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The 1967 attempt of structural analysis of the solid-state complex of caffeine and pyrogallol was a pioneering structural investigation in the supramolecular chemistry of caffeine, of what today would easily be considered an archetype of a model pharmaceutical cocrystal. Re-investigating this historically important system demonstrates that this long overlooked complex is most likely a tetrahydrate with a different structure and composition than initially proposed, and provides the crystal structure of the anhydrous cocrystal. [ABSTRACT FROM AUTHOR]

We report the structures of three new materials in the MDABCO-based perovskite family. Analysis of the Goldschmidt tolerance factor and octahedral factor enable us to propose compositional limits for pseudo-cubic perovskite phase formation and suggest directions for further materials discovery in this family of new ferroelectrics. [ABSTRACT FROM AUTHOR]

Carbazoles are widely exploited for their interesting photophysical and electronic properties, however bay (4,5-) functionalization is challenging, and previously inaccessible through carbazole C–H activation. We report a simple methodology which introduces a range of versatile 4,5-functionality, enabling the wider investigation of ring annulation and close proximity effects on carbazole properties. [ABSTRACT FROM AUTHOR]

A new chiral organometallic nucleoside analogue containing ruthenocene is reported, in which alkylthymine and alkylhydroxyl groups are attached in adjacent positions on one cyclopentadienyl ring. The synthetic procedures for this metallocene derivative and two control compounds are described, along with their characterisation by cyclic voltammetry and X-ray crystallography. Their biological activities in a human pancreatic cancer cell line (MIA-Pa-Ca-2) were significantly lower than those of three previously reported analogous ferrocene compounds, indicating that the choice of metallocene metal atom (Fe or Ru) plays a pivotal role in determining the anticancer properties of these nucleoside analogues, which in turn suggests a different mode of action from that of a conventional nucleoside analogue. [ABSTRACT FROM AUTHOR]

The study of organosulfates is a burgeoning area in biology, yet there are significant challenges with their synthesis. We report the development of a tributylsulfoammonium betaine as a high yielding route to organosulfates. The optimised reaction conditions were interrogated with a diverse range of alcohols, including natural products and amino acids. [ABSTRACT FROM AUTHOR]

Four novel bis-boronic acid compounds were synthesised via copper catalysed azide–alkyne cycloaddition (CuAAC) reactions. Glucose selectivity was observed for a particular structural motif. Moreover, a new glucose selective fluorescent sensor was designed and synthesised as a result. [ABSTRACT FROM AUTHOR]

A doubly pyrene-grafted bis-cyclometallated iridium complex with engineered electronically excited states demonstrates reversible electronic energy transfer between adjacent chromophores giving rise to extremely long-lived red luminescence in solution (τ = 480 μs). Time-resolved spectroscopic studies afforded determination of pertinent photophysical parameters including rates of energy transfer and energy distribution between constituent chromophores in the equilibrated excited molecule (ca. 98% on the organic chromophores). Incorporation into a nanostructured metal–oxide matrix (AP200/19) gave highly sensitive O2 sensing films, as the detection sensitivity was 200–300% higher than with the commonly used PtTFPP and approaches the sensitivity of the best O2-sensing dyes reported to date. [ABSTRACT FROM AUTHOR]

The use of electron-withdrawing substituents on the orthometalated phenyl ring is a common strategy to blue shift the emission of cyclometalated iridium complexes by stabilizing the highest occupied molecular orbital (HOMO), that is, increasing the oxidation potential of the complex. However, for application in blue organic light-emitting diodes (OLEDs), this approach imposes host materials with a deep HOMO, which negatively impacts the injection of charges, and hence the performance of the devices. In this context, we report new iridium complexes with an electron-donating substituent on the cyclometalated ligand to blue shift the emission while keeping a relatively low oxidation potential. As a result, bluish-green OLEDs based on host materials with shallow HOMOs (TCTA = 4,4′,4′′-tri(N-carbazolyl)-triphenylamine) display a higher performance than devices using FIrpic in the same architecture. The improvements are primarily attributed to the lower turn-on voltage (2.8 to 3 V) compared to those of FIrpic-device (3.6 V). White OLED was then prepared with a maximum brightness of 20 226 cd m−2 and current efficiency of 20.4 cd A−2 (at 100 cd m−2). Interestingly, a very small efficiency roll-off of about 1% at 1000 cd m−2 and high color stability were achieved. At a luminance level of 5000 cd m−2 the roll-off efficiency was still below 20%. The introduction of electron-donating substituents on a 2-phenylpyridine scaffold to obtain blue emitters with low oxidation potentials provides an alternative to strategies based on replacing the pyridine with imidazole, carbene, and pyrazole. [ABSTRACT FROM AUTHOR]

