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The first synthesis of 3,4-diarylpyrimido[1,2-b]indazole derivatives from 3-aminoindazoles has been realized. The FeCl3-catalyzed intermolecular epoxide ring-opening reaction altered the order of annulation, with the free primary NH2 groups in 3-aminoindazoles preferentially reacting with styrene oxides instead of aromatic aldehydes. This protocol is further highlighted by its broad substrate compatibility, high chemo- and regioselectivities, and the late-stage modifications of bioactive molecules. Without aromatic aldehydes, the synthesis of 3-aryl-4-acylpyrimido[1,2-b]indazole derivatives can also be accomplished using alternative reaction conditions. [ABSTRACT FROM AUTHOR]

The fixation of carbon dioxide (CO2) with epoxide to form cyclic carbonates is industrially important because of the high economic value of the products. Quaternized carbon dots have great potential in CO2 cycloaddition under their high activity and facile synthesis without cocatalysts. Herein, novel quaternized carbon dots were synthesized through a microwave method using citric acid and ethanolamine with different amounts of (2-bromoethyl)trimethylammonium bromide (Br-CDs) or (2-chloroethyl)trimethylammonium chloride (Cl-CDs). All carbon dots were characterized by TEM, XPS, FT-IR, UV-vis and zeta potential analyses as well as elemental analysis. Br1-CD showed the best catalytic activity (99%) and selectivity (99%) for CO2 cycloaddition with styrene oxide to 4-phenyl-1,3-dioxolan-2-one under suitable conditions (120 °C, 8 h, and 0.1 MPa). Furthermore, the catalyst can be easily recycled up to five times. [ABSTRACT FROM AUTHOR]

Oxidation of styrene is a key reaction in the synthesis of pharmaceuticals and fine chemicals, and therefore oxidizing styrene with selective, efficient, and recyclable heterogeneous catalysts is significant from an environmental and economic standpoint. In this study, we report the transition Cr-based metal–organic framework [NH2-MIL-101(Cr)] as a heterogeneous photocatalyst, which efficiently promotes styrene epoxidation using H2O2 as a green oxidant, achieving high conversion efficiency (98%) and excellent selectivity (82%) under ambient conditions. Radical detection and quenching experiments reveal that the superoxide radical anion (O2˙−) acts as an active oxygen species, selectively promoting the oxidation of styrene to its oxidized form. This work provides insight into the development of a sustainable and cost-effective method for producing styrene oxide. [ABSTRACT FROM AUTHOR]

The document is the contents list for the journal "Chemical Communications" published on September 25, 2024. It includes various articles on topics such as responsive DNA hydrogels, lithium metal-based battery systems, and strategies in photochemical alcohol oxidation. The journal is published by The Royal Society of Chemistry, a leading chemistry community, and aims to connect the world with the chemical sciences. [Extracted from the article]

Chiral carbon nanodots (CNDs) were fabricated through the hydrothermal processing of sulfanilic acid and chiral tartaric acid, exhibiting outstanding catalytic performance for the chiral catalysis of the ring-opening reaction. Furthermore, the catalytic mechanism was proposed to understand the link between the chiral structure and the performance of the catalyst. [ABSTRACT FROM AUTHOR]

The new homochiral 1D metal–organic coordination polymer {Cu[bdc-(N-MePro)H2O]·0.25H2O}n was synthesized using 2-[(1-methyl- L -prolyl)amino]terephthalic acid, which was obtained for the first time. The unique crystal structure of the new compound was determined using powder X-ray diffraction. The catalytic performance of {Cu[bdc-(N-MePro)H2O]·0.25H2O}n in the asymmetric ring opening reactions of styrene oxide and cyclohexene oxide with aniline was evaluated. [ABSTRACT FROM AUTHOR]

The CaO-supported Pt nanoparticle catalysts, herein referred to as the Pt/CaO-P catalysts, were synthesized for the first time to catalyze the selective hydrogenation of styrene oxide. All previously reported Pt- and Pd-based catalysts were prepared and evaluated under identical conditions, with 2-phenylethanol (2-PEA) being identified as the primary product in the selective hydrogenation of styrene oxide. The comparative analysis of the catalytic performance of Pt/CaO-P, Pt/CaO (unpurified), Pt/Ca(OH)2, and Pt/CaCO3 revealed that the purity of CaO is crucial for enhancing the selectivity towards 1-phenylethanol (1-PEA). Notably, the highest selectivity of 1-PEA over Pt/CaO-P reached up to 39%. Our SO-TPD, CO2-TPD and ex situ FT-IR results further indicated that strong basic sites can modify the adsorption site of SO over Pt nanoparticles, leading to the higher selectivity of 1-PEA. A proposed reaction mechanism for the ring opening of styrene oxide suggests that the breakage of conjugation between the benzene ring and the adjacent carbon cation by strong basic sites plays an important role. [ABSTRACT FROM AUTHOR]

