Jonathan C. Collings

Durham University, Durham, ENG, United Kingdom

Are you Jonathan C. Collings?

Claim your profile

Publications (40)118.78 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Borylation of quinolines provides an attractive method for the late-stage functionalization of this important heterocycle. The regiochemistry of this reaction is dominated by steric factors but, by undertaking reactions at room temperature, an underlying electronic selectivity becomes apparent, as exemplified by the comparative reactions of 7-halo-2-methylquinoline and 2,7-dimethylquinoline which afford variable amounts of the 5- and 4-borylated products. Similar electronic selectivities are observed for nonsymmetrical 1,2-disubstituted benzenes. The site of borylation can be simply estimated by analysis of the 1H NMR spectrum of the starting material with preferential borylation occurring at the site of the most deshielded sterically accessible hydrogen or carbon atom. Such effects can be linked with C–H acidity. Whilst DFT calculations of the pKa for the C–H bond show good correlation with the observed selectivity, small differences suggest that related alternative, but much more computationally demanding values, such as the M–C bond strength, may be better quantitative predictors of selectivity.
    Chemical Science 10/2012; 3(12):3505-3515. · 8.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Three polymorphs of pyrene-2,7-bis(Bpin)2 (1) and two of pyrene-2-(Bpin) (2), where Bpin = 4,4,5,5-tetramethyl-[1,3,2]dioxaborolane, two different 1:1 co-crystals of 1 with toluene, and co-crystals of hexafluorobenzene (HFB) with 1 (of highly unusual 2:1 composition) and 2 (of usual 1:1 composition) were isolated, studied by X-ray diffraction and differential scanning calorimetry, and described using Hirshfeld surfaces and two-dimensional fingerprint plots. Centrosymmetric phases β- and γ-1 have densities respectively lower and higher than the chiral α-1; α- and β-2 have different packing modes, both with Z′ = 3. Compound 1 is prone to form channel host–guest structures, for example, α- and β-1·PhMe and 1·2HFB. The drastically different stabilities of α- and β-1·PhMe are discussed. The complex 2·HFB has a mixed-stack packing motif. The structural versatility of 1 and 2 is explained by synthon frustration between structurally incongruent pyrene and Bpin moieties.
    Crystal Growth & Design 05/2012; 12(6):2794–2802. · 4.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An efficient synthetic route to 2- and 2,7-substituted pyrenes is described. The regiospecific direct C-H borylation of pyrene with an iridium-based catalyst, prepared in situ by the reaction of [{Ir(μ-OMe)cod}(2)] (cod = 1,5-cyclooctadiene) with 4,4'-di-tert-butyl-2,2'-bipyridine, gives 2,7-bis(Bpin)pyrene (1) and 2-(Bpin)pyrene (2, pin = OCMe(2)CMe(2)O). From 1, by simple derivatization strategies, we synthesized 2,7-bis(R)-pyrenes with R = BF(3)K (3), Br (4), OH (5), B(OH)(2) (6), and OTf (7). Using these nominally nucleophilic and electrophilic derivatives as coupling partners in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions, we obtained 2,7-bis(R)-pyrenes with R = (4-CO(2)C(8)H(17))C(6)H(4) (8), Ph (9), C≡CPh (10), C≡C[{4-B(Mes)(2)}C(6)H(4)] (11), C≡CTMS (12), C≡C[(4-NMe(2))C(6)H(4)] (14), C≡CH (15), N(Ph)[(4-OMe)C(6)H(4)] (16), and R = OTf, R' = C≡CTMS (13). Lithiation of 4, followed by reaction with CO(2), yielded pyrene-2,7-dicarboxylic acid (17), whilst borylation of 2-tBu-pyrene gave 2-tBu-7-Bpin-pyrene (18) selectively. By similar routes (including Negishi cross-coupling reactions), monosubstituted 2-R-pyrenes with R = BF(3)K (19), Br (20), OH (21), B(OH)(2) (22), [4-B(Mes)(2)]C(6)H(4) (23), B(Mes)(2) (24), OTf (25), C≡CPh (26), C≡CTMS (27), (4-CO(2)Me)C(6)H(4) (28), C≡CH (29), C(3)H(6)CO(2)Me (30), OC(3)H(6)CO(2)Me (31), C(3)H(6)CO(2)H (32), OC(3)H(6)CO(2)H (33), and O(CH(2))(12)Br (34) were obtained from 2. These derivatives are of synthetic and photophysical interest because they contain donor, acceptor, and conjugated substituents. The crystal structures of compounds 4, 5, 7, 12, 18, 19, 21, 23, 26, and 28-31 have also been obtained from single-crystal X-ray diffraction data, revealing a diversity of packing modes, which are described in the Supporting Information. A detailed discussion of the structures of 1 and 2, their polymorphs, solvates, and co-crystals is reported separately.
