Phenyl Acetylide Research Articles

Diphosphine-Protected IrAu12 Superatom with Open Site(s): Synthesis and Programmed Stepwise Assembly.

One or two phenylacetylide (PA) ligand(s) were successfully removed from the IrAu12 superatomic core of [IrAu12(dppe)5(PA)2]+ (dppe=1,2-bis(diphenylphosphino)ethane) by reaction with controlled amounts of tetrafluoroboric acid. Optical and nuclear magnetic resonance spectroscopies and density functional theory calculations revealed the formation of open Au site(s) on the IrAu12 core of [IrAu12(dppe)5(PA)1]2+ and [IrAu12(dppe)5]3+ with the remaining structure intact. Isocyanide was efficiently trapped at the open electrophilic site on [IrAu12(dppe)5(PA)1]2+, whereas a dimer or trimer of the IrAu12 superatoms was formed using diisocyanide as a linker. These results open the door to designed assembly of chemically modified metal superatoms.

Diphosphine‐Protected IrAu12 Superatom with Open Site(s): Synthesis and Programmed Stepwise Assembly

AbstractOne or two phenylacetylide (PA) ligand(s) were successfully removed from the IrAu12 superatomic core of [IrAu12(dppe)5(PA)2]+ (dppe=1,2‐bis(diphenylphosphino)ethane) by reaction with controlled amounts of tetrafluoroboric acid. Optical and nuclear magnetic resonance spectroscopies and density functional theory calculations revealed the formation of open Au site(s) on the IrAu12 core of [IrAu12(dppe)5(PA)1]2+ and [IrAu12(dppe)5]3+ with the remaining structure intact. Isocyanide was efficiently trapped at the open electrophilic site on [IrAu12(dppe)5(PA)1]2+, whereas a dimer or trimer of the IrAu12 superatoms was formed using diisocyanide as a linker. These results open the door to designed assembly of chemically modified metal superatoms.

Effect of bromine substitution on blue phosphorescent trans-(N-heterocyclic carbene)Pt(II) acetylide complexes.

N-heterocyclic carbene complexes of the type trans-(NHC)2PtII(CC-Ar)2 (where Ar = phenyl or substituted phenyl) are of interest as violet and blue phosphors. These complexes emit efficient phosphorescence in solution and in the solid state, and they have been applied as phosphors in organic light emitting diodes. This study explores the effect of bromine substitution on the trans-(NHC)2PtII(CC-Ar)2 chromophore through photophysical studies of a pair of complexes in which the phenyl groups feature either 3,5-dibromo- or 4-monobromo-substituents (IPt-DB and IPt-MB, respectively). The Br atoms were introduced as heavy atom(s) with the aim to enhance spin-orbit coupling and increase the radiative and non-radiative decay rates of the phosphorescent triplet state. Both IPt-MB and IPt-DB exhibit sky-blue phosphorescence in solution and in PMMA matrix. Interestingly, the emission quantum yield and lifetime of IPt-MB are substantially lower compared to IPt-DB in solution. This effect is attributed to a substantially larger non-radiative decay rate in the mono-bromo complex. Analysis of the photophysical data, combined with DFT and TD-DFT calculations, suggest that the difference in photophysical properties of the two complexes is related to the position of the Br-substituents on the phenyl acetylide rings. In short, in IPt-MB, the Br-substituents are located para-to the Pt-CC-unit, and this gives rise to stronger electron-vibrational coupling in the excited state, enhancing the rate of non-radiative decay.

Room-Temperature Phosphorescent Platinum(II) Alkynyls with Microsecond Lifetimes Bearing a Strong-Field Pincer Ligand.

The use of organometallic triplet emitters in organic light emitting diodes (OLEDs) is motivated by the premise of efficient intersystem crossing leading to unit internal quantum efficiencies. However, since most devices are based on solid-state components, an inherent limitation to square-planar platinum(II) phosphors is their tendency toward aggregation-based quenching. Here, a new class of emissive, four-coordinate PtII species based on the bisimidazolyl carbazolide (BIMCA) ligand is introduced, which displays highly efficient, long-lived solid-state phosphorescence at room temperature. A set of four BIMCAPt phenyl acetylides were synthesized that emit in the green (λmax =507-540 nm) with >60 % quantum yield and millisecond lifetimes. The structures of the resulting species reveal a non-planar structure imposed by steric clashes between BIMCA and the iodo or alkynyl co-ligand. Ground-state and photophysical characterization are presented. Density functional theory calculations indicate that the BIMCA ligand dominates the frontier orbitals along with the first Franck-Condon singlet and triplet excited states.