Quaternary ammonium salts of metal derivatives of polyoxometalates [XW11O39M(H2O)]n− (X = P, Si; M = Cr, Mn, Co, Ni, Zn) were successfully tested instead of quaternary ammonium halides as catalysts in the cycloaddition of CO2 to styrene oxide. Remarkably, they gave very satisfactory yields of styrene carbonate at moderate temperature (80 °C). [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations at the M062X-D3/def2-TZVP//M062X-D3/def2-SVP level of theory were employed to reveal the mechanism of the reaction between CO2 and styrene oxide for cyclic carbonate, mediated by guanidine and tetrabutylammonium iodide (TBAI) co-catalysts. The noncatalytic reaction occurred via a concerted mechanism, with energy barriers as high as 64.1 and 78.0 kcal mol−1. Three elementary steps were included in the catalytic reaction, and epoxide ring-opening by nucleophilic attack of an iodide anion was predicted to be the rate-determining step (RDS). Guanidine acted as the H-bond donor to activate styrene oxide by (N)H⋯O interaction, facilitating epoxide ring-opening with a low activation barrier (ΔG≠ = 22.2–29.6 kcal mol−1). A good linear correlation between the acidity of the NH group in the guanidine and the energy barrier in the epoxide ring-opening step was observed. The introduction of an amide group could strengthen the hydrogen bonding ability of the guanidine catalyst toward a styrene oxide substrate, decreasing the activation barrier for the cyclic carbonate product. When the guanidine–Cu(I) complex was used as the Lewis acid catalyst, the styrene oxide was activated by O⋯Cu(I) coordination in organometallic catalysis. The energy barriers in the presence of guanidine–Cu(I)/TBAI catalysts could be decreased in contrast to the non-catalytic reaction. [ABSTRACT FROM AUTHOR]

Inexpensive dyes available at the industrial scale, namely, rhodamine B (RhB), rhodamine 6G (Rh6G) and methylene blue (MB), were investigated as organocatalysts for the cycloaddition of CO2 to styrene oxide to yield styrene carbonate under solvent-free conditions (80 °C, 10 bar CO2, 24 h). Each of these dyes consists of a bulky cation, and a chloride anion that can act as a nucleophilic catalytic species in the target reaction. In order to prepare additional catalysts, the Cl− containing dyes were ion-exchanged with KX (X = Br, I) to afford their counterparts with Br− or I− as the anion. Among this set of nine organocatalysts (three dyes, each with three types of halide), the highest yield of styrene carbonate was obtained with Rh6G-I, and trends were identified based on the nature of the organic cation and halide, with the latter having a much larger impact on the activity (I− > Br− > Cl−). Additionally, we explored the effect of adding H2O as a green, inexpensive hydrogen bond donor acting as a co-catalyst, further optimising the styrene carbonate yield (96% with RhB-I and Rh6G-I in the presence of 50 mg H2O). However, the activity of these organocatalysts was only modest if the reaction temperature was decreased to 45 °C. To tackle this limitation, we designed a tailored yet straightforward modification of RhB-I to synthesise a bifunctional organocatalyst bearing a hydrogen bond donor in proximity of the iodide anion (RhB-EtOH-I). This strategy proved successful and the RhB-EtOH-I catalyst achieved a major increase in styrene carbonate yield (29% after 18 h at 45 °C, 10 bar CO2) compared to the RhB-I/H2O catalytic system (7%). The RhB-EtOH-I catalyst was also versatile and promoted the conversion of a broad scope of epoxides with good to high cyclic carbonate yields under relatively mild reaction conditions (60 °C, 10 bar, 24 h). Although these dye organocatalysts were homogeneous, RhB-EtOH-I could be easily recovered by precipitation with diethyl ether and reused without any loss of catalytic activity. Additionally, we demonstrated that nanofiltration was an effective technique for removing the dye organocatalysts from the cyclic carbonate, affording a high purity product (≤0.1 ppm of RhB in propylene carbonate). The metal-free nature of the optimum organocatalyst (RhB-EtOH-I), its facile preparation and the low cost and commercial availability of its precursors, its promising activity under mild reaction conditions and its reusability are all assets in the context of green chemistry and for potential large-scale applicability. [ABSTRACT FROM AUTHOR]

Inexpensive dyes available at the industrial scale, namely, rhodamine B (RhB), rhodamine 6G (Rh6G) and methylene blue (MB), were investigated as organocatalysts for the cycloaddition of CO2 to styrene oxide to yield styrene carbonate under solvent-free conditions (80 °C, 10 bar CO2, 24 h). Each of these dyes consists of a bulky cation, and a chloride anion that can act as a nucleophilic catalytic species in the target reaction. In order to prepare additional catalysts, the Cl− containing dyes were ion-exchanged with KX (X = Br, I) to afford their counterparts with Br− or I− as the anion. Among this set of nine organocatalysts (three dyes, each with three types of halide), the highest yield of styrene carbonate was obtained with Rh6G-I, and trends were identified based on the nature of the organic cation and halide, with the latter having a much larger impact on the activity (I− > Br− > Cl−). Additionally, we explored the effect of adding H2O as a green, inexpensive hydrogen bond donor acting as a co-catalyst, further optimising the styrene carbonate yield (96% with RhB-I and Rh6G-I in the presence of 50 mg H2O). However, the activity of these organocatalysts was only modest if the reaction temperature was decreased to 45 °C. To tackle this limitation, we designed a tailored yet straightforward modification of RhB-I to synthesise a bifunctional organocatalyst bearing a hydrogen bond donor in proximity of the iodide anion (RhB-EtOH-I). This strategy proved successful and the RhB-EtOH-I catalyst achieved a major increase in styrene carbonate yield (29% after 18 h at 45 °C, 10 bar CO2) compared to the RhB-I/H2O catalytic system (7%). The RhB-EtOH-I catalyst was also versatile and promoted the conversion of a broad scope of epoxides with good to high cyclic carbonate yields under relatively mild reaction conditions (60 °C, 10 bar, 24 h). Although these dye organocatalysts were homogeneous, RhB-EtOH-I could be easily recovered by precipitation with diethyl ether and reused without any loss of catalytic activity. Additionally, we demonstrated that nanofiltration was an effective technique for removing the dye organocatalysts from the cyclic carbonate, affording a high purity product (≤0.1 ppm of RhB in propylene carbonate). The metal-free nature of the optimum organocatalyst (RhB-EtOH-I), its facile preparation and the low cost and commercial availability of its precursors, its promising activity under mild reaction conditions and its reusability are all assets in the context of green chemistry and for potential large-scale applicability. [ABSTRACT FROM AUTHOR]