    Chemistry - A European Journal 03/2012; 18(16):5022-35. · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The 1:1 molecular complexes of octafluoronaphthalene (OFN) with fluorene (1) and with 9,10-dihydrophenanthrene (2) were prepared by cocrystallization of the components and characterized by single-crystal X-ray diffraction. The structure of 1 can be described as a mixed-stack or a laminar checkerboard motif of alternating OFN and fluorene molecules, whilst slanted mixed-stack, herringbone, and face-to-face heteromolecular dimer motifs can all be recognised in 2.Key words: single crystal, X-ray structure, π stacking, fluoroarene.
    Canadian Journal of Chemistry 02/2011; 84(2):238-242. · 0.96 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present a sequential molecular dynamics/quantum mechanics (MD/QM) study and steady-state spectroscopy measurements of the nanostar dendrimer (a phenylene−ethynylene dendrimer attached to a ethynylperylene chromophore) to determine the temperature dependence of the electronic absorption process. We studied the nanostar as separate units and performed MD simulations for each chromophore at 10 and 300 K to study the effects of the temperature on the structures. The absorption spectrum of the nanostar, at 10 and 300 K, was computed using an ensemble of 8000 structures for each chromophore. Quantum mechanical (QM) ZINDO/S calculations were performed for each conformation in the ensemble, including 16 excited states for a total of 128 000 excitation energies, and the intensity was scaled linearly with the number of conjugated units. Our calculations and experimental spectra measured for the individual chromophores and the nanostar are in good agreement. We found that for each system, the spectral features are narrow at 10 K because the transitions are localized in wavelength and the absorption energy depends primarily on the length of the chromophore, while at 300 K, the spectra features are quite broad and blue-shifted due to conformational changes on the systems. We explain in detail the effects of temperature and their consequence for the absorption process.
    The Journal of Physical Chemistry C. 10/2010; 114(48).
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 41(4).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Retinoid signalling pathways are involved in numerous processes in cells, particularly those mediating differentiation and apoptosis. The endogenous ligands that bind to the retinoid receptors, namely all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid, are prone to double-bond isomerisation and to oxidation by metabolic enzymes, which can have significant and deleterious effects on their activities and selectivities. Many of these problems can be overcome through the use of synthetic retinoids, which are often much more stable, as well as being more active. Modification of their molecular structures can result in retinoids that act as antagonists, rather than agonists, or exhibit a large degree of selectivity for particular retinoid-receptor isotypes. Several such selective retinoids are likely to be of value as pharmaceutical agents with reduced toxicities, particularly in cancer therapy, as reagents for controlling cell differentiation, and as tools for elucidating the precise roles that specific retinoid signalling pathways play within cells.
    Chemistry - A European Journal 10/2009; 15(43):11430-42. · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The natural retinoid, all-trans retinoic acid (ATRA), is widely used to direct the in vitro differentiation of stem cells. However, substantial degradation and isomerisation of ATRA in response to UV-vis light has serious implications with regard to experimental reproducibility and standardisation. We present the novel application of proteomic biomarker profiling technology to stem cell lysates to rapidly compare the differentiation effects of ATRA with those of two stable synthetic retinoid analogues, EC19 and EC23, which have both been shown to induce differentiation in the embryonal carcinoma cell line TERA2.cl.SP12. MALDI-TOF MS (matrix-assisted laser desorption ionisation time-of-flight mass spectrometry) protein profiles support previous findings into the functional relationships between these compounds in the TERA2.cl.SP12 line. Subsequent analysis of protein peak data enabled the semi-quantitative comparison of individual retinoid-responsive proteins. We have used ion exchange chromatographic protein separation to enrich for retinoid-inducible proteins, thereby facilitating their identification from SDS-PAGE gels. The cellular retinoid-responsive proteins CRABP-I, CRABP-II, and CRBP-I were up-regulated in response to ATRA and EC23, indicating a bona fide retinoid pathway response to the synthetic compound. In addition, the actin filament regulatory protein profilin-1 and the microtubule regulator stathmin were also elevated following treatment with both ATRA and EC23. The up-regulation of profilin-1 and stathmin associated with retinoid-induced neural differentiation correlates with their known roles in cytoskeletal reorganisation during axonal development. Immunological analysis via western blotting confirmed the identification of CRABP-I, profilin-1 and stathmin, and supported their observed regulation in response to the retinoid treatments.
