Multimetallic lithium complexes derived from the acids Ph 2 C(X)CO 2 H (X=OH, NH 2 ): Synthesis, structure and ring opening polymerization of lactides and lactones

Reaction of LiOR (R = t-Bu, Ph) with the acids 2,2/-Ph2C(X)(CO2H), X = OH (benzH), NH2 (pdgH) was investigated. For benzH, one equivalent LiOt-Bu in THF afforded [Li(benz)(THF)]2·2THF (1·2THF), which adopts a 1D chain structure. If acetonitrile is used (mild conditions), another solvate of 1 is isolated; LiOPh also led to 1. Robust work-up afforded [Li7(benz)7(MeCN)] (2·2MeCN·THF). Use of LiOt-Bu (2 equivalents) led to {Li8(Ot-Bu)2[(benz)](OCPh2CO2CPh2CO2t-Bu)2(THF)4} (3), the core of which comprises two open cubes linked by benz ligands. For dpgH, two equivalents of LiOt-Bu in THF afforded [Li6(Ot-Bu)2(dpg)2(THF)2] (4), which contains an Li2O2 6-step ladder. Similar reaction of LiOPh afforded [Li8(PhO)4(dpg)4(MeCN)4] (5). Complexes 1 - 5 were screened for their potential as catalysts for ring opening polymerization (ROP) of ε-caprolactone (ε-CL), rac-lactide (rac-LA) and δ-valerolactone (δ-VL). For ROP of ε-CL, conversions > 70% were achievable at 110 oC with good control. For rac-LA and δ-VL, temperatures of at least 110 oC over 12h were necessary for activity (conversions > 60%). Systems employing 2 were inactive

Vanadium(v) tetra-phenolate complexes: synthesis, structural studies and ethylene homo-(co-) polymerization capability

Reaction of the ligand α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xylene (p-L1H4) with two equivalents of [VO(OR)3] (R = nPr, tBu) in refluxing toluene afforded, after work-up, the complexes {[VO(OnPr)(THF)]2(-p-L1)}·2(THF) (1·2(THF)) or {[VO(OtBu)]2(-p-L1)}·2MeCN (2·2MeCN), respectively in moderate to good yield. A similar reaction using the meta ligand, namely α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-m-xylene (m-L2H4) afforded the complex {[VO(OnPr)(THF)]2(-p-L2)} (3). Use of [V(Np-R1C6H4)(tBuO)3] (R1 = Me, CF3) with p-L1H4 led to the isolation of the oxo-imido complexes {[VO(tBuO)][V(Np-R1C6H4)(tBuO)](-p-L1)} (R1 = Me, 4·CH2Cl2; CF3, 5·CH2Cl2), whereas use of [V(Np-R1C6H4)Cl3] (R1 = Me, CF3) in combination with Et3N/p-L1H4 or p-L1Na4 afforded the diimido complexes {[V(Np-MeC6H4)(THF)Cl]2(-p-L1)}·4toluene (6·4toluene) or {[V(Np-CF3C6H4)(THF)Cl]2(-p-L1)} (7). For comparative studies, the complex [(VO)(μ-OnPr)L3]2 (8) has also been prepared via the interaction of [VO(nPrO)3] and 2-(α-(2-hydroxy-3,5-di-tert-butylphenyl)benzyl)-4,6-di-tert-butylphenol (L3H2). The crystal structures of 1·2THF, 2·2MeCN, 3, 4·CH2Cl2, 5·CH2Cl2, 6·4toluene·thf, 7 and 8 have been determined. Complexes 1 – 3 and 5 - 8 have been screened as pre-catalysts for the polymerization of ethylene in the presence of a variety of co-catalysts (with and without a re-activator), including DMAC (dimethylaluminium chloride), DEAC (diethylaluminium chloride), EADC (ethylaluminium dichloride) and EASC (ethylaluminium sesquichloride) at various temperatures and for the co-polymerization of ethylene with propylene; results are compared versus the benchmark catalyst [VO(OEt)Cl2]. In some cases, activities as high as 243,400 g/mmolV.h (30.43 Kg PE/mmolV.h.bar) were achievable, whilst it also proved possible to obtain higher molecular weight polymers (in comparable yields to the use of [VO(OEt)Cl2]). In all cases with dimethylaluminium chloride (DMAC)/ethyltrichloroacetate (ETA) activation, the activities achieved surpassed those of the benchmark catalyst. In the case of the co-polymerization of ethylene with propylene, Complexes 1 – 3 and 5 - 8 showed comparable or higher molecular weight than [VO(OEt)Cl2] with comparable catalytic activities or higher in the case of the imido complexes 6 and 7

