Alkyl substituted [2.2]paracyclophane-1,9-dienes.

[2.2]Paracyclophane-1,9-dienes substituted with n-octyl chains have been synthesised from the corresponding dithia[3.3]paracyclophanes using a benzyne induced Stevens rearrangement. The use of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and tetra-n-butylammonium fluoride as the in situ benzyne source gave significantly improved yields over traditional sources of benzyne and enabled the preparation of n-octyl substituted [2.2]paracyclophane-1,9-dienes on a multi-gram scale.

Cyclometalated Ir(III) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence.

Six new tricationic Ir(III) complexes of cyclometalating ligands derived from 1-methyl-2-(2'-pyridyl)pyridinium or 1-methyl-4-(2'-pyridyl)pyridinium are described. These complexes of the form [Ir(III)(C^N)2(N^N)](3+) (C^N = cyclometalating ligand; N^N = α-diimine) have been isolated and characterised as their PF6(-) and Cl(-) salts. Four of the PF6(-) salts have been studied by X-ray crystallography, and structures have been obtained also for two complex salts containing MeCN and Cl(-) or two Cl(-) ligands instead of N^N. The influence of the position of the quaternised N atom in C^N and the substituents on N^N on the electronic/optical properties are compared with those of the analogous complexes where C^N derives from 1-methyl-3-(2'-pyridyl)pyridinium (B. J. Coe, et al., Dalton Trans., 2015, 44, 15420). Voltammetric studies reveal one irreversible oxidation and multiple reduction processes which are mostly reversible. The new complexes show intramolecular charge-transfer absorptions between 350 and 450 nm, and exhibit bright green luminescence, with λmax values in the range 508-530 nm in both aqueous and acetonitrile solutions. In order to gain insights into the factors that govern the emission properties, density functional theory (DFT) and time-dependent DFT calculations have been carried out. The results confirm that the emission arises largely from triplet excited states of the C^N ligand ((3)LC), with some triplet metal-to-ligand charge-transfer ((3)MLCT) contributions.

A latent reactive handle for functionalising heparin-like and LMWH deca- and dodecasaccharides.

d-Glucosamine derivatives bearing latent O4 functionality provide modified H/HS-type disaccharide donors for a final stage capping approach enabling introduction of conjugation-suitable, non-reducing terminal functionality to biologically important glycosaminoglycan oligosaccharides. Application to the synthesis of the first O4-terminus modified synthetic LMWH decasaccharide and an HS-like dodecasaccharide is reported.

Water-soluble Ir(iii) complexes of deprotonated N-methylbipyridinium ligands: fluorine-free blue emitters.

New blue or blue-green emitting iridium complexes have been synthesised with cyclometalating ligands derived from the 1-methyl-3-(2'-pyridyl)pyridinium cation. Efficient luminescence is observed in MeCN or aqueous solutions, with a large range of lifetimes in the µs region and relatively high quantum yields.

On the origin and variation of colors in lobster carapace.

The chemical basis of the blue-black to pink-orange color change on cooking of lobster, due to thermal denaturation of an astaxanthin-protein complex, α-crustacyanin, in the lobster carapace, has so far been elusive. Here, we investigate the relaxation of the astaxanthin pigment from its bound enolate form to its neutral hydroxyketone form, as origin of the spectral shift, by analyzing the response of UV-vis spectra of a water-soluble 3-hydroxy-4-oxo-ß-ionone model of astaxanthin to increases in pH, and by performing extensive quantum chemical calculations over a wide range of chemical conditions. The enolization of astaxanthin is consistent with the X-ray diffraction data of ß-crustacyanin (PDB code: ) whose crystals possess the distinct blue color. We find that enolate formation is possible within the protein environment and associated with a large bathochromic shift, thus offering a cogent explanation for the blue-black color and the response to thermal denaturation and revealing the chemistry of astaxanthin upon complex formation.

Synthesis, structures, and optical properties of ruthenium(II) complexes of the tris(1-pyrazolyl)methane ligand.

