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Atom Config Electrons H 1s 1 1 He 1s 2 2 Li 1s 2 2s 1 3 Be 1s 2 2s 2 4 B 1s 2 2s 2 2p 1 5 C 1s

Atom Config Electrons H 1s 1 1 He 1s 2 2 Li 1s 2 2s 1 3 Be 1s 2 2s 2 4 B 1s 2 2s 2 2p 1 5 C 1s 2 2s 2 2p 2 6 N 1s 2 2s 2 2p 3 7 O 1s 2 2s 2 2p 4 8 F 1s 2 2s 2 2p 5 9 Ne 1s 2 2s 2 2p 6 10. n = 1. n = 2. n = 3. Na 1s 2 2s 2 2p 6 3s 1 11

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Atom Config Electrons H 1s 1 1 He 1s 2 2 Li 1s 2 2s 1 3 Be 1s 2 2s 2 4 B 1s 2 2s 2 2p 1 5 C 1s

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  1. Atom Config Electrons H 1s1 1 He 1s2 2 Li 1s22s1 3 Be 1s22s2 4 B 1s22s22p15 C 1s22s22p26 N 1s22s22p3 7 O 1s22s22p4 8 F 1s22s22p5 9 Ne 1s22s22p610 n = 1 n = 2

  2. n = 3 Na 1s22s22p63s1 11 Mg 1s22s22p63s2 12 Al 1s22s22p63s23p1 13 Si 1s22s22p63s23p2 14 P 1s22s22p63s23p3 15 S 1s22s22p63s23p4 16 Cl 1s22s22p63s23p5 17 Ar 1s22s22p63s23p6 18 K 1s22s22p63s23p63d04s1 19 Ca 1s22s22p63s23p63d04s2 20 Sc 1s22s22p63s23p63d14s2 21 Ti 1s22s22p63s23p63d24s2 22 V 1s22s22p63s23p63d34s2 23 Cr 1s22s22p63s23p63d54s1 24 Mn 1s22s22p63s23p63d54s2 25 Fe 1s22s22p63s23p63d64s2 26 Co 1s22s22p63s23p63d74s2 27 Ni 1s22s22p63s23p63d84s2 28 Cu 1s22s22p63s23p63d104s1 29 Zn 1s22s22p63s23p63d104s2 30

  3. 3d metals (8 First transition series metals constitute the bulk of essential microminerals to life)

  4. Definition: What is a transition element? An element in the periodic table characterized by having partially filled d orbitals, created by having the adjoining s orbitals filled before the d. Properties: The 3d orbitals are split by ligands resulting in orbitals with higher and lower energy states that supersede the 5 degenerate orbitals. Characterized by Multi-valence states Importance: Resulting complexes take on specific geometrical shapes that relate to binding, color formation, and functionality

  5. Important Definitions Ligand: (Lat: that which ties) A ligand is a charged or neutral molecule that binds to a metal through either coordinate covalent or ionic bonds. Water is a neutral ligand, CN is a charged ligand. Chelator: (Lat. Claw) A chelator is an organic compound that is capable of wrapping around a metal in multiple bonds thus competing with other molecules (e.g., proteins, nucleic acids) for the metal. Multidentate: ( Lat: dentate, teeth) Referring to a molecule that has multiple binding groups within the same chain capable of forming multiple bonds with the metal ion, e.g., bidentate (2) tridentate (3) etc. Orbital Splitting: A process by which d orbitals are split into high and low energy levels in response to the binding of a ligand. Coordination Number: Referring to the number of ligands that attach Coordinate covalent: A type of bond created when a ligand provides the pair of bonding electrons (Lewis base) to share with the metal.

  6. O O C  C O O . . . . . . . . Multi-dentate Ligands CH2-CH2 Oxalate NH2 H2N Co3+ Cu2+ Ethylene diamine O O C - C O O CH2-CH2 OOC COO N N COO OOC Ethylenediamine tetraacetic acid (EDTA)

  7. 3d orbitals Z Z Z Z Z Y Y X X X Y dxz dxy dyz X Y X d Y d Z2 X2-Y2

  8. Octahedral Complex

  9. 3 of most common complexes with metal ions are: Octahedral (most common) An 8 sided figure featuring 6 ligands, 4 in one plane and two above and below the plane. Square planar A 4 sided figure with 4 ligands all in the same plane Tetrahedral 4 ligands vectorially positioned to have minimum interaction

