Biological evaluation of organometallic palladium(II) complexes containing 4‐hydroxybenzoic acid (3‐ethoxy‐2‐hydroxybenzylidene)hydrazide: Synthesis,structure, DNA/protein binding,antioxidant activity and cytotoxicity

New palladium(II) complexes, [Pd(PPh₃)L] ( 2 ) and [Pd(AsPh₃)L] ( 3 ), were synthesized using 4‐hydroxybenzoic acid (3‐ethoxy‐2‐hydroxybenzylidene)hydrazide ( 1 ) ligand (H₂L), and characterized using various physicochemical techniques. The molecular structures of 2 and 3 were determined using single‐crystal X‐ray diffraction, which reveals a square planar geometry around the palladium(II) metal ion. In vitro DNA binding studies were conducted using UV–visible absorption spectroscopy, emission spectroscopy, cyclic voltammetry and viscosity measurements, which suggest that the metal complexes act as efficient DNA binders. The interaction of ligand H₂L and complexes 2 and 3 with bovine serum albumin (BSA) was investigated using UV–visible and fluorescence spectroscopies. Absorption and emission spectral studies indicate that complexes 2 and 3 interact with BSA protein more strongly than the parent ligand. The free radical scavenging potential of all the synthesised compounds ( 1 – 3 ) was also investigated under in vitro conditions. In addition, the in vitro cytotoxicity of the complexes to tumour cells lines (HeLa and MCF‐7) was examined using the MTT assay method.     

One barbiturate and two solvated thiobarbiturates containing the triply hydrogen‐bonded ADA/DAD synthon,plus one ansolvate and three solvates of their coformer 2,4‐diaminopyrimidine

A path to new synthons for application in crystal engineering is the replacement of a strong hydrogen‐bond acceptor, like a C=O group, with a weaker acceptor, like a C=S group, in doubly or triply hydrogen‐bonded synthons. For instance, if the C=O group at the 2‐position of barbituric acid is changed into a C=S group, 2‐thiobarbituric acid is obtained. Each of the compounds comprises two ADA hydrogen‐bonding sites (D = donor and A = acceptor). We report the results of cocrystallization experiments of barbituric acid and 2‐thiobarbituric acid, respectively, with 2,4‐diaminopyrimidine, which contains a complementary DAD hydrogen‐bonding site and is therefore capable of forming an ADA/DAD synthon with barbituric acid and 2‐thiobarbituric acid. In addition, pure 2,4‐diaminopyrimidine was crystallized in order to study its preferred hydrogen‐bonding motifs. The experiments yielded one ansolvate of 2,4‐diaminopyrimidine (pyrimidine‐2,4‐diamine, DAPY), C₄H₆N₄, (I), three solvates of DAPY, namely 2,4‐diaminopyrimidine–1,4‐dioxane (2/1), 2C₄H₆N₄·C₄H₈O₂, (II), 2,4‐diaminopyrimidine–N,N‐dimethylacetamide (1/1), C₄H₆N₄·C₄H₉NO, (III), and 2,4‐diaminopyrimidine–1‐methylpyrrolidin‐2‐one (1/1), C₄H₆N₄·C₅H₉NO, (IV), one salt of barbituric acid, viz. 2,4‐diaminopyrimidinium barbiturate (barbiturate is 2,4,6‐trioxopyrimidin‐5‐ide), C₄H₇N₄⁺·C₄H₃N₂O₃⁻, (V), and two solvated salts of 2‐thiobarbituric acid, viz. 2,4‐diaminopyrimidinium 2‐thiobarbiturate–N,N‐dimethylformamide (1/2) (2‐thiobarbiturate is 4,6‐dioxo‐2‐sulfanylidenepyrimidin‐5‐ide), C₄H₇N₄⁺·C₄H₃N₂O₂S⁻·2C₃H₇NO, (VI), and 2,4‐diaminopyrimidinium 2‐thiobarbiturate–N,N‐dimethylacetamide (1/2), C₄H₇N₄⁺·C₄H₃N₂O₂S⁻·2C₄H₉NO, (VII). The ADA/DAD synthon was succesfully formed in the salt of barbituric acid, i.e. (V), as well as in the salts of 2‐thiobarbituric acid, i.e. (VI) and (VII). In the crystal structures of 2,4‐diaminopyrimidine, i.e. (I)–(IV), R₂²(8) N—H…N hydrogen‐bond motifs are preferred and, in two structures, additional R₃²(8) patterns were observed.     

Influence of methyl‐modified silyl groups on the properties of polymers and Si/B/N/C ceramics derived from N‐silylated borazine derivatives

Thermal silazane cleavage of dichloroboryldisilylamines (SiCl_mMe_3?m)N(SiMe₃)(BCl₂) (1: m = 1; 2: m = 2) at 196 °C leads to the borazine derivates [(SiCl_mMe_3?m)NB(Cl_nMe_1?n)]₃ (3: m = 1, n = 0.185; 4: m = 2, n = 0.111) characterized by NMR and IR spectroscopy and mass spectrometry. Single‐crystal X‐ray diffraction structure analyses reveal (BN)₃ units with unusual twisted boat conformations in both compounds. Additionally, more detailed studies are done to clear up the function of the by‐products (SiCl_mMe_3?m)N(SiClMe₂)(BClMe) formed during the cyclization step leading to asymmetrically boron substituted borazine derivatives. The single‐source precursors 3 and 4 were cross‐linked with methylamine producing polymers 3P and 4P, which were transformed into black amorphous materials with ceramic yields of 20.8 % and 50.3 %, respectively. Ceramic 4C (Si_1.00B_0.98 N_2.55 C_1.37O_0.05) was further investigated by ¹¹B and ²⁹Si magic angle spinning (MAS) NMR spectroscopy. A combined study of high‐temperature TG analyses and X‐ray powder diffraction analyses confirms the thermal stability of 4C up to 1670 °C. Copyright © 2012 John Wiley & Sons, Ltd.     