Four new complex salts [Ru(II)Cl(Tpm)(L(A))2][PF6]n [Tpm = tris(1-pyrazolyl)methane; n = 1, L(A) = pyridine (py) 1 or ethyl isonicotinate (EIN) 2; n = 3, L(A) = N-methyl-4,4'-bipyridinium (MeQ(+)) 3 or N-phenyl-4,4'-bipyridinium (PhQ(+)) 4] have been prepared and characterized. Electronic absorption spectra show intense d → π* metal-to-ligand charge-transfer (MLCT) absorption bands, while cyclic voltammetry reveals a reversible Ru(III/II) wave, accompanied by quasireversible or irreversible L(A)-based reductions for all except 1. Single crystal X-ray structures have been obtained for 1•Me2CO, 2, and 3•Me2CO. For 2-4, molecular first hyperpolarizabilities ß have been measured in acetonitrile solutions via the hyper-Rayleigh scattering (HRS) technique at 800 nm. Stark (electroabsorption) spectroscopic studies on the MLCT bands in frozen butyronitrile allow the indirect estimation of static first hyperpolarizabilities ß0. The various physical data obtained for 3 and 4 are compared with those reported previously for related cis-{Ru(II)(NH3)4}(2+) species [ Coe, B. J. et al. J. Am. Chem. Soc. 2005 , 127 , 4845 ]. TD-DFT calculations on the complexes in 1-4 confirm that their lowest energy absorption bands are primarily Ru(II) → L(A) MLCT in character, while Ru(II) → Tpm MLCT transitions are predicted at higher energies. DFT agrees with the Stark, but not the HRS measurements, in showing that ß0 increases with the electron-accepting strength of L(A). The 2D nature of the chromophores is evidenced by dominant ßxxy tensor components.

Synthesis and characterization of nickel(II) phosphonate complexes utilizing pyridonates and carboxylates as co-ligands.

The synthesis and structures of five new nickel complexes containing phosphonate ligands are reported. The compounds utilize pivalic acid (HPiv) and 6-chloro-2-pyridonate (Hchp) as co-ligands with the resulting complexes being of formulas [Ni10(chp)4(Hchp)4.5(O3P(t)Bu)3(Piv)5(HPiv)2(OH)6(H2O)4.5](HNEt3)·0.5MeCN·2.5H2O 1, [Ni12(chp)12(Hchp)2(PhPO3)2(Piv)5(HPiv)2(OH)2(H2O)6](F)·4.5MeCN·2H2O 2, [Ni10(chp)6(O3PCH2Ph)2(Piv)8(F)2(MeCN)4] 3, [Ni10(chp)6(O3PMe)2(Piv)8(F)2 (MeCN)4]·5MeCN·2H2O 4, and [Ni10(chp)6(O3PCH2Nap)2(Piv)8(F)2(MeCN)2(H2O)2] 5. The metallic core of compounds 1 and 2 display tetra- and hexa-capped trigonal prismatic arrangements, while the metallic and phosphorus core of 3, 4, and 5 display three face-sharing octahedra. Variable temperature direct current (dc) magnetic susceptibility measurements reveal dominant antiferromagnetic exchange interactions within each cluster, with diamagnetic spin ground states found.

catena-Poly[[tri-phenyl-tin(IV)]-µ-N-(4-acetyl-phen-yl)maleamato].

The crystal structure of the polymeric title compound, [Sn(C6H5)3(C12H10NO4)] n , comprises polymeric chains whereby adjacent Sn atoms are bridged by carboxyl-ate and amide carbonyl O atoms [Sn-O = 2.115 (15) and 2.653 (1) Å, respectively]. The Sn(IV) atom is five-coordinated showing a distorted trigonal-bipyramid geometry, with the three phenyl ipso-C atoms defining the trigonal plane and the axial positions occupied by O atoms [O-Sn-O = 171.91 (5)°]. Intra-molecular N-H⋯O hydrogen bonding leads to a seven-membered loop. There is an intra-molecular C-H⋯O inter-action within the polymeric chain. An inter-molecular C-H⋯O inter-action along c links the polymeric chains into sheets which are linked into a three-dimensional network via C-H⋯π inter-actions.

On the importance of unprecedented lone pair-salt bridge interactions in Cu(II)-malonate-2-amino-5-chloropyridine-perchlorate ternary system.

