Showing papers on "Substituent published in 2017"
TL;DR: In this article, four new 2-(substituted phenyl) benzimidazole derivatives have been synthesized and their inhibiting action on the corrosion of mild steel in 1-M HCl is compared with that of 2-phenyl benzimimide derivatives employing electrochemical and gravimetric measurements, as well as theoretical calculation.
219 citations
TL;DR: It is found that the quantum yields for photorelease with this photocage are highly sensitive to substituent effects and the insights gained from this structure-reactivity relationship may aid in the development of new highly efficient photoreactions.
Abstract: A detailed investigation of the photophysical parameters and photochemical reactivity of meso-methyl BODIPY photoremovable protecting groups was accomplished through systematic variation of the leaving group (LG) and core substituents as well as substitutions at boron. Efficiencies of the LG release were evaluated using both steady-state and transient absorption spectroscopies as well as computational analyses to identify the optimal structural features. We find that the quantum yields for photorelease with this photocage are highly sensitive to substituent effects. In particular, we find that the quantum yields of photorelease are improved with derivatives with higher intersystem crossing quantum yields, which can be promoted by core heavy atoms. Moreover, release quantum yields are dramatically improved by boron alkylation, whereas alkylation in the meso-methyl position has no effect. Better LGs are released considerably more efficiently than poorer LGs. We find that these substituent effects are additi...
144 citations
TL;DR: This work reports a new CP-MOF, [Cu4(tdhb)] (BUT-155), which is constructed from a judiciously designed carboxylate ligand with high coordination connectivity (octatopic), abundant hydrophobic substituents (six methyl groups), and substituent constrained geometry (tetrahedral backbone).
Abstract: Copper(II)-paddlewheel-based metal–organic frameworks (CP-MOFs) represent a unique subclass of MOFs with highly predictable porous structures, facile syntheses, and functional open metal sites. However, the lack of high hydrolytic stability is an obstacle for CP-MOFs in many practical applications. In this work, we report a new CP-MOF, [Cu4(tdhb)] (BUT-155), which is constructed from a judiciously designed carboxylate ligand with high coordination connectivity (octatopic), abundant hydrophobic substituents (six methyl groups), and substituent constrained geometry (tetrahedral backbone), tdhb8– [H8tdhb = 3,3′,5,5′-tetrakis(3,5-dicarboxyphenyl)-2,2′,4,4′,6,6′-hexamethylbiphenyl)]. BUT-155 shows high porosity with a Brunauer–Emmett–Teller surface area of 2070 m2/g. Quite interestingly, this CP-MOF retains its structural integrity after being treated in water for 10 days at room temperature or in boiling water for 24 h. To the best of our knowledge, BUT-155 represents the first CP-MOF that is demonstrated to ...
98 citations
TL;DR: In this article, five new organotin(IV) complexes were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques, and the results demonstrate that the compounds containing Sn-Ph ligands are more effective than those with Sn-Bz ligands.
Abstract: Five new organotin(IV) complexes of composition [Bz2SnL1]n (), [Bz3SnL1H⋅H2O] (), [Me2SnL2⋅H2O] (), [Me2SnL3] () and [Bz3SnL3H]n () (where L1 = (2S)-2-{[(E)-(4-hydroxypentan-2-ylidene)]amino}-4-methylpentanoate, L2 = (rac)-2-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}-4-methylpentanoate and L3 = (2S)- or (rac)-2-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}-4-methylpentanoate) were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques. The crystal structure of reveals a distorted trigonal-bipyramidal geometry around the tin atom where the oxygen atoms of the carboxylate ligand and a water ligand occupy the axial positions, while the three benzyl ligands are located at the equatorial positions. On the other hand, the analogous derivative of enantiopure L3H () consists of polymeric chains, in which the ligand-bridged tin atoms adopt the same trans-Bz3SnO2 trigonal-bipyramidal configuration and are now coordinated to a phenolic oxygen atom instead of H2O. In , the OH hydrogen of the ketoimine substituent has moved to the nearby nitrogen atom while in the salicylidene derivative , the OH is located almost midway between the phenolic oxygen atom and the nitrogen atom of the C[DOUBLE BOND]N group. For the dibenzyltin derivative , a polymeric chain structure is observed as a result of a long intermolecular Sn⋅⋅⋅O bond involving the exocyclic carbonyl oxygen atom from the tridentate ligand of a neighbouring tin-complex unit. The tin atom in this complex has distorted octahedral coordination geometry. In contrast, the racemic dimethyltin(IV) complexes and display discrete monomeric structures with a distorted octahedral- and trigonal-bipyramidal geometry, respectively. The structures show that the coordination mode of the Schiff base ligand depends primarily on the number of bulky benzyl ligands (R) at the tin atom, as indeed found in the structures of related complexes where R = phenyl. With three bulky R groups, the tridentate chelating O,N,O coordination mode is preferred, whereas with fewer or less bulky R ligands, only the carboxylate and hydroxy groups are involved, which leads to polymers. Larvicidal efficacies of two of the new tribenzyltin(IV) complexes ( and ) were assessed on the second larval instar of Anopheles stephensi mosquito larvae and compared with two triphenyltin(IV) analogues, [Ph3SnL1H]n and [Ph3SnL3H]n. The results demonstrate that the compounds containing Sn–Ph ligands are more effective than those with Sn–Bz ligands. Copyright © 2016 John Wiley & Sons, Ltd.