One-pot synthesis of new iso-DPP derivatives from terminal alkynes and isocyanates

The reaction of phenyl acetylide anion with aryl isocyanates followed by quenching with water is shown to produce pyrrolopyrrole (iso-DPP) derivatives in addition to the isomeric cyclopentadienone imines previously reported. If the reaction is quenched with dilute HCl, 5-ylidenepyrrol-2(5H)-ones, formed by a Meyer-Schuster rearrangement, can be isolated instead. A possible mechanism for this reaction is suggested.

Aromatic PCN pincer palladium complexes: forming and breaking C[sbnd]C bonds

Through a salt metathesis reaction, (t−BuPCN)Pd-ONO2 (2) was prepared and used as a precursor for producing (t−BuPCN)Pd-OH (3) and (t−BuPCN)Pd-aryl acetylide complexes 4 (phenyl acetylide) and 5 (p-tolyl acetylide). The aryl acetylide complexes could also be prepared through another synthetic route: by condensation of 3 with the corresponding aryl acetylene. The reactivity of complexes 3 and 4 toward carbon dioxide was studied and it was found that both reactions give the hydrogen carbonate complex (6). The low reactivity of the Pd-acetylide bond was further confirmed by the fact that the propiolate complex undergoes decarboxylation to give 4. PCN palladium complexes are good catalysts for the decarboxylative cross coupling reactions between acetylene carboxylic acids and aryl halides. The yield of the cross coupling product was improved by adding a catalytic amount of CuI.

Reaction of ruthenium phenyl acetylide with iron-chalcogen clusters and iron pentacarbonyl

Photolysis of a THF solution containing ruthenium acetylide [(η5-C5H5)Ru(PPh3)2(η1-CCPh)] with [Fe3(CO)9(μ3-Se)2] cluster affords an adduct [{μ-SeC(CpRu(PPh3)(CO))C(Ph)Se}(CO)6Fe2] (1), while under similar reaction condition with [Fe3(CO)9(μ3-Te)2] cluster a Ru-inserted product [(η5-C5H5)(PPh3)(η1-CCPh)RuFe2(μ3-Te)2(CO)6] (2) was obtained. Under thermal condition [(η5-C5H5)Ru(PPh3)2(η1-CCPh)] react with Fe(CO)5 to give an acetylide stabilised Fe2Ru mixed metal cluster [(η5-C5H5)RuFe2(CO)7(η2:η2:η1-CCPh)], (3).

Visible light-harvesting trans bis(alkylphosphine) platinum(ii)-alkynyl complexes showing long-lived triplet excited states as triplet photosensitizers for triplet–triplet annihilation upconversion

Symmetric and asymmetric linear trans-bis(tributylphosphine) Pt(II) bis(acetylide) complexes with functionalized aryl alkynyl ligands (coumarin, naphthalimide and phenyl acetylides) were prepared, which show enhanced absorption in the visible region (molar absorption coefficients up to 76,800 M(-1) cm(-1) at 459 nm) and long-lived triplet excited states (up to 139.9 μs). At room temperature, the naphthalimide acetylide-phenyl acetylide complex (Pt-4) shows dual emission (fluorescence-phosphorescence), whereas other complexes show only fluorescence emission. The triplet excited states of the complexes were studied with nanosecond time-resolved transient difference absorption spectroscopy and DFT calculations on the spin density surface. The complexes were used as triplet photosensitizers for ratiometric O2 sensing, as well as triplet-triplet annihilation (TTA) upconversion (upconversion quantum yield up to 27.2%). The TTA upconversion of the complexes requires triplet acceptors with different T1 state energy levels and was studied with nanosecond time-resolved emission spectroscopy. Our results are useful for designing new Pt(II) complexes that show strong absorption of visible light and long-lived triplet excited states, as well as for the application of these complexes as triplet photosensitizers for O2 sensing, photocatalysis and TTA upconversion.

