Control of intramolecular π-π stacking interaction in cationic iridium complexes via fluorination of pendant phenyl rings

Intramolecular π-π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)(2)(F2phpzpy)]PF(6) (2) and [Ir(ppy)(2)(F5phpzpy)]PF(6) (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)(2)(phpzpy)]PF(6) (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 ? for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular π-π stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face π-π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π-π stacking interaction remains on the lowest triplet state.     

Guanidine is a Zn(2+)-binding ligand at neutral pH in aqueous solution

We have found the first well-characterized coordination of guanidine with Zn(2+) in a 1:1 complex (ZnL(1)) with cyclen (= 1,4,7,10-tetraazacyclododecane) functionalized with guanidinylethyl group (L(1) = (2-guanidinyl)ethyl-cyclen). The X-ray structure analysis of the 1:1 complex crystallized at pH 7.5 revealed an apical coordination of the pendant guanidinyl group to Zn(2+) ion in ZnL(1). By potentiometrtic pH titration, initial formation of a 1:1 Zn(L(1).H(+)) complex was indicated, where only the cyclen N's bind to Zn(2+) with the complexation constant, log K(s) (K(s) = [Zn(L(1).H(+))]/[Zn(2+)][L(1).H(+)] (M(-1))), being 12.4 +/- 0.1. Facile deprotonation of the guanidinium pendant in the Zn(L(1).H(+)) occurred with a pK(a) value of 5.9 +/- 0.1 at 25 degrees C with I = 0.1 (NaNO(3)) to yield the guanidine-coordinating complex ZnL(1). 4-Nitrophenyl phosphate dianion (NPP(2-)) interacted with ZnL(1) through a new Zn(2+)-phosphate coordination, as indicated by (31)P NMR titration and potentiometric pH titration. An apparent complexation constant for this new species, log K(app)(Zn(L(1).H(+))-NPP), was 4.0 +/- 0.1, which is larger than the log K(app)(ZnL(2)-NPP) value of 3.1 for the 1:1 complex of Zn(2+)-cyclen (ZnL(2)) with NPP at the common pH 5.6. The interaction of ZnL(1) with a phosphate dianion was proven by the X-ray crystal structure analysis of the 1:1 ZnL(1)-PP(2-) complex (PP(2-) is a dianion of phenyl phosphate) obtained from an aqueous solution at pH 6.5. At higher pH, the pendant guanidinium cation is deprotonated to displace the phosphate to yield the Zn(2+)-guanidine bond.     

Tuning the electronic properties of conjugated polymer by tethering low‐bandgap rhenium(I) complex on the main chain

Low‐bandgap rhenium(I) complex with absorption onset at 795 nm in solution was tethered onto π‐conjugated polymer. The conjugated copolymer provides solution processability of the metallopolymer, and the pendant allows the low energy‐absorbing Re(I) complex units to be evenly distributed on the thin film. The copolymer tethered with low‐bandgap rhenium complex was synthesized by Suzuki cross‐coupling reaction. The metal‐free polymer ( poly‐1 ) tethered with functionalized intramolecular charge transfer dye, 2‐phenyl‐3‐pyridin‐2‐yl‐5,7‐di‐2‐thienylthieno[3,4‐b]pyrazine, exhibited high molecular weight, good film‐forming properties, and excellent solution processability. The pendants of the conjugated polymer possess donor–acceptor characters and broaden the absorption band. These pendants can function as bidentate ligands for metal chelation. The solubilizing groups on the monomers provide good solubility to the polymer even with high content of metal chelation. Upon the complexation with rhenium(I) pentacarbonyl chloride, the absorption spectrum of the resulting metallopolymer was further extended toward the near‐infrared region. Photovoltaic performances based on this metallopolymer have been studied. The design approach of these metallopolymers provides synthetic feasibility for coordinating wide range of metal ions on the pendant, and the resulting low‐bandgap polymer can be a potential candidate for light harvesting material in solar cell applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2311–2319, 2010     

Applicability of photochemically generated pendant benzoyl peroxides in both “grafting from” and “grafting to” techniques

