Preface

Chapter 8 **Metal Oxide Polymer Nanocomposites in Water**

Francis Opoku, Ephraim M. Kiarii, Penny P. Govender and Messai

Chapter 9 **Nature, Sources, Resources, and Production of Thorium 201**

**Treatments 173**

Adenew Mamo

Miloš René

**VI** Contents

Metal ions play an important role in analytical chemistry, organometallic chemistry, bioinor‐ ganic chemistry, and materials chemistry. This book, *Descriptive Inorganic Chemistry Research‐ es of Metal Compounds*, collects research articles, review articles, and tutorial description about metal compounds. To perspective contemporary researches of inorganic chemistry widely, the kinds of metal elements (typical and transition metals including rare earth; p, d, f-blocks) and compounds (molecular coordination compounds, ionic solid materials, or nat‐ ural metalloenzyme) or simple substance (bulk, clusters, or alloys) to be focused are not lim‐ ited.

In undergraduate level lectures on inorganic chemistry, as shown below, descriptive facts are introduced in typical fashions with important viewpoints, e.g., periodic table, electron (some principles), abundance, simple substance, basic reactions, complexes in addition ap‐ plications or new topics, and so on. As you can notice, new developing researches provide and add more important information (applications or new topics) to inorganic chemistry, which will be written in this book.

For example, the 12 group elements (Zn, Cd, Hg, and Cn) are sometimes not classified into transition elements but classified into d-block elements. They are easy to be divalent cations like two group elements, which have filled d-shells as electron configuration of Zn and Zn2+ indicates:

> 30Zn: (1s)2 (2s)2 (2p)6 (3s)2 (3p)*<sup>6</sup>* (3d)*<sup>10</sup>*(4s)*<sup>2</sup>* (4p)*<sup>0</sup>* Zn2+: (1s)2 (2s)2 (2p)6 (3s)2 (3p)*<sup>6</sup>* (3d)10(4s)*<sup>0</sup>* (4p)*<sup>0</sup>*

Typical similarity of 2 and 12 group elements may be structures and properties of solutions, while differences are distortion due to filled d-shell (d10 configuration), which results in no color (no d-d transition), and diamagnetic and four-coordinated complexes afford sterically favored tetrahedral geometry.

Natural sphalerite (both zinc blend and wurtzite are ZnS) contains Zn, which coexists in ga‐ lena (PbS). Simple substance Zn can be dissolved by water (Zn2+(aq) + H2O → ZnH+ (aq) + H + ), acid, and base (Zn + 2OH- → ZnO2 2- + H2). ZnSO4.7H2O, ZnO (photocatalysts, pigments), ZnS (emitting phosphor, semiconductor), and ZnF2 (rutile-type crystal) are known common‐ ly. As Irving-Williams series Ni < Cu > Zn exhibits, formation constants of Zn2+ complexes are relatively small.

In many cases, properties of 3d metals are different from that of 4d and 5d ones. Naturally, isostructural replacement of Cd to Zn is found in minerals. Simple substance Cd can be dis‐ solved by acid and base, and Zn is more ionized than Cd (Zn + Cd2+ = Zn2+ + Cd E0 = +0.36V). CdO, CdS, and CdF2 (fluorite-type crystal) are known commonly, and Cd2+ reacts with water (2Cd2+(aq) + H2O = CdOH3+(aq) + H+ ).

Metal Hg is known as a sole liquid simple substance at room temperature or component of amalgam alloy, which is obtained by reduction of slightly soluble cinnabar HgS (solubility product = 10-54) or Hg2 2+ + 2OH- → Hg + HgO(s) + H2O and red HgO(s) → Hg(l) + 1/2 O2 ∆Hdiss = 90.4 kJmol-1. Hg(OH)2 is a weak acid (K=[Hg2+][OH- ] 2 / [Hg(OH)2] = 1.8 x 10-22), and salts are easy to be hydrolyzed (covalent HgCl2 + H2O = Hg(OH)Cl + H+ + Cl- , but only HgF2 is an ionic halide). Complexes afford two-coordinated linear or four-coordinated tetrahedral geometries ([Hg(CN)4] 2-). Because of Hg2+/Hg2 2+ equilibrium, disproportionation (Hg2 2+ = Hg + Hg2+, E0 = -0.131V; K = [Hg2+]/[Hg2 2+] = 6.0 x 10-3) can occur because of these redox poten‐ tials (Hg2 2+ + 2e- = 2Hg, E0 = 0.789V; 2Hg2+ + 2e- = 2Hg2 2+, E0 = 0.920V; Hg2+ + 2e- = Hg, E0 = 0.854V).

As for solid-state chemistry, magnetic moment of spinel in Fe oxides that is increased by doping of diamagnetic Zn2+ is a famous theme of students' experiments. Basically, spin ori‐ entation of solid-state magnetic oxides is paramagnetism (random), ferromagnetism (paral‐ lel), antiferromagnetism (antiparallel), and ferrimagnetism (antiparallel of strong and weak spins). Evaluating meff for inverse spinel ferrite Fe3O4 (per formula) is to be [Fe3+]tet[Fe2+,Fe3+]octO4, Fe3+(3d5 ) =5µBM, and Fe2+(3d6 ) =4µBM; therefore, (5+4)-5 = 4µBM. The rea‐ son why increasing magnetic moment after doping ZnFe2O4 in Fe3O4 is explained to be com‐ position Fe2+1-x+Zn2+xFe3+2O4, tetrahedral site: Fe3+1-x+Zn2+x, octahedral site: Fe3+1+x+Fe2+1-x, hence, [5µBM(1+x) + 4µΒΜ(1-x)]- 5µBM(1-x) = (4+6x)µΒΜ. As doped Zn2+ (x) increased, magnetic mo‐ ment is increased.

As for biochemical application, some Zn2+ complexes are used as fluorescence probes. Re‐ cently, Zn2+ ion has a wide range of different roles in immunity such as the second messen‐ ger in signal transduction. Zn2+ ion is an inhibited phosphatase PTEN, which enhances the phosphorylation of AKT by interleukin 2 (IL2). Therefore, went and put a stimulus to the cells in a state in which a certain amount of fluorescence by the addition of Zn2+ complex was out fluorescence disappears, and external field stimulation sex fluorescent probe has been sought as a medical research tool. This is either Zn2+ complex that has been made to work in the same way as zinc, range of applications will change depending on whether there is an inhibitory effect as of pyrithione.

> **Takashiro Akitsu** Department of Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