92 citations
TL;DR: First-principles density functional calculations show that the bonding of the functional groups with the 1T phase is stronger than with the 2H phase, reflected in notable changes in the electronic structure of the former upon functionalization.
Abstract: Covalent functionalization has been effectively employed to attach benzene functionalities to MoS2 and MoSe2 nanosheets by the reaction with para-substituted iodobenzenes bearing −OCH3, −H, and −NO2 as the substituents, where the electron-donating and electron-withdrawing power of the para substituent varies significantly. The functionalization is based on the formation of a C−S or C−Se linkage at the expense of the C−I bond on reaction of the iodobenzene with electron-rich 1T-MoS2 or 1T-MoSe2. The degree of functionalization is in the range 4–24 % range, the value increases with the electron-withdrawing power of the para substituent. Semiconducting 2H-MoS2 and 2H-MoSe2 nanosheets can also be functionalized with iodobenzene by carrying out the reaction in the presence of a Pd0 catalyst. We have also carried out functionalization of 1T-MoS2 with pyrene, coumarin, and porphyrin derivatives. By using first-principles density functional calculations, we show that the bonding of the functional groups with the 1T phase is stronger than with the 2H phase. This is reflected in notable changes in the electronic structure of the former upon functionalization; a gap opens up in the electronic spectrum of the 1T phase. Functionalization with para-substituted benzenes leads to a change in the work function.
85 citations
TL;DR: In this article, the synthesis and optical properties of a series of anthracenyl-o-carborane dyads exhibiting highly-efficient luminescence with various types of substituent groups at the adjacent carbon atom of o-Carborane were described.
Abstract: This manuscript describes the synthesis and optical properties of a series of anthracenyl-o-carborane dyads exhibiting highly-efficient luminescence with various types of substituent groups at the adjacent carbon atom of o-carborane The restricted rotational motion of the anthracene moiety and the ideal orientation for intramolecular charge transfer from the anthracene moiety to the carborane cluster resulted in yellow and orange emissions (λem = 563 nm and 604 nm) with approximately 100% absolute fluorescence quantum efficiencies in the crystalline state of the methyl- and trimethylsilyl (TMS)-substituted dyads, respectively In additional, clear thermochromic luminescence properties were also observed Computer calculations were carried out to investigate the influence of the substituent effect on emission efficiency
85 citations
TL;DR: A linear correlation between logKa (Ka = association constant) and the Hammett substituent constant σpara is observed, confirming predictions by the Hunter-Sanders model experimentally.
Abstract: Host–guest systems with Rebek imide type receptors and a 2,6-di(isobutyramido)pyridine ligand were employed to investigate substituent effects in parallel-displaced π–π stacking interactions. Changing the intermolecular distance between the para substituent on the aromatic platform of the receptor and the pyridine ring of the guest results in a strongly different substituent effect. With a short ethyne-1,2-diyl spacer between the Rebek imide and the aromatic platform, partial overlap of substituent and guest stabilizes the π–π stacking interactions independent of the electronic nature of the substituent (Wheeler–Houk model). When the substituent is shifted further away by using a buta-1,3-diyne-1,4-diyl spacer, direct, through-space interactions between substituent and guest are prevented. A linear correlation between logKa (Ka=association constant) and the Hammett substituent constant σpara is observed, confirming predictions by the Hunter–Sanders model experimentally.