Developing a simple and efficient heterogeneous catalyst for the cycloaddition of epoxides with CO2 under atmospheric pressure and cocatalyst-/metal-/solvent-free conditions remains a great challenge. Herein, poly(ionic liquid)s (P-[VRIm]Br-crosslinker-x) with unique adsorption-swelling ability toward epoxides are designed and facilely synthesized via free radical polymerization in water. The adsorption-swelling of epoxides by P-[VRIm]Br-crosslinker-x is controllable, reversible, and widespread, resulting from the strong interactions between the poly(ionic liquid)s and epoxide molecules, especially the hydrogenbonding interaction. Superior CO2 cycloaddition is realized in the P-[VRIm]Br-crosslinker-x catalyst through the adsorption-swelling effect. Specifically, P-[VC6Im]Br-C8-5% with 54.1 mmol g-1 adsorptionswelling ability toward styrene oxide achieves 89.3% yield and >99% selectivity in the cycloaddition of styrene oxide with CO2 to styrene carbonate under mild conditions (1 atm, 80 °C) without cocatalyst/metal/solvent consumption. Moreover, P-[VC6Im]Br-C8-5% can be easily recovered by deswelling, and shows good reusability and stability after five cycles for a total of 180 h. The adsorption-swelling property of P-[VRIm]Br-crosslinker-x to epoxides not only prompts the active centers to be fully exposed to the reactants but also induces the enrichment of epoxides during the whole catalytic process, thus accelerating the CO2 cycloaddition reaction rate. This work furnishes new insights for improving the activity of CO2 cycloaddition and would guide the design of efficient poly(ionic liquid) catalysts for atmospheric CO2 conversion. [ABSTRACT FROM AUTHOR]

A non-porous version of SU-101 (herein n-SU-101) was evaluated for the CO2 cycloaddition reaction. The findings revealed that open metal sites (Bi3+) are necessary for the reaction. n-SU-101 displays a high styrene oxide conversion of 96.6% under mild conditions (3 bar and 80 °C). The catalytic activity of n-SU-101 demonstrated its potential application for the cycloaddition of CO2 using styrene oxide. [ABSTRACT FROM AUTHOR]

In this work, a series of new lignin-graft copolymers were successfully prepared through enzymatic hydrolytic lignin (EHL)-initiated ring-opening alternating copolymerization of 3,4-dihydrocoumarin (DHC) and epoxides (EPO) through organocatalysis. A series of EPOs, including styrene oxide (SO), propylene oxide (PO), cyclohexane oxide (CHO) and lignin-derived-2-(2-methoxy-4-methyl-phenoxy) (MPO), together with DHC, were selected as model compounds to prepare EHL-g-P(DHC-alt-EPO), demonstrating the tailor-made potential of this synthetic protocol. The reaction conditions were optimized and the structures and thermal properties of EHL-g-P(DHC-alt-EPO) were fully elucidated by 1H, 13C and 31P NMR, FTIR spectroscopy, MALDI-TOF MS and GPC, DSC, and TGA. It was found that EHL-g-P(DHC-alt-SO) with a monomer conversion of 81.52%, DP of 3.21 and Mn of 62.9 kDa was prepared at a molar ratio of 5 : 5 : 1, 140 °C and 24 h. The UV shielding properties, antioxidant activity and biocompatibility of the as-prepared EHL-g-P(DHC-alt-EPO) was systematically evaluated. As a 'proof of concept' application, the potential of EHL-g-P(DHC-alt-SO) as an active ingredient in sunscreen was demonstrated, and a high sun protection factor (SPF) of 22.42 was achieved at 5 wt% dosage of EHL-g-P(DHC-alt-SO) in the cream, and the possible mechanism for the outstanding performance is also discussed. [ABSTRACT FROM AUTHOR]

Herein, we present the synthesis of three new neutral aryl-BIAN ZnCl2 complexes (where aryl-BIAN = bis(aryl-imino)acenaphthene) with formulations [Zn(4-iPrC6H4-BIAN)Cl2] (1), [Zn(2-iPrC6H4-BIAN)Cl2] (2) and [Zn(4-NO2C6H4-BIAN)Cl2] (3) obtained through a green synthesis methodology. Compounds 1 and 2 were fully characterized by elemental analysis, ESI-LS mass spectrometry, FT-IR ATR mode, and multinuclear NMR spectroscopic techniques. Compound 3 was characterized by elemental analysis, ESI-LS mass spectrometry and FT-IR, ATR mode. The solid-state molecular structures of compounds 1 and 2 were determined by single crystal X-ray diffraction. The new complexes 1, 2 and 3, and the known complexes of formulations [Zn(2,6-iPr2C6H3-BIAN)Cl2] (4) and [Zn(2,4,6-Me3C6H2-BIAN)Cl2] (5) were tested as catalysts in the cycloaddition reaction of CO2 and epoxides using the tetrabutylammonium bromide salt as a co-catalyst. Primary studies revealed that complex 4 presented the highest catalytic activity among all synthetized complexes. Good reaction TOFs were obtained for the conversion of propylene oxide (112 h−1) after 3 hours and for the conversion of styrene oxide (23 h−1) after 8 hours, at 4 MPa and 333 K. For more sterically hindered cyclohexene oxide, no cyclic carbonate formation was observed, under the same operational conditions. Furthermore, the effect of reaction time (1–40 h), pressure (0.5–40 MPa) and nucleophile to metal ratio (0.5–100) on final cyclic carbonate formation was investigated. [ABSTRACT FROM AUTHOR]

Here, we report a visible promotion effect of the B2O3 additive on FeOx/Si3N4 catalysts in the oxidative dehydrogenation of ethylbenzene. The oxygen reactivity of FeOx was alleviated by the strong interaction between FeOx and BOx species, which suppresses the overoxidation of ethylbenzene and styrene to carbon oxides, thus promoting styrene selectivity. [ABSTRACT FROM AUTHOR]

