornadiene palladium chloride has been refined with data obtained by counter methods from crystals maintained at liquid nitrogen temperature. After refinement the conventional discrepancy index R=0.0275. The carbon-carbon single bond distances in the norbornadiene molecule are normal: 1.547, 1.552, 1.554 (=0.006) A; the double bond distances are barely significantly longer than normal: 1.366, 1.366 (=0.010) A. The observed double bond distance is now compatible with the infrared spectrum of the complexed olefin. (Author)