Terphenyl Groups Research Articles

Synthesis and characterization of poly(aryl ether sulfone) copolymers containing terphenyl groups in the backbone

A linear rigid bisphenol monomer, 4,4′-dihydroxyterphenyl (DHTP), has been incorporated into poly(aryl ether sulfone)s (PAESs) in a study to impart crystallization to these amorphous polymers. The PAES made from DHTP and dichlorodiphenylsulfone (DCDPS) is semi-crystalline but not soluble or thermally processable. Three bisphenols, 4,4′-isopropylidenediphenol (BPA), 4,4′-(hexafluoroisopropylidene)diphenol (BPAF) and 4,4′-dihydroxybiphenyl (BP), have been copolymerized with DHTP and DCDPS in order to study the effect of structure on crystallinity and processability. Both random and segmented copolymers containing different amounts of DHTP have been prepared via standard solution nucleophilic aromatic substitution polymerization technique. Only segmented polysulfone containing 50% BP and 50% DHTP was found to be semi-crystalline. This PAES had a melting temperature (Tm) 320°C in the first heating cycle of a DSC measurement and the presence of crystallites was confirmed by wide angle X-ray diffraction (WAXS).

Synthesis and Characterization of Low-Coordinate Divalent Aryl Transition-Metal Halide Analogues of Grignard Reagents: Precursors for Reduction to Metal−Metal-Bonded Complexes

The synthesis and characterization of the series of divalent first-row aryl transition-metal(II) halide compounds [Cr(mu-Cl)Ar']2 (1) and (Li(OEt2)Ar'MI2]2 (M=Mn (2), Fe (3), and Co (4); Ar'=C6H3-2,6-(C6H3-2,6-iPr2)2) are described. 1-4 were prepared by the addition of one equiv of Ar'Li to the respective transition-metal dihalides. They were characterized by UV-vis spectroscopy, magnetic measurements, and by X-ray crystallography. In dimeric 1, each chromium center has quasi-four-coordinate, square-planar geometry, in which the metal is terminally bound to a terphenyl ligand through the ipso carbon of the central ring and to two bridging chloride ligands. There is a further interaction between chromium and an ipso carbon from one of the flanking -C6H3-2,6iPr2 rings. In contrast, for the iodo derivatives 2-4, LiI is not eliminated upon addition of LiAr' to MI2. Instead, the diethyl ether solvated adducts, [Li(OEt2)Ar'MI2]2 (M=Mn (2), Fe (3), or Co (4)) were isolated. These possess a distorted cubane Li2M2I4 core, in which the lithiums are bound to an ether and the transition metals are bound to a terphenyl group. Magnetic measurements between 2 and 300 K reveal the expected weak antiferromagnetic exchange coupling in each of the complexes.

Orthoconic antiferroelectric liquid crystals containing biphenyl, terphenyl, or naphthyl mesogenic unit

AbstractThree homologous series of orthoconic (45 degree tilt) antiferroelectric liquid crystals containing either naphthyl or terphenyl groups as mesogenic unit have been synthesized and their mesomorphic behaviour investigated by DSC and polarized light microscopy, and their properties discussed. X-ray diffraction studies have shown the presence of a de Vries-type smectic A phase which does not exhibit a layer shrinkage on transition to the ferroelectric smectic C phase. Mixtures of the new materials have been formulated and their electro-optical properties investigated for their use in surface stabilized orthoconic antiferroelectric liquid crystal (SSOAFLC) devices

Ipso-and para-Functionalization of meta-terphenyl ligands with substituted methyl groups: Unusual head-to-tail coupling of terphenyl moieties