    Molecular BioSystems 06/2009; 5(5):458-71. · 3.35 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A series of bis(E-dimesitylborylethenyl)-substituted arenes, namely arene = 1,4-benzene, 1,4-tetrafluorobenzene, 2,5-thiophene, 1,4-naphthalene, 9,10-anthracene, 4,4'-biphenyl, 2,7-fluorene, 4,4'-E-stilbene, 4,4'-tolan, 5,5'-(2,2'-bithiophene), 1,4-bis(4-phenylethynyl) benzene, 1,4-bis(4-phenylethynyl) tetrafluorobenzene and 5,5 `'-(2,2':5',2 `'-terthiophene), have been synthesised via hydroboration of the corresponding diethynylarenes with dimesitylborane. Their absorption and emission maxima, fluorescence lifetimes and quantum yields are reported along with the two-photon absorption (TPA) spectra and TPA cross-sections for the 5,5 `-bis(E-dimesitylborylethenyl)- 2,2'-bithiophene and 5,5'-bis(E-dimesitylborylethenyl)-2,2':5',2 `'-terthiophene derivatives. The TPA crosssection of the latter compound of ca. 1800 GM is the largest yet reported for a 3-coordinate boron compound and is in the range of the largest values measured for quadrupolar compounds with similar conjugation lengths. The X-ray crystal structures of 1,4-benzene, 2,5-thiophene, 4,4'-biphenyl and 5,500( 2,2':5',2 `'- terthiophene) derivatives indicate pi-conjugation along the BC=C-arene-C=CB chain. Theoretical studies show that the second molecular hyperpolarisabilities, gamma, in each series of compounds are generally related to the HOMO energy, which itself increases with increasing donor strength of the of the spacer. A strong enhancement of gamma is predicted as the number of thiophene rings in the spacer increases.
    Journal of Materials Chemistry 01/2009; 19(40):7532-7544. · 6.63 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: All-trans-retinoic acid (ATRA) and its associated analogues are important mediators of cell differentiation and function during the development of the nervous system. It is well known that ATRA can induce the differentiation of neural tissues from human pluripotent stem cells. However, it is not always appreciated that ATRA is highly susceptible to isomerisation when in solution, which can influence the effective concentration of ATRA and subsequently its biological activity. To address this source of variability, synthetic retinoid analogues have been designed and synthesised that retain stability during use and maintain biological function in comparison to ATRA. It is also shown that subtle modifications to the structure of the synthetic retinoid compound impacts significantly on biological activity, as when exposed to cultured human pluripotent stem cells, synthetic retinoid 4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-ylethynyl)benzoic acid, 4a (para-isomer), induces neural differentiation similarly to ATRA. In contrast, stem cells exposed to synthetic retinoid 3-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-ylethynyl)benzoic acid, 4b (meta-isomer), produce very few neurons and large numbers of epithelial-like cells. This type of structure-activity-relationship information for such synthetic retinoid compounds will further the ability to design more targeted systems capable of mediating robust and reproducible tissue differentiation.
    Organic & Biomolecular Chemistry 11/2008; 6(19):3497-507. · 3.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Sonogashira cross-coupling of two equivalents of para-substituted ethynylbenzenes with 2,5-diiodothiophene provides a simple synthetic route for the preparation of 2,5-bis(para-R- phenylethynyl)thiophenes (R = H, Me, OMe, CF3, NMe2 ,N O 2, CN and CO2Me) (1a-h). Likewise, 2,5-bis(pentafluorophenylethynyl)thiophene (2) was prepared by the coupling of 2,5- diiodothiophene with pentafluorophenylacetylene. All compounds were characterised by NMR, IR, Raman and mass spectroscopy, elemental analysis, and their absorption and emission spectra, quantum yields and lifetimes were also measured. The spectroscopic studies of 1a-h and 2 show that both electron donating and electron withdrawing para-subsituents on the phenyl rings shift the absorption and emission maxima to lower energies, but that acceptors are more efficient in this regard. The short singlet lifetimes and modest fluorescence quantum yields (ca. 0.2-0.3) observed are characteristic of rapid intersystem crossing. The single-crystal structures of 2,5- bis(phenylethynyl)thiophene, 2,5-bis(para-carbomethoxyphenylethynyl)thiophene, 2,5-bis(para- methylphenylethynyl)thiophene and 2,5-bis(pentafluorophenylethynyl)thiophene were determined by X-ray diffraction at 120 K. DFT calculations show that the all-planar form of the compounds is the lowest in energy, although rotation of the phenyl groups about the CRC bond is facile and TD-DFT calculations suggest that, similar to 1,4-bis(phenylethynyl)benzene analogues, the absorption spectra in solution arise from a variety of rotational conformations. Frequency calculations confirm the assignments of the compounds' IR and Raman spectra.
