Assessing the potential of boronic acid/chitosan/bioglass composite materials for tissue engineering applications.

Composite materials aimed at bone tissue engineering need to have suitable bioactivity in order to promote cell proliferation and adhesion. In this article, we study the potential of boronic acids to improve the bioactivity of chitosan-based composite materials. Samples were prepared using boronic acid functionalised chitosan and Bioglass 45S5. These composite materials, prepared by freeze-drying, exhibit 3D interconnected porosity. The materials were fully characterized using scanning electron microscopy (SEM), FT-IR and x-ray diffraction. Their bioactivity was assessed by immersion in simulated body fluid and cell cytotoxicity assays. Composite materials containing boronic acid show no toxicity for Mouse Sertoli (TM4), Human embryonic kidney 293 (Hek293) and Human bone marrow/stroma (HS-5) cells, as opposed to composites containing non-functionalised chitosan.

Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2,2'-Biphenyl Complexes.

Reactions of [Rh(κ(2) -O,O-acac)(PMe3 )2 ] (acac=acetylacetonato) and α,ω-bis(arylbutadiynyl)alkanes afford two isomeric types of MC4 metallacycles with very different photophysical properties. As a result of a [2+2] reductive coupling at Rh, 2,5-bis(arylethynyl)rhodacyclopentadienes (A) are formed, which display intense fluorescence (Φ=0.07-0.54, τ=0.2-2.5 ns) despite the presence of the heavy metal atom. Rhodium biphenyl complexes (B), which show exceptionally long-lived (hundreds of µs) phosphorescence (Φ=0.01-0.33) at room temperature in solution, have been isolated as a second isomer originating from an unusual [4+2] cycloaddition reaction and a subsequent ß-H-shift. We attribute the different photophysical properties of isomers A and B to a higher excited state density and a less stabilized T1 state in the biphenyl complexes B, allowing for more efficient intersystem crossing S1 →Tn and T1 →S0 . Control of the isomer distribution is achieved by modification of the bis- (diyne) linker length, providing a fundamentally new route to access photoactive metal biphenyl compounds.

Characterization of Shrimp Oil from Pandalus borealis by High Performance Liquid Chromatography and High Resolution Mass Spectrometry.

Northern shrimp (Pandalus borealis) oil, which is rich in omega-3 fatty acids, was recovered from the cooking water of shrimp processing facilities. The oil contains significant amounts of omega-3 fatty acids in triglyceride form, along with substantial long-chain monounsaturated fatty acids (MUFAs). It also features natural isomeric forms of astaxanthin, a nutritional carotenoid, which gives the oil a brilliant red color. As part of our efforts in developing value added products from waste streams of the seafood processing industry, we present in this paper a comprehensive characterization of the triacylglycerols (TAGs) and astaxanthin esters that predominate in the shrimp oil by using HPLC-HRMS and MS/MS, as well as 13C-NMR. This approach, in combination with FAME analysis, offers direct characterization of fatty acid molecules in their intact forms, including the distribution of regioisomers in TAGs. The information is important for the standardization and quality control, as well as for differentiation of composition features of shrimp oil, which could be sold as an ingredient in health supplements and functional foods.

Fluorescence in rhoda- and iridacyclopentadienes neglecting the spin-orbit coupling of the heavy atom: the ligand dominates.

We present a detailed photophysical study and theoretical analysis of 2,5-bis(arylethynyl)rhodacyclopenta-2,4-dienes (1a­c and 2a­c) and a 2,5-bis(arylethynyl)iridacyclopenta-2,4-diene (3). Despite the presence of heavy atoms, these systems display unusually intense fluorescence from the S1 excited state and no phosphorescence from T1. The S1 → T1 intersystem crossing (ISC) is remarkably slow with a rate constant of 108 s­1 (i.e., on the nanosecond time scale). Traditionally, for organometallic systems bearing 4d or 5d metals, ISC is 2­3 orders of magnitude faster. Emission lifetime measurements suggest that the title compounds undergo S1 → T1 interconversion mainly via a thermally activated ISC channel above 233 K. The associated experimental activation energy is found to be ΔHISC = 28 kJ mol­1 (2340 cm­1) for 1a, which is supported by density functional theory (DFT) and time-dependent DFT calculations [ΔHISC(calc.) = 11 kJ mol­1 (920 cm­1) for 1a-H]. However, below 233 K a second, temperature-independent ISC process via spin­orbit coupling occurs. The calculated lifetime for this S1 → T1 ISC process is 1.1 s, indicating that although this is the main path for triplet state formation upon photoexcitation in common organometallic luminophores, it plays a minor role in our Rh compounds. Thus, the organic π-chromophore ligand seems to neglect the presence of the heavy rhodium or iridium atom, winning control over the excited-state photophysical behavior. This is attributed to a large energy separation of the ligand-centered highest occupied molecular orbital (HOMO) and lowest unoccupied MO (LUMO) from the metal-centered orbitals. The lowest excited states S1 and T1 arise exclusively from a HOMO-to-LUMO transition. The weak metal participation and the cumulenic distortion of the T1 state associated with a large S1­T1 energy separation favor an "organic-like" photophysical behavior.

