pinecone/core-2020-05-10-deduplication huggingface dataset:
D–π–A triarylboron compounds with tunable push–pull character achieved by modification of both the donor and acceptor moieties.

The push–pull character of a series of donor–bithienyl–acceptor compounds has been tuned by adopting triphenylamine or 1,1,7,7-tetramethyljulolidine as a donor and B(2,6-Me2-4-RC6H2)2 (R=Me, C6F5 or 3,5-(CF3)2C6H3) or B[2,4,6-(CF3)3C6H2]2 as an acceptor. Ir-catalyzed C[BOND]H borylation was utilized in the derivatization of the boryl acceptors and the tetramethyljulolidine donor. The donor and acceptor strengths were evaluated by electrochemical and photophysical measurements. In solution, the compound with the strongest acceptor, B[2,4,6-(CF3)3C6H2]2 ((FMes)2B), has strongly quenched emission, while all other compounds show efficient green to red (ΦF=0.80–1.00) or near-IR (NIR; ΦF=0.27–0.48) emission, depending on solvent. Notably, this study presents the first examples of efficient NIR emission from three-coordinate boron compounds. Efficient solid-state red emission was observed for some derivatives, and interesting aggregation-induced emission of the (FMes)2B-containing compound was studied. Moreover, each compound showed a strong and clearly visible response to fluoride addition, with either a large emission-color change or turn-on fluorescence
The gold(I)-catalysed protodecarboxylation mechanism

The authors thank the EPSRC and the ERC (FUNCAT) for funding. S.P.N. is a Royal Society Wolfson Merit Award holder.A mechanistic study of the gold-catalysed protodecarboxylation is described. Each reaction step has been investigated experimentally and computationally. More specifically, the activation parameters for the decarboxylation step have been determined through kinetic studies. Further experimental studies on the hydrolysis of the arylgold intermediate have revealed that the protodeauration can become competitive with the decarboxylation process at high conversions. This switch in rate-limiting step has been shown to be pKa-dependent. These studies have been supported by DFT calculations and permit a better understanding of which prevalent features of the reaction mechanism account for the decarboxylation process.PostprintPeer reviewe
Gold(I)-Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho-(Alkynyl)styrenes

Indenes and related polycyclic structures have been efficiently synthesized by gold(I)-catalyzed cycloisomerizations of appropriate ortho-(alkynyl)styrenes. Disubstitution at the terminal position of the olefin was demonstrated to be essential to obtain products originating from a formal 5-endo-dig cyclization. Interestingly, a complete switch in the selectivity of the cyclization of o-(alkynyl)-α-methylstyrenes from 6-endo to 5-endo was observed by adding an alcohol to the reaction media. This allowed the synthesis of interesting indenes bearing an all-carbon quaternary center at C1. Moreover, dihydrobenzo[a]fluorenes can be obtained from substrates bearing a secondary alkyl group at the β-position of the styrene moiety by a tandem cycloisomerization/1,2-hydride migration process. In addition, diverse polycyclic compounds were obtained by an intramolecular gold-catalyzed alkoxycyclization of o-(alkynyl)styrenes bearing a nucleophile in their structure. Finally, the use of a chiral gold complex allowed access to elusive chiral 1H-indenes in good enantioselectivitiesMinisterio de Economia y Competitividad (MINECO) and FEDER (CTQ2010-15358 and CTQ2013-48937-C2-1-P) and Junta de Castilla y Leon (BU237U13) for financial support. A.M.S. thanks the Junta de Castilla y Leon (Consejeria de Educacion) and the Fondo Social Europeo for a PIRTU contract. M.A.R. and P.G.-G. thank MEC for a "Young Foreign Researchers" (SB2009-0186) contract and MINECO for "Juan de la Cierva" contract, respectivelyThis is the peer reviewed version of the following article: Sanjuán, A. M., Rashid, M. A., García-García, P., Martínez-Cuezva, A., Fernández-Rodríguez, M. A., Rodríguez, F. and Sanz, R. (2015), Gold(I)-Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho-(Alkynyl)styrenes. Chem. Eur. J., 21: 3042–3052. doi: 10.1002/chem.201405789, which has been published in final form at 10.1002/chem.201405789. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archivin
Photoisomerisation in Aminoazobenzene-Substituted Ruthenium(II) Tris(bipyridine) Complexes: Influence of the Conjugation Pathway.

International audienceTransition-metal complexes containing stimuli-responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor-acceptor azobenzene derivatives that possess bipyridine groups connected to a 4-dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD-DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes
Dual-modal magnetic resonance/fluorescent zinc probes for pancreatic β-Cell mass imaging.