    New Journal of Chemistry 01/2007; 31(6). · 3.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The crystal and molecular structures of 4-ethynyl-N,N-dimethylaniline (1), and 4-(trimethylsilylethynyl)-N,N-dimethylaniline (2), have been obtained from X-ray diffraction data. Crystals of 1 exhibit a phase transition at 122.5 ± 2 K. Both polymorphs are triclinic with Z′ = 12, and the molecules are linked into dodecamers by weak hydrogen bonds involving C–H groups. The orthorhombic crystals of 2 show no phase changes and have Z′ = 1.5 (3 half molecules) without short intermolecular contacts.
    CrystEngComm 08/2006; 8(8):622-628. · 3.88 Impact Factor
  • Source
    Andrei S Batsanov, Jonathan C Collings, Todd B Marder
    [Show abstract] [Hide abstract]
    ABSTRACT: The title crystal, [Fe(C5H5)2].C12F10, comprises infinite chains of alternating component molecules, linked through face-to-face contacts of nearly parallel cyclopentadienyl and pentafluorophenyl rings. The decafluorobiphenyl molecule has a crystallographic twofold axis and the Fe atom of the ferrocene molecule is on a crystallographic inversion centre, with both cyclopentadienyl rings disordered.
    Acta Crystallographica Section C Crystal Structure Communications 07/2006; 62(Pt 6):m229-31. · 0.78 Impact Factor
  • Andrei S. Batsanov, Jonathan C. Collings, Todd B. Marder
    [Show abstract] [Hide abstract]
    ABSTRACT: The title crystal, [Fe(C5H5)2]·C12F10, comprises infinite chains of alternating component mol­ecules, linked through face-to-face contacts of nearly parallel cyclo­penta­dienyl and penta­fluoro­phenyl rings. The deca­fluoro­biphenyl mol­ecule has a crystallographic twofold axis and the Fe atom of the ferrocene mol­ecule is on a crystallographic inversion centre, with both cyclo­penta­dienyl rings disordered.
    Acta Crystallographica Section C Crystal Structure Communications 06/2006; 62(6). · 0.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The (p-R-phenyl)dimesitylboranes (R=Me(2)N, MeO, MeS, Br, I), (p-R-phenylethynyl)dimesitylboranes (R=Me(2)N, MeO, MeS, H), (E)-[2-(p-R-phenyl)ethenyl]dimesitylboranes (R=Me(2)N, H(2)N, MeO, MeS, H, CN, NO(2)), (E)-[2-(2-thienyl)ethenyl]dimesitylborane, and (E)-[2-(o-carboranyl)ethenyl]dimesitylborane have been prepared through the reaction of the appropriate p-R-phenyl- and p-R-phenylethynyllithium reagents with dimesitylboron fluoride and by hydroboration of the appropriate p-R-phenylacetylene, 2-ethynylthiophene, and o-ethynylcarborane with dimesitylborane. Their UV/Vis absorption and emission spectra have been recorded in a range of solvents with the fluorescence maxima of the donor-substituted compounds in particular exhibiting large bathochromic shifts in highly polar solvents, indicative of charge transfer leading to large dipole moments in the excited state. The molecular structures of the (p-R-phenyl)dimesitylboranes (R=Me(2)N, MeO, MeS, Br, I), the (E)-[2-(p-R-phenyl)ethenyl]dimesitylboranes (R=Me(2)N, H(2)N MeO, MeS, H), (p-R-phenylethynyl)dimesitylborane (R=Me(2)N), and (E)-[2-(2-thienyl)ethenyl]dimesitylborane, which have been determined from single-crystal X-ray diffraction measurements, offer evidence of increased conjugation in the ground state with increased donor strength of the R substituent. Their first- and second-order molecular hyperpolarizabilities have been obtained from EFISH and THG measurements, the first-order hyperpolarizabilities being largest for the strongest R-substituent donors. AM1 calculations have been performed on these compounds, showing reasonable agreement with the experimentally obtained bond lengths and hyperpolarizabilities, as well as on several related hypothetical compounds containing multiple C==C bonds, most of which are proposed to have even larger hyperpolarizabilities.
