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.

No description available.

A series of dimolybdenum compounds having a Mo2 4+ core coordinated by various ligands, including formamidinate (e.g. DAniF = N, NN-di-p-ansisylformamidinate ), acetate and/or acetonitrile molecules, have been synthesized as building blocks for the construction of Mo2-containing supramolecular arrays. Compound Mo2(DAniF)3(O2CCH3) was specifically designed for the preparation of dimolybdenum pairs, whereas the others meet the needs of Mo2 4+ units for different geometry settings. Compounds described by a general formula [Mo2]L[Mo2], where [Mo2] = [Mo2(DAniF)3]+, have two dimetal units electronically coupled by the central unit L , which consequently engender significant impact on the redox property and electronic structure of the molecule. It is found that in the weakly coupled complex system, [Mo2]M(OCH3)4[Mo2] (M = Zn and Co), the mixed-valence complexes present asymmetric molecular structures with two distinct [Mo2] units corresponding to be a bond order 4.0 (F2B4*2) and 3.5 (F2B4*1), respectively. EPR and magnetic susceptibility measurements for the doubly oxidized species show that there is no significant antifferromagnetic spin coupling. Electron delocalization occurs in the complex system where a N, N'-dimethyloxamidate binds two [Mo2] units within two fused six-membered rings. In this case, the mixed-valence complex has a symmetric molecular structure, implying that the odd electron is fully delocalized over two [Mo2]units. Strong metal-metal interaction is also evidenced by intervalence charge transfer of the mixed-valence species and the diamanetism of the doubly oxidized complex. Remarkably, two isomers varying in linkage conformation, namely, alpha and beta, have been isolated as diaryloxamidate ligands are used as the linker. Studies on the neutral and the oxidized compounds of the two isomers by employing various techniques consistently show that in the alpha form intramolecular electron transfer is blocked , while in the beta form, the electrons are delocalized over the two [Mo2] units. Thus, the mixed-valence complexes of the two isomers are appropriately described by alpha-[Mo2]0(oxamidate)[Mo2]1+ and beta- [Mo2]0.5+(oxamidate)[Mo2]0.5+ respectively.

No description available.

No description available.