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

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

Extended [pi]-conjugated pyrene derivatives: structural, photophysical and electrochemical properties

This article presents a set of extended [pi]-conjugated pyrene derivatives, namely 1,3-di(arylethynyl)-7-tert-butylpyrenes, which were synthesized by a Pd-catalyzed Sonogashira coupling reaction of 1,3-dibromo-7-tert-butylpyrenes with the corresponding arylethynyl group in good yields. Despite the presence of the tert-butyl group located at the 7-position of pyrene, X-ray crystallographic analyses show that the planarity of the Y-shaped molecules still exhibits strong face-to-face [pi]-[pi] stacking in the solid state; all of the compounds exhibit blue or green emission with high quantum yields (QYs) in dichloromethane. DFT calculations and electrochemistry revealed that this category of compound possesses hole-transporting characteristics. In addition, with strong electron-donating (-N(CH3)2) or electron-withdrawing (-CHO) groups in 2 d or 2 f, these molecules displayed efficient intramolecular charge-transfer (ICT) emissions with solvatochromic shifts from blue to yellow (green) on increasing the solvent polarity. Furthermore, the compounds 2 d and 2 f possess strong CT characteristics

Novel fluorinated benzimidazole-based scaffolds and their anticancer activity in vitro

A small library of twelve, structurally diverse, fluoroaryl benzimidazoles was prepared using a simple synthetic strategy employing SNAr reactions. This allowed rapid assembly of heterocyclic structures containing linked and tethered fluoroaryl benzimidazoles. X-ray crystal structures of seven compounds were obtained including those of two macrocyclic compounds containing 21- and 24-membered rings. Three tethered fluoroaryl benzimidazole derivatives demonstrated micromolar inhibition against K-562 and MCF-7 cell lines. These compounds, in addition to 1-tetrafluoropyrid-4-yl-2-tetrafluoropyrid-4-ylsulfanyl-1H-benzimidazole, also demonstrated micromolar inhibition against G361 and HOS cell lines. Two of the compounds were found to activate caspases leading to apoptosis

Pillared Two-Dimensional Metal–Organic Frameworks Based on a Lower-Rim Acid Appended Calix[4]arene

Solvothermal reactions of the lower-rim functionalized diacid calix[4]­arene 25,27-bis­(methoxycarboxylic, acid)-26,28-dihydroxy-4-<i>tert-</i>butylcalix­[4]­arene, (<b>L</b>H₂) with Zn­(NO₃)₂·6H₂O and the dipyridyl ligands 4,4′-bipyridyl (4,4′-bipy), 12-di­(4-pyridyl)­ethylene (DPE), or 4,4′-azopyridyl (4,4′-azopy) afforded a series of two-dimensional structures of the formulas {[Zn­(4,4′-bipy)­(<b>L</b>)]·2¹/₄DEF}_<i>n</i>, (<b>1</b>), {[Zn₂(<b>L</b>)­(DPE)]·DEF}_<i>n</i> (<b>2</b>), and {[Zn­(OH₂)₂(<b>L</b>)­(4,4′-azopy)]·DEF}_<i>n</i><i>,</i> (<b>3</b>) (DEF = diethylformamide)

Iron(III) bromide catalyzed bromination of 2-tert-butylpyrene and corresponding position-dependent aryl-functionalized pyrene derivatives

The present work probes the bromination mechanism of 2-tert-butylpyrene (1), which regioselectively affords mono-, di-, tri- and tetra-bromopyrenes, by theoretical calculation and detailed experimental methods. The bromine atom may be directed to the K-region (positions 5- and 9-) instead of the more reactive 6- and 8-positions in the presence of iron powder. In this process, FeBr3 plays a significant role to release steric hindrance or lower the activation energy of the rearrangement. The intermediate bromopyrene derivatives were isolated and confirmed by 1H NMR spectrometry, mass spectroscopy and elemental analysis. Further evidence on substitution position originated from a series of aryl substituted pyrene derivatives, which were obtained from the corresponding bromopyrenes on reaction with 4-methoxy-phenylboronic acid by a Suzuki–Miyaura cross-coupling reaction. All position-dependent aryl-functionalized pyrene derivatives are characterized by single X-ray diffraction, 1H/13C NMR, FT-IR and MS, and offered straightforward evidence to support our conclusion. Furthermore, the photophysical properties of a series of compounds were confirmed by fluorescence and absorption, as well as by fluorescence lifetime measurements