    Chemistry 04/2006; 12(10):2758-71. · 5.83 Impact Factor
  • Andrei S. Batsanov, Jonathan C. Collings, Todd B. Marder
    Acta Crystallographica Section C-crystal Structure Communications - ACTA CRYSTALLOGR C-CRYST STR. 01/2006; 62(6).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Donor-acceptor phenylene ethynylene systems containing the 6-methylpyran-2-one group, synthesized via classic or microwave-assisted Sonogashira cross-coupling, exhibit pronounced solvatochromism in fluorescence suggesting a highly polar excited state; 4-[4-(4-N,N-dihexylaminophenylethynyl)phenylethynyl]-6-methylpyran-2-one has a fluorescence quantum yield >0.9 in cyclohexane.
    Chemical Communications 07/2005; · 6.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Palladium-catalyzed terminal alkyne dimerization, through oxidative homocoupling, is a useful approach to the synthesis of symmetrical 1,4-diynes. Recent investigations have suggested that this reaction might be accomplished in the absence of intentionally added stoichiometric oxidants (to reoxidize Pd(0) to Pd(II)). In this paper, we have fully addressed the question of whether oxygen (or added oxidant) is required to facilitate this process. The presence of a stoichiometric quantity of air (or added oxidant such as I2) is essential for alkyne dimerization. Excess PPh3 inhibits alkyne dimerization to enyne, which only occurs to a significant extent when the reaction is starved of oxidant. Theoretical studies shed more light on the requirement for an oxidant in the homocoupling reaction in order for the process to be theromodynamically favorable. The employment of I2 as the stoichiometric oxidant appears to be the method of choice. The dual role of Cu both in transmetalation of alkynyl units to Pd(II) and in assisting reoxidation of Pd(0) to Pd(II) is suggested.
    The Journal of Organic Chemistry 02/2005; 70(2):703-6. · 4.56 Impact Factor
  • Source
    A.S. Batsanov, J.C. Collings, T.B. Marder
    [Show abstract] [Hide abstract]
    ABSTRACT: In the cation of the title compound C11H18ClN2+·Cl−, the quaternary N atom has a distorted tetrahedral geometry, and the other N a nearly planar-trigonal (owing to conjugation with the benzene ring) bonding geometry.
    Acta Crystallographica Section E Structure Reports Online 01/2005; 61(2). · 0.35 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The synthesis of monodentate and bidentate phosphinite ligands, possessing the unusual bicyclo[3.2.0]heptane framework, are reported. A convenient, tin-free synthesis of a key intermediate, namely 3-endo-6-endo-dihydroxybicyclo[3.2.0]heptane, is described. The air-sensitive phosphinite ligand 1 was either protected as the borane adduct, which is air-stable, or reacted directly with bis(acetonitrile)palladium(II)chloride to give the novel air and moisture stable palladium(II) complex 11. A platinum(II) relative 12 has also been synthesised by reaction of phosphinite 1 with bis(benzonitrile)platinum(II)chloride. Each complex has been thoroughly characterised and their molecular structures confirmed by X-ray diffraction studies. In catalytic applications, such as cross-coupling reactions of organometallic reagents with organohalides, an unexpectedly poor activity has been established for 11. For example, Suzuki–Miyaura cross-coupling of activated and deactivated aryl bromides with aryl boronic acids, in the presence of catalytic quantities of 11, proceed in low yield, accompanied by substantial homocoupling. Palladium agglomeration, to produce catalytically inactive Pd black, is rapid in these reactions, under both aqueous and non-aqueous conditions. The poor reactivity is proposed to arise through an unfavourable near tetrahedral ‘(PP′)Pd(0)’ geometry, which slows the oxidative addition step in the catalytic cycle with either activated or deactivated aryl halides. The steric bulk of the ligand and the associated large P–M–P′ bite angle, particularly at the palladium zero oxidation state, is proposed to account for the poor reactivity. However, we have established that cationic derivatives of 11 promote the cycloisomerisation of diallylmalonate in a regioselective fashion.
    Journal of Organometallic Chemistry - J ORGANOMET CHEM. 01/2005; 690(20):4462-4477.

Publication Stats

208 Citations
118.78 Total Impact Points

Institutions

  • 2000–2012
    • Durham University
      • Department of Chemistry
      Durham, ENG, United Kingdom
  • 2006
    • University of Waterloo
      • Department of Chemistry
      Waterloo, Quebec, Canada
  • 2005
    • The University of York
      • Department of Chemistry
      York, England, United Kingdom
  • 2004
    • Heriot-Watt University
      • Department of Chemistry
      Edinburgh, SCT, United Kingdom