Despite the contribution of changes in pancreatic β-cell mass to the development of all forms of diabetes mellitus, few robust approaches currently exist to monitor these changes prospectively in vivo. Although magnetic-resonance imaging (MRI) provides a potentially useful technique, targeting MRI-active probes to the β cell has proved challenging. Zinc ions are highly concentrated in the secretory granule, but they are relatively less abundant in the exocrine pancreas and in other tissues. We have therefore developed functional dual-modal probes based on transition-metal chelates capable of binding zinc. The first of these, Gd⋅1, binds ZnII directly by means of an amidoquinoline moiety (AQA), thus causing a large ratiometric Stokes shift in the fluorescence from λem=410 to 500 nm with an increase in relaxivity from r1=4.2 up to 4.9 mm−1 s−1. The probe is efficiently accumulated into secretory granules in β-cell-derived lines and isolated islets, but more poorly by non-endocrine cells, and leads to a reduction in T1 in human islets. In vivo murine studies of Gd⋅1 have shown accumulation of the probe in the pancreas with increased signal intensity over 140 minutes
Chemical synthesis of Burkholderia Lipid A modified with glycosyl phosphodiester-linked 4-amino-4-deoxy-beta-L-arabinose and its immunomodulatory potential

Modification of the Lipid A phosphates by positively charged appendages is a part of the survival strategy of numerous opportunistic Gram-negative bacteria. The phosphate groups of the cystic fibrosis adapted Burkholderia Lipid A are abundantly esterified by 4-amino-4-deoxy-beta-L-arabinose (beta-L-Ara4N), which imposes resistance to antibiotic treatment and contributes to bacterial virulence. To establish structural features accounting for the unique pro-inflammatory activity of Burkholderia LPS we have synthesised Lipid A substituted by beta-L-Ara4N at the anomeric phosphate and its Ara4N-free counterpart. The double glycosyl phosphodiester was assembled by triazolyl-tris-(pyrrolidinyl) phosphonium-assisted coupling of the beta-L-Ara4N H-phosphonate to a-lactol of beta(1 -> 6) diglucosamine, pentaacylated with (R)-(3)-acyloxyacyl- and Alloc-protected (R)-(3)-hydroxyacyl residues. The intermediate 1,1'-glycosyl-H-phosphonate diester was oxidised in anhydrous conditions to provide, after total deprotection, beta-L-Ara4N-substituted Burkholderia Lipid A. The beta-L-Ara4N modification significantly enhanced the pro-inflammatory innate immune signaling of otherwise non-endotoxic Burkholderia Lipid A
Total synthesis and absolute configuration assignment of MRSA active garcinol and isogarcinol

A short total synthesis of (±)-garcinol and (±)-isogarcinol, two endo-type B PPAPs with reported activity against methiciline resistant Staphylococcus aureus (MRSA), is presented. The separation of framework-constructing from framework-decorating steps and the application of two highly regio- and stereoselective Pd-catalysed allylations, that is, the Pd-catalysed decarboxylative Tsuji-Trost allylation and the diastereoselective Pd-catalysed allyl-allyl cross-coupling, are key elements that allowed the total synthesis to be accomplished within 13 steps starting from acetylacetone. After separation of the enantiomers the absolute configurations of the four natural products (i.e., (-)-garcinol, (+)-guttiferone E (i.e., ent-garcinol), (-)-isogarcinol, and (+)-isoxanthochymol (i.e., ent-isogarcinol)) were assigned based on ECD spectroscopy.Fil: Socolsky, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán; ArgentinaFil: Plietker, Bernd .  Universität Stuttgart. Institut für Organische Chemie; Alemani
Oligo(p-phenyleneethynylene) (OPE) molecular wires : synthesis and length dependence of photoinduced charge transfer in OPEs with triarylamine and diaryloxadiazole end groups.