Excited State Absorption Properties of Pt(II) Terpyridyl Complexes Bearing π-Conjugated Arylacetylides

The synthesis, photophysics, and excited state absorption properties of three platinum(II) terpyridyl acetylide charge transfer (CT) complexes possessing a lone ancillary ligand systematically varied in phenylacetylide (PA) π-conjugation length, [Pt((t)Bu(3)tpy)([C≡C-C(6)H(4)](n)-H)]ClO(4) (n = 1, 2, 3), are described. Density functional theory (DFT) calculations performed on the ground states of complexes 1, 2, and 3 reveal that their HOMOs reside mainly on the ancillary π-conjugated PA moiety, ranging from 86 to 97%, with LUMOs predominantly centered on the terpyridyl acceptor ligand (91-92%). This electronic structure leads to the production of a triplet ligand-to-ligand CT ((3)LLCT) excited state upon visible light excitation with minor contributions from the corresponding triplet metal-to-ligand CT ((3)MLCT) excited state. Unusually strong red-to-near-IR transient absorptions are produced in the excited states of these molecules following selective long wavelength visible excitation of the low energy CT bands that do not emanate from the terpyridyl radical anion produced in the CT excited state or from an arylacetylide-based triplet intraligand ((3)IL) excited state. The extinction coefficients of these low energy absorption transients were determined using the energy transfer method with anthracene serving as the triplet acceptor. A detailed theoretical investigation using DFT and TDDFT methods reveals that these intense near-IR transient absorptions involve transitions resulting from transient oxidation of the PA subunit. In essence, the production of the (3)LLCT excited state transiently oxidizes the PA moiety by one electron, producing the corresponding highly absorbing radical cation-like species, analogous to that experienced in related intramolecular photoinduced electron transfer reactions. The computational work successfully predicts the oscillator strength and peak wavelength of the measured excited state absorption transients across this series of molecules. In the present effort, there is a convergence of theory and experiment given that the excited state absorption properties of these Pt(II) chromophores are determined by localized transitions that resemble open shell radical cation species.

Molecular logic circuit based on a multi-state mononuclear platinum(ii) terpyridyl complex

A new type of multi-state platinum(ii) terpyridyl acetylide complex: platinum(ii) 4'-(4-dimethylaminophenyl)-2,2' : 6',2''-terpyridyl ferrocenyl acetylide (1), together with its reference complexes: platinum(ii) 4'-(4-methylphenyl)-2,2' : 6',2''-terpyridyl ferrocenyl acetylide (2), platinum(ii) 4'-(4-dimethylaminophenyl)-2,2' : 6',2''-terpyridyl phenyl acetylide (3) and platinum(ii) 4'-(4-methylphenyl)-2,2' : 6',2''-terpyridyl phenyl acetylide (4), are designed and synthesized. UV-vis-NIR absorption and electrochemical studies demonstrate that complex 1 possesses three ordered intraligand charge transfer (ILCT), ligand-to-ligand charge transfer (LLCT) and metal-to-ligand charge transfer (MLCT) states, and the successive modulation of the intramolecular ILCT, LLCT and MLCT states in a single mononuclear platinum(ii) complex 1 is well evidenced by their reference complexes 2-4. More interestingly, a near-infrared absorption band ranging from 720-1000 nm was clearly observed for complexes 1 and 2 upon oxidation of the σ-bonded ferrocene-ethynyl group by Fe(ClO(4))(3), which was tentatively assigned to platinum(ii)-disturbed ligand-to-metal charge transfer (LM'CT) of the ferrocenium group. These promising features allow us to integrate the multiple states to reproduce basic logic operations at the molecular level. A four-state (LLCT, ILCT, MLCT and LM'CT) molecular switch of complex 1 that responds to the stimulation of H(+), Fe(ClO(4))(3) and Zn producing four outputs has been encoded in binary digits. The logic function executed by complex 1 is equivalent to that of a combinational logic circuit integrating seven or eight logic functions as AND, OR, NOT. A three-input-four-output molecular logic circuit has been established.

