Showing papers on "Norbornadiene published in 2019"
TL;DR: A cobalt-substrate complex was crystallographically characterized as the opposite diastereomer to that expected for productive hydrogenation demonstrating a Curtin-Hammett kinetic regime similar to rhodium catalysis.
Abstract: Chloride abstraction from [(R,R)-(iPr DuPhos)Co(μ-Cl)]2 with NaBArF 4 (BArF 4 =B[(3,5-(CF3 )2 )C6 H3 ]4 ) in the presence of dienes, such as 1,5-cyclooctadiene (COD) or norbornadiene (NBD), yielded long sought-after cationic bis(phosphine) cobalt complexes, [(R,R)-(iPr DuPhos)Co(η2 ,η2 -diene)][BArF 4 ]. The COD complex proved substitutionally labile undergoing diene substitution with tetrahydrofuran, NBD, or arenes. The resulting 18-electron, cationic cobalt(I) arene complexes, as well as the [(R,R)-(iPr DuPhos)Co(diene)][BArF 4 ] derivatives, proved to be highly active and enantioselective precatalysts for asymmetric alkene hydrogenation. A cobalt-substrate complex, [(R,R)-(iPr DuPhos)Co(MAA)][BArF 4 ] (MAA=methyl 2-acetamidoacrylate) was crystallographically characterized as the opposite diastereomer to that expected for productive hydrogenation demonstrating a Curtin-Hammett kinetic regime similar to rhodium catalysis.
45 citations
TL;DR: It is demonstrated that the anchored CNBD monolayer remains operational and can be photo-converted to its energy-rich counterpart 2-cyano-3-(4-carboxyphenyl)quadricyclane (CQC).
Abstract: Molecular photoswitches provide an extremely simple solution for solar energy conversion and storage. To convert stored energy to electricity, however, the photoswitch has to be coupled to a semiconducting electrode. In this work, we report on the assembly of an operational solar-energy-storing organic-oxide hybrid interface, which consists of a tailor-made molecular photoswitch and an atomically-defined semiconducting oxide film. The synthesized norbornadiene derivative 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD) was anchored to a well-ordered Co3O4(111) surface by physical vapor deposition in ultrahigh vacuum. Using a photochemical infrared reflection absorption spectroscopy experiment, we demonstrate that the anchored CNBD monolayer remains operational, i.e., can be photo-converted to its energy-rich counterpart 2-cyano-3-(4-carboxyphenyl)quadricyclane (CQC). We show that the activation barrier for energy release remains unaffected by the anchoring reaction and the anchored photoswitch can be charged and discharged with high reversibility. Our atomically-defined solar-energy-storing model interface enables detailed studies of energy conversion processes at organic/oxide hybrid interfaces.
36 citations
TL;DR: In this paper, the photochemical conversion of the energy-lean 2-cyano-3-(3,4-dimethoxyphenyl)-norbornadiene (NBD) to its energy-rich counterpart 2-cyano-3-dimethyl-quadricyclane (QC) and the electrochemically triggered reconversion were investigated.
27 citations
TL;DR: In this article, solvent effects on photowitches based on the norbornadiene-quadricyclane (NBD-QC) couple were explored for the first time.
Abstract: Molecular photoswitches based on the norbornadiene-quadricyclane (NBD-QC) couple can be used to store solar energy and to release the stored energy as heat on demand. In this context, the energy storage time as well as the quantum yield of the energy storing reaction are important parameters. Here, we explore for the first time solvent effects on these processes for a series of four NBD-QC compounds in four different solvents with different polarity (acetonitrile, tetrahydrofuran, toluene, and hexane). We show that the energy storage time of the QC forms can vary by up to a factor of 2 when going from the most to the least polar solvent. Moreover, we show that for the norbornadiene derivatives with an asymmetric 1,2 substitution pattern, the quantum yield of conversion is highly solvent dependent, whereas this is not the case for the symmetrically substituted compounds. The spectroscopic observations are further rationalized using classical molecular dynamics (MD) simulations and time-dependent density functional theory (TDDFT) calculations. These demonstrate the importance of vibrational and rotational excitations for obtaining broad-band absorption, which is a prerequisite for capturing a wide range of the solar spectrum.