An ideal strategy for the management of greenhouse gas carbon dioxide (CO2) and surplus industrial product-glycerol (Gly) is to convert them into the valuable glycerol carbonate (GC). However, conventional conversion processes rely on high CO2 pressure and reaction temperature. In this work, a series of easily prepared protic ionic liquids (ILs) were studied for the one-pot synthesis of GC using CO2, Gly, and styrene oxide (SO). A 94% yield of GC was obtained with the catalysis of 1,8-diazabicyclo[5.4.0]undec-7-enenium iodide (HDBUI) under atmospheric pressure at 45 °C. Experimental results and density functional theory (DFT) calculations suggest that the high catalytic activity of HDBUI is attributed to the strong nucleophilicity and substrate activation afforded by the synergistic effect of the protic HDBU+ cation and I− anion. In addition, high GC yields were also obtained when simulated flue gas and crude Gly were used as substrates. [ABSTRACT FROM AUTHOR]

The effect of solvent has been investigated for the synthesis of bismuth gallate compounds, of which the water-based bismuth subgallate has been used as an active pharmaceutical ingredient (API) for over a century. Using methanol as a solvent, two new bismuth gallates were acquired: first a flexible 3-periodic metal–organic framework (MOF) forms, which transforms upon extended synthesis times into a layered 2-periodic coordination polymer of the same bismuth-to-gallate ratio. The structures were determined by three-dimensional electron diffraction. Synthesis in ethanol resulted in the formation of the MOF phase, but not the layered phase. The layered material of the methanol-based synthesis was used as a Lewis acid catalyst due to its higher stability, showing a comparatively quick and regiospecific conversion of styrene oxide to 2-methoxy-2-phenylethanol, indicating the presence of open metal sites in the material. The acquisition of bismuth gallate structures of varying periodicity highlights the prospect of acquiring novel MOFs and coordination polymers from the same components of APIs. [ABSTRACT FROM AUTHOR]

Cobalt-catalyzed cascade C–N and C–O bond formation of epoxides with hydrazones is described to furnish oxadiazines using air as an oxidant. The catalyst plays a dual role as a Lewis acid followed by a redox catalyst to accomplish the C–H/O–H cyclization. Optically active styrene oxide can be reacted enantiospecifically (>99% ee). [ABSTRACT FROM AUTHOR]

New chiral Mn(III)–salen complexes 1a–e and 2a–e were synthesized from the reaction of C2-symmetric chiral salen ligands and Mn(CH3COO)2·4H2O under an inert atmosphere followed by aerobic oxidation. These complexes were obtained in 91–96% yields and characterized by HRMS, FT-IR, UV-visible spectroscopy, TGA, and elemental analysis. The chiral Mn(III)–salen complexes 1a–e and 2a–e were evaluated in the asymmetric epoxidation of styrene using NaOCl as an oxidant in ethyl acetate as a green solvent. The chiral Mn(III)–salen complexes 1b and 2b (2 mol%) catalyzed the asymmetric epoxidation of substituted styrenes and chromenes to afford the corresponding epoxides in 95–98% yields with 29–88% ee's. The catalysts 1b and 2b were recovered and reused for up to 2 and 3 runs, respectively, in the asymmetric epoxidation of styrene, and the yield of styrene oxide gradually decreased but the ee was consistent. [ABSTRACT FROM AUTHOR]

Octahedral complexes of the type [Ni(L)(H2O)3](ClO4)2 (1 and 2), where L is the tridentate 3N ligand 4-methyl-1-(pyrid-2-ylmethyl)-1,4-diazacycloheptane (L1, 1), or 4-methyl-1-(N-methylimidazolyl)-1,4-diazacycloheptane (L2, 2), have been isolated and characterized using elemental analysis, ESI-MS and electronic absorption spectroscopy. The DFT optimized structures of 1 and 2 reveal that the tridentate 3N ligands are coordinated meridionally constituting a distorted octahedral coordination geometry around nickel(II). In methanol solution, the complexes, upon treatment with triethylamine, generate the reactive red colored low-spin square planar Ni–OH intermediate [Ni(L1/L2)(OH)]+ (1a and 2a), as characterized by ESI-MS and electronic absorption spectroscopy, and energy minimized structures. The latter when exposed to the atmosphere rapidly absorbs atmospheric CO2 to produce the carbonate bridged dinickel(II) complexes [Ni2(L1/L2)2(μ-CO3)(H2O)2](ClO4)2 (3 and 4), as characterized by elemental analysis and the IR spectral feature (∼1608 cm−1) characteristic of bridging carbonate. The single crystal X-ray structure of 3 reveals the presence of a dinickel(II) core bridged by a carbonate anion in a symmetric mode. Both the Ni(II) centers are identical to each other with each Ni(II) possessing a distorted octahedral coordination geometry constituted by a meridionally coordinated 3N ligand, a carbonate ion and a water molecule. The decay kinetics of the red intermediates generated by 1 (kobs, 7.7 ± 0.1 × 10−5 s−1) and 2 (kobs, 5.8 ± 0.3 × 10−4 s−1) in basic methanol solution with atmospheric CO2 has been determined by absorption spectroscopy. DFT studies illustrate that meridional coordination of the 3N ligand and the electron-releasing imidazole ring as in 2 facilitate fixation of CO2. The carbonate complex 3 efficiently catalyzes the conversion of styrene oxide into cyclic carbonate by absorbing atmospheric and pure CO2 with excellent selectivity. [ABSTRACT FROM AUTHOR]