Optimization of cuprous oxide nanocrystals deposition on multiwalled carbon nanotubes

Cu (I) phenyl acetylide was used as a source of copper to achieve a homogeneous distribution of Cu2O nanocrystals (10–80 nm) decorated on multiwalled carbon nanotubes (MWCNTs) having an average diameter of 10 nm. Pristine MWCNTs were first oxygen-functionalized by treating them with a mixture of concentrated (H2SO4/HNO3 : 3/1) acids and the products were characterized by X-ray powder diffraction, transmission and scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy and thermogravimetric analysis. An easy, efficient and one-step impregnation method was followed to produce copper-containing nanoparticles on the MWCNTs. The copper-treated MWCNTs dried at room temperature were seen to be well decorated by copper-containing nanoparticles on their outer surface. The MWCNTs were then heat-treated at 400 °C in a nitrogen atmosphere to produce a homogeneous distribution of cuprous oxide nanocrystals on their surface. By varying the ratio of copper to oxygen-functionalized MWCNTs, Cu2O nanocrystals decorated on MWCNTs with different copper content can be obtained.

Coupled cluster study of the phenyl-acetylide anion

Using coupled cluster theory with singles and doubles substitutions (CCSD) we have characterized the ground-state geometry and electronic structure of the phenyl acetylide anion ( 1) which has been recently isolated and characterized by NMR spectroscopy [Y. Tanaka et al., Chem. Asian. J. 1 (2006) 581]. Calculations indicate the bond in the acetylide moiety being an elongated triple carbon carbon bond which becomes strengthened upon interaction with the Li + ion. Fluorine substitution stabilizes the carbanion, as testified by the increase in the HOMO–LUMO energy gap. Minor structural problems encountered with the DFT-optimized geometries are also discussed.

Heterometallic Pt–Ag and Pt 2Ag transition metal complexes

Complexes of type { cis-[Pt](μ-σ,π-C CPh) 2}AgX ( 3a, [Pt] = (bipy′)Pt, X = FBF 3; 3b, [Pt] = (bipy′)Pt, X = FPF 5; 3c, [Pt] = (bipy)Pt, X = OClO 3; 3d, [Pt] = (bipy′)Pt, X = BPh 4; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](C CPh) 2 ( 1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] ( 2a, X = BF 4; 2b, X = PF 6; 2c, X = ClO 4; 2d, X = BPh 4). In 3a– 3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{ cis-[Pt](μ-C CPh) 2} 2Ag]X ( 8a, [Pt] = (bipy)Pt, X = BF 4; 8b, [Pt] = (bipy′)Pt, X = PF 6; 8c, [Pt] = (bipy)Pt, X = BF 4) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](C CPh) 2 units. Within this structural arrangement the phenyl acetylides of individual [Pt](C CPh) 2 entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt–Ag 2.8965(3) Å). The respective silver carbon distances Ag–C α (2.548(7), 2.447(7) Å) and Ag–C β (3.042(7), 2.799(8) Å)(PtC α C βPh) confirm this structural motif. Complexes 8a– 8c isomerize in solution to form trimetallic [{ cis-[Pt](μ-σ,π-C CPh) 2} 2Ag]X ( 9a, [Pt] = (bipy)Pt, X = BF 4; 9b, [Pt] = (bipy′)Pt, X = PF 6; 9c, [Pt] = (bipy)Pt, X = ClO 4). In the latter molecules the organometallic cation [{ cis-[Pt](μ-σ,π- C CPh) 2} 2Ag] + is set-up by two nearly orthogonal positioned [Pt](C CPh) 2 entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhC C units are η 2-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.

Tetracene Sulfoxides and Sulfones via a Cascade Cyclization

The authors report an unconventional synthesis of tetracene derivatives through the cyclization of ortho-diallene intermediates. They also report a one-pot synthesis of tetracene sulfoxide 3 (R1 = R2 = H) from the dialdehyde and lithium phenyl acetylide in 22% yield.