Methyl methacrylate and styrene copolymers containing pendant benzil groups, such as 1-[4-(2-methacroyloxyethoxy)phenyl]-2-phenyl-1,2-ethanedione-co-methyl metacrylate (BzMA/MMA), 1-[4-(2-methacroyloxyethoxy)phenyl]-2-phenyl-1,2-ethanedione-co-styrene (BzMA/S), and 1-phenyl-2-(4-propenoylphenyl)-1,2-ethanedione-co-styrene (PCOCO/S), were prepared and used as precursors for photochemically generated pendant benzoyl peroxides. Decomposition of the pendant benzoyl peroxides was subsequently used in grafting processes. Either irradiation or a combination of irradiation with subsequent thermal treatment was adopted for grafting a thin layer of BzMA/MMA copolymer onto the surface of LDPE films. The grafting resulted in a significant decrease in contact angle of the film surface. The same activation strategy was successfully adopted to initiate the polymerisation of acrylic or methacrylic acids from the surface of styrene copolymer films containing the initiator precursor in the polymer side chains (BzMA/S and PCOCO/S). The successful surface grafting was proved by contact angles measurement as well as by infrared spectroscopic analysis.     

Biphenyl derived Schiff-base vanadium(V) complexes with pendant OH-groups--structure, characterization and hydrogen peroxide mediated sulfide oxygenation

A series of mononuclear oxovanadium(v) complexes of tridentate Schiff bases HL(1)-HL(4) and H(2)L(5)-H(2)L(8) derived from 6-phenylsalicylaldehyde and 6-(2-hydroxyphenyl)salicylaldehyde and four different amines was synthesized. The systematically selected ligands contain aliphatic or aromatic nitrogen, or alkoxy- and phenoxy-oxygen as third donor atom. The complexes were characterised by spectroscopic methods in solution and the solid state. Single-crystal X-ray analyses were performed with VO(2)L(1)(), VO(2)L(3)x1/2EtOH (), VO(2)L(4)(), VO(OiPr)L(7)xiPrOH, VO(OiPr)L(8) and H(2)L(8). For all compounds the vanadium(v) cores contain distorted tetragonal pyramidal geometry around the dioxo- and oxovanadium site at which the N(2)O- and NO(2)-donor ligands bind equatorially. Complexes and display intramolecular hydrogen bonding of the pendant hydroxyphenyl group to a coordinated oxygen trans to a nitrogen atom and therefore serve as suitable models for the native site of vanadium dependent haloperoxidases. Variable-temperature (1)H NMR spectra revealed significant hydrogen bond interaction in acetonitrile solution. In situ prepared catalysts are active for hydrogen peroxide mediated oxygenation of ethyl phenyl sulfide and showed complete conversion of the substrate to ethyl phenyl sulfoxide, together with small amounts of the corresponding sulfone, as detected by GC/MS after 10 min. The complex of H(2)L(7) turned out to be most efficient while HL(1) and HL(2) were completely inactive. Catalysis is supported by the pendant OH group in the complex of HL(3), the catalyst is twice as active as the complex of HL(4).     

Novel synthesis of polyimide with pendant 1-phenylethyl ester using DBU and its thermal acid-catalyzed deesterification

A model reaction of o-(N-phenylcarbamoyl)benzoic acid (amic acid) with threefold amounts of 1-phenylethyl bromide (PEB) and 1,8-diazabicyclo-[5,4,0]-7-undecene (DBU) was carried out in NMP. The reaction gave N-[m-(1-phenylethoxycarbonyl)phenyl]phthalimide in almost quantitative yield at room temperature for 2 h. Polyimide containing pendant 1-phenylethyl ester (P-1a) was also prepared from polyamic acid with PEB using DBU according to the model reaction. The obtained polymer was exactly consistent with P-1a synthesized stepwise from the esterification of the corresponding polyimide containing pendant carboxylic acid with PEB. Therefore, the reaction of polyamic acid bearing pendant carboxylic acid with alkyl bromide proceeded quantitatively to give polyimide containing pendant ester in the presence of DBU. Also, this method was applied to the synthesis of polyimide containing 1-phenylethyl ether. However, the polyimide with quantitative etherification was not synthesized. The acid-catalyzed deesterification of P-1a film was carried out by heating the irradiated polymer film containing 10 wt % of p-nitrobenzyl 9,10-diethoxyanthracene-2-sulfonate, which produced sulfonic acid by irradiation, at various temperatures. Although thermal deesterification of P-1a started at 220°C without any acid catalyst, the deesterification occurred when the irradiated film was heated at the lower temperature. The degree of esterification can be determined from the disappearance of absorption at 700 cm⁻¹. The deesterification obeyed first-order kinetics. © 1996 John Wiley & Sons, Inc.     