Synthesis and photophysical properties of novel butterfly-shaped blue emitters based on pyrene

Synthesis and photophysical properties of novel butterfly-shaped blue emitters based on pyren

Using supercritical CO2 in the preparation of metal-organic frameworks: Investigating effects on crystallisation

In this report, we explore the use of supercritical CO2 (scCO2) in the synthesis of well-known metal-organic frameworks (MOFs) including Zn-MOF-74 and UiO-66, as well as on the preparation of [Cu24(OH-mBDC)24]n metal-organic polyhedra (MOPs) and two new MOF structures {[Zn2(L1)(DPE)]∙4H2O}n and {[Zn3(L1)3(4,4’-azopy)]∙7.5H2O}n, where BTC = benzene-1,3,5-tricarboxylate, BDC = benzene-1,4-dicarboxylate, L1 = 4-carboxy-phenylene- methyleneamino-4-benzoate, DPE = 1,2-di(4-pyridyl)ethylene, 4.4’-azopy = 4,4’- azopyridine, and compare the results versus traditional solvothermal preparations at low temperatures (i.e., 40 °Ϲ). The objective of the work was to see if the same or different products would result from the ssCO2 route versus the solvothermal method. We were interested to see which method produced the highest yield, the cleanest product and what types of morphology resulted. While there was no evidence of additional meso- or macroporosity in these MOFs/MOPs nor any significant improvements in product yields through the addition of scCO2 to these systems, it was shown that the use of scCO2 can have an effect on crystallinity, crystal size and morphology

Organoaluminium complexes derived from anilines or Schiff bases for the ring-opening polymerization of ε-Caprolactone, δ-Valerolactone and rac-Lactide

Reaction of R1R2CHN=CH(3,5-tBu2C6H2-OH-2) (R1 = R2 = Me L1H; R1 = Me, R2 = Ph L2H; R1 = R2 = Ph L3H) with slightly greater than one equivalent of R33Al (R3 = Me, Et) afforded the complexes [(L1–3)AlR32] (L1, R3 = Me 1, R3 = Et 2; L2, R3 = Me 3, R3 = Et 4; L3 R3 = Me 5, R3 = Et 6); complex 1 has been previously reported. Use of the N,O-ligand derived from 2,2′-diphenylglycine afforded either 5 or the byproduct [Ph2NCH2(3,5-tBu2C6H2-O-2)AlMe2] (7). The known Schiff base complex [2-Ph2PC6H4CH2(3,5-tBu2C6H2-O-2)AlMe2] (8) and the product of the reaction of 2-diphenylphosphinoaniline 1-NH2,2-PPh2C6H4 with Me3Al, namely {Ph2PC6H4N[(Me2Al)2µ-Me](µ-Me2Al)} (9), were also isolated. For structural and catalytic comparisons, complexes resulting from the interaction of Me3Al with diphenylamine (or benzhydrylamine), namely {Ph2N[(Me2Al)2µ-Me]} (10) and [Ph2CHNH(µ-Me2Al)]2·MeCN (11), were prepared. The molecular structures of the Schiff proligands derived from Ph2CHNH2 and 2,2′-Ph2C(CO2H)(NH2), together with those of complexes 5, 7 and 9–11·MeCN were determined; 5 contains a chelating imino/phenoxide ligand, whereas 7 contains the imino function outside of the metallocyclic ring. Complex 9 contains three nitrogen-bound Al centres, two of which are linked by a methyl bridge, whilst the third bridges the N and P centres. In 10, the structure resembles 9 with a bridging methyl group, whereas the introduction of the extra carbon in 11 results in the formation of a dimer. All complexes have been screened for their ability to promote the ring-opening polymerization (ROP) ε-caprolactone, δ-valerolactone or rac-lactide, in the presence of benzyl alcohol, with or without solvent present. Reasonable conversions were achievable at room temperature for ε-caprolactone when using complexes 7, 9 and 12, whilst at higher temperatures (80–110 °C), all complexes produced good (> 65 %) to quantitative conversions over periods as short as 3 min, albeit with poor control. In the absence of solvent, conversions were nearly quantitative at 80 °C in 5 min with better agreement between observed and calculated molecular weight (Mn). For rac-lactide, conversions were typically in the range 71–86 % at 110 °C in 12 h, with poor control affording atactic polylactide (PLA), whilst for δ-valerolactone more forcing conditions (12–24 h at 110 °C) were required for high conversion. Co-polymerization of ε-caprolactone with rac-lactide afforded co-polymers with appreciable lactide content (35–62.5 %); the reverse addition was ineffective, affording only (polycaprolactone) PCL

