A series of metal-organic complexes which all contain two bridged
dimolybdenum cores were synthesized and studied. Common building blocks involved in
this series of syntheses include Mo2(DAniF)3(O2CCH3) (DAniF = N, N'-di-panisylformamidinate)
and [Mo2(cis-DAniF)2(NCCH3)4](BF4)2. Bridges that were used to
connect two different dimolybdenum cores in the synthesized structures include single
metal complexes like ZnCl2 and Ni(acac)2 (acac = acetyl acetone), dimetal complex like
Rh2(O2CCH3)4, as well as organic ligands like 1,2-dihydroxyl-4,5-dimethylaminbenzene
and 1,3-dihydroxyl-2,5-dimethylaminbenzene.
Several heterometallic supramolecules were obtained through self-assembly
reactions. In these structures, the two dimolybdenum cores were bridged through
different metal complexes; between these metal complexes and the molybdenum cores,
isonicotinic acid anion acts as the key linkage. Depending on the geometry of the
building blocks and their available binding site, these heterometallic supramolecules bear
a variety of shapes, which include rod-like molecules with three metal centers, a squareshaped
molecule with its four corners occupied by metal complexes, and also a zigzagshaped
infinite metal complex chain. Although these molecules do show reversible redox
peaks in electrochemistry studies, they demonstrated very poor electronic communication between the dimolybdenum centers. Possible explanations to this result may be that the
dimolybdenum cores are far away from each other in these molecules (Mo2–Mo2
separation in compound 4, being 21 Å, is the longest among all dimolybdenum pairs
synthesized to date) and that the calculated frontier orbital overlaps do not favor electron
delocalization over the entire molecule.
However, another type of molybdenum dimer of dimers where the
dimolybdenum centers are united by conjugated organic ligands, namely 1,2-dihydroxyl-
4,5-dimethylaminbenzene and 1,3-dihydroxyl-2,5-dimethylaminbenzene, were also
synthesized and found to bear significantly stronger electronic communication between
the Mo2 centers. In fact, as electrochemistry reveals, these molecules demonstrated the
greatest comproportionation constant values (Kc ~ 1014) than any other analogues
synthesized so far. This interesting result is most likely due to the well conjugated linker
ligands that would allow electrons on the metal centers to delocalize over the entire
molecule. Computational studies of these compounds also show clear evidence of π
overlapping in their molecular frontier orbitals.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1434 |
| Date | 15 May 2009 |
| Creators | Jin, Jiayi |
| Contributors | Fackler, John P., Murillo, Carlos A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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