A Cu(II)-malonate complex with formula {(C5H6N2Cl)12[Cu(1)(C3H2O4)2][Cu(2)(C3H2O4)2(H2O)2][Cu(4)(C3H2O4)2][Cu(3)(C3H2O4)2(H2O)2](ClO4)4}n (1) [C5H6N2Cl = protonated 2-amino-5-chloropyridine, C3H4O4 = malonic acid, ClO4(-) = perchlorate] has been synthesized from purely aqueous media simple by mixing the reactants in their stoichiometric ratio, and its crystal structure has been determined by single-crystal X-ray diffraction. In 1, copper(II) malonate units form infinite 1D polymeric chains, which are interlinked by hydrogen bonds to generate 2D sheets. These 2D sheets are joined side by side primarily by various hydrogen bonds to form a 3D structure. A multitude of salt bridges are formed in this structure, connecting the protonated 2-amino-5-chloropyridines and the malonate ligands of the polymeric polyanion. Examining this characteristic of the solid-state architecture, we noticed several salt-bridge (sb)···π interactions and an unexplored interaction between the lone pair (lp) of one malonate oxygen atom and a planar salt bridge. The combination of this interaction with various other weak intermolecular forces results in a remarkably extended supramolecular network combining a wide variety of interactions involving π-systems (Cl···π, π···π) and salt bridges (sb···π and lp···sb). We describe the energetic and geometric features of this lone pair-salt-bridge interaction and explore its impact on the resultant supramolecular organization using theoretical DFT-D3 calculations.

Multicomponent synthesis of 4-aminophthalazin-1(2H)-ones by palladium-catalyzed isocyanide insertion.

4-Aminophthalazin-1(2H)-ones (APOs) are underexplored heterocyclic compounds with promising and diverse biological activities. The classical synthesis of these compounds is tedious and does not allow the regioselective introduction of substituents. Here, we present our full studies on the Pd-catalyzed cross-coupling of substituted o-(pseudo)halobenzoates and hydrazines with isocyanide insertion allowing straightforward access to diversely substituted APOs. We illustrate the advantages of this method compared to other approaches and describe solutions for the limitations we encountered. In addition, we have developed efficient diversifications of this heterocyclic scaffold that allow access to more diverse APOs as well as novel heterocyclic scaffolds.

Heptametallic, octupolar nonlinear optical chromophores with six ferrocenyl substituents.

New complexes with six ferrocenyl (Fc) groups connected to Zn(II) or Cd(II) tris(2,2'-bipyridyl) cores are described. A thorough characterisation of their BPh4(-) salts includes two single-crystal X-ray structures, highly unusual for such species with multiple, extended substituents. Intense, visible d(Fe(II))→π* metal-to-ligand charge-transfer (MLCT) bands accompany the π→π* intraligand charge-transfer absorptions in the near UV region. Each complex shows a single, fully reversible Fe(III/II) wave when probed electrochemically. Molecular quadratic nonlinear optical (NLO) responses are determined by using hyper-Rayleigh scattering and Stark spectroscopy. The latter gives static first hyperpolarisabilities ß0 reaching as high as approximately 10(-27)  esu and generally increasing with π-conjugation extension. Z-scan cubic NLO measurements reveal high two-photon absorption cross-sections σ2 of up to 5400 GM in one case. DFT calculations reproduce the π-conjugation dependence of ß0, and TD-DFT predicts three transitions close in energy contributing to the MLCT bands. The lowest energy transition has octupolar character, whereas the other two are degenerate and dipolar in nature.

Lanthanide speciation in potential SANEX and GANEX actinide/lanthanide separations using tetra-N-donor extractants.

Lanthanide(III) complexes with N-donor extractants, which exhibit the potential for the separation of minor actinides from lanthanides in the management of spent nuclear fuel, have been directly synthesized and characterized in both solution and solid states. Crystal structures of the Pr(3+), Eu(3+), Tb(3+), and Yb(3+) complexes of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BTPhen) and the Pr(3+), Eu(3+), and Tb(3+) complexes of 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'-bypyridine (CyMe4-BTBP) were obtained. The majority of these structures displayed coordination of two of the tetra-N-donor ligands to each Ln(3+) ion, even when in some cases the complexations were performed with equimolar amounts of lanthanide and N-donor ligand. The structures showed that generally the lighter lanthanides had their coordination spheres completed by a bidentate nitrate ion, giving a 2+ charged complex cation, whereas the structures of the heavier lanthanides displayed tricationic complex species with a single water molecule completing their coordination environments. Electronic absorption spectroscopic titrations showed formation of the 1:2 Ln(3+)/L(N4-donor) species (Ln = Pr(3+), Eu(3+), Tb(3+)) in methanol when the N-donor ligand was in excess. When the Ln(3+) ion was in excess, evidence for formation of a 1:1 Ln(3+)/L(N4-donor) complex species was observed. Luminescent lifetime studies of mixtures of Eu(3+) with excess CyMe4-BTBP and CyMe4-BTPhen in methanol indicated that the nitrate-coordinated species is dominant in solution. X-ray absorption spectra of Eu(3+) and Tb(3+) species, formed by extraction from an acidic aqueous phase into an organic solution consisting of excess N-donor extractant in pure cyclohexanone or 30% tri-n-butyl phosphate (TBP) in cyclohexanone, were obtained. The presence of TBP in the organic phase did not alter lanthanide speciation. Extended X-ray absorption fine structure data from these spectra were fitted using chemical models established by crystallography and solution spectroscopy and showed the dominant lanthanide species in the bulk organic phase was a 1:2 Ln(3+)/L(N-donor) species.