The synthesis and characterization of several ipso-functionalized derivatives of the bulky terphenyl group C 6 H 3 - 2 , 6 ( C 6 H 3 - 2 ′ , 6 ′ - Pr 2 i ) 2 ( Ar ′ ) are described. These include the primary alcohol Ar′CH 2OH ( 1), the bromo derivative Ar′CH 2Br ( 2), and the terphenyl formate Ar′CH 2OC(O)H ( 3). The alcohol 1 was obtained by treatment of LiAr′ with formaldehyde, and 1 was readily converted to the bromo derivative 2 using HBr. The reaction of 1 with formic acid afforded 3 in good yield. Attempts to form the Grignard derivative of 1, i.e., Ar′CH 2MgBr, resulted in a head-to-tail reaction of the terphenyl benzyl units to yield an unusual coupled product 4. An approach to the avoidance of this coupling involved the synthesis of the terphenyl derivatives 1 - I - C 6 H 2 - 2 , 6 ( C 6 H 3 - 2 ′ , 6 ′ - Pr 2 i ) 2 - 4 - Me ( 5 ) and 1 - I - C 6 H 2 - 2 , 6 ( C 6 H 2 - 2 ′ , 4 ′ , 6 ′ - Pr 3 i ) 2 - 4 - Me ( 6 ) , bearing methyl groups in the para positions of the central aryl ring, which could be prepared in good yield, and converted to their respective lithium salts 7 and 8 without complication . The compounds were characterized by 1H and 13C NMR spectroscopy, IR spectroscopy ( 1) and X-ray crystallography ( 2, 4, 5 and 6).

Synthesis and Color Tuning of Poly(p-phenylenevinylene) Containing Terphenyl Units for Light Emitting Diodes

New PPV based conjugated polymers, containing terphenyl units, were prepared as the electroluminescent (EL) layer in light-emitting diodes (LEDs). The prepared polymers, poly[2,5-bis(4-(2-etylhexyloxy)phenyl)-1,4-phenylenevinylenej (BEHP-PPV), poly[2-(2-ethylhexyloxy)-5-(4-(4-(2-etylhexyloxy)phenyl)phenyl)-1,4-phenylenevinylene] (EEPP-PPV) and poly[2-(2-ethylhexyloxy)-5-(9,9-bis(2-etylhexyl)fluorenyl)-1,4-phenylenevinylene] (EHF-PPV), were soluble in common organic solvents and used as the EL layer in double layer light-emitting diodes (LEDs) (ITO/PEDOT/polymer/Al). The polymers were prepared by the Gilch reaction. The number-average molecular weight (M n ), weight-average molecular weight (M w ), and the polydispersities (PDI) of these polymers were in the range of 9000-58000, 27000-231000, 2.9-3.9, respectively. These polymers have quite good thermal stability with decomposition starting above 320-350. The polymers show photoluminescence (PL) with maximum peaks at around 526-562 nm (exciting wavelength, 410 nm) and blue EL with maximum peaks at around λ m a x = 526-552 nm. The current-voltage-luminance (I-V-L) characteristics of polymers show turn-on voltages of 5 V. Even though both of EEPP-PPV and BEHP-PPV have the same terphenyl group in the repeating unit, EEPP-PPV with directly substituted alkoxy group in the back bone has longer effective conjugation length than BEHP-PPV, and exhibits red shift in the PL spectra. Both of EEPP-PPV and EHE-PPV have ter-phenyl units and directly substituted alkoxy group in back bone. EHF-PPV with fluorenyl unit attached to the PPV backbone has shorter effective conjugation length than EEPP-PPV with biphenyl unit, and exhibits blue shift in the PL spectra.

Novel cyanoterphenyl self-assembly monolayers on Au(111) studied by ellipsometry, x-ray photoelectron spectroscopy, and vibrational spectroscopies