Crystal structures of six 1 : 1 triiodide salts of a series of enantiopure bis(pyrrolo[3,4-d])TTF derivatives, the first structures of radical cation salts reported for this bis(pyrrolo) donor system, show three different arrangements of triiodide ions, organised either in head-to-tail pairs, in infinite lines, or in a castellated arrangement. The complex crystal structures, obtained by electrocrystallisation, are influenced by the presence of solvent, for example changing an ABCABC packing arrangement to ABAB with inclusion of THF, as well as by the size of the chiral side chain. [ABSTRACT FROM AUTHOR]

A new series of chiral ureas containing one or two redox-active ferrocene units was synthesised and studied in order to investigate the effect of planar chirality and central chirality on electrochemical chiral sensing. Binding of chiral carboxylate anions in organic solvents through H-bond formation caused a negative shift in the potentials of the ferrocene/ferrocenium (Fc/Fc+) couples of the receptors, demonstrating their use as electrochemical sensors in solution. While the presence of two ferrocene units gave no marked improvement in the chiral sensing capabilities of these systems, the introduction of planar chirality, in addition to central chirality, switched the enantiomeric binding preference of the system and also caused an interesting change in the appearance of some voltammograms, with unusual two-wave behaviour observed upon binding a protected prolinate guest. [ABSTRACT FROM AUTHOR]

The interaction of salphen-type NiII, CuII and ZnII complexes with native DNA was investigated by exploiting linear dichroism experiments. The NiII complex behaves as a typical intercalator, binding strongly and stiffening and unwinding the DNA. The strength of the DNA interaction is slightly weaker for the copper complex and much weaker for the zinc complex. Plasmid-DNA gel electrophoresis experiments indicated that while CuII and ZnII complexes do not induce the unwinding of supercoiled DNA, the NiII complex has a nuclease activity without the addition of external agents. On the other hand, as shown in the PCR assays, we demonstrate that, at the used concentrations, only the CuII complex is able to inhibit the DNA amplification mediated by Taq DNA polymerase. In this paper we have also reported a detailed characterization of the three compounds including 2D-NMR and ESI-mass experiments and X-ray single crystal structure of the copper and nickel compounds. [ABSTRACT FROM AUTHOR]

A series of trimethylsilyl-protected di-alkynes incorporating 3,4-ethylenedioxythiophene (EDOT) linker groups Me3Si–CC–R–CC–SiMe3(R = ethylenedioxythiophene-3,4-diyl 1a, 2,2′-bis-3,4-ethylenedioxythiophene-5,5′-diyl 2a, 2,2′,5′,2′′-ter-3,4-ethylenedioxythiophene-5,5′′-diyl 3a) and the corresponding terminal di-alkynes, H–CC–R–CC–H 1b–2bhas been synthesized and characterized and the single crystal X-ray structure of 1ahas been determined. CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et3P)2PtCl] and the terminal di-alkynes 1b–2bin iPr2NH/CH2Cl2(2 : 1 mole ratio) gives the Pt(ii) di-ynes trans-[(Et3P)2(Ph)Pt–CC–R–CC–Pt(Ph)(Et3P)2] 1M–2Mwhile the dehydrohalogenation polycondensation reaction between trans-[(nBu3P)2PtCl2] and 1b–2b(1 : 1 mole ratio) under similar reaction conditions affords the Pt(ii) poly-ynes trans-[Pt(PnBu3)2–CC–R–CC-]n1P–2P. The di-ynes and poly-ynes have been characterized spectroscopically and, for 1Mand 2M, by single-crystal X-ray which confirms the “rigid rod” di-yne backbone. The materials possess excellent thermal stability, are soluble in common organic solvents and readily cast into thin films. Optical absorption spectroscopic measurements reveal that the EDOT spacers create stronger donor-acceptor interactions between the platinum(ii) centres and conjugated ligands along the rigid backbone of the organometallic polymers compared to the related non-fused and fused oligothiophene spacers. [ABSTRACT FROM AUTHOR]

The reaction of the five-membered C,N-palladacycle [(L)PdCl]2, where LH= 1-methyl-5-phenyl- 1H-1,4-benzodiazepin-2(3H)-one, with 1,2-ethanebis(diphenylphosphine), dppe, leads to the formation of the bridged palladacycle. [Pd2L2(μ-dppe)Cl2] 3, which was characterised in solution by 1H and 31P NMR spectroscopy and in the solid state by X-ray crystallography. Complex 3 was tested in vitro against a number of cell lines. For example, it inhibited K562 leukaemia cells with an IC50value of 4.3 μM (1 h exposure) and displayed cathepsin B inhibitory action with an IC50 value of 3 μM. [ABSTRACT FROM AUTHOR]