磺化侧苯基杂萘联苯聚醚酮酮的合成与性能

以4-(3-苯基-4-羟基苯基)-2,3-二氮杂萘-1-酮(DHPZ-P)、 4-(4-羟基苯基)-2,3-二氮杂萘-1-酮(DHPZ)和1,4-二(4'-氟苯甲酰基)苯(BFBB)为原料, 经溶液亲核取代缩聚反应, 通过调节DHPZ-P和DHPZ的比例, 合成了一系列侧苯基杂萘联苯聚醚酮酮(PPEKK-P), 然后以浓硫酸为磺化剂, 制备出一系列磺化侧苯基杂萘联苯聚醚酮酮(SPPEKK-P). 利用傅里叶变换红外光谱(FTIR)和氢核磁共振谱(¹H NMR)对聚合物结构进行表征, 结果表明, 磺酸基团引入到聚合物链的侧苯基上. 采用溶液浇铸法制备SPPEKK-P质子交换膜. SPPEKK-P膜的吸水率、 溶胀率和质子传导率均随离子交换容量(IEC)的增加而增加, 且具有较好的耐氧化性. IEC最高的SPPEKK-P-100膜的质子传导率在95℃能达到7.44×10^-2 S/cm, 且甲醇渗透系数为5.57×10^-8 cm²/s, 阻醇性能优于Nafion117膜.     

Metallacarbenes from diazoalkanes: an experimental and computational study of the reaction mechanism

PCP ligand (1,3-bis-[(diisopropyl-phosphanyl)-methyl]-benzene), and PCN ligand ([3-[(di-tert-butyl-phosphanyl)-methyl]-benzyl]-diethyl-amine) based rhodium dinitrogen complexes (1 and 2, respectively) react with phenyl diazomethane at room temperature to give PCP and PCN-Rh carbene complexes (3 and 5, respectively). At low temperature (-70 degrees C), PCP and PCN phenyl diazomethane complexes (4 and 6, respectively) are formed upon addition of phenyl diazomethane to 1 and 2. In these complexes, the diazo moiety is eta(1) coordinated through the terminal nitrogen atom. Decomposition of complexes 4 and 6 at low temperatures leads only to a relatively small amount of the corresponding carbene complexes, the major products of decomposition being the dinitrogen complexes 1 and 2 and stilbene. This and competition experiments (decomposition of 6 in the presence of 1) suggests that phenyl diazomethane can dissociate under the reaction conditions and attack the metal center through the diazo carbon producing a eta(1)-C bound diazo complex. Computational studies based on a two-layer ONIOM model, using the mPW1K exchange-correlation functional and a variety of basis sets for PCP based systems, provide mechanistic insight. In the case of less bulky PCP ligand bearing H-substituents on the phosphines, a variety of mechanisms are possible, including both dissociative and nondissociative pathways. On the other hand, in the case of i-Pr substituents, the eta(1)-C bound diazo complex appears to be a critical intermediate for carbene complex formation, in good agreement with the experimental results. Our results and the analysis of reported data suggest that the outcome of the reaction between a diazoalkane and a late transition metal complex can be anticipated considering steric requirements relevant to eta(1)-C diazo complex formation.     

Synthesis and pharmacological evaluation of 2-(1-alkylpiperidin-4-yl)-n-[(1r)-1-(4-fluorophenyl)-2-methylpropyl]acetamide Derivatives as Novel Antihypertensive Agents

We synthesized and evaluated the inhibitory activity of a series of 2-(1-alkylpiperidin-4-yl)-N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]acetamide derivatives against T-type Ca(2+) channels. Structure-activity relationship studies revealed that the position of the amide structure was important for the potent inhibitory activity toward T-type Ca(2+) channels. In addition, the introduction of an appropriate substituent on the pendant benzene ring played a crucial role for the selectivity towards T-type Ca(2+) channels over L-type Ca(2+) channels and the potent bradycardic activity of these derivatives. Oral administration of N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]-2-(1-{2-[2-(2-methoxyethoxy)phenyl]ethyl}piperidin-4-yl)acetamide (4f), which had superior selectivity for T-type Ca(2+) channels over L-type Ca(2+) channels, lowered blood pressure in spontaneously hypertensive rats without inducing reflex tachycardia, which is often caused by traditional L-type Ca(2+) channel blockers.     