  10. Transition metals that form octahedral complexes Fe Ni Cr Co Mn Zn

  11. Transition metals that form tetrahedral complexes Zn Cu Co Transition metals that form square planar and 5-coordination complexes Cu Zn Cu

  12. Orbital splitting Insights into the properties of ligands Take Home: By altering the energy state of electrons in a metal ion, ligands are capable of determining valence, reactivity, and even the color of the complex

  13. 3d Orbitals dx2-y2 dz2

  14. Octahedral Iron Fe forms an octahedral (8 sided figure, six ligands) complex by having its 5, 3d orbitals split into two 2 new orbitals, eg and t2g. eg Before splitting x2-y2 z2 o Energy difference xz yz x2-y2 z2 xy t2g xy xz yz After splitting

  15. [Ar]3d2 [Ar]3d1 [Ar]4s23d2 Ti(II) = Ti(III) = Ti = Ti3+ Ti2+ hv x2-y2 z2 x2-y2 z2 Ti(III) One 3d xy xz yz xy xz yz Ground state Excited state L t12g e1g L L Ti L L L

  16. Feo [Ar]4s23d6 Ionizes (loses 4s2 electrons to form Fe2+) Fe2+ [Ar]3d6 CN- as a ligand (water as a ligand) [Fe(CN)6]4- [Fe(H2O)6]2+ Fe(II) x2-y2 z2 x2-y2 z2 xy xz yz xy xz yz t62g t42ge2g Low Spin (Highly energetic) Diamagnetic High Spin (Low energetic) Paramagnetic

  17. V [Ar]4s23d3 No low spin possible V(II) Cr [Ar]4s13d5 Cr(II) Mn [Ar]4s23d5 Mn(II) Low Spin High Spin

  18. Fe [Ar]4s23d6 Fe(II) Co [Ar]4s23d7 Co(II) Ni [Ar]4s23d8 No low spin possible Ni(II)

  19. Cu [Ar]4s13d10 No low spin possible Cu(I) Cu [Ar]4s13d9 No low spin possible Cu(II) Zn [Ar]4s23d10 No low spin possible Zn(II)

  20. Class Exercise: Draw the electronic configuration of octahedral [Zn(H2O)6]2+ and predict the color. Zn is [Ar]4s23d10 Solution Upon ionization, Zn loses its 2, 4s electrons and becomes 3d10 x2-y2 z2 All orbitals are filled, no color is possible xy xz yz

  21. Common Ligands Ligand Name Name as ligand F- Fluoride Fluoro Cl- Chloride Chloro Br- Bromide Bromo I- Iodide Iodo CN- Cyanide Cyano NCS- Isothiocyanate Isothiocyanato SCN- Thiocyanate Thiocyanato OH- Hydroxide Hydroxo O2- Oxide Oxo ONO- Nitrite Nitro CO Carbon monoxide Carbonyl H2O Water Aqua NH3 Ammonia Ammine Underline indicates atom bonded to metal

  22. Ligand Strength and Numbers as a determinant Rule: Ligands differ in the strength of their orbital splitting. The following has been determined experimentally Cl < F- < H2O < NH3 < NO2- < CN- < CO Rule: Low spin complexes are created by ligands with strong orbital splitting properties Rule: Octahedral complexes that have 3, 4, 5, or 6 electrons in the t2g orbital tend to be very stable (inert). All others are labile.

  23. Biological Relevance

  24. Myoglobin Heme group O=O Interfere Spherical- 90% -helix

  25. A linear carbon monoxide can bind with less interference C O Ferrous (Fe(II) Histidine F8 His E7 O2 binding to Heme O2 binds above the ring plane Histidine binds below the plane of the ring Only Fe(II) will bind O2

  26. COLOR

  27. garnet aquamarine ruby amethyst topaz kyanite

  28. Red Blood vs Blue Blood O2 binding to the heme ring of hemoglobin is coordinated to iron (II). When O2 is bound to one of the coordinates, Fe(II) is in a low spin (high energy) state and the light emitted is a red. Without O2 the iron binds water resulting in high spin (low energy) and takes on a bluish color.  red  blue Hmb 4O2 red (low spin) Hmb blue (high spin) + 4O2 Arterial blood Venous blood

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