The systematic synthesis and photophysical, electrochemical and computational studies on an extended series of triphenylamine-[C[TRIPLE BOND]C-1,4-C6H2(OR)2]n-C[TRIPLE BOND]C-diphenyl-1,3,4-oxadiazole dyad molecules (the OR groups are at 2,5-positions of the para-phenylene ring and R=C6H13; n=0–5, compounds 1, 2, 3, 4 and 5, respectively) are reported. Related molecules with identical end groups, triphenylamine-C[TRIPLE BOND]C-1,4-C6H2(OR)2-C[TRIPLE BOND]C-triphenylamine (R=C6H13; 6) and diphenyl-1,3,4-oxadiazole-[C[TRIPLE BOND]C-C6H2(OR)2]2-C[TRIPLE BOND]C-diphenyl-1,3,4-oxadiazole (R=C6H13; 7) were also studied. These D–B–A 1–5, D–B–D 6 and A–B–A 7 (D=electron donor, B=bridge, A=electron acceptor) systems were synthesized using palladium-catalysed cross-coupling reactions of new p-phenyleneethynylene building blocks. Steady-state emission studies on the dyads 1–5 reveal a complicated behavior of the emission that is strongly medium dependent. In low polarity solvents the emission is characterized by a sharp high-energy peak attributed to fluorescence from a locally excited (LE) state. In more polar environments the LE state is effectively quenched by transfer into an intramolecular charge-transfer (ICT) state. The medium dependence is also observed in the quantum yields (QYs) which are high in cyclohexane and low in acetonitrile, thus also indicating charge-transfer character. Low-temperature emission spectra for 2–5 in dichloromethane and diethyl ether also reveal two distinct excited states, namely the LE state and the conventional ICT state, depending on solvent and temperature. Hybrid DFT calculations for 1–7 establish that the OPE bridge is involved in both frontier orbitals where the bridge character increases as the bridge length increases. Computed TD-DFT data on 1–5 assign the emission maxima in cyclohexane as LE transitions. Each time-resolved emission measurement on 2–7 in cyclohexane and diethyl ether reveals a wavelength dependent bi-exponential decay of the emission with a fast component in the 5–61 ps range on blue detection and a slower approximately 1 ns phase, independent of detection wavelength. The fast component is attributed to LE fluorescence and this emission component is rate limited and quenched by transfer into an ICT state. The fast LE fluorescence component varies systematically with conjugation length for the series of D–B–A dyads 2–5. An attenuation factor β of 0.15 Å−1 was determined in accordance with an ICT superexchange mechanism
Vanadium(V) oxo and Imido calix[8]arene complexes: synthesis, structural studies, and ethylene homo/copolymerisation capability

This is the peer reviewed version of the article which has been published in final form at http://dx.doi.org/10.1002/chem.201406084 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Interaction of p-tert-butylcalix[8]areneH8 (L8H8) with [NaVO(OtBu)4] (formed in situ from VOCl3) afforded the complex [Na(NCMe)5][(VO)2L8H]·4 MeCN (1·4 MeCN). Increasing [NaVO(OtBu)4] to 4 equiv led to [Na(NCMe)6]2[(Na(VO)4L8)(Na(NCMe))3]2·10 MeCN (2·10 MeCN). With adventitious oxygen, reaction of 4 equiv of [VO(OtBu)3] with L8H8 afforded the alkali-metal-free complex [(VO)4L8(μ3-O)2] (3); solvates 3×3 MeCN and 3×3 CH2Cl2 were isolated. For the lithium analogue, the order of addition had to be reversed such that lithium tert-butoxide was added to L8H8 and then treated with 2 equiv of VOCl3; crystallisation afforded [(VO2)2Li6[L8](thf)2(OtBu)2(Et2O)2]·Et2O (4·Et2O). Upon extraction into acetonitrile, [Li(NCMe)4][(VO)2L8H]·8 MeCN (5·8 MeCN) was formed. Use of the imido precursors [V(NtBu)(OtBu)3] and [V(Np-tolyl)(OtBu)3] and L8H8, afforded [tBuNH3][{V(p-tolylN)}2L8H]·3 1/2 MeCN (6·3 1/2 MeCN). The molecular structures of 1 to 6 are reported. Complexes 1, 3, and 4 were screened as precatalysts for the polymerisation of ethylene in the presence of cocatalysts at various temperatures and for the copolymerisation of ethylene with propylene. Activities as high as 136 000 g (mmol(V) h)-1 were sometimes achieved; higher molecular weight polymers could be obtained versus the benchmark [VO(OEt)Cl2]. For copolymerisation, incorporation of propylene was 7.1-10.9 mol% (compare 10 mol% for [VO(OEt)Cl2]), although catalytic activities were lower than [VO(OEt)Cl2]
Two‐Dimensional Crystals from Reduced Symmetry Analogues of Trimesic Acid