78 citations
TL;DR: Although the emission wavelengths are only marginally affected by the ring substitution pattern, the PL intensities respond sensitively to the presence of substituents in the ortho or meta positions, with strong luminescence in compounds with Au-O-C-C torsion angles <50°.
Abstract: Copper and gold halide and pseudo-halide complexes stabilized by methyl-, ethyl- and adamantyl-substituted cyclic (alkyl)(amino)¬carbene (CAAC) ligands are mostly linear monomers in the solid state, without aurophilic Au···Au interactions. (Et2L)CuCl shows the highest photoluminescence quantum yield (PLQY) in the series, 70%. The photoemissions of Me2L and Et2L copper halide complexes show S1 → S0 fluorescence on the ns time scale, in agreement with theory, as well as a minor long-lived emission. Monomeric (Me2L)CuNCS is a white emitter, while dimeric [(Et2L)Cu(µ-NCS)]2 shows intense yellow emission with a PLQY of 49%. The reaction of (AdL)MCl (M = Cu or Au) with phenols ArOH (Ar = Ph, 2,6-F2C6H3, 2,6-Me2C6H3, 3,5-But2C6H3, 2-But-5-MeC6H3, 2-pyridyl), thiophenol, or aromatic amines H2NAr' (Ar' = Ph, 3,5-(CF3)2C6H3, C6F5, 2-py) afforded the corresponding phenolato, thiophenolato and amido complexes. Whereas the emission wavelengths are only marginally affected by the ring substitution pattern, the PL intensities respond sensitively to the presence of substituents in ortho or meta position. In gold aryloxides PL is controlled by steric factors, with strong luminescence in compounds with Au-O-C-C torsion angles <50. Calculations confirm the dependence of oscillator strength on the torsion angle, as well as the inter-ligand charge transfer nature of the emission. The HOMO/LUMO energy levels were estimated based on first reduction and oxidation potentials.
77 citations
TL;DR: The combination of various ligand-design strategies in one molecule has been realized in 1-PPh3 to achieve a high catalytic HER performance and these factors are valuable to be used in other molecular catalyst systems.
Abstract: A cobalt complex of 5,15-bis(pentafluorophenyl)-10-(4)-(1-pyrenyl)phenyl corrole that contains a triphenylphosphine axial ligand (1-PPh3 ) was synthesized and examined as an electrocatalyst for the hydrogen evolution reaction (HER). If supported on graphene (G), the resulting 1-PPh3 /G material can catalyze the HER in aqueous solutions over a wide pH range of 0-14 with a high efficiency and durability. The significantly enhanced activity of 1-PPh3 /G, compared with that of its analogues 1-py/G (the Co-bound axial ligand is pyridine instead of triphenylphosphine) and 2-py/G (Co complex of 5,10,15-tris(pentafluorophenyl)corrole), highlights the effects of the pyrenyl substituent and the triphenylphosphine axial ligand on the HER activity. On one hand, the pyrenyl moiety can increase the π-π interactions between 1 and graphene and thus lead to a fast electron transfer from the electrode to 1. On the other hand, the triphenylphosphine axial ligand can increase the electron density (basicity) of Co and thus make the metal center more reactive to protons at the trans position through a so-called "push effect". This study concerns a significant example that shows the trans effect of the axial ligand on the HER, which has been investigated rarely. The combination of various ligand-design strategies in one molecule has been realized in 1-PPh3 to achieve a high catalytic HER performance. These factors are valuable to be used in other molecular catalyst systems.
72 citations
TL;DR: Triphenylamine (TPA) has been used to generate stimuli-responsive smart fluorescent organic materials and correlate the effect of subtle structural changes on the molecular packing and mechanochromic fluorescence as mentioned in this paper.