Two novel enantiopure bis(pyrrolo[3,4-d])tetrathiafulvalene derivatives, substrates for preparing chiral conducting materials, show chiral crystal packing arrangements in which successive layers are rotated in accordance with an exact or approximate 43axis. The corresponding donors containing fused dihydropyrrole groups, and thus four more hydrogen atoms, form stacks along a crystal axis. [ABSTRACT FROM AUTHOR]

The reaction of the five-membered C,N-palladacycle [(L)PdCl]2, where LH = 1-methyl-5-phenyl-1H-1,4-benzodiazepin-2(3H)-one, with 1,2-ethanebis(diphenylphosphine), dppe, leads to the formation of the bridged palladacycle. [Pd2L2(μ-dppe)Cl2] 3, which was characterised in solution by 1H and 31P NMR spectroscopy and in the solid state by X-ray crystallography. Complex 3was tested in vitroagainst a number of cell lines. For example, it inhibited K562 leukaemia cells with an IC50value of 4.3 μM (1 h exposure) and displayed cathepsin B inhibitory action with an IC50value of 3 μM. [ABSTRACT FROM AUTHOR]

The Grignard reagent ArF'MgBr (ArF' = 4-(C6F5)C6F4) reacts withMe2SiCl,Me2SiCl2 andMe3SnCl to give the 4-nonafluorobiphenyl group 14 complexes ArF'Me3Si, (ArF')2Me2Si and ArF'Me3Sn respectively. ArF'Me3Sn undergoes only methyl group exchange when treated with BBr3, yielding ArF'Me2SnBr. The solid state structures of ArF'Me3Sn and ArF'Me2SnBr have been determined and exhibit the expected distorted tetrahedral geometries at tin. The reaction between three equivalents of ArF'MgBr and BF3 was not selective, while one equivalent of ArF'MgBr and (ArF)2BF (ArF = C6F5) reacted cleanly to give (ArF)2ArF'B. Treatment of BCl3 with three equivalents of ArF'Li, prepared at low temperature from the reaction between ArF'Br and n-BuLi, yielded (ArF')3B. The molecular structures of the acetonitrile adducts of (ArF)2ArF'B and (ArF')3B closely resemble that of (ArF)3B.NCMe. During the course of the boron investigations, reaction with adventitious water led to the structural characterization of (ArF')2BOH.OH2 as a hydrogen-bonded dimer. The Grignard reagent reacts selectively with ZnCl2 in diethyl ether giving first [(ArF')Zn(m-Cl)(OEt2)]2 then (ArF')2Zn(OEt2)2, both of which have been characterised by X-ray diffraction. The corresponding reaction with HgCl2 requires the use of tetrahydrofuran as the solvent and yields (ArF')2Hg(THF)2. [ABSTRACT FROM AUTHOR]

The Knoevenagel condensation of 1,3-dihydro-2H-indol-2- one 1 with ferrocene carboxaldehyde 2 afforded an approximate 2:1 mixture of the geometrical isomers (E)- and (Z)-3- ferrocenylmethylidene-1,3-dihydro-2H-indol-2-one 3 respectively in an overall 67% yield; the air and solution-stable isomers were readily separated by preparative thin layer chromatography and their structures were unequivocally elucidated in solution, by 1H NMR spectroscopy, and in the solid phase, by X-ray crystallography; both isomers of 3 displayed in vitro toxicity against B16 melanoma and Vero cell lines in the micromolar range and inhibited the kinase VEGFR-2 with IC50 values of ca. 200 nM. [ABSTRACT FROM AUTHOR]

Three new fumaramide-derived [3]rotaxanes have been synthesized, with the aim of macrocycle linking to form a molecular box. In one case, a nine-component templated [3]rotaxane synthesis was accomplished in 40% yield. Rotaxane reduction resulted in an unexpectedly facile de-slipping process. [ABSTRACT FROM AUTHOR]

N-Alkylation of a novel pyridine sensor results in pyridinium salts whose conformations are stabilised by pyridinium cation–π interactions resulting in a fluorescent response that can be used to sense the presence of alkylating agents in solution at low concentration. [ABSTRACT FROM AUTHOR]

A new chiral organometallic nucleoside analogue containing ruthenocene is reported, in which alkylthymine and alkylhydroxyl groups are attached in adjacent positions on one cyclopentadienyl ring. The synthetic procedures for this metallocene derivative and two control compounds are described, along with their characterisation by cyclic voltammetry and X-ray crystallography. Their biological activities in a human pancreatic cancer cell line (MIA-Pa-Ca-2) were significantly lower than those of three previously reported analogous ferrocene compounds, indicating that the choice of metallocene metal atom (Fe or Ru) plays a pivotal role in determining the anticancer properties of these nucleoside analogues, which in turn suggests a different mode of action from that of a conventional nucleoside analogue.