Glass transition temperatures of some linear polymers containing phenyl side groups

The glass transition temperatures of a number of poly(vinyl phenyl ketones), poly-(vinyl benzoates), and poly(phenyl acrylates) have been measured by a refractometric method. The effects exerted on T_g by the nature and position of the ring substituents and by the different groups binding the pendant phenyl rings to the polyvinyl chain are discussed. The importance of knowledge of the side-group motions in the glassy state for the interpretation of glass temperature data is emphasized.     

Network formation of a phenyl vinyl ketone copolymer with 4-vinylbenzil and its photodecrosslinking in films

The irradiation (λ > 400 nm) in air of a copolymer of phenyl vinyl ketone with 4-vinylbenzil (VBZ) containing 1.5 wt % VBZ structural units in film, followed by the thermal decomposition of the resulting pendant benzoyl peroxide groups, leads to crosslinking. The subsequent irradiation of the crosslinked polymer at 366 nm results in the cleavage of the poly(phenyl vinyl ketone) chain between the junction points of the polymer network through a Norrish type II reaction. Therefore, poly(phenyl vinyl ketone-co-4-vinylbenzil) represents a novel type of photoresist based on polymer network decrosslinking. The process involves three steps: photogeneration of peroxide, crosslinking by its thermal decomposition, and subsequent photodecrosslinking of the polymer network. This material provides positive-tone images after UV exposure (λ > 330 nm) and development in an organic medium such as isopropyl methyl ketone. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 765–771, 2004     

Highly chromic, proton-responsive phenyl pyrimidones

Aryl pyrimidones are pharmacologically relevant compounds whose optical properties have only been partially explored. We report the synthesis and optical characterization of a series of aryl- and diaryl-2(1H)-pyrimidones. The electronic transitions of these chromophores are modulated by the extent of conjugation between the pendant phenyl ring and the pyrimidone core as well as the presence of electron-donating auxochromes. Monoprotonation of the pyrimidone ring results in large hyperchromic and bathochromic shifts as well as switching of fluorescence making these phenyl pyrimidones of interest as sensory materials.     

Discovery of a novel acyl-CoA: cholesterol acyltransferase inhibitor: the synthesis, biological evaluation, and reduced adrenal toxicity of (4-phenylcoumarin)acetanilide derivatives with a carboxylic acid moiety

As a part of our research for novel potent and orally available acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors that can be used as anti-atherosclerotic agents, we recently reported the discovery of the (4-phenylcoumarine)acetanilide derivative 1. However, compound 1 showed adrenal toxicity in animal models. In order to search for safer ACAT inhibitors that do not have adrenal toxicity, we examined the inhibitory activity of ACAT in human macrophage and adrenal cells. The introduction of a carboxylic acid moiety on the pendant phenyl ring and the adjustment of the lipophilicity led to the discovery of (2E)-3-[7-chloro-3-[2-[[4-fluoro-2-(trifluoromethyl)phenyl]amino]-2-oxoethyl]-6-methyl-2-oxo-2H-chromen-4-yl]phenyl]acrylic acid (21e), which showed potent ACAT inhibitory activity in macrophages and a selectivity of around 30-fold over adrenal cells. In addition, compound 21e showed high adrenal safety in guinea pigs.     

Preparation and thermal properties of polyquinazolones containing m-substituted phenyl groups on the quinazolone ring

Polyquinazolones containing m-substituted phenyl groups (Br, Cl, F, CH₃O, NO₂, and CH₃) on the quinazolone ring were synthesized in m-cresol, and their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss. Polyquinazolones with intrinsic viscosities in the range 0.2–1.6 dL/g were synthesized. The introduction of substituted groups into the pendant phenyl group resulted in a decrease in the glass transition temperature and the thermal stability. Oxidative thermal stability of the polyquinazolones was dependent on the position of substituted groups on the pendant phenyl group. The introduction of substituted groups into the meta position reduced thermal stability more than did the introduction into the para position.     

Thermal degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers

Vinylidene chloride polymers containing comonomer units capable of consuming evolved hydrogen chloride to expose good radical-scavenging sites might be expected to display greater thermal stability than similar polymers containing simple alkyl acrylates as comonomer. Incorporation of a comonomer containing the phenyl t-butyl carbonate moiety into a vinylidene chloride polymer has the potential to afford a polymer with pendant groups which might interact with hydrogen chloride to expose phenolic groups. Copolymers of vinylidene chloride with [4-(t-butoxycarbonyloxy)phenyl]methyl acrylate have been prepared, characterized, and subjected to thermal degradation. The degradation has been characterized by thermal and spectroscopic techniques. The degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers is much more facile than the same process for similar copolymers containing either [4-(isobutoxycarbonyloxy)phenyl]methyl acrylate or methyl acrylate, a simple alkyl acrylate, as comonomer. During copolymer degradation, [4-(t-butoxycarbonyloxy) phenylmethyl acrylate units are apparently converted to acrylic acid units by extensive fragmentation of the sidechain. Thus, the phenyl t-butyl carbonate moiety does function as a labile acid-sensitive pendant group but its decomposition in this instance leads to the generation of a phenoxybenzyl carboxylate capable of further fragmentation.     