DFT calculations (M06-L functional) were used to investigate the structure and electronic properties of bimetallic M–Cu–BTC paddlewheels (M = Mg, Ca, Al, and Ga) and their catalytic activity for CO2 cycloaddition with styrene oxide (SO) in the absence of a co-catalyst. The electrostatic interactions play a vital role in the CO2 and SO adsorptions on the metal center of the bimetallic paddlewheels. The appearance of the substituted metal is strongly dominated in the adsorption of SO and CO2 molecules on the Cu center of the bimetallic paddlewheels. The free energy of adsorption increases from −1.7 (Ca–Cu–BTC) to −10.7 (Ga–Cu–BTC) kcal mol−1 for SO adsorption on the Cu site of the M–Cu–BTC paddlewheels. Highly exposed Cu active site in the cases of Al–Cu–BTC and Ga–Cu–BTC is the key to activating the SO in the chemical reaction compared to the Cu center of Mg–Cu–BTC and Ca–Cu–BTC nodes. The substituted metal centers are revealed as key active sites for the CO2 cycloaddition with SO in the absence of a co-catalyst. The stronger interaction of an SO molecule on the substituted metal center as compared to that on the Cu site in the corresponding systems promotes the polarization of the C–O σ-bond of the adsorbed SO, facilitating the CO2 cycloaddition reaction efficiently. Among them, the Al site of the bimetallic Al–Cu–BTC paddlewheel is a candidate catalyst for CO2 cycloaddition with SO. The SO molecule is strongly adsorbed on the Al site of Al–Cu–BTC with the free energy of −29.0 kcal mol−1. The Cα–O bond length of adsorbed SO increases from 1.425 to 1.492 Å. The activation free energies of the concerted reaction were calculated to be 29.9 and 36.4 kcal mol−1 for the catalytic process on the Al and Cu centers of the bimetallic Al–Cu–BTC paddlewheel. [ABSTRACT FROM AUTHOR]

Two isostructural lanthanide metal–organic frameworks (Ln-MOF-589, Ln = La3+, Ce3+), constructed from a tetratopic linker, benzoimidephenanthroline tetracarboxylic acid (H4BIPA-TC), have been solvothermally synthesized and characterized. These Ln-MOF-589 materials consist of Lewis acid [Ln2(-COO)6(-COOH)2(H2O)6] units and a naphthalene diimide core, which exhibited promising catalytic activity for the oxidation of olefins. Among them, Ce-MOF-589 exhibited outstanding performance with high conversions of styrene and cyclohexene (94 and 90%, respectively), and good selectivities towards styrene oxide and 2-cyclohexen-1-one (85, and 95%, respectively). Notably, the catalytic activity of Ce-MOF-589 outperformed that of homogeneous and heterogeneous catalysts, and representative MOFs. Also, Ce-MOF-589 can be recycled for at least up to six cycles with no significant loss of catalytic performance. [ABSTRACT FROM AUTHOR]

Taking the reaction between styrene oxide and CO2 to yield cyclocarbonate as the target, the activities of synergistic catalysts, which are composed of Br− and alcohol compounds serving as hydrogen bond donors (HBDs), were predicted by DFT calculations and confirmed by subsequent experiments. Intramolecular reactions of the active intermediate as well as intermolecular reactions between the active intermediate and styrene oxide were possible side reactions. DFT calculation results show that the most likely by-product is phenylacetone, which is produced from the intramolecular reaction of the active intermediate. According to the calculation results, the catalytic activity of a synergistic catalyst is related to the pKa of the HBD, and the optimal calculated pKa is about 3–4 fold higher than the pKa of 2-bromo-1-phenylethanol, which is the protonated active intermediate of the target reaction. The combination of water and tetraethylammonium bromide (TEAB) was found to be a promising synergistic catalyst, and it can give a conversion of 50% and a yield of 43% under the conditions of 1% (mol%) catalyst loading, solvent free, 100 °C, 1.0 MPa and 1 h. Additionally, the TEAB can be reused. The observed catalytic activity of water is higher than expected but similar to that of styrene glycol, which is the hydration product of styrene oxide. Water is therefore an indirect catalyst and the catalytic activity is mainly contributed by the styrene glycol. [ABSTRACT FROM AUTHOR]

Taking the reaction between styrene oxide and CO2 to yield cyclocarbonate as the target, the activities of synergistic catalysts, which are composed of Br− and alcohol compounds serving as hydrogen bond donors (HBDs), were predicted by DFT calculations and confirmed by subsequent experiments. Intramolecular reactions of the active intermediate as well as intermolecular reactions between the active intermediate and styrene oxide were possible side reactions. DFT calculation results show that the most likely by-product is phenylacetone, which is produced from the intramolecular reaction of the active intermediate. According to the calculation results, the catalytic activity of a synergistic catalyst is related to the pKa of the HBD, and the optimal calculated pKa is about 3–4 fold higher than the pKa of 2-bromo-1-phenylethanol, which is the protonated active intermediate of the target reaction. The combination of water and tetraethylammonium bromide (TEAB) was found to be a promising synergistic catalyst, and it can give a conversion of 50% and a yield of 43% under the conditions of 1% (mol%) catalyst loading, solvent free, 100 °C, 1.0 MPa and 1 h. Additionally, the TEAB can be reused. The observed catalytic activity of water is higher than expected but similar to that of styrene glycol, which is the hydration product of styrene oxide. Water is therefore an indirect catalyst and the catalytic activity is mainly contributed by the styrene glycol. [ABSTRACT FROM AUTHOR]