A new series of chiral ureas containing one or two redox-active ferrocene units was synthesised and studied in order to investigate the effect of planar chirality and central chirality on electrochemical chiral sensing. Binding of chiral carboxylate anions in organic solvents through H-bond formation caused a negative shift in the potentials of the ferrocene/ferrocenium (Fc/Fc(+)) couples of the receptors, demonstrating their use as electrochemical sensors in solution. While the presence of two ferrocene units gave no marked improvement in the chiral sensing capabilities of these systems, the introduction of planar chirality, in addition to central chirality, switched the enantiomeric binding preference of the system and also caused an interesting change in the appearance of some voltammograms, with unusual two-wave behaviour observed upon binding a protected prolinate guest.

α-Hydroxyalkylidene carbenes, generated from thermolysis of α,β-epoxy-N-aziridinylimines, undergo diastereotopic group selective 1,5 C–H insertion reactions on 2,4-dimethyl-8-oxabicyclo[3.2.1]oct-6-ene ring systems. Protection of a tertiary alcohol at C-3 of the bridged oxabicycle as a trimethylsilyl ether reverses the sense of diastereoselectivity. 1,5 C–H insertion into a methine adjacent to an OBn group, 1,5 O–R insertion into a tertiary alcohol (R = H) or silylether (R = TMS) at C-3 to form spirocyclic dihydrofurans, 1,2-rearrangement to an alkyne and fragmentation to a ketone are competing major pathways for 2-benzyloxy-substituted 8-oxabicyclo[3.2.1]oct-6-ene systems. Dihydrofuran formation is shown to be a result of substitution on the oxabicyclic ring system through comparison with other methods of alkylidene carbene formation.

The interaction of salphen-type NiII, CuII and ZnII complexes with native DNA was investigated by exploiting linear dichroism experiments. The NiII complex behaves as a typical intercalator, binding strongly and stiffening and unwinding the DNA. The strength of the DNA interaction is slightly weaker for the copper complex and much weaker for the zinc complex. Plasmid-DNA gel electrophoresis experiments indicated that while CuII and ZnII complexes do not induce the unwinding of supercoiled DNA, the NiII complex has a nuclease activity without the addition of external agents. On the other hand, as shown in the PCR assays, we demonstrate that, at the used concentrations, only the CuII complex is able to inhibit the DNA amplification mediated by Taq DNA polymerase. In this paper we have also reported a detailed characterization of the three compounds including 2D-NMR and ESI-mass experiments and X-ray single crystal structure of the copper and nickel compounds.

The design, synthesis and electrochemical behaviour of an oligomer consisting of linked thymine-functionalised ferrocene units are reported, which, as a so-called form of ferrocene nucleic acid (FcNA), acts as a structural mimic of DNA.

A concise, stereoselective synthesis of the trans-hydrindane core of the marine natural product dictyoxetane is reported, starting from a Robinson annelation derived bicyclic enone. A phosphorane-mediated, pinacol-like rearrangement of a cis-diol, via a formal 1,2-hydride shift, is used to establish the requisite trans ring junction. (31)P NMR supports the formation of the intermediate phosphorane, generated in situ from the reaction of a diol with Ph(3)PCl(2).

A new and very rapid access to indoline intermediates useful for the synthesis of alkaloids related to the stephacidins has been established using a radical cascade process initiated from a sulphur-substituted diketopiperazine., (This journal is © The Royal Society of Chemistry 2012)

