COORDINATION CHEMISTRY: RESEARCH FROM T.S. KURTIKYAN AND CO-AUTHORS YIELDS NEW DATA ON COORDINATION CHEMISTRY

Science Letter
September 23, 2008

According to a study from Yerevan, Armenia, "The formation of a
series of six-coordinate complexes (B)Co(TPP)(NO2) (B is ketone,
aldehyde, ether or epoxide; TPP is meso-tetraphenylporphyrin dianion)
on exposure of thin films of five-coordinate Co(TPP)(NO2) to vapors
of the O-donor ligands was established by IR and UV/Vis spectroscopy
(resorting to the data on isotope-substituted (NO2)-N-15)."

"The complex formation is accompanied by shifts of the vibration
frequencies of the trans-NO2 ligand and gives rise to new IR bands
corresponding to the O-donors in the nu(C=O) or nu(C-O) region
shifted with respect to these bands of free ligands. The complexes
are rather stable in the solid phase but eliminate the O-donor
ligand upon dissolution in an inert solvent (or upon maintenance
in a vacuum for some complexes) being converted into the initial
five-coordinate nitro complex," wrote T.S. Kurtikyan and colleagues
(see also Coordination Chemistry).

The researchers concluded: "Using the IR spectra of CCl4 solutions
of the complexes containing a large excess of O-donor molecules,
the equilibrium constants and the formation enthalpies of some
(B)Co(TPP)(NO2) complexes were determined, indicating weak coordination
of these ligands."

Kurtikyan and colleagues published the results of their research
in Russian Journal of Coordination Chemistry (Direct synthesis of
six-coordinate nitro complexes of cobalt meso-tetraphenylporphyrinate
with trans-O-donor ligands. Russian Journal of Coordination Chemistry,
2008;34(8):606-611).

For additional information, contact T.S. Kurtikyan, National Academy
Science Armenia, Center Invest Molecular Structural, Yerevan, Armenia.

The publisher of the Russian Journal of Coordination Chemistry can be
contacted at: Maik Nauka, Interperiodica, Springer, 233 Spring St.,
New York, NY 10013-1578, USA.

From: Emil Lazarian | Ararat NewsPress