Abstract: Triphenylamine (TPA), a propeller-shaped optoelectronic molecule, has been used to generate stimuli-responsive smart fluorescent organic materials and correlate the effect of subtle structural changes on the molecular packing and mechanochromic fluorescence (MCF). The substituent (OCH3) position in the TPA phenyl ring and acceptors (malononitrile, cyanoacetamide, cyanoacetic acid, ethyl cyanoacetate, and diethylmalonate) strongly influenced the solid state and mechanochromic fluorescence as well as the molecular packing. The structure–property studies revealed that (i) TPA derivatives without the OCH3 substituent exhibit strong fluorescence (Φf = 85% (TCAAD-1, 55% (TDEM)), (ii) higher dihedral angle (τ) between donor (aminophenyl) and acceptor lead to weak/non fluorescent material, (iii) substituent at the ortho position to acceptor increased the dihedral angle (τ = 26.49 (TCAAD-2), τ = 27.14 (TDMM)), and (iv) the increase of alkyl groups produced self-reversible high contrast off-on fluorescence switchin...
70 citations
TL;DR: In this paper, copolymerization of ethylene with polar monomers such as 5-hexene-1-yl acetate and allylacetate is explored using nickel complexes bearing a class of anilinonaphthoquinone ligands.
Abstract: Copolymerizations of ethylene with polar monomers such as 5-hexene-1-yl acetate and allyl acetate are explored using nickel complexes bearing a class of anilinonaphthoquinone ligands. High tolerability of this complex toward polar comonomer is achieved by the installation of sterically bulky substituent on the aniline ligand. Moreover, the heterogenization of the nickel complexes using silica-supported modified methylaluminoxane enhances the copolymerization performances. The catalyst is highly active and thermally stabile to give semicrystalline ester-functionalized high molecular weight polyethylenes.
TL;DR: The synthesis and properties of azulene-substituted 1,1,4,4-tetracyanobutadienes (AzTCBDs) and heteroazulenyl TCBDs are described, showing a multi-step color change under electrochemical redox conditions.
Abstract: We describe the synthesis and properties of azulene-substituted 1,1,4,4-tetracyanobutadienes (AzTCBDs) and heteroazulenyl TCBDs. TCBD derivatives were prepared in good to excellent yields through reaction of the corresponding 1-ethynylazulenes with tetracyanoethylene (TCNE). In contrast, the reaction between propargyl alcohols and the 1-azulenyl group in TCNE generated 2-aminofuran derivatives, which were transformed into 6-aminofulvenes with a 1-azulenyl substituent upon treatment with several amines. The optical and electrochemical properties of the AzTCBDs were clarified by UV/Vis and voltammetry. The AzTCBD derivatives exhibited electrochromism, showing a multi-step color change under electrochemical redox conditions. The multistage redox properties of AzTCBDs could be useful for the development of novel organic electronic materials.
TL;DR: An enzymatic mechanism relying on a long-range electron transfer is concluded, which is without parallel in vitamin B12-dependent biochemistry and represents an effective mode of RDase catalysis.
Abstract: The capacity of metal-containing porphyrinoids to mediate reductive dehalogenation is implemented in cobamide-containing reductive dehalogenases (RDases), which serve as terminal reductases in organohalide-respiring microbes. RDases allow for the exploitation of halogenated compounds as electron acceptors. Their reaction mechanism is under debate. Here we report on substrate-enzyme interactions in a tetrachloroethene RDase (PceA) that also converts aryl halides. The shape of PceA's highly apolar active site directs binding of bromophenols at some distance from the cobalt and with the hydroxyl substituent towards the metal. A close cobalt-substrate interaction is not observed by electron paramagnetic resonance spectroscopy. Nonetheless, a halogen substituent para to the hydroxyl group is reductively eliminated and the path of the leaving halide is traced in the structure. Based on these findings, an enzymatic mechanism relying on a long-range electron transfer is concluded, which is without parallel in vitamin B12-dependent biochemistry and represents an effective mode of RDase catalysis.
TL;DR: A novel and efficient Cu(OAc)2-mediated oxysulfonylation of alkenyl oximes with sodium sulfonates was developed and form a broad range of sulfone-substituted isoxazolines in good yields.
TL;DR: Structural and theoretical analysis of silanones 2 indicate a short Si=O bond and an enhanced polarization toward the O atom compared to Me2Si=O owing to the strong π-electron donation from the phosphonium ylide substituent.