An in situ generated zinc ascorbate pre-catalyst for cyclic carbonate (CC) synthesis via CO2 coupling with epoxides under ambient conditions was reported. Spectroscopic measurements indicated that CO2 was inserted into the zinc ascorbate complex through the formation of an activated zinc carbonate catalyst upon abstracting the enediol protons with sodium hydride. The aliphatic diols were not activated under the applied conditions and did not interfere with either the process of cycloaddition or CO2 activation. The catalyst was active against different terminal epoxides, with a conversion of 75 and 85%, when propylene oxide and styrene oxide were used at 20 and 50 °C, respectively under 1 atm CO2 for 17 h, which was considered a good advancement for heterogeneous based catalysis. Moreover, green chemistry principles were applied to ultimately end up with more ecofriendly approaches for the synthesis of CC following a simple balloon technique. Herein, we used zinc as a sustainable metal, together with ascorbic acid as a bio-renewable material in addition to CO2 as a renewable feed-stock. Furthermore, waste prevention was achieved using the reaction side product, viz., NaBr as a co-catalyst. [ABSTRACT FROM AUTHOR]

This work reports the synthesis and multifunctionality of 2D layered coordination polymers formulated as [Ln2(H3nmp)2]·xH2O (1, where Ln = Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+ and Y3+) (x = 1 to 4). We describe detailed synthesis of the materials using various methods [typical hydrothermal reaction (HT), microwave-assisted synthesis (MWAS) and one-pot method (OP)], while discussing the various crystal morphologies which can be fine tuned by varying systematically the conditions. We further explore the multifunctionality of this material by studying its heterogeneous catalytic activity in the ring opening of styrene oxide, its photoluminescence behaviour and its cytotoxicity. A conversion of 88%/100% yield at 4 h/24 h reaction respectively, with excellent selectivity towards 2-methoxy-2-phenylethanol product (100%) was observed. Photoluminescence properties of the optically-active [Eu2(H3nmp)2]·xH2O (1Eu) and the mixed-lanthanide [(Gd0.95Eu0.5)2(H3nmp)2]·xH2O (1GdEu), on the other hand, show potential use for UV-to-visible light converters, with lifetimes of 2.31 ± 0.01 and 2.61 ± 0.01 ms at ambient temperature for 1Eu and 1GdEu samples. Preliminary cytotoxic studies showed no effects on metabolic activity of both in vitro human epithelial kidney (HK-2) and human hepatocellular carcinoma (HepG2) cell lines. A reduction of NR uptake was, however, observed indicating some cytotoxic effect on lysosomal activity. [ABSTRACT FROM AUTHOR]

We report the syntheses and structural characterization of a Zn(II) metallacycle [Zn2{(L)2(DMF)2(NO3)2}]·(NO3)2 (1) along with a Cd(II) coordination polymer [{Cd1(L)2(DMF)2}·(NO3)2]n (2) (where L = N,N′-bis-(3-pyridyl)terephthalamide; DMF = dimethylformamide) and their utilization as fluorescent probes for highly selective recognition (turn-off) of Fe3+ and CrO42− ions. Compounds 1 and 2 were prepared by utilizing ligand L and the nitrate salt of zinc and cadmium, respectively. Single crystal X-ray analysis reveals that 1 adopts an overall Zn(II) metallacycle architecture, whereas 2 displays a one-dimensional (1D) polymeric structure. Both 1 and 2 showed high fluorescence stability in aqueous solution and selectively detected Fe3+ and CrO42− ions with high quenching constants and low detection limits of 2.34 × 106 M−1 and 0.153 μM for Fe3+, 6.72 × 105 and 0.205 μM for CrO42− (for 1); 3.25 × 106 and 0.193 μM for Fe3+, 6.94 × 105 and 0.155 μM for CrO42− (for 2). Notably, ligand L itself did not display any type of recognition for any ions in DMF as well as in aqueous media. Moreover, 1 and 2 were also employed as heterogeneous catalysts for the ring-opening reaction (ROR) of epoxides with various assorted amines and up to 95% yield (TON, 47.5 and TOF, 11.9 h−1) was observed with perfect regioselectivity in the case of styrene oxide. [ABSTRACT FROM AUTHOR]

The base-free styrene epoxidation with H2O2 as an oxidant was strongly in accordance with the requirements for a sustainable chemical industry. Aiming at the low efficiency of a non-noble metal catalyst system, we proposed utilizing the synergistic effect and manipulating the surface acid–basic property of materials to increase the catalytic performance in this reaction. Herein, to combine two promoting approaches, we synthesized a series of mixed metal oxide (MMO) materials to screen promising active components with a suitable acid–basic property for H2O2–styrene epoxidation. As a result, the highest styrene conversion (82.8%) and best styrene oxide selectivity (79.7%) were achieved over a CuCr-MMO catalyst. The catalytic performance was considerably enhanced compared with the CuO and CrOx references. Detailed characterizations were performed to investigate the dispersion, electronic structure, and acid–basic property to explain the structure–performance relationship. On one hand, the promoted dispersion of the Cu and Cr components contributed to more catalytic sites and the electron transfer between Cu and Cr improved the intrinsic activity, which were both responsible for the enhanced activity. On the other hand, the unique structure modulated the acid–basic properties to be suitable for this catalytic system. In particular, a suitable basicity was facilitated to selectively transform H2O2 into HOO˙ radicals, while a low acidity suppressed the epoxide ring opening to form phenylacetaldehyde. By combining the high accessibility, suitable basic–acid property, and fast electron transfer, CuCr-MMO exhibited a high styrene conversion and selectivity to styrene oxide. [ABSTRACT FROM AUTHOR]