24 citations
TL;DR: In this paper, the surface chemistry of the molecular solar thermal energy storage system of the valence isomer pair norbornadiene (NBD)/quadricyclane (QC) on Ni(111) was investigated.
Abstract: We have investigated the surface chemistry of the molecular solar thermal energy storage system of the valence isomer pair norbornadiene (NBD)/quadricyclane (QC) on Ni(111). Our multimethod approach includes UV-photoelectron spectroscopy (UPS), high-resolution X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure (NEXAFS), and density functional theory (DFT) calculations. The NBD/QC system holds the potential to be utilized in future energy storage technologies due to its comparably high gravimetric energy storage density, and the release of energy in a catalytic and sustainable cycle. UPS shows molecular adsorption of both compounds at 120 K, as is also predicted by DFT. NEXAFS and DFT suggest an adsorption geometry of NBD with both double bonds binding to the surface (η2:η2). For QC, no preference is found, and both the η2:η2 and the η2:η1 adsorption geometry are stable. The conversion of QC to NBD is thermally activated. From UPS, a reaction temperature of ∼175 K is determin...
22 citations
TL;DR: The synthesis and characterisation of a series of covalently linked norbornadiene/dihydroazulene (NBD/DHA) conjugates are presented, using the Sonogashira coupling as the key synthetic step and revealed an energy storage capacity of 106-110 kJ mol-1 of the QC-VHF isomers, which is higher than the sum of the capacities of the individual, separate units.
Abstract: The introduction of various photochromic units into the same molecule is an attractive approach for the development of novel molecular solar thermal (MOST) energy storage systems. Here, we present the synthesis and characterisation of a series of covalently linked norbornadiene/dihydroazulene (NBD/DHA) conjugates, using the Sonogashira coupling as the key synthetic step. Generation of the fully photoisomerized quadricyclane/vinylheptafulvene (QC/VHF) isomer was found to depend strongly on how the two units are connected - by linear conjugation (a para-phenylene bridge) or cross-conjugation (a meta-phenylene bridge) or by linking to the five- or seven-membered ring of DHA - as well as on the electronic character of another substituent group on the NBD unit. When the QC-VHF system could be reached, the QC-to-NBD back-reaction occurred faster than the VHF-to-DHA back-reaction, while the latter could be promoted simply by the addition of Cu(i) ions. The absence or presence of Cu(i) can thus be used to control whether heat releases should occur on different or identical time scales. The experimental findings were rationalized in a computational study by comparing natural transition orbitals (NTOs). Moreover, the calculations revealed an energy storage capacity of 106-110 kJ mol-1 of the QC-VHF isomers, which is higher than the sum of the capacities of the individual, separate units. The major contribution to the energy storage relates to the energetic QC form, while the major contribution to the absorption of visible light originates from the DHA photochrome; some of the NBD-DHA conjugates had absorption onsets at 450 nm or beyond.
20 citations
TL;DR: The lithiocarbyne (Tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate) reacts with [PtCl2 (L2 )] to furnish ditungsten ethanediylidyne complexes, which are displaced by monodentate CO or isocyanide ligands to provide derivatives where both W≡C bonds coordinate to a single Pt0 center.
Abstract: The lithiocarbyne [W(≡CLi)(CO)2 (Tp*)] (Tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate) reacts with [PtCl2 (L2 )] (L2 =1,5-cyclo-octadiene, norbornadiene) to furnish ditungsten ethanediylidyne complexes, [W2 {μ-C2 Pt(L2 )}(CO)4 (Tp*)2 ], wherein a trigonal platinum(0) center unsymmetrically ligates one W≡C bond in the solid state but rapidly shimmies between the two W≡C bonds in solution. The η4 -dienes are displaced by monodentate CO or isocyanide ligands to provide derivatives where both W≡C bonds coordinate to a single Pt0 center, attended by significant distortion of the WCCW spine.
19 citations
TL;DR: The adsorption behavior, energy release, and surface chemistry on Ni(111) is studied using high-resolution X-ray photoelectron spectroscopy (HR-XPS), UV photo Electron Spectroscopy, and density functional theory calculations.