Stereodivergent Synthesis of 5a‐Carba‐hexopyranoses from Carbohydrates via 6‐exo‐dig Radical Cyclization: Preparation of 5a‐Carba‐β‐D‐manno‐, α‐D‐allo‐, β‐L‐talo‐ and α‐L‐Gulopyranose Pentaacetates from D‐Mannose.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Stereodivergent synthesis of 5a-carba-hexopyranoses from carbohydrates via 6- exo- dig radical cyclization: preparation of 5a-carba-β- d-manno-, α- d-allo-, β- l-talo- and α- l-gulopyranose pentaacetates from d-mannose

Four carbasugars, 5a-carba-β- d-manno-, α- d-allo-, β- l-talo- and α- l-gulopyranose pentaacetates, have been prepared in a stereodivergent manner from d-mannose. Alkynyl derivatives of 2,3:4,6-di- O-isopropylidene- d-mannopyranose, which are prepared by homologation at C-1, by reaction with phenyl acetylide, undergo a 6- exo- dig radical cyclization, from a radical located at C-5, to yield a mixture of highly functionalized cyclohexanes. Some of these compounds, after transformation of their exocyclic double bond in a hydroxy function, were correlated with polyhydroxylated cyclohexanes, which were then selectively deoxygenated either at position C-4 or C-5a (carbohydrate numbering) to afford carbasugars of the d- or l- series.

Hydrogen-Bonded Complexes of Methanol and Acetylides. Structure and Energy Correlations

We examine the connection between acid−base chemistry and hydrogen bond stability for anionic ion−molecule complexes. Ion−molecule complexes of substituted acetylides, RCC- (R = tert-butyl, H, phenyl, p-tolyl), and methanol were studied using Fourier transform ion cyclotron resonance mass spectrometry. These complexes, RCC-·HOCH3, all have complexation energies of −21 kcal/mol and are, therefore, hydrogen bonded. The acetylides vary in basicity over an 8 kcal/mol range, but all have the same complexation energy with methanol. In contrast, results reported by Bartmess show that the complexation energies of aliphatic alcohols with phenyl acetylide vary with the acidity of the alcohol. These results show that the frequently observed relationship between acid−base energetics and complexation energy is a property of the specific system and not a general one. We believe that these results demonstrate that the existence, and magnitude, of these correlations cannot be used to infer structural information about the complexes.

A novel entry to 5a-carba-hexopyranoses from carbohydrates based on a 6-exo-dig radical cyclization: synthesis of 5a-carba-β-d-mannopyranose pentaacetate

Carbohydrate-derived 2,3:4,6-diacetonides which are homologated at C-1 by reaction with phenyl acetylide undergo a 6-exo-dig radical cyclization, from a radical located at C-5, to yield highly functionalized cyclohexanes that are correlated with carba-sugars.

Synthesis of B/C materials from boron-containing phenyl acetylides

This paper discusses the synthesis and graphitization of three boron-containing phenyl acetylides, with B/C ratios between 1 18 and 1 8 . The experimental results show that the initial rate at which the graphitic structure develops is strongly related to the molecular structure of the phenyl acetylides. The formation of non-coplanar molecular structure in the stabilization reaction slows down the graphitization reaction. However, all three precursors show effective transformation reactions to produce the boron-substitutional graphitic (B/C) materials at relatively low temperature (2200 °C), despite the significant differences in boron concentration and chemical nature of the precursors. Relatively large crystallite size and small d-spacing between interlayers of B/C products were observed by X-ray diffraction. Clearly, boron is not only substitutionally incorporated in the graphitic structure but also enhances the graphitization reaction.

Carbonyl ligands from alkynes: oxidative decarbonation of acetylide bridged complexes

The organometal acetylides Cp(CO) 2MCCR ( 1, M  Fe, R  Ph and 2, M  Ru, R  Ph, t-Bu, Me) react with Co 2(CO) 8 to form the acetylide bridged trinuclear complexes Co 2(CO) 6-μ-[Cp(CO) 2MCCR] ( 3, M  Fe, and 4, M  Ru). Of these, the phenyl acetylide compounds undergo a non-destructive reaction with oxygen which results in the net loss of one carbon atom together with a CO ligand and the formation of the alkylidyne bridged clusters Co 2MCp(CO) 7(μ 3-CPh) ( 5, M  Fe, and 6, M  Ru). The molecular structure of 6 has been determined by an X-ray analysis. The mechanism of the oxidation reaction has been elucidated by 13C labelling of the acetylide α-C atom and EI mass spectrometry. It has been found that this C atom is converted to CO which, with a probability of 7/9, ends up as a CO ligand in the product cluster. This means that the oxidation converts the α-C to CO before elimination of the CO ligands.