Synthesis of 2- and 2,7-functionalized pyrene derivatives: an application of selective C-H borylation.

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.

Aluminium complexes bearing functionalized trisamido ligands and their reactivity in the polymerization of epsilon-caprolactone and rac-lactide.

The addition of 1 and 2 equivalents of AlMe(3) to cis,cis-C(6)H(9)(NHCH(2)C(6)H(4)-o-R)(3) (R = PPh(2) (3) and SPh (4)) gives complexes [cis,cis-C(6)H(9)(NCH(2)C(6)H(4)-o-R-kappaN)(2)(NHCH(2)C(6)H(4)-o-R-kappaN)]AlMe (R = PPh(2) (7) and SPh (8)) and [cis,cis-C(6)H(9)(NCH(2)C(6)H(4)-o-R)(3)-kappa(5)mu(2)N]Al(2)Me(3) (R = PPh(2) (5) and SPh (6)), respectively. The bimetallic complexes are active in the polymerization of epsilon-caprolactone and rac-lactide whereas the monometallic complexes are not, although no cooperative behaviour is observed between the two aluminium atoms of 5 and 6. The polycaprolactone samples, which were characterized using (1)H NMR, MALDI-TOF, and SEC, show the presence of residual ligands 3 or 4 bound to the polymer and the in situ NMR studies confirm that the insertion occurs in an Al-N bond.

Synthesis and solid-state characterization of platinum complexes with hexadentate amino- and iminophosphine ligands.

Hexadentate ligands cis,cis-C(6)H(9)(N[double bond, length as m-dash]CHC(6)H(4)(PPh(2)))(3) () and cis,cis-C(6)H(9)(NHCH(2)C(6)H(4)(PPh(2)))(3) () were synthesized starting from cis,cis-1,3,5-triaminocyclohexane, and characterized using NMR spectroscopy and single-crystal X-ray diffraction. These ligands can bind both Pt(0) and Pt(II) metal centers using either or both of the soft phosphine moieties and the hard amine/imine moieties. In many cases the resulting complexes are negligibly soluble; hence, (31)P and (195)Pt solid-state NMR (SSNMR) spectroscopy was applied to analyse the bonding modes of the hexadentate ligands. The (195)Pt SSNMR spectroscopy of these complexes is particularly challenging, since (1)H-(195)Pt cross polarization is extremely inefficient, the (195)Pt longitudinal relaxation times are extremely long and the (195)Pt powder patterns are expected to be quite broad due to platinum chemical shift anisotropy. It is demonstrated that the ultra-wideline (195)Pt SSNMR spectra can be efficiently acquired with a combination of frequency-stepped piecewise acquisitions and cross-polarization/Carr-Purcell Meiboom-Gill (CP/CPMG) NMR experiments. The (195)Pt and (31)P SSNMR data are correlated to important structural features in both Pt(0) and Pt(II) species.

(η-Cyclo-octa-1,5-diene)diiodidoplatinum(II).

The monoclinic title complex, [PtI(2)(C(8)H(12))], characterized by a twisted cyclo-octa-diene ring, is similar to its Cl and Br ortho-rhom-bic homologues. The observed Pt-I bond distances of 2.6094 (5) and 2.6130 (5) Šare in the expected range for PtI(2) complexes. The C=C double bonds in the mol-ecule differ significantly [1.373 (10) and 1.403 (10) Å]. As expected for a platinum(II) complex, the Pt(II) atom is in a square-planar environment (ΣPt(α)= 359.71°).