Self-assembled Transition Metal Coordination Frameworks of ...

Chapter 4
4.3.3. Electronic spectral characteristics
The electronic spectra of all the compounds except 8, 13 and l4 were
recorded in DMF solution. The spectrum of 13 was taken in methanol solution and 14
in DMSO solution, while that of 8 in ethanol solution. The absorption bands with
extinction coefficients are listed in Table 4.3. Copper(H) complexes are known in a
wide
_y
variety of structures and the d9 configuration _leads to decrease from cubic
symmetries of environments around the Cu(H) ion and extensive Jahn Teller distortion
results to more splitting in energy levels compared to that in typical coordination
geometries. However, the expecting possibilities include tetragonal distorted
octahedral, square planar and distorted square based pyramidal geometries. The
dx. 2 orbital is the most common ground state, the d _, is quite common, and the
d U occurs occasionally for Cu(H) complexes. For the present series of complexes,
EPR studies are found very consistent with a d 2 , ground state. All the compounds
x -y­
have more than one Cu(H) center and the electronic spectra are often of little value in
structural assignment making difficult for identifying the geometry.
The electronic absorptions of carbohydrazone Cu(H) complexes (13 to 19)
differ considerably from thiocarbohydrazone Cu(H) complexes. The intense bands at
~2000O cm" of thiocarbohydrazone Cu(H) complexes mainly include S —>Cu charge
transfer transitions and possible 2 E I