A series of trimethylsilyl-protected di-alkynes incorporating 3,4-ethylenedioxythiophene (EDOT) linker groups Me(3)Si-C≡C-R-C≡C-SiMe(3) (R = ethylenedioxythiophene-3,4-diyl 1a, 2,2'-bis-3,4-ethylenedioxythiophene-5,5'-diyl 2a, 2,2',5',2''-ter-3,4-ethylenedioxythiophene-5,5''-diyl 3a) and the corresponding terminal di-alkynes, H-C≡C-R-C≡C-H 1b-2b has been synthesized and characterized and the single crystal X-ray structure of 1a has been determined. CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et(3)P)(2)PtCl] and the terminal di-alkynes 1b-2b in (i)Pr(2)NH/CH(2)Cl(2) (2:1 mole ratio) gives the Pt(II) di-ynes trans-[(Et(3)P)(2)(Ph)Pt-C≡C-R-C≡C-Pt(Ph)(Et(3)P)(2)] 1M-2M while the dehydrohalogenation polycondensation reaction between trans-[((n)Bu(3)P)(2)PtCl(2)] and 1b-2b (1:1 mole ratio) under similar reaction conditions affords the Pt(II) poly-ynes trans-[Pt(P(n)Bu(3))(2)-C≡C-R-C≡C-](n)1P-2P. The di-ynes and poly-ynes have been characterized spectroscopically and, for 1M and 2M, by single-crystal X-ray which confirms the "rigid rod" di-yne backbone. The materials possess excellent thermal stability, are soluble in common organic solvents and readily cast into thin films. Optical absorption spectroscopic measurements reveal that the EDOT spacers create stronger donor-acceptor interactions between the platinum(II) centres and conjugated ligands along the rigid backbone of the organometallic polymers compared to the related non-fused and fused oligothiophene spacers., (This journal is © The Royal Society of Chemistry 2011)

Treatment of methyl indole-3-carboxylate with bromine in acetic acid gives methyl 5,6-dibromoindole-3-carboxylate regioselectively, from which the parent 5,6-dibromoindole can be accessed via a one-pot, microwave-mediated ester hydrolysis and decarboxylation. Application of these building blocks in syntheses of natural and non-natural 5,6-dibromoindole derivatives, including meridianin F and 5,6-dibromo-2'-demethylaplysinopsin, is reported.

Acyclic bissulfonylnitroxides have never been isolated, and degrade through fragmentation. In an approach to stabilising a bissulfonylnitroxide radical, the cyclic, peri-substituted N,N-bissulfonylhydroxylamine, 2-hydroxynaphtho[1,8-de][1,3,2]dithiazine 1,1,3,3-tetraoxide (1), has been prepared by formal nitrogen insertion into the sulfur-sulfur bond of a sulfinylsulfone, naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxide. The heterocyclic ring of 1 is shown to adopt a sofa conformation by X-ray crystallography, with a pseudo-axial hydroxyl group. N,N-Bissulfonylhydroxylamine 1 displays high thermal, photochemical and hydrolytic stability compared to acyclic systems. EPR analysis reveals formation of the corresponding bissulfonylnitroxide 2 upon oxidation of 1 with the Ce(IV) salts CAN and CTAN. Although 2 does not undergo fragmentation, it cannot be isolated, since hydrogen atom abstraction to reform 1 occurs in situ. The stability and reactivity of 1 and 2 are compared with the known cyclic benzo-fused N,N-bissulfonylhydroxylamine, N-hydroxy-O-benzenedisulfonimide (6), for which the X-ray data, and EPR of the corresponding nitroxide 10, are also reported for the first time.

N-alkylation of a novel pyridine sensor results in pyridinium salts whose conformations are stabilised by pyridinium cation-π interactions resulting in a fluorescent response that can be used to sense the presence of alkylating agents in solution at low concentration.

The ammonia adduct of tris(pentafluorophenyl)boron, (C6F5)3B.NH3, is a potentially tri-functional hydrogen-bond donor. Co-crystallisation with the bases acetonitrile, pyridine, tetrahydrofuran, tetramethylethylenediamine, 15-crown-5, 1,4-diazabicyclo[2.2.2]octane (DABCO), pyrazine and 4,4'-bipyridine results, not in donor exchange, but in the formation of supermolecules assembled through hydrogen bonding to second coordination sphere acceptors. The complexes have been characterised by elemental analysis, multinuclear NMR and single-crystal diffraction methods. The solid-state architectures range in complexity, from the hydrogen bonded pairing of (C6F5)3B.NH3, with a single monodentate acceptor molecule (e.g. MeCN to form (C6F5)3B.NH3.NCMe), through complexation with all three N-H groups to the macrocycle 15-crown-5, to the formation of infinite one-dimensional chains with pyrazine and DABCO, and to two-dimensional networks with the divergent acceptor 4,4'-bipyridine.

A simple, one-step synthesis of multinuclear Lewis acids can be driven with high selectivity towards either macrocyclic or polymeric arrays by appropriate choice of backbone framework.