Abstract: Silanones substituted by bulky amino- and phosphonium ylide substituents have been synthesized and isolated in crystalline form. Thanks to the steric protection and the strong electron-donating ability of substituents, silanones 2 are persistent and only slowly dimerizes at room temperature (t1/2 = 0.5 or 5 h). Structural and theoretical analysis of the silanone indicate a short Si=O bond (1.533 A) and an enhanced polarization toward O atom compared to Me2Si=O due to the strong pi-electron donation from the phosphonium ylide substituent.
TL;DR: A transition-metal-free coupling of aldehydes and ketones with geminal bis(boron) building blocks which provides the coupled, homologated carbonyl compound upon oxidation.
TL;DR: The origin of asymmetric induction in the addition of carbon and nitrogen-centered radicals to octahedral centrochiral rhodium enolates has been investigated with density functional theory calculations.
Abstract: The origin of asymmetric induction in the additions of carbon- and nitrogen-centered radicals to octahedral centrochiral rhodium enolates has been investigated with density functional theory calculations. Computed free energies of activation reproduce the preference for the experimentally observed major enantiomer. Good levels of enantioselectivity are maintained upon replacement of the bulky tert-butyl substituents on the ligands with methyl groups. Distortion-interaction analysis indicates that for both carbon- and nitrogen-centered radicals, which have relatively early and late transition states, respectively, the difference in the distortion energies controls the enantioselectivity. In the enolate derived from the Λ-configured catalyst, the tert-butyl group that shields the si face of the substrate plays the most sterically significant steric role by directly hindering access to the enolate double bond. Exploration of the effect of the N substituent size and shape on the imidazole substrate shows that...
TL;DR: A site-selective hydroxylative dearomatization of 2-substituted phenols to either 1,2-benzoquinols or their cyclodimers, catalyzed by 4,5-dimethyl-2-iodoxybenzenesulfonic acid with Oxone has been developed and could be synthesized efficiently under mild reaction conditions.
Abstract: A site-selective hydroxylative dearomatization of 2-substituted phenols to either 1,2-benzoquinols or their cyclodimers, catalyzed by 4,5-dimethyl-2-iodoxybenzenesulfonic acid with Oxone, has been developed. Natural products such as biscarvacrol and lacinilene C methyl ether could be synthesized efficiently under mild reaction conditions. Furthermore, both the reaction rate and site selectivity could be further improved by the introduction of a trialkylsilylmethyl substituent at the 2-position of phenols. The corresponding 1,2-quinols could be transformed into various useful structural motifs by [4+2] cycloaddition cascade reactions.
TL;DR: The great sensitivity of this model allowed us to show unambiguously that a methyl appears bigger than a chlorine and gave the following order in size: CN > OMe > OH.
Abstract: A steric scale of 20 recurrent groups was established from comparison of rotational barriers on N-(o-substituted aryl)thiazoline-2-thione atropisomers. The resulting energy of activation ΔG⧧rot reflects the spatial requirement of the ortho substituent borne by the aryl moiety, electronic aspects and external parameters (temperature and solvent) generating negligible contributions. Concerning divergent rankings reported in the literature, the great sensitivity of this model allowed us to show unambiguously that a methyl appears bigger than a chlorine and gave the following order in size: CN > OMe > OH. For the very bulky CF3 and iPr groups, constraints in the ground state decreased the expected ΔG⧧rot values resulting in a minimization of their apparent sizes.
TL;DR: The contributions from various noncovalent interactions of halogens introduced into proteins, to drive the application of XBs, particularly in biomolecular design are dissected.
Abstract: The structures and stabilities of proteins are defined by a series of weak noncovalent electrostatic, van der Waals, and hydrogen bond (HB) interactions. In this study, we have designed and engineered halogen bonds (XBs) site-specifically to study their structure–energy relationship in a model protein, T4 lysozyme. The evidence for XBs is the displacement of the aromatic side chain toward an oxygen acceptor, at distances that are equal to or less than the sums of their respective van der Waals radii, when the hydroxyl substituent of the wild-type tyrosine is replaced by a halogen. In addition, thermal melting studies show that the iodine XB rescues the stabilization energy from an otherwise destabilizing substitution (at an equivalent noninteracting site), indicating that the interaction is also present in solution. Quantum chemical calculations show that the XB complements an HB at this site and that solvent structure must also be considered in trying to design molecular interactions such as XBs into bio...