Novel polymeric structures via the chlorination of cis-1,4-polybutadiene in the presence of aryl nucleophiles

The addition chlorination of cis-1,4-polybutadiene in the presence of a variety of aryl nucleophiles resulted in the formation of head-to-head poly(vinyl chloride) with pendant aromatic functional groups. Chlorination in methylene chloride solution with benzoic acid gave chlorinated polymers with pendant benzoate esters. Chlorination in the presence of phenol and benzhydrol provided polymers with pendent phenyl and diphenyl methyl ethers, respectively. Acetophenone participated during chlorination to affored polymer with pendant α-chloroether groups, while benzonitrile gave a polymer with pendant imidoyl chlorides. The extent of participation of these nucleophiles was estimated from elemental analysis and NMR spectral data, and the effect of aryl substitution on density, glass transition temperature, and linear coefficient of thermal expansion was determined. © 1993 John Wiley & Sons, Inc.     

三元铕配合物Eu(DBM)3L1的合成、晶体结构及发光性能

新型三元铕配合物Eu(DBM)3L1(DBM=二苯甲酰甲烷,L1=2-(3-硝基苯基)-咪唑并[4,5-f]-1,10-邻二氮杂菲)的晶体属单斜晶系,Cc空间群.中心铕离子分别与DBM配体的六个氧原子和第二配体的两个鳌合氮原子配位,形成八配位的扭曲四方反棱柱构型.配合物中性配体的共轭平面与相邻分子的DBM苯环平面(C(25),C(26),C(27),C(28),C(29))之间有明显的π-π相互作用.在紫外光激发下,配合物表现出较强的Eu3+的特征发射,第二配体对中心离子有较强的敏化发光作用.     

Low‐Valent Ruthenium Induced Simultaneous Reduction of Nitro Group and C‐C Double Bond in Nitroolefin 1‐Phenyl‐2‐Nitropropene‐1

The reduction of 1‐phenyl‐2‐nitropropene‐1 ( 1 ) on using ruthenium complexes was studied in detail in order to correlate this method with those previously recorded in the literature for the hydrogenation of nitroolefins. A variety of products was isolated by varying the reaction temperature and solvent. Among them was 1‐phenyl‐2‐propylamine ( 4 ), completely reduced from the selective both double bond and nitro group. 1‐Phenyl‐2‐propanol ( 5 ) was observed due to reduction of phenylacetone at 125 °C in the presence of ruthenium catalyst. When reaction temperature was lower than 125 °C, by employing RuCl₂(PPh₃)₃ complex, 1‐phenyl‐2‐nitropropane ( 2 ) and phenylacetone ( 3 ) were obtained, respectively. Ru‐BINAP complexes were attempted to produce chiral amine from starting material 1‐phenyl‐2‐nitropropene‐1 ( 1 ).     

Helical polymer brushes with a preferred-handed helix-sense triggered by a terminal optically active group in the pendant

Helical polymer brushes with a preferred-handed helix-sense composed of a poly(phenylacetylene) backbone and poly(phenyl isocyanate) pendants are synthesized. The helix-sense of the backbone is effectively controlled by the helical chirality of the pendants, which is triggered by an optically active group introduced at the pendant terminal.     

Phenyl(fluoro)chlorodisiloxanes

Cohydrolysis of phenyltrichlorosilane with phenyl(fluoro)dichloro- and phenyl(difluoro)-chlorosilanes and thermolysis of the formed siloxanes leading to the formation of phenyl(difluoro)chlorosilane are studied. The scheme of thermal decomposition of disiloxanes possessing fluorine atoms in the 1,3 positions is suggested. The scheme is based on the intermediate formation of an active four-membered cyclic complex closed by the fluorine bridge between the silicon atoms. In agreement with the scheme, no thermolysis of 1,3-diphenyl-1-fluoro-1,3,3-trichlorodisiloxane is observed under the studied conditions.