The self-assembled monolayers (SAMs) of two asymmetric disulfides derivatives (namely, LC1 and LC2) were prepared on Au(111). The disulfides contain a pure alkyl chain and an alkyl chain terminated by a cyanoterphenyl group. LC1 and LC2 differ by the way the cyanoterphenyl group is attached onto the alkyl chain: it is expected to be aligned with the alkyl chain in the case of LC1 and perpendicular to it in the case of LC2 (T shape). The consequences in terms of surface coverage, chemical composition, and molecular conformation of the two SAMs are studied using ellipsometry, x-ray photoelectron spectroscopy (XPS), reflection absorption infrared spectroscopy (RAIRS), and broadband femtosecond sum-frequency generation (SFG). A model of coverage and tilt angle based on ellipsometry and XPS results shows that the SAM "manages" the large size of the terphenyl group by lowering the terphenyl containing chain coverage and by increasing the tilt. In the case of LC2, the disulfide breaks during molecular assembly, less terphenyl chains adsorb than pure alkyl chains, and the overall chain coverage is smaller than for LC1. RAIRS and SFG results show that these differences in surface coverage correspond to a drastically different orientation of the terphenyl axis, which lies nearly parallel to the surface for LC2, while it is tilted by approximately 28 degrees for LC1. This shows that the terphenyl group takes much more space on the surface in the case of LC2 and explains why the terphenyl coverage is found smaller for LC2. The anomalous SFG relative intensities observed in the region of CH stretch between CH2 and CH3 modes, and symmetric and antisymmetric modes, show that the chains are not in the fully stretched, all-trans conformation, LC2 being probably more distorted than LC1. These distorsions allow the molecules to occupy the space available below the large terphenyl group. The relative intensities of symmetric and antisymmetric modes are discussed qualitatively for some typical molecular conformations and orientations of the alkyl chain.

Synthesis and Reactivity of Dimeric Ar‘TlTlAr‘ and Trimeric (Ar‘ ‘Tl)3 (Ar‘, Ar‘ ‘ = Bulky Terphenyl Group) Thallium(I) Derivatives: Tl(I)−Tl(I) Bonding in Species Ligated by Monodentate Ligands

The synthesis and characterization of three new organothallium(I) compounds are reported. Reaction of (Ar'Li)(2) (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)) and Ar"Li (Ar" = C(6)H(3)-2,6-(C(6)H(3)-2,6-Me(2))(2)) with TlCl in Et(2)O afforded (Ar'Tl)(2) (1) and (Ar' 'Tl)(3) (2). The "dithallene" 1 is the heaviest group 13 dimetallene and features a planar, trans-bent structure with Ar'Tl-Tl = 119.74(14) degrees and Tl-Tl = 3.0936(8) A. Compound 2 is the first structurally characterized neutral, three-membered ring species of formula c-(MR)(3) (M = Al-Tl; R = organo group). The Tl(3) ring has Tl-Tl distances in the range ca. 3.21-3.37 A as well as pyramidal Tl geometries. The Tl-Tl bonds in 1 and 2 are outside the range (2.88-2.97 A) of Tl-Tl single bonds in R(2)TlTlR(2) compounds. The weak Tl-Tl bonding in 1 and 2 leads to their dissociation into Ar'Tl and Ar' 'Tl monomers in hexane. The Ar'Tl monomer behaves as a Lewis base and readily forms a 1:1 donor-acceptor complex with B(C(6)F(5))(3) to give Ar'TlB(C(6)F(5))(3), 3. Adduct 3 features an almost linear thallium C(ipso)-Tl-B angle of 174.358(7) degrees and a Tl-B distance of 2.311(2) A, which indicates strong association. Treatment of 1 with a variety of reagents resulted in no reactions. The lower reactivity of 1 is in accord with the reluctance of Tl(I) to undergo oxidation to Tl(III) due to the unreactive character of the 6s(2) electrons.

Mapping molecular orientation of pentacene on patterned Au surface

With a photoemission electron microscope, we investigated the orientation of pentacene films deposited on Au surface that has been patterned with self-assembled monolayers (SAMs). Organic thiols X(CH 2) nSH with X = COOH or CH 3 and an aromatic thiol; served as alignment layers to control the orientation of pentacene molecules thermally deposited on top of the SAM. According to the PEEM images and near-edge X-ray absorption fine structure spectra, a SAM exposing a non-polar methyl group, a terphenyl group or a polar carboxyl group all induced perpendicular alignment of the pentacene moiety, in contrast with parallel alignment on a bare gold surface.