Abstract: Dwindling fossil fuels force humanity to search for new energy production routes. Besides energy generation, its storage is a crucial aspect. One promising approach is to store energy from the sun chemically in strained organic molecules, so-called molecular solar thermal (MOST) systems, which can release the stored energy catalytically. A prototypical MOST system is norbornadiene/quadricyclane (NBD/QC) whose energy release and surface chemistry need to be understood. Besides important key parameters such as molecular weight, endergonic reaction profiles, and sufficient quantum yields, the position of the absorption onset of NBD is crucial to cover preferably a large range of sunlight’s spectrum. For this purpose, one typically derivatizes NBD with electron-donating and/or electron-accepting substituents. To keep the model system simple enough to be investigated with photoemission techniques, we introduced bromine atoms at the 2,3-position of both compounds. We study the adsorption behavior, energy release, and surface chemistry on Ni(111) using high-resolution X-ray photoelectron spectroscopy (HR-XPS), UV photoelectron spectroscopy, and density functional theory calculations. Both Br2-NBD and Br2-QC partially dissociate on the surface at ∼120 K, with Br2-QC being more stable. Several stable adsorption geometries for intact and dissociated species were calculated, and the most stable structures are determined for both molecules. By temperature-programmed HR-XPS, we were able to observe the conversion of Br2-QC to Br2-NBD in situ at 170 K. The decomposition of Br2-NBD starts at 190 K when C–Br bond cleavage occurs and benzene and methylidene are formed. For Br2-QC, the cleavage already occurs at 130 K when cycloreversion to Br2-NBD sets in.
17 citations
TL;DR: Under the optimized conditions, a broad range of 3D-type heterocyclic sulfoximines with good functional group tolerance were generated.
Abstract: The Pd-catalyzed multicomponent reactions of NH-sulfoximine, aryl iodide and norbornadiene (NBD) are reported to chemoselectively produce fused medium-sized sulfoximine polyheterocycles in good to excellent yields. The addition of the dibenzylideneacetone (dba) ligand was found to be useful for this tandem annulation reaction. Under the optimized conditions, a broad range of 3D-type heterocyclic sulfoximines with good functional group tolerance were generated.
13 citations
TL;DR: A novel palladium-catalyzed reaction that results in phenanthrene derivatives using aryl iodides, ortho-bromobenzoyl chlorides and norbornadiene in one pot has a wider substrate range, shorter reaction times and higher yields of products than previously reported methods.
Abstract: Herein we report a novel palladium-catalyzed reaction that results in phenanthrene derivatives using aryl iodides, ortho-bromobenzoyl chlorides and norbornadiene in one pot. This dramatic transformation undergoes ortho-C–H activation, decarbonylation and subsequent a retro-Diels–Alder process. Pleasantly, this protocol has a wider substrate range, shorter reaction times and higher yields of products than previously reported methods.
12 citations
TL;DR: Novel bis(isoselenocarbonyl) complexes eliminate the diene upon heating to provide W2Pt(μ-CSe)2(CO)4(L2)(Tp*)2, in which the CSe ligands close to bridge W-Pt bonds in a σ-π mode.
TL;DR: First successful conversion of NBD to QC under UHV conditions is reported and the conversion behavior is followed as a function of the photon dose and NBD/MK ratio, indicating good electronic coupling between NBD and MK even in a frozen multilayer.
Abstract: Photochemical in situ studies in a well-controlled surface science environment can help to understand photochemical reactions in organic thin films in more detail. To perform such studies without external focusing or light guiding systems, we designed a high-intensity UV-photon source, which is compatible with an ultra-high vacuum (UHV) environment. The UV source is based on a high power light-emitting diode (LED), soldered onto a copper heat reservoir to avoid overheating. The LED can be placed in close vicinity in front of a single crystal, providing flux densities of 2 × 1018 photons s-1 cm-2 at a wavelength of 365 nm. Thus, the device provides light intensities one order of magnitude higher as compared to conventional continuous wave arc lamps, at only a small variation of the flux of less than ±20% over a sample surface of 10 × 8 mm2. The UV source is mounted in a UHV infrared reflection absorption spectroscopy system and triggered by using the IR spectrometer. This allows fully automatized in situ IR studies of photochemical reactions at interfaces and thin films. We prove the functionality of the device by studying the photochemical conversion of norbornadiene (NBD) to quadricyclane (QC) mediated by the photosensitizer 4,4'-bis(dimethylamino)benzophenone (Michler's ketone, MK). NBD and MK were grown by physical vapor deposition in the form of thin films on Pt(111) at 120 K. Even at prolonged UV irradiation (>100 s), the temperature of the sample increased by less than 10 K. We report first successful conversion of NBD to QC under UHV conditions and follow the conversion behavior as a function of the photon dose and NBD/MK ratio. Initial quantum yields of up to 23% and selectivity for a QC of 70% are obtained at NBD/MK of 7.4:1, indicating good electronic coupling between NBD and MK even in a frozen multilayer. For both very small and very large NBD loadings, the conversion efficiency decreases, which is attributed to the effect of the metallic substrate and phase separation in thick multilayers, respectively.