The CO2 cycloaddition of styrene oxide (SO) catalyzed by different paddlewheel-type di-metal clusters has been investigated by means of density functional calculations. Without a co-catalyst, the reaction proceeds in a single step involving the breaking of a C–O bond of adsorbed epoxide and the simultaneous formation of two new C–O bonds between the adsorbed epoxide and a carbon dioxide. The reaction starts with the adsorption of a styrene oxide molecule on the catalytic site of an M–BTC catalyst via its oxygen atom with adsorption free energies of −12.3, −10.2, −8.0, −3.9, and −13.9 kcal mol−1 for SO adsorption on Fe–, Co–, Ni–, Cu–, and Zn–BTC systems, respectively. From NBO analysis, it was found that the interaction between SO and M–BTC causes a higher polarization of C–O bonds of the epoxide. The more polarized C–O bond of the adsorbed SO allows the nucleophile to attack more easily. The calculated results unambiguously highlight the important role of unsaturated cationic sites in the paddlewheel unit in promoting the catalytic cycloaddition of CO2 with SO. Based on the activation energy, the trend of catalytic activity is in the order Fe–BTC ＞ Zn–BTC ＞ Co–BTC ＞ Ni–BTC ＞ Cu–BTC. From DFT calculations, the Fe–BTC is theoretically proved to have the potential to be a desirable catalyst for the CO2 cycloaddition of styrene oxide in the absence of a co-catalyst. [ABSTRACT FROM AUTHOR]

An emerging strategy to improve the performance of porous metal–organic framework (MOF) materials as heterogeneous catalysts is reported. The incorporation of the iron-substituted polyoxometalate (POM) TBA4[PW11Fe(H2O)O39] (PW11Fe) in porous MOF NH2-MIL-101(Fe), leading to a novel composite based MOF material, PW11Fe@NH2-MIL-101(Fe), was revealed to be a significant approach to increase the efficiency of the MOF material as a regioselective catalyst for the ring opening of styrene oxide with aniline. The conversion after 1 h of reaction using NH2-MIL-101(Fe) is 22% and increases to 100% when PW11Fe@NH2-MIL-101(Fe) is employed as catalyst. It is noteworthy that the catalytic performance of this composite material is also considerably better than that obtained with the respective physical mixture under similar conditions. Furthermore, PW11Fe@NH2-MIL-101(Fe) revealed to be a remarkable selective heterogeneous catalyst for the studied reaction (100% selectivity to the 2-phenylamino-2-phenylethanol isomer) with significant robustness and recyclability. [ABSTRACT FROM AUTHOR]

We report herein a green and economical strategy for oxidative modification of carbon nanotubes (CNT) by a facile ozone treatment in the presence of solvent vapor (H2O, 30% H2O2 solution and ethanol). This procedure is able to introduce a considerable level of oxygen groups with a dominant population of carboxyl groups at near ambient temperature. The optimization study of the process provides the reaction temperature and time, as well as the source and partial pressure of the vapor, key parameters determining the oxidation efficiency. The process efficiency and sustainability are assessed to compare with conventional oxidative treatment (e.g., nitric acid oxidation). Ozone treatment assisted by water or H2O2/H2O vapor can introduce abundant oxygenated groups on the sidewalls of CNT, and the process with H2O2/H2O vapor can deliver a much higher selectivity towards carboxyl species on the sidewalls of CNT. With the appropriate functionalization temperature (40 °C) and incremental partial pressure of vapor, the surface defect and oxygen content on the CNT could be dramatically increased. The ozone treated CNT can be used for diverse applications such as metal-free catalyst and support; the modified CNT display higher activity for the ring-opening reaction of styrene oxide than HNO3 treated CNT and develop strong interaction for anchoring iron oxide nanoparticles even up to 350 °C. This ozone treatment in the presence of vapor could also be accomplished by using compressed air as the carrier gas, which can be considered an efficient and eco-friendly functionalization process. [ABSTRACT FROM AUTHOR]

A highly stable and easy to synthesize aluminium complex bearing a flexible N2O2-donor salabza ligand (N,N′-bis(salicylene)-2-aminobenzylamine) in combination with tetrabutylammonium bromide forms an active binary catalytic system for the cycloaddition of CO2 to epoxides (TOFs 120–3434 h−1) under mild conditions (10 bar, 80 °C) and low catalyst loadings (0.05–0.2 mol%). Kinetic experiments have shown that the cycloaddition of CO2 to styrene oxide catalyzed by 1/TBAB is first order in 1, TBAB, CO2 and epoxide. A reaction mechanism is proposed based on these observations. Fe(iii) and Co(iii) related complexes are less active catalysts for this reaction. [ABSTRACT FROM AUTHOR]

We developed a facile and new method for the production of a 4A-zeolite supported silver nanoparticle (Ag NP) composite catalyst using supercritical carbon dioxide (scCO2). The small (3–6 nm) and highly dispersed silver nanoparticles were formed on the 4A-zeolite with the assistance of scCO2 and hydrogen reduction. The anchored Ag NPs are smaller in size and more uniform in distribution on the 4A-zeolite, and favor a wide range of physical and chemical properties. In order to test the properties of the synthesized composite catalyst, the selective oxidation of styrene was introduced into the experiment. The composite catalyst synthesized by this new method exhibited excellent catalytic properties in the selective oxidation reaction of styrene compared with previous reports. Furthermore, two kinds of important chemical product, styrene oxide (SO) and benzaldehyde (BZ), could be controlled selectively by changing the oxidants and solvents used. [ABSTRACT FROM AUTHOR]

This work reports a novel and efficient protocol for the synthesis of 2-phenylnaphthalenes from styrene oxides using a recyclable ionic liquid. The ionic liquid N-methyl-2-pyrrolidone hydrogensulfate [HNMP]+HSO4− played the dual role of a catalyst and a solvent. It efficiently constructs 2-phenylnaphthalene and its derivatives in excellent yields with much simplicity in the operation. The present protocol has higher atom efficiency and wider substrate applicability. The [HNMP]+HSO4− has been effectively recycled for up to five consecutive cycles without appreciable loss in its activity. [ABSTRACT FROM AUTHOR]