Fluorescence Probing of Self-Assembled Monolayer with Terphenyl-Derivatized Disulfides

The formation processes of and molecular ordering in self-assembled monolayers were investigated by fluorescence probing with p-terphenyl chromophores binding to disulfides at the o- or p-positions. In mixtures with dodecanethiol, the derivatized disulfides formed ordered monolayers. As compared with the broad monotonic fluorescence spectra in solutions, their emission bands were split into distinct peaks upon chemisorption on gold substrates due to intermolecular interactions between adjacent terphenyl groups. Their emission peak positions were interpreted in terms of the exciton coupling of various dimeric terphenyl configurations in the monolayers depending on the o- and p-isomeric structures.

2,2′′‐Dimethoxy‐1,1′:3′,1′′‐terphenyl as a Novel Protective Group for Low‐Coordinated Phosphorus Compounds: The Case of Diphosphenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Theoretical Investigation of Triple Bonding between Transition Metal and Main Group Elements in (η5-C5H5)(CO)2M≡ER (M = Cr, Mo, W; E = Si, Ge, Sn, Pb; R = Terphenyl Groups)

To extend the knowledge of triple bonding between group 6 transition metal and heavier group 14 elements, the structural and bonding aspects of (<TEX>$η^5-C_5H_5$</TEX>)<TEX>$(CO)_2$</TEX>M≡ER (M = Cr, Mo, W; E = Si, Ge, Sn, Pb) are investigated by hybrid density functional calculations at the B3PW91 level. Substituent effects are also investigated with R = H, Me, <TEX>$SiH_3$</TEX>, Ph, <TEX>$C_6H_3-2,6-Ph_2$</TEX>, <TEX>$C_6H_3-2,6-(C_6H_2-2,4,6-Me_3)_2$</TEX>, and <TEX>$C_6H_3-2,6-(C_6H_2-2,4,6- iPr_3)_2$</TEX>.

2,2″‐Dimethoxy‐1,1′:3′,1″‐terphenyl as a novel protective group for low‐coordinated phosphorus compounds: The case of diphosphenes

AbstractA synthetic approach to meta‐terphenyls iodides bearing methoxy groups in the 2 and 2′′′ positions has been described. 2,2″‐Dimethoxy‐1,1′:3′,1″‐terphenyl groups have been shown to stabilize diphosphenes in solution. The existence of conformers of the diphosphene 7 has also been recorded. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:360–360, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10162

Unusual structures of lithium terphenyl derivatives

The synthesis, spectroscopic and structural characterization of three new lithium derivatives of terphenyl ligands are reported. These are the mixed lithium alkyl–lithium aryl compound {Li( t-Bu)LiC 6H 3-2,6-Trip 2} ( 1, Trip=C 6H 2-2,4,6- i-Pr 3), the dilithiated {LiC 6H 3-2-(C 6H 3-2-Me-5- t-Bu)-6-(C 6H 3-2-CH 2Li-5- t-Bu)·Et 2O} 2 ( 2), and the ether solvated (Et 2O)LiC 6H 3-2,6-(C 6H 4-4- t-Bu) 2 ( 3). The synthesis of the terphenyl halide precursors for 2 and 3 is also given. The compound 1 resulted from the treatment of 1-IC 6H 3-2,6-Trip with two equivalents of Li( t-Bu) in hexane. It features the alkyl and aryl (terphenyl) groups bridged by two lithium ions. The lithium ions are further solvated by ortho aryl substituents and methyls of the t-Bu groups. This compound is a very rare example of a mixed lithium alkyl–lithium aryl species. Compound 2 was obtained in low yield from the treatment of 1-BrC 6H 3-2,6-(C 6H 3-2-Me-5- t-Bu) 2 with two equivalents of Li( t-Bu). The terphenyl ligand was dilithiated by replacement of the bromine and a hydrogen from one of the methyl groups on the ortho aryl substituents. The ether solvated, dimeric, tetrametallic structure illustrated in the Table of Contents resulted. The compound 3 was obtained from the straightforward lithiation of the iodoterphenyl precursor in the presence of diethyl ether and features a lithium ion solvated by two ethers terminally bound to the ipso-carbon of the terphenyl group.