TL;DR: In this work, it is proved that it is possible to tailor the PL properties of carborane-stilbene dyads by changing the Cc substituent and theCarborane isomer.
Abstract: Two novel styrene-containing meta-carborane derivatives substituted at the second carbon cluster atom (Cc) with either a methyl (Me) or a phenyl (Ph) group are introduced herein along with a new set of stilbene-containing ortho- (o-) and meta- (m-) carborane dyads. The latter set of compounds have been prepared from styrene-containing carborane derivatives via a Heck coupling reaction. High regioselectivity has been achieved for these compounds by using a combination of palladium complexes [Pd2(dba)3]/[Pd(t-Bu3P)2] as a catalytic system, yielding exclusively E isomers. All compounds have been fully characterised and the crystal structures of seven of them were analysed by X-ray diffraction. The absorption spectra of these compounds are similar to those of their respective fluorophore groups (styrene or stilbene), showing a very small influence of the substituent (Me or Ph) linked to the second Cc atom or the cluster isomer (o- or m-). On the other hand, fluorescence spectroscopy revealed high emission intensities for Me-o-carborane derivatives, whereas their Ph-o-carborane analogues evidenced an almost total lack of fluorescence, confirming the significant role of the substituent bound to the adjacent Cc in o-carboranes. In contrast, all the m-carborane derivatives display similar photoluminescence (PL) behavior regardless of the substituent attached to the second Cc, demonstrating its small influence on emission properties. Additionally, m-carborane derivatives are significantly more fluorescent than their o-counterparts, reaching quantum yield values as high as 30.2%. Regarding solid state emission, only stilbene-containing Ph-o-carborane derivatives, which showed very low fluorescence in solution, exhibited notable PL emission in films attributed to aggregation-induced emission. DFT calculations were performed to successfully complement the photoluminescence studies, supporting the experimentally observed photophysical behavior of the styrene and stilbene-containing carborane derivatives. In conclusion, in this work it is proved that it is possible to tailor the PL properties of carborane-stilbene dyads by changing the Cc substituent and the carborane isomer.
TL;DR: The result indicates that the β and β' substituents have a significant effect on the catalytic properties of the cobalt porphyrins for ORRs in acid media.
Abstract: Three series of cobalt tetraarylporphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry. The investigated compounds have the general formula (TpYPP)Co, butano(TpYPP)CoII, and benzo(TpYPP)CoII, where TpYPP represents the dianion of the meso-substituted porphyrin, Y is a CH3, H, or Cl substituent on the para position of the four phenyl rings, and butano and benzo are respectively the β- and β′-substituted groups on the four pyrrole rings of the compound. Each porphyrin undergoes one or two reductions depending upon the meso substituent and solvent utilized. Two irreversible reductions are observed for (TpYPP)CoII and butano(TpYPP)CoII in CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate; the first leads to the formation of a highly reactive cobalt(I) porphyrin, which can then rapidly react with a solvent to give a CoIIICH2Cl as the product. Only one reversible reduction is seen for benzo(TpYPP)CoII under the same solution conditions, and the one-electron-reducti...
TL;DR: In this article, the electron-withdrawing group is first attached to a p carbon of the parent TTM radical, and two novel stable open-shell adducts based on the benzimidazole unit with red-orange emission are obtained.
Abstract: Luminescent radicals have various applications because they simultaneously possess optoelectronic, electronic, and magnetic properties. Despite the development of some luminescent tris(2,4,6-trichlorophenyl)methyl (TTM)-based radicals, all the substituents directly attached to the TTM skeleton are electron-donating groups. Herein, the electron-withdrawing group is first attached to a p carbon of the parent TTM radical, and two novel stable open-shell adducts based on the benzimidazole unit with red-orange emission are obtained. Their photophysical properties, photochemical stabilities, and electroluminescent performances are fully investigated. Because of the introduction of the benzimidazole unit, the intramolecular charge transfer property of D–A type molecules is suppressed to a large extent, and the delocalization of the sole electron is strengthened. Both radicals exhibit largely improved photostability compared to that of the TTM core. High PL quantum yields (ΦF) of 0.39 and 0.36 in doped films are ...
