Importance of the field: Metal oxide nanoparticles, including zinc oxide, are versatile platforms for biomedical applications and therapeutic intervention. There is an urgent need to develop new classes of anticancer agents, and recent studies demonstrate that ZnO nanomaterials hold considerable promise.Areas covered in this review: This review analyzes the biomedical applications of metal oxide and ZnO nanomaterials under development at the experimental, preclinical and clinical levels. A discussion regarding the advantages, approaches and limitations surrounding the use of metal oxide nanoparticles for cancer applications and drug delivery is presented. The scope of this article is focused on ZnO, and other metal oxide nanomaterial systems, and their proposed mechanisms of cytotoxic action, as well as current approaches to improve their targeting and cytotoxicity against cancer cells.What the reader will gain: This review aims to give an overview of ZnO nanomaterials in biomedical applications.Take home...

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Zinc oxide nanoparticles for selective destruction of tumor cells and potential for drug delivery applications.

Hybrid organic–inorganic perovskites (HOIPs) can have a diverse range of compositions including halides, azides, formates, dicyanamides, cyanides and dicyanometallates. These materials have several common features, including their classical ABX3 perovskite architecture and the presence of organic amine cations that occupy the A-sites. Current research in HOIPs tends to focus on metal halide HOIPs, which show promise for use in solar cells and optoelectronic devices; however, the other subclasses also exhibit a diverse range of physical properties. In this Review, we summarize the chemical variability and structural diversity of all known HOIP subclasses. We also present a comprehensive account of their intriguing physical properties, including photovoltaic and optoelectronic properties, dielectricity, magnetism, ferroelectricity, ferroelasticity and multiferroicity. Moreover, we discuss the current challenges and future opportunities in this exciting field. Hybrid organic–inorganic perovskites (HOIPs) comprise a diverse range of chemical compositions from halides and azides to formates, dicyanamides, cyanides and dicyanometallates. In this Review, advances in the synthesis, structures and properties of all HOIP subclasses are summarized and their future opportunities are discussed.

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Chemically diverse and multifunctional hybrid organic–inorganic perovskites

Mononuclear, oligonuclear and polynuclear metal coordination compounds with 1,2,4-triazole derivatives as ligands

Palladium-catalyzed bond-forming processes (e.g., C-C, C-X, C-Y; X ) F; Y ) NR2, OR, SR, etc.) represent essential tools for the synthetic chemist. A fascinating myriad of adventurous and unique Pd-catalyzed transformations are routinely found as key steps in target-oriented syntheses, affording complex natural products, functional advanced materials, fluorescent compounds, pharmaceutical lead compounds, and other high-value commercial products. Innovative Pd catalyst design, the identification of new synthetic methodologies, and the acquirement of detailed mechanistic insight, spanning both homogeneous and heterogeneous fields, underpin the numerous developments seen in this area over the past 40 years. Most commonly, Pd-catalyzed bond-forming processes involve Pd0/PdII complexes as intermediates. In recent times, the involvement of PdIV complexes have been implicated in many new synthetic methodologies, for which important advances have been made in the last 5 years or so. While observing the emergence of catalytic PdIV chemistry, particularly in organic synthesis, we identified the need to comprehensively review this area, which draws on aspects from both inorganic (organometallic) and organic chemistry fields. The historical background to organopalladium(IV) chemistry is therefore detailed. We have selected a wide range of diverse transformations where PdIV complexes are believed to act as key intermediates. It is clear that catalytic reaction manifolds involving PdIV intermediates offer new * Corresponding author. E-mail: ijsf1@york.ac.uk. Telephone: +44 (0)1904 434091. Fax: +44 (0)1904 432516. Chem. Rev. 2010, 110, 824–889 824

Emergence of palladium(IV) chemistry in synthesis and catalysis.

Supercapacitors are energy-storage and power-supply devices that are developed to meet the increasing demand for applications in powering vehicles and portable electronic devices. Supercapacitive energy storage operates on electric double layers by accumulation of charges at the electrode/ electrolyte interfaces, at which the stored energy is proportional to the capacitance of the electrodes. Therefore, a breakthrough in electrode materials holds promise for fundamental advances in supercapacitor materials. As electrode materials, activated carbon has been intensively studied with capacitances up to 270 Fg . Recently, nanostructured carbon materials such as templated carbon materials, graphenes, carbon nanotubes, aerogels, and heteroatom-hybridized carbon materials have been developed with the aim to improve the performance and exhibit capacitances of 50– 370 Fg . Despite the extensive efforts in synthesis, the rational design of supercapacitive electrodes that meet large capacitance, high energy density, and outstanding stability remains a substantial challenge. p-Conjugated microporous polymers (CMPs) are a class of porous frameworks consisting of an extended p-conjugated system and inherent nanopores. As high surface-area porous materials, CMPs emerge as a new medium for gas adsorption and have been developed as a new type of nanoreactors and heterogeneous catalysts upon the integration of catalytic sites into the skeletons. The extended pconjugated system endows CMPs with noteworthy lightemitting properties and allows the construction of lightharvesting antennae that trigger efficient, rapid, and vectorial energy funneling from the skeleton to entrapped acceptors. From a synthetic point of view, CMPs are unique because they allow the elaborate control of both skeletons and pores. In this context, a promising way to the exploration of CMPs is to combine the structural advantages of a p-conjugated system and inherent pores. Herein, we report the synthesis of such co-operative porous frameworks based on aza-fused CMPs (Scheme 1, Aza-CMPs) and highlight their functions in supercapacitive energy storage and electric power supply.