Exchange-coupled oxygen- and sulfur-bridged cyclopentadienyl-manganese(II) cages.

The trimetallic complex [{CpMn(µ-OSiPh3)2}2Mn] (1) and the heterocubane [CpMn(µ3-SSiPh3)]4 (2) are formed by deprotonation of Ph3SiQH (Q = O, S) by manganocene, or by transmetallation of manganocene by Ph3SiQLi. The Mn(II) centres in 1 and 2 are antiferromagnetically coupled, with J = −4.4 and −3.0 cm(−1) in 1 and 2, respectively (−2J formalism).

2,4-Dimethyl-1,3-thiazole-5-carboxylic acid: an X-ray structural study at 100 K and Hirshfeld surface analysis.

The crystal structure of the title thiazolecarboxylic acid derivative, C(6)H(7)NO(2)S, (I), has been determined from single-crystal X-ray analysis at 100 K. In the crystal packing, an interplay of O-H···N and C-H···O hydrogen bonds connects the molecules to form C(6)R(2)(2)(8) polymeric chains, which are further linked via weak C-H···O hydrogen bonds into a two-dimensional supramolecular framework. The relative contributions of different interactions to the Hirshfeld surface in (I) and a few related thiazolecarboxylic acid derivatives indicate that the H···H, N···H and O···H contacts can account for about 50-70% of the total Hirshfeld surface area in this class of compound.

Three anilides of 2,2'-thiodibenzoic acid.

The structures of N,N'-bis(2-methylphenyl)-2,2'-thiodibenzamide, C(28)H(24)N(2)O(2)S, (Ia), N,N'-bis(2-ethylphenyl)-2,2'-thiodibenzamide, C(30)H(28)N(2)O(2)S, (Ib), and N,N'-bis(2-bromophenyl)-2,2'-thiodibenzamide, C(26)H(18)Br(2)N(2)O(2)S, (Ic), are compared with each other. For the 19 atoms of the consistent thiodibenzamide core, the r.m.s. deviations of the molecules in pairs are 0.29, 0.90 and 0.80 Å for (Ia)/(Ib), (Ia)/(Ic) and (Ib)/(Ic), respectively. The conformations of the central parts of molecules (Ia) and (Ib) are similar due to an intramolecular N-H···O hydrogen-bonding interaction. The molecules of (Ia) are further linked into infinite chains along the c axis by intermolecular N-H···O interactions, whereas the molecules of (Ib) are linked into chains along b by an intermolecular N-H···π contact. The conformation of (Ic) is quite different from those of (Ia) and (Ib), since there is no intramolecular N-H···O hydrogen bond, but instead there is a possible intramolecular N-H···Br hydrogen bond. The molecules are linked into chains along c by intermolecular N-H···O hydrogen bonds.

Synthesis and characterisation of cobalt(II) phosphonate cage complexes utilizing carboxylates and pyridonates as co-ligands.