D-π-D chromophores based on dithieno[3,2-b:2',3'-d]thiophene (DTT): Potential application in the fabrication of solar cell

© 2016 Elsevier LtdIn this work, four stable dithieno[3,2-b:2',3'-d]thiophene-based π-extended molecules were designed and synthesized via a Pd-catalysed Sonogashira coupling reaction. The structures of these symmetrical compounds, including dithieno[3,2-b:2',3'-d]thiophene (DTT) as the π-center and various donor (D) groups, were determined on the basis of NMR spectral data, elemental analysis, and X-ray crystallography. The photo-physical properties of the DTT-based derivatives 2 were fully investigated in both solution and the solid state. The notable optical features of their solid-state powders showed significant red-shifts in comparison with the luminescence of their dilute dichloromethane solutions. These results combined with the theoretical calculations indicate that they are promising candidates for several applications in electronic and optoelectronic devices, as well as organic dyes for solar cells

An efficient approach to the synthesis of novel pyrene-fused azaacenes

An efficient approach to the synthesis of novel pyrene-fused azaacene

Synthesis and fluorescence emission properties of 1,3,6,8-tetraarylpyrenes

Synthesis and fluorescence emission properties of 1,3,6,8-tetraarylpyrene

Mono- and tetra-nuclear copper complexes bearing bis(imino)phenoxide derived ligands: catalytic evaluation for benzene oxidation and ROP of epsilon-caprolactone

Complexes of the type [Cu(L)2] (1) and [Cu4L2(μ4−O)(OAc)4] (2) have been obtained from the reaction of the phenoxydiimine 1,3-(2,6-R22C6H3N=CH)2-5-R1C6H2OH-2 (LH) (where R1 = Me, tBu, Cl; R2 = Me, iPr) with copper(II) acetate [Cu(OAc)2]; changing the molar ratio of the reactants affords 10 differing amounts of 1 or 2. Reaction of the parent dialdehyde [1,3-(CHO)2-5-MeC6H2OH-2] with [Cu(OAc)2] in the presence of Et3N afforded, following work-up, a polymeric chain (3) comprising {[Cu2(OAc)4]OAc}n, HNEt3 and MeCN. The crystal structures of 1 (R1 = Me, R2 = iPr 1a; R1 = Cl, R2 = iPr 1b), 2 (R1 = Me, R2 = Me 2a; R1 = Me, R2 = iPr 2b; R1 = tBu, R2 = Me 2c; R1 = Cl, R2 = Me 2d; R1 = Cl, R2 = iPr 2e; R1 = tBu, R2 =iPr 2f) and 3 are reported (synchrotron radiation was necessary for 3). The 15 magnetic properties of the cluster 2b are presented. Complexes of type 2 and 3 were screened for the ring opening polymerization (ROP) of ε-caprolactone, with or without benzyl alcohol present, under a variety of conditions, however only trace polymer was isolated. The electrochemistry of all complexes was also investigated, together with their ability to catalyze benzene oxidation (using hydrogen peroxide); although low conversions were observed, the tetra-nuclear complexes exhibited excellent selectivity

Pyrene-cored blue-light emitting [4]helicenes: synthesis, crystal structures, and photophysical properties

The synthesis, crystal structures and photophysical properties of two types of pyrene-cored blue-light emitting [4]helicenes are reported, in which two naphthalene rings of condensed pyrenes were constructed resulting in helical architectures. The photophysical properties and electrochemical characteristics of these pyrene-cored [4]helicenes were fully investigated in both solutions and films, along with that of the pre-cyclization Q4 products, 4,9- and 4,10-(phenylethenyl)pyrenes