Attempted Isolation of Heavier Group 14 Element Ketone Analogues: Effect of O−H···π-Ar Hydrogen Bonding on Geometry

The terphenyl group 14 element gem-dihydroxy (gem-diol) derivatives Ar2M(OH)2 (Ar = C6H3-2,6-Mes2; Mes = C6H2-2,4,6-Me3), M = Ge (1); Sn (2), were synthesized and characterized by X-ray crystallography, NMR, IR spectroscopy, and combustion analysis. The synthetic route involved treatment of the divalent MAr2 compounds with N2O or Me3NO in hydrocarbon solution. The objective was the isolation of the heavier group 14 element ketone analogues Ar2MO. Despite stringent precautions to exclude moisture and oxygen during the synthesis, the products 1 and 2 were isolated in ca. 30−50% yield. These results are in contrast to the recently reported stabilization of the terphenyl-protected, essentially strain-free, species (bisap)2GeO (bisap = 2,6-di(1‘-naphthyl)phenyl). Seemingly, 1 and 2 represent the addition of H2O to Ar2MO. The identity of the other products is currently unknown. Compound 1 represents the second example of a germanium gem-diol to be structurally characterized, and it features the expected distorted tetrahedral germanium environment. Compound 2 is the first instance of a monomeric gem-dihydroxy derivative of tin. Surprisingly, the C−Sn−C angle is ca. 20° wider than the corresponding angle in 1 even though the larger size of tin is expected to reduce steric congestion and so afford a narrower C−Sn−C angle. This unanticipated result was attributed to the nonclassical hydrogen-bonding interaction of the O−H groups with the mesityl ring substituents, which for geometric reasons is more favorable in the tin compound.

A Silicon–Silicon Triple Bond Surrounded by Bulky Terphenyl Groups

Abstract In search of a stable disilyne, effects of bulky 2,6-bis(2,4,6-triisopropylphenyl)phenyl (Ar*) groups on silicon–silicon triple bonding are investigated using density functional theory. It is predicted that Ar*Si≡SiAr* is very stable to isomerization and dimerization.

Synthesis, Spectroscopy, Electrochemistry, and Mesomorphism of Triple-Decker Porphyrins Consisting of Two Cerium Ions and Three 5,15-Diarylporphyrins

Abstract Triple-decker sandwich complexes, which consist of two cerium ions and three strip-like diarylporphyrins, have been synthesized and their spectroscopic and electrochemical properties and mesomorphism are reported and compared with those of the corresponding double deckers and the parent monomers. The Soret band of the triple-deckers lies at longer and shorter wavelengths than those of the double-deckers and monomers, respectively, while a sequence of small absorptions is observed in the Q band region. These are interpreted on the basis of knowledge of triple-deckers made from tetraphenylporphyrin and octaethylporphyrin. Magnetic circular dichroism (MCD) spectroscopy suggests that the Soret bands of the triple-deckers are a superimposition of at least two transitions to orbitally degenerate states. In the MCD spectra, Faraday A-terms are observed corresponding to each absorption band, suggesting that these triple-deckers take D4h or more plausibly D4d structures. Triple-deckers containing dialkoxyphenyl groups at the 5,15-positions of their parent porphyrin show a mesophase possessing both lamellar and columnar structures at lower temperatures and a columnar mesophase at higher temperatures, which differ in stacking distances. On the other hand, those containing tetraalkoxylated terphenyl groups at the 5,15-positions of their parent porphyrin show only a columnar mesophase with a single stacking distance. These differences in the mesomorphism are explained by differences of the magnitude of the steric hindrance of the side chains for rotation along the axis connecting the center of the three porphyrins.