Supercapacitive Energy Storage and Electric Power Supply Using an Aza‐Fused π‐Conjugated Microporous Framework

The antiferroelectric phase transition of a metal–organic perovskite with a dimethylammonium cation, [(CH3)2NH2][Zn(HCOO)3], at Tc = 156 K was investigated using 1H nuclear magnetic resonance spectroscopy. The temperature dependence of the spin–lattice relaxation time, T1, was measured to elucidate the methyl group reorientation and cation reorientation. The proton–proton distance of NH2 protons was estimated to be 1.71 ± 0.03 A from line-shape measurements of the deuterated compound, [(CD3)2NH2][Zn(DCOO)3], and the cationic motion was shown to be the 120° reorientation of the dimethylammonium ion around the axis through the two carbon atoms of the cation. The activation energy for cationic motion was determined to be 23 kJ mol–1. The two methyl groups of the cation in the low-temperature antiferroelectric phase become nonequivalent and have activation energies of 8 and 10 kJ mol–1 for reorientation about the methyl group C3 axis. The phase transition was revealed to be first-order from line-shape measure...

Phase Transition and Cationic Motion in a Metal–Organic Perovskite, Dimethylammonium Zinc Formate [(CH3)2NH2][Zn(HCOO)3]

The temperature dependences of 1H spin-lattice relaxation times T1, at the Larmor frequencies of 10.5, 16.0, 20.0, and 45.5 MHz, and of 1H NMR second moments M2 were determined for (pyH)AuCl4 and (pyH)AuBr4, where pyH+ indicates a pyridinium ion. The small M2 data less than 1 G2 obtained above ca. 380 K indicated that the cations perform reorientational motion rapidly enough about its pseudohexad C′6 axis existing at the center of the cation and perpendicular to its plane. Below 140 K, both complexes yielded rigid lattice M2 values of the cation. It is interesting features for these complexes that motional narrowing for the NMR line occurs over an extremely wide range of temperature, the log T1, vs. T−1 plots are asymmetric about the 1H T1 minimum with a gentler gradient on the low temperature side, and the minima are extraordinarily long. These unusual results were interpreted by assuming the C′6 reorientation of the cations having electric dipoles among nonequivalent in-plane orientations. Three potential barriers to the C′6 reorientation were determined as 21.8, 17.2, and 13.5 kJ mol−1 for (pyH)AuCl4, and 22.2,17.4, and 13.7 kJ mol−1 for (pyH)AuBr4. The fade-out phenomenon of 3SCl NQR signals observed for (pyH)AuCl4 at ca. 230 K when the sample temperature was lowered is also discussed, by referring to the motion of the pyridinium cations.

1H NMR and 35Cl NQR Studies on the Motion of Pyridinium Ions in Crystalline Pyridinium Tetrachloro- and Tetrabromoaurate(III): (pyH)AuX4 (X = Cl, Br)

Protons involved in the H-bond system in 1,2-diazine–chloranilic acid (2 : 1) are assumed to be in jumping motion in the double-minimum potential corresponding to the two extreme electronic states of O–H⋯N and O−⋯H–N+. 14N nuclear quadrupole coupling constants were determined by 1H–14N nuclear quadrupole double resonance. Assuming that the observed coupling constants are result of a fast exchange of the two extreme electronic states, the coupling constants for each state were estimated by use of the equilibrium populations of the two extreme states determined from multi-temperature X-ray single-crystal diffraction. It was suggested that not only the population but also the electron distribution of the extreme electronic states itself changes with temperature.

Hydrogen bonding in 1,2-diazine–chloranilic acid (2 : 1) studied by a 14N nuclear quadrupole coupling tensor and multi-temperature X-ray diffraction

Phase transition and cationic motion in the perovskite formate framework [(CH3)2NH2][Mg(HCOO)3]

The crystal structures in two solid phases, i.e. phase II stable between 146 and 253 K and phase IV below 136 K, of the title compound [phenazine-chloranilic acid (1/1), C12H8N2 center dot C6H2Cl2O4, in phase II, and phenazinium hydrogen chloranilate, C12H9N2+center dot C6HCl2O4-, in phase IV], have been determined. Both phases crystallize in P2(1), and each structure was refined as an inversion twin. In phase II, the phenazine and chloranilic acid molecules are arranged alternately through two kinds of O-H center dot center dot center dot N hydrogen bonds. In phase IV, salt formation occurs by donation of one H atom from the chloranilic acid molecule to the phenazine molecule; the resulting monocation and monoanion are linked by N-H center dot center dot center dot O and O-H center dot center dot center dot N hydrogen bonds.

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Tetsuo Asaji

Papers

Phase Transition and Cationic Motion in a Metal–Organic Perovskite, Dimethylammonium Zinc Formate [(CH3)2NH2][Zn(HCOO)3]

1H NMR and 35Cl NQR Studies on the Motion of Pyridinium Ions in Crystalline Pyridinium Tetrachloro- and Tetrabromoaurate(III): (pyH)AuX4 (X = Cl, Br)

Hydrogen bonding in 1,2-diazine–chloranilic acid (2 : 1) studied by a 14N nuclear quadrupole coupling tensor and multi-temperature X-ray diffraction

Phase transition and cationic motion in the perovskite formate framework [(CH3)2NH2][Mg(HCOO)3]

Hydrogen bonding in two solid phases of phenazine-chloranilic acid (1/1) determined at 170 and 93 K