Studies of electronic communication between dimolybdenum cores joined by various bridges

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Title: Studies of electronic communication between dimolybdenum cores joined by various bridges
Author: Jin, Jiayi
Abstract: 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 ? , 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 ? overlapping in their molecular frontier orbitals .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1434
Date: 2009-05-15

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Studies of electronic communication between dimolybdenum cores joined by various bridges. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1434 .

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