Lecture 20. The d-Block Elements. VII-VIII B groups PhD. Halina Falfushynska

Manganese Manganese is obtained mainly from the mineral pyrolusite, MnO2. Ferromanganese alloys are wear resistant and shock resistant and are used for railroad tracks, bulldozers, and road scrapers. Manganese(IV) oxide is the starting point for making most other manganese compounds. Potassium permanganate, KMnO4, is an important oxidizing agent that is used in both analytical and organic chemistry laboratories, and in water treatment.

The Iron Triad: Fe, Co, and Ni Iron is the fourth most abundant element in Earth’s crust. Cobalt and nickel are not nearly as common. All three elements form 2+ and 3+ ions. The most common ions of Co and of Ni are the 2+. The most common ion of Fe is the 3+ due to the half-filled d-subshell:

Ferromagnetism The iron triad exhibits ferromagnetism which is a much stronger magnetic effect than paramagnetism. A ferromagnetic solid consists of regions called domains in which atoms have their magnetic moments aligned. When placed in a magnetic field, all the domains are aligned and the solid becomes magnetized.

Manganese Mn (Manganum) 22.4.2017 Manganese Mn (Manganum) trace element cofactor of enzymes: superoxide dismutase pyruvate carboxylase KMnO4 Potassium permanganate (INN: Kalii permanganas) - in water dissolves to give deep purple solutions - strong oxidizing agent - dilute solutions can act as desinfectant

Biological role of Manganese Manganese is required for the metabolism of proteins and fats.  A partial list of manganese-dependent enzyme families includes oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.  Manganese is involved in the function of numerous organ systems and is needed for normal immune function, regulation of blood sugars, production of cellular energy, reproduction, digestion, and bone growth.  Manganese works with vitamin K to support clotting of the blood.   The National Research Council has recommended an Estimated Safe and Adequate Daily Dietary Intake (ESADDI) for Mn of 2 to 5 mg per day for adults.

Manganese in pharmacy Manganese has been examined as a treatment for a variety of conditions, including osteoarthritis and wound healing. However, manganese is often used in combination with other vitamins and/or minerals. Therefore, the effects of manganese alone are difficult to determine. Manganese in combination with calcium and zinc may be beneficial in patients with chronic wounds. A combination of calcium and manganese may alleviate symptoms associated with premenstrual syndrome.

Source of manganese Excellent food sources of manganese include mustard greens, kale, chard, raspberries, pineapple, strawberries, romaine lettuce, collard greens, spinach, garlic, summer squash, grapes, turnip greens, eggplant, brown rice, blackstrap molasses, maple syrup, cloves, cinnamon, thyme, black pepper, and turmeric.

Fe in food 10-30 mg/day absorption: only 7-10%  ~ 1 mg/day 22.4.2017 Iron Fe (Ferrum) important microelement human body: 4–5 g Fe a) functional form - heme iron proteins hemoglobin 70 % myoglobin 5 % some enzymes - non-heme iron proteins b) tranport form (transferrin) c) storage of iron (ferritin, hemosiderin)-20 % Fe in food 10-30 mg/day absorption: only 7-10%  ~ 1 mg/day

HEME iron proteins Hemoglobin - O2 transport in blood 22.4.2017 HEME iron proteins Hemoglobin - O2 transport in blood - in red blood cells - tetramer = 4 subunits (each subunit: one heme + one globin) HbA ("adult") a2b2 HbF ("fetal") a2g2 Myoglobin - "O2 storage" in muscle cell Cytochromes - electron transport - their function is based on: Fe2+ (reduced) Fe3+ (oxidized) heme

iron–sulphur proteins (FeS proteins) 22.4.2017 Non-heme iron proteins FeII or FeIII bound to protein SH iron–sulphur proteins (FeS proteins) Transferrin - blood plasma protein ( b1 globulin ) - transport of Fe - 1 molecule of transferrin can carry 2 iron ions in form of Fe3+ Ferritin - intracellular iron storage protein (liver, bone marrow) - 1 ferritin complex can store about 4500 Fe3+ - ferritin without iron = apoferritin Hemosiderin - "damaged (Fe-overloaded) ferritin" - Fe from it is less available

OVERVIEW OF IRON METABOLISM 22.4.2017 OVERVIEW OF IRON METABOLISM liver FERRITIN HEMOSIDERIN blood plasma TRANSFERRIN bone marrow red blood cells HEMOGLOBIN spleen tissues CYTOCHROMES Fe-S proteins muscles MYOGLOBIN BLEEDING (Fe losses) FOOD

Iron metabolism = unique - reutilization ! (closed system) 22.4.2017 Iron metabolism = unique - reutilization ! (closed system) NO regulated excretion system for Fe ! Fe absorption must be "regulated" Loss of Fe  through loss of blood (females - mestrual bleeding) Iron deficiency - microcytic anemia "iron deficiency anemia" Iron overload - hemochromatosis = accumulation of iron in the body (depositions as hemosiderin) organ dysfunction (liver, heart, ...)

IRON ABSORPTION FOOD Fe3+ STOMACH Fe2+ Fe3+ BLOOD transferrin (Fe3+) 22.4.2017 IRON ABSORPTION FOOD Fe3+ STOMACH HCl pH 1-2 ascorbic acid gastroferrin - iron binding protein reduction Fe2+ Fe3+ BLOOD transferrin (Fe3+) ferritin (Fe3+) apoferritin Fe2+ INTESTINAL MUCOSA CELL

Measurement of Iron (Phenanthroline Method) Interferences : Phosphate Heavy metals 1,10 phenonthroline combines with Fe2+ to form complex ion orange in red color Color produced confirms Beer’s Law Visual Photometric comparison

Phenanthroline Method Sample exposed to atmospfere contains Fe2+ , Fe3+ , ppt of ferric hydroxide. All iron  must be in soluble form HCl is used Fe(OH)3 + 3 H+  Fe3+ + 3 H2O 1,10 phenonthroline  specific for measuring Fe(II) Fe3+ is reduced to Fe2+ Hydroxylamine is used as reducing agent 4Fe(III) + 2 NH2OH  4Fe(II) + N2O + H2O + 4 H+ 3 molecules of 1,10 phenantrhroline complex with each Fe2+

Manganese measurement Colorimetric method  depend upon oxidation of Mn to  VII forms highly colored permanganete ion Obeys Beer’s Law Visual or photometric comparison AAS ICP

Manganese measurement (Persulphate Method) Ammonium persulphate  oxidizing agent Cl- interference: Because of reducing action in acid medium. use Hg2+ for interference. HgCl2 complex is formed Ag2+ is used as catalyst Oxidation of Mn in lower valence to permanganete by persulfate. Ag+ 2Mn2++5S2O82- +8H2O  2MnO4- +10SO42- +16H+ (permanganete colored)