Mono-amidinate complexes stabilized by a new sterically-hindered amidine†

A novel amidinate ligand incorporating a bulky terphenyl group is used to prepare unusual, low-coordinate lithium and yttrium mono-amidinate complexes.

Semisynthetic chemical modification of the antifungal lipopeptide echinocandin B (ECB): structure-activity studies of the lipophilic and geometric parameters of polyarylated acyl analogs of ECB.

Echinocandin B (ECB) is a lipopeptide composed of a complex cyclic peptide acylated at the N-terminus by linoleic acid. Enzymatic deacylation of ECB provided the peptide "nucleus" as a biologically inactive substrate from which novel ECB analogs were generated by chemical reacylation at the N-terminus. Varying the acyl group revealed that the structure and physical properties of the side chain, particularly its geometry and lipophilicity, played a pivotal role in determining the antifungal potency properties of the analog. Using CLOGP values to describe and compare the lipophilicities of the side chain fragments, it was shown that values of > 3.5 were required for expression of antifungal activity. Secondly, a linearly rigid geometry of the side chain was the most effective shape in enhancing the antifungal potency. Using these parameters as a guide, a variety of novel ECB analogs were synthesized which included arylacyl groups that incorporated biphenyl, terphenyl, tetraphenyl, and arylethynyl groups. Generally the glucan synthase inhibition by these analogs correlated well with in vitro and in vivo activities and was likewise influenced by the structure of the side chain. These structural variations resulted in enhancement of antifungal activity in both in vitro and in vivo assays. Some of these analogs, including LY303366 (14a), were effective by the oral route of administration.

The echinocandins: antifungals targeted to the fungal cell wall

The greater incidence of AIDS and use of myelosuppressive therapy has increased the demand for effective antifungal therapy. Currently availiable therapy has limitations associated with toxicity and resistance potential. The ideal agent is selectively targeted to the fungal pathogen. The echinocandins, a family of cyclic lipopeptides, interfere with cell wall formation by noncompetitive inhibition of β-glucan synthase. Since mammalian cells lack a cell wall, this mode of action is likely responsible for the potent fungicidal activity and non-toxic properties of the echinocandin lipopeptides. New analogues of the echinocandins were prepared at the Lilly Laboratories by removal of the native fatty acid acyl group (“side chain”) from the cyclic peptide followed by its replacement with a new synthetic side chain. This scheme gave several analogues with improved therapeutic potential. A new analogue, LY303366, having a side chain containing a substituted terphenyl group, had improved potency against Candida albicans, Pneumocystis carinii, Histoplasma capsulatum and Aspergillus species, had oral bioavailability as well as an extended elimination half life. Newer developments in the discovery and modification of the pneumocandins by the Merck Laboratories are reported. New semi-synthetic water-soluble pneumocandin analogues L-705,589, L-731-373 and L-733,560 also have activity against disseminated aspergillosis.

Liquid crystal birefringence for millimeter wave radar

Abstract Many liquid crystals are found to have relatively high birefringence (Δn) values in the microwave and millimeter wave regions, as calculated from the phase shift induced by their reorientation by magnetic or electric fields. At 30 GHz, Δn values were obtained in the range of 0.08 to 0.18 for eleven liquid crystal mixtures of various types. The most favourable liquid crystal structures for high millimeter wave birefringence are highly conjugated rod-like molecules containing biphenyl, terphenyl, phenylpyrimidine, biphenylpyrimidine, and tolane groups in nematics of positive dielectric anisotropy (Δε). However, other liquid crystal structures including Schiffs base, azoxybenzene, and aromatic ester groups also have substantial birefringence, including nematics with negative and crossover Δε, as well as cholesteric nematics. The Δn varied only slightly at different frequencies of microwave millimeter wave in the 15–94 GHz range. Studies on magnetic and electrical field liquid crystal orientation in specially designed waveguides provide a basis for new types of modulators and scanning array antennae in the millimeter wave region, where more compact liquid crystal modulation media can be used than in the microwave region. These scanners can be used for both sending and receiving radar signals for potentially low cost radar systems.