The two‐dimensional assembly of multicarboxylated arenes is explored at the liquid–graphite interface using scanning tunneling microscopy. Symmetry variations were introduced via phenylene spacer addition and the influence of these perturbations on the formation of hydrogen‐bonded motifs from an alkanoic acid solvent is observed. This work demonstrates the importance of symmetry in 2D crystal formation and draws possible links of this behavior to prediction of coordination modes in three‐dimensional coordination polymers.Crystal clear: 2D assemblies of a series of five reduced symmetry multicarboxylated molecules (such as depicted) related to trimesic acid, a prototypical high symmetry adsorbate, through the addition of phenylene spacers, are explored at the liquid–graphite interface using scanning tunneling microscopy. The 2D assembly behaviors of these multicarboxylate molecules mirror their coordination modes in 3D coordination polymers
Unexpected Migratory Insertion Reactions of M(alkyl)2 (M = Zn, Cd) and Diamidocarbenes

The electrophilic character of free diamidocarbenes (DACs) allows them to activate inert bonds in small molecules, such as NH3 and P4. Herein, we report that metal coordinated DACs also exhibit electrophilic reactivity, undergoing attack by Zn and Cd dialkyl precursors to afford the migratory insertion products [(6-MesDAC-R)MR] (M = Zn, Cd; R = Et, Me; Mes = mesityl). These species were formed via the spectroscopically characterised intermediates, [(6-MesDAC)MR2], exhibiting barriers to migratory insertion which increase in the order MR2 = ZnEt2 < ZnMe2 < CdMe2. Compound [(6-MesDAC-Me)CdMe] showed limited stability, undergoing deposition of Cd metal, by an apparent beta-H elimination pathway. These results raise doubts about the suitability of diamidocarbenes as ligands in catalytic reactions involving metal species bearing nucleophilic ligands (M-R, M-H)
General and mild Ni0-catalyzed α-arylation of ketones using aryl chlorides

The authors thank the ERC (Advanced Researcher award-FUNCAT), 7th Framework Program NMP2-LA-2010-246461 (SYNFLOW), the EPSRC and King Saud University for funding.A general methodology for the α-arylation of ketones using a nickel catalyst has been developed. The new well-defined [Ni(IPr*)(cin)Cl] (1c) pre-catalyst showed great efficiency for this transformation, allowing the coupling of a wide range of ketones, including acetophenone derivatives, with various functionalised aryl chlorides. This cinnamyl-based Ni(NHC) complex has demonstrated a different behaviour to previously reported NHC-Ni catalysts. Preliminary mechanistic studies suggest a Ni0/NiII catalytic cycle to be at play.PostprintPeer reviewe
Enhanced electrochemiluminescence from a stoichiometric ruthenium(II)-iridium(III) complex soft salt

The authors thank NSERC, CFI, FQRNT, PREA, and The University of Western Ontario for generous financial support to this research.Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)3][Ir(ppy)2(CN)2]2 ([Ir][Ru][Ir]), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]2+ and [Ir]− moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)3]2+, ECL in the co-reactant path with tri-n-propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]2+* excited state and no [Ir]−* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low-energy-cost ECL detection systems.PostprintPeer reviewe
Gold-acetonyl complexes : from side-products to valuable synthons

The ERC (Advanced Investigator Award-FUNCAT), EPSRC and Syngenta are gratefully acknowledged for support. Umicore AG is acknowledged for their generous gift of materials. S.P.N. is a Royal Society Wolfson Research Merit Award holder.A new synthetic strategy was devised leading to the formation of complexes, such as [Au(IPr)(CH2COCH3)]. The approach capitalizes on the formation of a decomposition product observed in the course of the synthesis of [Au(IPr)(Cl)]. A library of gold acetonyl complexes containing the most common N-heterocyclic carbene (NHC) ligands has been synthesized. These acetonyl complexes are good synthons for the preparation of numerous organogold complexes. Moreover, they have proven to be precatalysts in common gold(I)-catalyzed reactions.PostprintPeer reviewe
A Si Photocathode Protected and Activated with a Catalytic Ti and Ni Composite Film for Solar Hydrogen Production in Water

An efficient, stable and scalable hybrid photoelectrode for
visible light driven H2 generation in an aqueous pH 9.2 electrolyte
solution is reported. The photocathode consists of a p-type Si
substrate layered with a Ti and Ni-containing composite film, which
acts as both a protection and electrocatalyst layer on the Si
substrate. The film is prepared by the simple drop casting of the
molecular single source precursor, [Ti2(OEt)9(NiCl)]2 (TiNipre), onto
the p-Si surface at room temperature, followed by cathodic in-situ
activation to form the catalytically active TiNi film (TiNicat). The pSi|TiNicat
photocathode exhibits prolonged hydrogen generation with
a stable photocurrent of approximately –5 mA cm–2 at 0 V vs. RHE in
an aqueous pH 9.2 borate solution for several hours, and serves as
a benchmark non-noble photocathode for solar H2 evolution that
operates efficiently under neutral-alkaline conditions.This is the final published version of a paper published in Chemistry - A European Journal Volume 21, Issue 10, pages 3919–3923, March 2, 2015, DOI: 10.1002/chem.20140656
Iron-catalyzed diboration and carboboration of alkynes.

