Question

Read through the assigned reading, Lessons from Nature: A Bio-Inspired Approach to Molecular Design:

1. Describe the key design features that led to the development of the picket-fence porphyrin.

2. Give two examples of how hydrogen bonds effect the properties of metal complexes

Answer 1

1ANS :A model oxygen-binding porphyrin in which bulky side chains on one face of the ring permit binding of molecular oxygen while preventing oxidation of Fe2+, which is co-ordinated on the other face of the ring by an organic base.The synthesis of "picket fence" porphyrin derivatives bearing covalently attached axial bases is described. These porphyrins have been well characterized, primarily as the iron(II) complexes, meso-tri(α,α,α-o-pivalamidophenyl)-β-o-5-(N-imidazolyl) valeramidophenylporphyrinatoiron(II) and meso-tri(α,α,α-o-pivalamidophenyl)-β-o-4-(N-imidazolyl) butyramidophenylporphyrinatoiron(II), by UV/visible, MCD, 1H NMR, and Mössbauer spectroscopy, magnetic susceptibility, and elemental analysis. Preliminary results of carbon monoxide binding studies are reported.

2 ANS:properties of hydrigen bond is ,properties include its relatively high melting and boiling point temperatures, accounted for by the collection of intermolecular forces between water molecules. Thus the hydrogen bonds require a high input of energy in order to break the bonds between molecules.

The structures of molecular solids , have also been touched on in the section on intermolecular forces. These molecules are held to one another by hydrogen bonds, dispersion forces, and other dipolar forces in that order of decreasing importance and the molecules stack together in a pattern that minimizes their total energy.

Examples of such solids include ice, in which hydrogen bonding is of paramount importance, and polyethylene, in which dispersion forces are dominant. Unless hydrogen bonds are present (in which case molecular solids resemble ionic solids in brittleness), molecular solids are generally soft and have low melting points because the bonds between the molecules are easily overcome .