TL;DR: In this paper, the adsorption structures and properties of typical volatile organic compounds on the anatase TiO2 (001) surface were investigated systematically with density functional theory (DFT) to understand their further catalytic degradation mechanisms.
Abstract: The carbonyl-containing compounds (CCs) are typical volatile organic compounds (VOCs) and ubiquitously present in the environment. Therefore, the adsorption structures and properties of typical CCs on the anatase TiO2 (001) surface were investigated systematically with density functional theory (DFT) to understand their further catalytic degradation mechanisms. The adsorption mechanisms show that three selected typical CCs, acetaldehyde, acetone, and methyl acetate, can easily be trapped on the anatase TiO2 (001) surface via the interaction between the carbonyl group with Ti5c sites of catalyst surface. Especially for acetaldehyde with the bare carbonyl group and the strongest adsorption energy, it is the most stable on the surface, because the bare carbonyl group can interact with not only the Ti5c atom, but also the O2c atom of the surface. The substituent effect of different CCs has less impact on its adsorption models in this studied system and the bare carbonyl group is the key functional group withi...
TL;DR: In this paper, a helix-sense-selective polymerization of an achiral substituted phenylacetylene which has two hydroxymethyl groups and a relatively hydrophobic substituent by using a chiral catalytic system was described.
Abstract: One of the authors discovered helix-sense-selective polymerization (HSSP) of an achiral substituted phenylacetylene which has two hydroxymethyl groups and a relatively hydrophobic substituent by using a chiral catalytic system in 2003. The one-handed helicity is stable and static in nonpolar solvents because it is maintained by intramolecular hydrogen bonds. Since the resulting polymer has extremely tight helicity in its main chain, it shows many interesting and unusual properties including highly selective photocyclic aromatization (SCAT). In this review, the discovery and development of the HSSP and SCAT reactions, and the properties and application of the resulting polymers prepared by HSSP and the resulting supramolecular polymers prepared by SCAT will be examined.
TL;DR: In this article, six isostructural MIL-101(Cr)-X (X: H, NO2, SO3H, Cl, CH3, and NH2) materials have been prepared directly by the reaction of CrIII salts and the corresponding terephthalic acid or by postsynthetic treatments of preformed MIL 101(Cr) following reported procedures.
Abstract: Six isostructural MIL-101(Cr)-X (X: H, NO2, SO3H, Cl, CH3, and NH2) materials have been prepared directly by the reaction of CrIII salts and the corresponding terephthalic acid or by postsynthetic treatments of preformed MIL-101(Cr) following reported procedures. The materials were characterized by using XRD (crystallinity and coincident diffraction pattern), isothermal N2 adsorption (specific surface areas range from 2740 m2 g−1 for MIL-101(Cr)-H to 1250 m2 g−1 for MIL-101(Cr)-Cl), thermogravimetry (thermal stability up to 400 °C), and IR spectroscopy (detection of the corresponding substituents), and the results were all in agreement with the reported data for these materials. The MIL-101(Cr) materials were tested as heterogeneous catalysts for epoxide ring opening by methanol, benzaldehyde acetalization by methanol, and Prins coupling, observing a clear influence of the substituent that in general follows a linear relationship with the Hammett σmeta constant of the substituent: the catalytic activity increases as the electron-withdrawing ability of the substituents increases. An up to three orders of magnitude enhancement in the presence of the NO2 substituent was found for some of these reactions. The present study illustrates the versatility that metal–organic frameworks offer as heterogeneous catalysts that allow the design of actives sites with adequate properties tuned for each reaction.
TL;DR: Evaluation of pKa data using the Fujita-Nishioka model for ortho substituent effects reveals that both steric and electronic substituENT properties influence RSL pH responsiveness, with pKa values increasing as substituents size and electron withdrawing character increase.