Crystal structure of meso‐substituted pyrazolyl porphyrin complexes and their highly active catalyst for oxidation of alkylbenzenes

During the past few years, a great deal of effort has been devoted to the anchoring of catalytic oxidation. In this work, three new catalysts CuPp, MnPp and ZnPp by solvothermal methods with 5, 10, 15, 20‐tetrakis(4‐N‐pyrazolyl)‐phenyl porphyrin (H₂Pp) and the corresponding metal salts have been synthesized and structurally characterized. The single crystal structures determined by X‐ray diffraction show the bond distances of M‐N in porphyrin cores determined the conformation of porphyrin rings. We explored the catalytic activity of CoPp, CuPp, MnPp and ZnPp for oxidation of alkylbenzenes. The experimental results display these products exhibit high catalytic activities and selectivities for oxidation of ethylbenzene to acetophenone, and can be reused by filtration without appreciable decrease in catalytic activity and selectivity.     

Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3-20 μm by the Ni 70 Mn 25 Co 5 alloy infiltration technique at high temperature and high pressure (HPHT).The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD).Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa,which increase with th...     

Synthesis and mesomorphism of ionic self-assembled complexes of anthraquinones

Anthraquinones are known to exhibit mesomorphism upon appropriate substitutions. In this report, the concept of ionic self-assembly has been applied to design and synthesise new anthraquinone-based liquid crystals. Four different anthraquinones were used as polyelectrolytes which form ionic complexes with double-tail ammonium surfactants. The chemical structures were characterised by spectral techniques and elemental analysis. The thermal behaviour of the complexes was investigated by polarising optical microscopy, differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction studies. All these complexes display lamellar mesomorphism. The amphotropic nature of the complexes has also been studied.     

A Pd4Br4 macrocycle trapped by cocrystallization from a highly dynamic equilibrium of η3‐cycloheptatrienide complexes

In the coordination chemistry of palladium, dimers bridged via halides are a common motif. Higher oligomers, however, are still rare. We report the structure of an alternating eight‐membered [Pd₄Br₄]⁴⁻ ring framed by cycloheptatrienide ligands, which was obtained by cocrystallization of dimers and tetramers of the complex salt bromido{η³‐[3‐(2,6‐diisopropylphenyl)imidazolium‐1‐yl]cycloheptatrienido}palladium(II) tetrafluoroborate, namely bis[di‐μ‐bromido‐bis({η³‐[3‐(2,6‐diisopropylphenyl)imidazolium‐1‐yl]cycloheptatrienido}palladium(II))] cyclo‐tetra‐μ‐bromido‐tetrakis({η³‐[3‐(2,6‐diisopropylphenyl)imidazolium‐1‐yl]cycloheptatrienido}palladium(II)) octakis(tetrafluoroborate) dichloromethane octasolvate, [Pd₄Br₄(C₂₂H₂₆N₂)₄][Pd₂Br₂(C₂₂H₂₆N₂)₂]₂(BF₄)₈·8CH₂Cl₂. These dimers and tetramers form a highly dynamic equilibrium in solution which was studied by low‐temperature NMR spectroscopy. In the light of the presented results, tetrameric Pd^II species can be assumed to co‐exist as a second species in many cases where by current knowledge only a dimeric compound would be expected.     

A Fast Electrochemical Quartz Crystal Microbalance,which Acquires Frequency and Bandwidth on Multiple Overtones

An electrochemical quartz crystal microbalance (EQCM) is described, which measures the shifts of frequency and bandwidth on multiple harmonics with a time‐resolution of 10 milliseconds. The technique requires the process under study to be repetitive. Examples are square wave amperometry and cyclovoltammetry. Data acquisition is fast because the raw data consist of traces of the electrical admittance at fixed frequencies . A few (∼10) such time traces are acquired sequentially at a set of frequencies evenly spaced around the crystal's resonance. Since all time‐traces are triggered by the same repetitive process, plots of the conductance G (ω_i , t ) and the susceptance B (ω_i , t ) from constant time delays, t , versus frequency can be produced a posteriori. The shifts, ΔG (ω_i ) and ΔB (ω_i ) quantify a difference between two resonance curves, pertaining to the sample's reference state and the state at time t . Fitting a difference of two resonance curves to these data, one obtains shifts of frequency, Δf (t ) and shifts of bandwidth, ΔΓ(t ), versus time. This procedure is repeated for the different overtones. Given the repetitive nature of the process, one may accumulate and average, which lowers the noise down to a few tens of mHz. The capabilities of this instrument are demonstrated with two examples, which are copper deposition/dissolution and electro‐responsivity of a polymer film containing weakly acidic side groups.     

The Cambridge Structural Database in Retrospect and Prospect

The Cambridge Crystallographic Data Centre (CCDC) was established in 1965 to record numerical, chemical and bibliographic data relating to published organic and metal–organic crystal structures. The Cambridge Structural Database (CSD) now stores data for nearly 700 000 structures and is a comprehensive and fully retrospective historical archive of small‐molecule crystallography. Nearly 40 000 new structures are added each year. As X‐ray crystallography celebrates its centenary as a subject, and the CCDC approaches its own 50th year, this article traces the origins of the CCDC as a publicly funded organization and its onward development into a self‐financing charitable institution. Principally, however, we describe the growth of the CSD and its extensive associated software system, and summarize its impact and value as a basis for research in structural chemistry, materials science and the life sciences, including drug discovery and drug development. Finally, the article considers the CCDC’s funding model in relation to open access and open data paradigms.