Issue published online: 27 FEB 2015An iron-catalyzed diboration reaction of alkynes with bis(pinacolato)diboron (B2pin2) and external borating agents (MeOB(OR)2) affords diverse symmetrical or unsymmetrical cis-1, 2-diborylalkenes. The simple protocol for the diboration reaction can be extended to the iron-catalyzed carboboration of alkynes with primary and, unprecedentedly, secondary alkyl halides, affording various tetrasubstituted monoborylalkenes in a highly stereoselective manner. DFT calculations indicate that a boryliron intermediate adds across the triple bond of an alkyne to afford an alkenyliron intermediate, which can react with the external trapping agents, borates and alkyl halides. In situ trapping experiments support the intermediacy of the alkenyl iron species using radical probe stubstrates
Bridgehead substitution via putative norborn-1-en-3-ones: Application in the synthesis of complex molecules

The base-mediated formation of a bridgehead double bond in a bicyclo[2.2.1]heptane system (anit-Bredt molecules) is described. The synthesis of exocyclic norbornyl enones by Wittig reaction of α-diketones is reported. These enones and their Michael adducts are used as substrates for the generation of transient bridgehead enones and their trapping with MeOH and H2O. Bridgehead alcohols are easily synthesized from norbornyl enones and are exploited for the diversity oriented synthesis of frameworks of natural and unnatural products
Importance of outer-sphere and aggregation phenomena in the relaxation properties of phosphonated gadolinium complexes with potential applications as MRI contrast agents

[Abstract] A series composed of a tetra-, a tris- and a bisphosphonated ligand based on a pyridine scaffold (L4, L3 and L2, respectively) was studied within the frame of lanthanide (Ln) coordination. The stability constants of the complexes formed with lanthanide cations (Ln=La, Nd, Eu, Gd, Tb, Er and Lu) were determined by potentiometry in aqueous solutions (25.0 °C, 0.1 M NaClO4), showing that the tetraphosphonated complexes are among the most stable LnIII complexes reported in the literature. The complexation of L4 was further studied by different titration experiments using mass spectrometry and various spectroscopic techniques including UV/Vis absorption, and steady state and time-resolved luminescence (Ln=Eu and Tb). Titration experiments confirmed the formation of highly stable [LnL4] complexes. 31P NMR experiments of the LuL4 complex revealed an intramolecular interconversion process which was studied at different temperatures and was rationalized by DFT modelling. The relaxivity properties of the GdIII complexes were studied by recording their 1H NMRD profiles at various temperatures, by temperature dependent 17O NMR experiments (GdL4) and by pH dependent relaxivity measurements at 0.47 T (GdL3 and GdL2). In addition to the high relaxivity values observed for all complexes, the results showed an important second-sphere contribution to relaxivity and pH dependent variations associated with the formation of aggregates for GdL2 and GdL3. Finally, intravenous injection of GdL4 to a mouse was followed by dynamic MRI imaging at 1.5 T, which showed that the complex can be immediately found in the blood stream and rapidly eliminated through the liver and in large part through the kidneys.Compagnia di San Paolo; CSP-2012 NANOPROGL
Catalytic asymmetric crotylation of aldehydes: application in total synthesis of (- )-elisabethadione

This is the peer reviewed version of the following article: O'HORA, P. ... et al, 2015. Catalytic asymmetric crotylation of aldehydes: application in total synthesis of (- )-elisabethadione. Chemistry - A European Journal, 21(12), pp.4551-4555, which has been published in final form at http://dx.doi.org/10.1002/chem.201500176. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.A new, highly efficient Lewis base catalyst for\ud
a practical enantio- and diastereoselective crotylation of\ud
unsaturated aldehydes with E- and Z-crotyltrichlorosilanes\ud
has been developed. The method was employed as a key\ud
step in a novel asymmetric synthesis of bioactive serrulatane diterpene (À)-elisabethadione. Other strategic reactions for setting up the stereogenic centers included\ud
anionic oxy-Cope rearrangement and cationic cyclization.\ud
The synthetic route relies on simple, high yielding reactions and avoids use of protecting groups or chiral auxiliaries