TL;DR: In this article, the synthesis of derivatives of a well-studied compound, 2-cyano-3-anisyl norbornadiene (NBD5) was extended by conversion of the nitrile into acrylonitrile and acrylate derivatives over two steps.
TL;DR: In this paper, a simple one-step approach for the selective synthesis of exo-norbornenes with organosilicon substituents is suggested through the direct hydrosilylation of norbornadiene-2,5 with chlorine-free silanes.
Abstract: A simple one-step approach for the selective synthesis of exo-norbornenes with organosilicon substituents is suggested through the direct hydrosilylation of norbornadiene-2,5 with chlorine-free silanes. Using the example of norbornadiene-2,5 hydrosilylation with pentamethyldisiloxane and 1,1,1,3,5,5,5-heptamethyltrisiloxane, the possibility of obtaining exo-isomers of norbornenes with 100 exo-/endo-selectivity is shown. The investigation of Pt-, Rh-, and Pd-complexes in combination with various ligands as catalysts was performed. The hydrosilylation of norbornadiene-2,5 in the presence of Pt- or Rh-catalysts was not selective and led to a mixture consisting of three isomers (exo-/endo-norbornenes and substituted nortricyclane). In the case of the Pd-salt/ligand catalytic system, the formation of an endo-isomer was not observed at all and only two isomers were formed (exo-norbornene and nortricyclane). The selectivity of exo-norbornene/nortricyclane formation strongly depended on the nature of the ligand in the Pd-catalyst. The best selectivity was revealed when R-MOP was the ligand, while the highest catalytic activity was reached with a dioxalane-containing ligand.
TL;DR: In this article, a poly(3,5-tricyclo[2.02,6]heptylene) [poly(norbornadiene) (PNBD)] mediated by the TiCl4/Et2AlCl catalytic system is reported.
TL;DR: In this article, the reaction of benzonorbornadiene and ethyl acetoacetate with 1,3-cyclohexanedione and Cu(OAc)2 was studied.
TL;DR: The remaining two alkynyl groups in benzoindenotetracene were further reacted with norbornadiene or arylamine through transition metal-catalyzed cyclization to giveπ-extended pyracylene derivatives.
TL;DR: In this article, the value of the kinetic isotope effect and the nature of the limiting step in the reaction of hydroallylation of norbornadiene are determined using deuterated reagents.
Abstract: Norbornadiene allylation by allyl formate in the presence of palladium catalytic systems has a number of features associated with different directions of β-hydride transfer in key intermediates, which can be carried out with the participation of allyl, norbornenyl, or formyl fragments. The value of the kinetic isotope effect and the nature of the limiting step in the reaction of hydroallylation of norbornadiene are determined using deuterated reagents.
TL;DR: POPs featuring the normal oxyethylene chain in the side-chain exhibit excellent yields and high molecular weights in methanol and N,N-dimethylformamide at 40 °C, compared with poly(n-alkyl propiolate)s (PnAP)s.
Abstract: In this study, poly(oxyethyl propiolate)s (POP)s featuring various oxyethylene derivatives are synthesized using a [Rh(norbornadiene)Cl]₂ catalyst. In particular, POPs featuring the normal oxyethylene chain in the side-chain exhibit excellent yields and high molecular weights in methanol and N,N-dimethylformamide at 40 °C, compared with poly(n-alkyl propiolate)s (PnAP)s. The high reactivity of the oxyethyl propiolate (OP) monomers is clarified by considering the time dependences of the polymerization yields of OPs and alkyl propiolates (Aps). Furthermore, the monomer structure and intermediate conformation of the Rh complex are optimized using Density Function theory (DFT) methods (B3LYP/6-31G** and B3LYP/LANL2DZ) and a polymerization mechanism is proposed.