Ultrathin copper oxide (CuO) nanorods with diameters of ∼3.6 nm were obtained in one step using oleylamine (OAm) as both the solvent and the surface controller. The oriented attachment is responsible for the formation of the ultrathin CuO nanorods. Furthermore, this ultrathin nanostructure catalyst exhibited excellent activity and high styrene oxide yields in styrene epoxidation. [ABSTRACT FROM AUTHOR]

Mesoporous chromium-based terephthalate metal-organic framework (MIL-101) encapsulated Keggin phosphotungstic acid (HPW) [MIL-101(HPW)] was demonstrated to be an active heterogeneous catalyst for selective catalysis of the ring opening reaction of styrene oxide with methanol, achieving 99% yield of 2-methoxy-2-phenylethanol in 20 minutes at 40 °C. Similar MIL-101 samples prepared using one-pot microwave synthesis in the absence of HPW or in the presence of hydrofluoric acid (HF) were less active. The impact of fluoride and HPW polyanion incorporation on the acidity of MIL-101 was investigated by the in situ infrared spectroscopy technique using CO as a probe molecule. Additional hydroxyl groups and Lewis acid sites are present in MIL-101(HPW) explaining the observed superior catalytic performance in styrene oxide methanolysis. [ABSTRACT FROM AUTHOR]

A series of materials containing the tris(2,2'-bipyridine)iron(II) (Fe(bpy)3 2+) complex inside zeolite Y cavities with alkaline earth metals (Mg2+, Ca2+, Sr2+, Ba2+) as charge compensating cations have been synthesized via a "ship in the bottle" method. The influence of the alkaline earth metal cations on the physicochemical properties and catalytic activity was investigated. The successful formation of the Fe(bpy)3 2+ complex was verified by XRD, diffuse-reflectance UV-vis spectroscopy, and Fe K-edge XAFS measurements. The BET surface area and the Fe content decreased in the presence of the larger alkaline earth metal, but the intensity of the MLCT adsorption band of Fe(bpy)3 2+ increased with the heavier cation. The electron density of the Fe atoms decreased, and the average interatomic bond distance Fe-N/O and the coordination number increased with the heavier alkaline earth metal cation. The encapsulation of Fe(bpy)3 2+ resulted in the creation of a photocatalytic system able to oxidize styrene to benzaldehyde and styrene oxide under visible light irradiation (λ > 430 nm) in the presence of molecular oxygen. [ABSTRACT FROM AUTHOR]

A diamine-bis(phenolate) chromium(iii) complex, {CrCl[O2NN′]BuBu}2 catalyzes the copolymerization of propylene oxide with carbon dioxide. The synthesis of this metal complex is straightforward and it can be obtained in high yields. This catalyst incorporates a tripodal amine-bis(phenolate) ligand, which differs from the salen or salan ligands typically used with Cr and Co complexes that have been employed as catalysts for the synthesis of such polycarbonates. The catalyst reported herein yields low molecular weight polymers with narrow polydispersities when the reaction is performed at room temperature. Performing the reaction at elevated temperatures causes the selective synthesis of propylene carbonate. The copolymerization activity for propylene oxide and carbon dioxide, as well as the coupling of carbon dioxide and styrene oxide to give styrene carbonate are presented. [ABSTRACT FROM AUTHOR]

Hybrid sol–gel catalysts of zinc hexacyanocobaltate and SiO2 were prepared by co-precipitation of the double metal cyanide with silica. Hybrid catalysts prepared at moderately acidic conditions showed the best performance with respect to activity, selectivity and stability. The hybrid sol–gel materials displayed high catalytic activity for the copolymerisation of styrene oxide and carbon dioxide (up to 650 molSO (molZn h)−1) and high productivity (575 gPolymer gCatalyst−1). They also displayed good selectivity to the polymeric product (80–87%), while only little cyclic styrene carbonate was formed as side product. A detailed electron microscopy study of the hybrid sol–gel materials showed that the active phase consisted of thin platelets containing the metals in a molar ratio nZn/nCo = 2.1, whereby the double metal cyanide was closely associated with silica. [ABSTRACT FROM AUTHOR]

Hybrid sol–gel catalysts of zinc hexacyanocobaltate and SiO2 were prepared by co-precipitation of the double metal cyanide with silica. Hybrid catalysts prepared at moderately acidic conditions showed the best performance with respect to activity, selectivity and stability. The hybrid sol–gel materials displayed high catalytic activity for the copolymerisation of styrene oxide and carbon dioxide (up to 650 molSO (molZn h)−1) and high productivity (575 gPolymer gCatalyst−1). They also displayed good selectivity to the polymeric product (80–87%), while only little cyclic styrene carbonate was formed as side product. A detailed electron microscopy study of the hybrid sol–gel materials showed that the active phase consisted of thin platelets containing the metals in a molar ratio nZn/nCo = 2.1, whereby the double metal cyanide was closely associated with silica. [ABSTRACT FROM AUTHOR]

A rapid, mild and high-yield microwave synthesis of 1D isotypical [Ln(H4bmt)(H5bmt)(H2O)2]·3H2O coordination polymers is presented. The La3+-based material is highly active as a heterogeneous catalyst in the methanolysis of styrene oxide at nearly room temperature. Eu3+- and Tb3+-doped materials are very effective UV-to-visible light converters. [ABSTRACT FROM AUTHOR]

The methanolytic kinetic resolution of styrene oxide catalyzed by chiral metal–organic framework crystals afforded both 2-methoxy-2-phenylethanol and unreacted styrene oxide in good enantiomeric excesses. [ABSTRACT FROM AUTHOR]

With the assistance of PVP, a novel magnetically recyclable Ag-based catalyst has been synthesized in one pot, and it is found that this catalyst is highly efficient in selectively catalyzing styrene conversion to styrene oxide. [ABSTRACT FROM AUTHOR]