Synthesis of mono-O-alkylated homooxacalix[3]arene and a protection–deprotection strategy for homooxacalix[3]arene

The regioselective synthesis of mono-O-alkylated homooxacalix[3]arene is accomplished for the first time. The synthetic route relies on two key steps: (i) a facile protection of two OH groups at the lower rim of the homooxacalix[3]arene and (ii) the deprotection of 9- anthrylmethyl groups via the Pd/C-catalyzed hydrogenation under atmospheric hydrogen. An efficient protection- deprotection strategy for the functionalization of homooxacalix[ 3]arene is presented

Manganese coordination chemistry of bis(imino)phenoxide derived [2 + 2] Schiff-base macrocyclic ligands

The [2 + 2] Schiff base macrocycles [2,2'-(CH₂CH₂)(C₆H₄N)₂-2,6-(4-RC₆H₃OH)]₂ (IʳH₂), upon reaction with MnCl₂ (two equivalents) afforded the bimetallic complex [Cl₃Mn(NCMe)][MnCl(IᵗᵇᵘH₂)] (2). Under similar conditions, use of the related [2 + 2] oxy-bridged macrocycle [2,2'-O(C₆H₄N=CH)₂4-RC₆H₃OH] (IIʳH₂), afforded the bimetallic complexes [(MnCl)₂IIʳ] (R = Me 3, tBu 4), whilst the macrocycle derived from 1,2-diaminobenzene and 5,5'-di-tert-butyl-2,2'-dihydroxy-3,3'-methylenedibenzaldehyde (IIIH₄) afforded the complex [(MnCl)₂(III)]·2MeCN (5·2MeCN). For comparative studies, the salt complexes [2,6-(ArNHCH)₂-4-MeC₆H₂O][MnCl₃(NCMe)] (Ar = 2,4-Me₂C₆H₃, 6) and {[2,6-(ArNHCH)₂-4-MeC₆H₂O][MnCl}₂[MnCl₄]·8CH₂Cl₂ (Ar = 4-MeC₆H₄, 7·8CH₂Cl₂) were prepared. The crystal structures of 1 - 7 are reported (synchrotron radiation was necessary for complexes 1, 3 and 5). Complexes 1 - 7 (not 5) were screened for their potential to act as pre-catalysts for the ring opening polymerization (ROP) of ε-caprolactone; 3, 4 and 6, 7 were inactive, whilst 1 and 2 exhibited only poor activity low conversion (<15 %) at temperatures above 60 °C

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

In 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 solid state. The notable optical features of their solid-state powders showed significant red-shift in comparison with the luminescence of their dilute dichloromethane solutions. These results combined with the theoretical calculations indicate that they are promising candidates for the several applications in electronic and optoelectronic devices, as well as organic dyes for solar cells

A hexahomotrioxacalix[3]arene-based ditopic receptor for alkylammonium ions controlled by Ag + ions 4

A receptor cone-1 based on a hexahomotrioxacalix[3]arene bearing three pyridyl groups 21 was successfully synthesized, which has a C3-symmetric conformation and is capable of binding 22 alkylammonium and metal ions simultaneously in a cooperative fashion. It can bind 23 alkylammonium ions through the -cavity formed by three aryl rings. This behaviour is consistent 24 with the cone-in/cone-out conformational rearrangement needed to reorganize the cavity for 25 endo-complexation. As a C3-symmetrical pyridyl-substituted calixarene, receptor cone-1 can also 26 bind a Ag + ion and the nitrogen atoms are turned towards the inside of the cavity and interact with 27 Ag +. After complexation of tris(2-pyridylamide) derivative receptor cone-1 with Ag + , the original 28 C3-symmetry was retained and higher complexation selectivity for n-BuNH3 + versus t-BuNH3 + was 29 observed. Thus, it is believed that this receptor will have a role to play in the sensing, detection, and 30 recognition of Ag + and n-BuNH3 + ions. 3

Multiple photoluminescence from pyrene-fused hexaarylbenzenes with aggregation-enhanced emission features

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Multiple photoluminescence, which included monomer emission, excimer emission, and charge-transfer emission processes, has been observed from new pyrene-fused hexaarylbenzene (HAB) compounds, which were synthesized in high yields through a Diels–Alder reaction between bis(2-tert-butylpyren-6-yl)acetylene and tetraphenylcyclopentadienone. Although the differentiation between the two molecules only arose from the geometrical position of one of the pyrenes, the NMR spectra, crystal packing, and physicochemical properties of these pyrene-based HAB hybrids were distinctly different in both the solution and aggregate states. X-ray diffraction analysis clearly indicated that the pyrene moieties adopted different crystal packing arrangements in the crystalline state that could induce a multiple-photoluminescence phenomenon

Pyrene-fused pyrazaacenes with eight rectilinearly arranged aromatic rings

A series of pyrene-fused azaacene-type conjugated molecules containing two pyrazine units and up to eight rectilinearly arranged aromatic rings were prepared by condensation coupling reactions in moderate yields. The geometries and electronic structures associated with 2 and 5 were evaluated by DFT calculations. Photophysical properties indicated that these systems possess delocalized structures, and their optoelectronic properties can be tuned by extending the π-conjugated length and introducing electronic-withdrawing groups. The compounds were thoroughly investigated by XRD studies, electrochemistry and DFT calculations. High thermal stability and tunable energy levels make them excellent candidates as a class of organic molecular materials

Synthesis and conformational studies of calixarene analogue chiral [3.3.1]metacyclophanes

Trihydroxy[3.3.1]metacyclophane, which can be regarded as an unsymmetrical or incomplete “homocalix[3]arene”, has been prepared from trimethoxy[3.3.1]metacyclophane by demethylation with trimethylsilyl iodide in MeCN. Di-O-methylation at the lower rim of trihydroxy[3.3.1]metacyclophane in the presence of K₂CO₃ in acetone afforded a novel, inherently chiral calixarene–analogue, namely a macrocyclic [3.3.1]metacyclophane, possessing C₁ symmetry. The inherent chirality of the two conformers was characterized by ¹H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent [(S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol], which caused a splitting of the OMe group and AB patterns corresponding to the methylene protons

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

This paper was accepted for publication in the Journal of Molecular Structure and the definitive version can be found at: http://dx.doi.org/10.1016/j.molstruc.2013.04.07

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Blue-emitting butterfly-shaped 1,3,5,9-tetraarylpyrenes: Synthesis, crystal structures, and photophysical properties

The first example of aryl-functionalized, butterfly-shaped, highly fluorescent and stable blue-emitting monomers, namely, 7-tert-butyl-1,3,5,9- tetrakis(p-R-phenyl)pyrenes, were synthesized by the Suzuki-Miyaura cross-coupling reaction from a novel bromide precursor of 1,3,5,9-tetrabromo-7- tert-butylpyrene. The crystal structures and optical and electronic properties have been investigated. © 2013 American Chemical Society