TL;DR: In this paper, an efficient synthetic approach to phenazone derivatives containing a 1,2,4-triazine or pyridine fragment has been proposed on the basis of successive nucleophilic substitution of hydrogen ( $S_N^H) in 1, 2, 4 -triazine 4-oxides and aza-Diels-Alder reaction with norbornadiene as dienophile.
Abstract: An efficient synthetic approach to phenazone derivatives containing a 1,2,4-triazine or pyridine fragment has been proposed on the basis of successive nucleophilic substitution of hydrogen (
$${\rm{S_N^H}}$$
) in 1,2,4-triazine 4-oxides and aza-Diels-Alder reaction with norbornadiene as dienophile.
TL;DR: This study reveals important new isomers and isomerization pathways on the C7H8+ potential energy surface, through the application of gas-phase electronic photodissociation spectroscopy in conjunction with ab initio calculations.
Abstract: The unimolecular reactions of C7H8+ radical cations are among those most studied by mass spectrometry, especially the rearrangement of toluene and cycloheptatriene molecular ions, which are directly connected to the formation of benzylium and tropylium cations. This study reveals important new isomers and isomerization pathways on the C7H8+ potential energy surface, through the application of gas-phase electronic photodissociation spectroscopy in conjunction with ab initio calculations. Presented are the first gas-phase vibrationally resolved electronic spectra of the o-isotoluene, norcaradiene, bicyclo[3.2.0]hepta-2,6-diene radical cations, and ring-opened products from cyclic C7H8+ species. The isomerization route from the norbornadiene radical cation to the toluene radical cation, which competes with isomerization to the bicyclo[2.2.1]hepta-2-ene-5-yl-7-ylium radical cation, is identified. Further, this work expands understanding of the C7H8+ potential energy surface by connecting spiro[2.4]hepta-4,6-diene and acyclic 1,2,4,6-heptatetraene radical cations, and confirms the important role of the o-isotoluene radical cation in the interconversion pathways of C7H8+ species.
TL;DR: The theoretical results indicate that the exoselective pathway for the cyclohexadiene substrate proceeds by a novel two-step successive C-C coupling, while the endoselectives pathway undergoes the C- C coupling reaction in a conventional concerted manner.
Abstract: The recent success of Krische et al. ( Angew. Chem., Int. Ed. 2017, 56, 14667–14671) in achieving a ruthenium(0)-catalyzed transfer hydrogenative cycloaddition of 1,2-diols with cyclohexadiene and ...
TL;DR: In this paper, a series of addition copolymers of 3-trimethylsilyltricyclo[4.2.1.5]non-7-ene with a bifunctional comonomer (2,5-norbornadiene dimer) was synthesized.
Abstract: A series of addition copolymers of 3-trimethylsilyltricyclo[4.2.1.02.5]non-7-ene with a bifunctional comonomer—2,5-norbornadiene dimer—are synthesized. It is shown that, with the introduction of a small amount of the 2,5-norbornadiene dimer (up to 0.3 mol %), the molecular weight of the polymer increases. When using a large amount of the 2,5-norbornadiene dimer, crosslinked insoluble polymers are formed. As exemplified by a copolymer containing 0.3 mol % 2,5-norbornadiene dimer units, the introduction of the bifunctional comonomer does not lead to a significant decrease in gas permeability, and the developed method can be used to increase the molecular weights of polymers, improve their mechanical properties, and make polymers resistant against plasticization.
TL;DR: In this paper, a series of [RuCl(dppb)(μ-Cl)3Ru(dplb)(amine)] complexes, where amine is pyrrolidine (1), piperidine (2) or perhydroazepine (3), were synthesized and characterized by elemental analysis, FTIR, UV-Vis, and 1H, 13C{1H} and 31P{ 1H} NMR spectroscopy.