Abstract: Rhodamine spirolactams (RSLs) have recently emerged as popular fluorescent pH probes due to their fluorescence turn-on capability and ease of functionalization at the spirolactam nitrogen. Design of RSLs is often driven by biological targeting or compatibility concerns rather than the pH sensitivity of the probe, and the relationship between RSL structure and pKa is not well-understood. Here we present a series of 19 aniline-derived RSLs designed to elucidate the relationship between pKa values and the properties of substituents attached to the spirolactam nitrogen. RSLs derived from di-ortho-substituted anilines exhibit pKa tunability across the moderately acidic region (ca. pH 4 - 6). Evaluation of pKa data using the Fujita-Nishioka model for ortho substituent effects reveals that both steric and electronic substituent properties influence RSL pH responsiveness, with pKa values increasing as substituent size and electron withdrawing character increase. These trends are attributed to changes in the RSL structure induced by large substituents and to electronic influences on the protonated spirocyclic reaction intermediate. To demonstrate the practical applicability of these probes in completely aqueous environments, we present RSL-doped conjugated polymer nanoparticles, which exhibit a ratiometric fluorescence response to changing pH levels.
TL;DR: Substrates with an alkyl substituent on the allylic position reacted to form E-aryl-dienes rather than the expected 1,2-dihydronaphthalenes, indicating metalloradical activation of o-styryl N-tosyl hydrazones was responsible.
Abstract: Catalytic synthesis of substituted 1,2-dihydronaphthalenes via metalloradical activation of o-styryl N-tosyl hydrazones ((E)-2-(prop-1-en-1-yl)benzene-N-tosyl hydrazones) is presented, taking advantage of the intrinsic reactivity of a cobalt(III)–carbene radical intermediate. The method has been successfully applied to a broad range of substrates with various R1 substituents at the aromatic ring, producing the desired ring products in good to excellent isolated yields for substrates with an R2 = COOEt substituent at the vinylic position (∼70–90%). Changing the R2 moiety from an ester to other substituents has a surprisingly large influence on the (isolated) yields. This behaviour is unexpected for a radical rebound ring-closure mechanism, and points to a mechanism proceeding via ortho-quinodimethane (o-QDM) intermediates. Furthermore, substrates with an alkyl substituent on the allylic position reacted to form E-aryl-dienes in excellent yields, rather than the expected 1,2-dihydronaphthalenes. This result, combined with the outcome of supporting DFT calculations, strongly points to the release of reactive o-QDM intermediates from the metal centre in all cases, which either undergo a 6π-cyclisation step to form the 1,2-dihydronaphthalenes, or a [1,7]-hydride shift to produce the E-aryl-dienes. Trapping experiments using TEMPO confirm the involvement of cobalt(III)–carbene radical intermediates. EPR spectroscopic spin-trapping experiments using phenyl N-tert-butylnitrone (PBN) confirm the radical nature of the catalytic reaction.
TL;DR: In this paper, the glass transition temperature (Tg) and solvent resistance of lignin-inspired poly(dimethoxyphenyl methacrylate)s were controlled by varying the position of the dimethoxy substituents in the constituent monomers.
Abstract: The macromolecular properties, including the glass transition temperature (Tg) and solvent resistance, of lignin-inspired poly(dimethoxyphenyl methacrylate)s were controlled by varying the position of the dimethoxy substituents in the constituent monomers. For the four dimethoxyphenyl methacrylate isomers investigated, with substituents at different locations on the phenyl ring (i.e., 3,5-; 2,3-; 2,4-; and 2,6-), the Tg’s of the resulting polymers spanned a wide range from less than 100 °C to greater than 200 °C. Rotational freedom and segmental interactions were responsible for the varying Tg’s. The polymers were thermally stable in air up to ∼300 °C, providing a suitable thermal processing window. The poly(dimethoxyphenol methacrylate) homopolymers also exhibited remarkably different solvent resistances to organic solvents, including tetrahydrofuran and chloroform. Furthermore, by copolymerizing various dimethoxyphenyl methacrylate isomers, the Tg and solvent resistance of the resulting macromolecules c...
TL;DR: In this paper, a series of 2-(2-hydroxyphenyl)benzothiazole (HBT) derivatives are synthesized through Sonogashira-coupling reaction, and their electronic structures are systematically tuned through various substitutions with different Hammett substituent constants (σ) in the 5-position of the phenol ring.