donor atom

Examples of donor atom in the following topics:

• Reactions of Coordination Compounds

  • The atom within a ligand that is bonded to the central atom or ion is called the donor atom.
  • A typical complex is bound to several donor atoms, which can be same or different elements.
  • Polydentate (multiple bonded) ligands consist of several donor atoms, several of which are bound to the central atom or ion.
  • The central atoms or ion and the donor atoms comprise the first coordination sphere.
  • The EDTA molecule has six different donor atoms that form the complex.

• Hydrogen Bonding

  • A hydrogen bond is the electromagnetic attraction created between a partially positively charged hydrogen atom attached to a highly electronegative atom and another nearby electronegative atom.
  • A hydrogen atom attached to a relatively electronegative atom is a hydrogen bond donor.
  • In the molecule ethanol, there is one hydrogen atom bonded to an oxygen atom, which is very electronegative.
  • This hydrogen atom is a hydrogen bond donor.
  • Ethanol contains a hydrogen atom that is a hydrogen bond donor because it is bonded to an electronegative oxygen atom, which is very electronegative, so the hydrogen atom is slightly positive.

• Coordination Number, Ligands, and Geometries

  • In coordination chemistry, the coordination number is the number of ligands attached to the central ion (more specifically, the number of donor atoms).
  • Denticity refers to the number of times a ligand bonds to a metal through donor atoms.
  • Chelating ligands are commonly formed by linking donor groups via organic linkers.
  • Ambidentate ligands can attach to the central atom in two places but not both.
  • Geometry of atoms around central atoms with coordination numbers 3, 4, and 6.

• Naming Coordination Compounds

  • The atom within a ligand that is bonded to the central atom or ion is called the donor atom.
  • A typical complex is bound to several donor atoms, which can be the same or different.
  • Coordination refers to the coordinate covalent bonds (dipolar bonds) between the ligands and the central atom.
  • Write the name of the central atom/ion.
  • Here, the number of ions and atoms are the same.

• Biomolecules

  • These donor groups are often provided by side-chains on the amino acid residues.
  • Important donor groups include:
  • The peptide backbone also provides donor groups; these include deprotonated amides and the amide carbonyl oxygen centers (oxygen and nitrogen atoms as ligands).
  • In addition to donor groups that are provided by amino acid residues, a large number of organic cofactors function as ligands.
  • It consists of a zinc ion coordinated by three imidazole nitrogen atoms from three histidine units.

• Semiconductors

  • Doping atom usually have one more valence electron than one type of the host atoms.
  • For example, in III-V semiconductors such as gallium arsenide, silicon can be a donor when it substitutes for gallium or an acceptor when it replaces arsenic.
  • Some donors have fewer valence electrons than the host, such as alkali metals, which are donors in most solids.
  • Therefore the dopant atom can accept an electron from a neighboring atom's covalent bond to complete the fourth bond.
  • When the dopant atom accepts an electron, this causes the loss of half of one bond from the neighboring atom, resulting in the formation of a hole.

• Electron Affinity

  • Electron affinity is measured for atoms and molecules in the gaseous state only, since in the solid or liquid states their energy levels would be changed by contact with other atoms or molecules.
  • A molecule or atom that has a more positive electron affinity value is often called an electron acceptor; one with a less positive electron affinity is called an electron donor.
  • Atoms, such as Group 7 elements, whose anions are more stable than neutral atoms have a higher Eea.
  • For instance, within the same period, a Group-17 atom releases more energy than a Group-1 atom upon gaining an electron because the added electron creates a filled valence shell and therefore is more stable.
  • However, this trend applies only to Group-1 atoms.

• Comparison between Covalent and Ionic Compounds

  • Covalent bonds are characterized by the sharing of electrons between two or more atoms.
  • Ionic bonding occurs when there is a large difference in electronegativity between two atoms.
  • This large difference leads to the loss of an electron from the less electronegative atom and the gain of that electron by the more electronegative atom, resulting in two ions.
  • Ionic bonding occurs between a nonmetal, which acts as an electron acceptor, and a metal, which acts as an electron donor.
  • The transfer of an electron from a neutral sodium atom to a neutral fluorine atom creates two oppositely charge ions: Na+ and F-.

• Chelating Agents

  • Chelating agents are ligands for metals that bind via multiple atoms, thus taking up several coordination sites on the metal.
  • Chelate complexes are contrasted with coordination complexes composed of monodentate ligands, which form only one bond with the central atom.
  • Chelating agents, unlike the other ligands in coordination compounds, bind via multiple atoms in the ligand molecule, not just one.
  • In (2), the two monodentate methylamine ligands of approximately the same donor power (the enthalpy of formation of Cu—N bonds is approximately the same in the two reactions) forms a complex.
  • Ethylenediamine serves as a chelating agent by binding via its two nitrogen atoms.

• Hydrogen Bonding

  • Hydrogen forms polar covalent bonds to more electronegative atoms such as oxygen, and because a hydrogen atom is quite small, the positive end of the bond dipole (the hydrogen) can approach neighboring nucleophilic or basic sites more closely than can other polar bonds.
  • The molecule providing a polar hydrogen for a hydrogen bond is called a donor.
  • Water and alcohols may serve as both donors and acceptors, whereas ethers, aldehydes, ketones and esters can function only as acceptors.
  • Similarly, primary and secondary amines are both donors and acceptors, but tertiary amines function only as acceptors.