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Related Concept Videos

Valence Bond Theory02:42

Valence Bond Theory

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Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
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Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
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For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.
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The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
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In most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH4. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl (Figure 1a). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a...
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Crystal Field Theory
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Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
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Unique Eu(II) Coordination Environments with a Janus Cryptand.

Guo-Xia Jin1,2, Matthew D Bailey2, Matthew J Allen2

  • 1College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Normal University , Jinan 250014, P. R. China.

Inorganic Chemistry
|August 23, 2016
PubMed
Summary
This summary is machine-generated.

Researchers synthesized novel Europium(II) cryptates featuring benzo groups, creating lopsided coordination environments. One complex shows the first direct observation of a bis-aquo Europium(II) cryptate with nonadjacent water molecules.

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Area of Science:

  • Coordination Chemistry
  • Supramolecular Chemistry
  • Lanthanide Chemistry

Background:

  • Cryptands are macrocyclic ligands that encapsulate metal ions.
  • Europium(II) complexes are of interest for their unique electronic and magnetic properties.
  • Functionalizing ligands can tune the properties of metal complexes.

Purpose of the Study:

  • To synthesize and characterize new Europium(II)-containing cryptates with benzo-functionalized ligands.
  • To investigate the structural and electronic consequences of introducing aromatic groups into the cryptand backbone.
  • To explore the formation of bis-aquo Europium(II) cryptates.

Main Methods:

  • Synthesis of novel nitrogenous cryptands and their Europium(II) complexes.
  • X-ray crystallography for solid-phase structural determination.
  • UV-visible absorption and emission spectroscopy in acetonitrile solution.

Main Results:

  • Two new Eu(II) cryptates were successfully prepared, exhibiting lopsided coordination environments due to benzo groups.
  • The first direct observation of a bis-aquo Eu(II) cryptate with two nonadjacent inner-sphere water molecules was achieved.
  • Spectroscopic studies revealed that decreased Lewis basicity of the aromatic face caused hypsochromic shifts in absorbance and emission.

Conclusions:

  • Benzo-functionalization of cryptands leads to asymmetric Eu(II) coordination spheres.
  • The novel bis-aquo Eu(II) cryptate provides new insights into lanthanide-water interactions.
  • Electronic properties of Eu(II) cryptates can be modulated by ligand design and Lewis basicity.