TL;DR: In this paper, the use of improved protocol for the reaction of rhodium acetylacetonate complexes (diene)RhAcac [diene is 1,5-cyclooctadiene or norbornadiene] with exo-nido-ruthenacarboranes 5,6,10-[RuCl(PPh3)2]-5, 6,10-(μ-H)3-10-H-7,8-R2-7-8-C2B8H6 (R = H or Me)
TL;DR: In this paper, a mini-review is devoted to the polymerization of tricyclo [4.2.1.5]non-7-enes (tricyclononenes), which is a product of norbornadiene photo-isomerization.
Abstract: The expansion of the range of available and reactive monomers allowing preparation of novel polymeric materials, is an actual task of polymer chemistry. This mini-review is devoted to the polymerization of tricyclo [4.2.1.02,5]non-7-enes (tricyclononenes) and tricyclo[4.2.1.02,5]nona-3,7-dienes (tricyclonona-dienes)–norbornene type monomers containing norbornene and cyclobutane or cyclobutene fragments in the molecules. Their synthesis is carried out using available cyclopentadiene or quadricyclane, which is a product of norbornadiene photo-isomerization. The features of ring-opening metathesis and addition polymerization of tricyclononenes with participation of double bond in the norbornene fragment are highlighted. Examples of the polymerization of a wide range of tricyclononenes with F-, Si-, O-, and N-containing substituents have demonstrated that they are noticeably more active monomers than norbornenes with the same substituents. The main successes have been achieved in the synthesis of F- and Si-substituted polytricyclononenes, which are promising materials for lithography and membrane gas separation.
TL;DR: Inorganic ionic liquids are first shown to catalyze the alcoholysis of heptacyclo [8.4.0.1] and tetradecane as mentioned in this paper.
Abstract: Inorganic ionic liquids are first shown to catalyze the alcoholysis of heptacyclo-[8.4.0.02,12.03,8.04,6.05,9.011,13]tetradecane (heptacyclic dimer of norbornadiene, binor-S) with primary and secondary alcohols. The reaction occurs at 65−100°C for 6−14 h via regioselective cleavage of the cyclopropane C4−C5 bond in binor-S to form 10-exo-alkoxyhexacyclo[9.2.1.02,7.03,5.04,8.09,13] tetradecanes in 85−90% yields.
TL;DR: In this article, double adducts of anthracene derivatives and norbornadiene (2,5-(bicyclo-[2.2.1]-hepta-2.5-diene)) have been synthesized and their structure investigated.
Abstract: Double adducts of norbornadiene-2,5 and anthracene derivatives have been synthesized using the Diels–Alder reaction. The possibility of selective preparation of both symmetrical and unsymmetrical adducts depending on the reaction conditions has been shown. For these cycloadducts exclusively consisting of carbon and hydrogen, an unusual and interesting feature has been revealed, namely, the signals of the protons of the bridge methylene groups in the 1H NMR spectra have chemical shifts in the negative region. In this work, double adducts of anthracene derivatives and norbornadiene (2,5-(bicyclo-[2.2.1]-hepta-2,5-diene)) have been synthesized and their structure investigated. The synthesized compounds possess a rigid, branched, and bulky structure suitable for the fabrication of composite membrane materials.
Patent•
06 Jun 2019
TL;DR: In this article, the present invention relates to norbornadiene compounds (Formula I), and the corresponding quadricyclane compounds (formula III), which are to be included in a molecular thermal systems (MOST), and to be used for storing solar energy.
Abstract: The present invention relates to norbornadiene compounds (Formula I), and the corresponding quadricyclane compounds (Formula III). The compounds are to be included in a molecular thermal systems (MOST), and to be used for storing solar energy.
Patent•
21 Oct 2019
TL;DR: In this article, a method of producing a norbornadiene fullerene derivative of formula 1:, which can be used as a complexing agent, a sorbent, a biologically active compound.
Abstract: FIELD: chemistry.SUBSTANCE: present invention relates to a method of producing a norbornadiene fullerene derivative of formula 1:,which can be used as a complexing agent, a sorbent, a biologically active compound. Method consists in the fact that C-fullerene reacts with norbornadiene ether of chloroacetic acidin dry toluene in the presence of t-BuOK, taken in molar ratio C:ether:t-BuOK = 1:(1–2):(2–4), at temperature of 20 °C for 5–15 minutes.EFFECT: disclosed method enables to obtain an end product with output of 10–52 %.1 cl, 1 tbl, 7 ex