The synthesis and structures of fifteen new cobalt complexes containing phosphonate ligands are reported. The compounds also utilize carboxylates and 6-chloro-2-pyridonate (chp) as co-ligands. The majority of the compounds are decametallic: [Co(10)(chp)(12)(O(3)PPh)(2)(O(2)CPh)(4)(H(2)O)(4)], [Co(10)(chp)(12)(O(3)PPh)(2)(O(2)C(t)Bu)(4)(H(2)O)(4)], [Co(10)(chp)(12)(O(3)PPh)(2)(O(2)CPh(t)Bu)(4)(H(2)O)(4)], [Co(10)(chp)(6)(O(3)PCH(2)Ph)(2)(O(2)CPh)(8)(F)(2) (H(2)O)(2)(EtOAc)(2)], [Co(10)(chp)(8)(O(3)PCH(2)Ph)(2)(O(2)CPh)(8)(F)(2)(MeCN)(2)](HNEt(3))(2), [Co(10)(chp)(6)(O(3)PCH(2)Ph)(2)(O(2)C(t)Bu)(8)(F)(2)(H(2)O)(2)(MeCOMe)(2)], [Co(10)(chp)(6)(O(3)PMe)(2) (O(2)C(t)Bu)(8)(F)(2)(MeCN)(4)], [Co(10)(chp)(6)(O(3)PEt)(2)(O(2)CPh)(8)(F)(2)(MeCN)(4)], [Co(10)(chp)(6)(O(3)POct)(2)(O(2)CPh)(8)(F)(2)(MeCN)(4)], [Co(10)(chp)(8)(Hchp)(2)(O(3)PCH(2)Nap) (O(2)CPh)(7)(OH)(3)(H(2)O)], [Co(10)(chp)(12)(O(3)PPh)(2)(O(2)CPh-2-Ph)(4)(H(2)O)(4)] and [Co(10)(chp)(12)(O(3)PMe)(2)(O(2)CPh-2-Ph)(4)(H(2)O)(4)]. Two nine-metal cages and one hexametallic cage are also reported: [Co(9)(chp)(9)(O(3)P(t)Bu)(O(2)C(t)Bu)(6)(OH)], [Co(9)(chp)(7)(O(3)PCH(2)Ph)(2)(O(3)PCH(2)Ph)(O(2)CCPh(3))(5)(OH)(H(2)O)(2)(MeCN)] and [Co(6)(chp)(6)(Hchp)(2)(O(3)P(t)Bu)(O(2)CPh-2-Ph)(3)(F)(H(2)O)](HNEt(3))(Cl). Magnetic studies show predominantly anti-ferromagnetic exchange interactions between the cobalt(ii) sites, with diamagnetic ground states for most of the compounds studied.

Synthesis and scalable conversion of L-iduronamides to heparin-related di- and tetrasaccharides.

A diastereomerically pure cyanohydrin, preparable on kilogram scale, is efficiently converted in one step into a novel L-iduronamide. A new regioselective acylation of this iduronamide and a new mild amide hydrolysis method mediated by amyl nitrite enables short, scalable syntheses of an L-iduronate diacetate C-4 acceptor, and also L-iduronate C-4 acceptor thioglycosides. Efficient conversions of these to a range of heparin-related gluco-ido disaccharide building blocks (various C-4 protection options) including efficient multigram access to key heparin-building block ido-thioglycoside donors are described. A 1-OAc disaccharide is converted into a heparin-related tetrasaccharide, via divergence to both acceptor and donor disaccharides. X-ray and NMR data of the 1,2-diacetyl iduronate methyl ester and the analogous iduronamide show that while both adopt (1)C(4) conformations in solution, the iduronate ester adopts the (4)C(1) conformation in solid state. An X-ray structure is also reported for the novel, (4)C(1)-conformationally locked bicyclic 1,6-anhydro iduronate lactone along with an X-ray structures of a novel distorted (4)C(1) iduronate 4,6-lactone. Deuterium labeling also provides mechanistic insight into the formation of lactone products during the novel amyl nitrite-mediated hydrolysis of iduronamide into the parent iduronic acid functionality.

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles.

A versatile nitro-Mannich/lactamisation cascade for the direct stereoselective synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles has been developed. A highly enantioenriched substituted 5-nitropiperidin-2-one was synthesised in a four component one-pot reaction combining an enantioselective organocatalytic Michael addition with the diastereoselective nitro-Mannich/lactamisation cascade. Protodenitration and chemoselective reductive manipulation of the heterocycles was used to install contiguous and fully substituted stereocentres in the synthesis of substituted piperidines.

Chemical communication: conductors and insulators of screw-sense preference between helical oligo(aminoisobutyric acid) domains.

(1)H NMR studies quantify the abilities of achiral amino acids to communicate a left-handed screw-sense preference from one helical Aib(4) domain to another: certain quaternary amino acids (e.g. Ac(6)c) act as effective conductors of conformational preference while others (e.g. diphenylglycine) acts as insulators.