Compounds with two quadruply bonded Mo
24+ units, Mo
2(DAniF)
3 (DAniF =
N,
N '-di-
p-anisylformamidinate), linked by unsaturated dicarboxylate dianions of various lengths have been preparedand their spectroscopic and electrochemical properties studied. As identified by the dicarboxylate linkers,these compounds are maleate (
7), allene-1,3-dicarboxylate (
10),
cis,cis-muconate (
11),
trans,trans-muconate(
12), octa-2,4,6-
trans,trans,trans-hexatriene-1,8-
dioate (tamuate,
13), and deca-2,4,6,8-
trans,trans,trans,trans-octatetraene-1,10-
dioate (texate,
14). The latter three molecules complete the five-membered (all
trans) series [Mo
2(DAniF)
3](O
2C(CH=CH)
nCO
2)[Mo
2(DAniF)
3] (
n = 0-4). Several unsymmetrical paddlewheel compounds of the type Mo
2(DAniF)
3(O
2CX) (X = C
![](/images/entities/tbd1.gif)
CH (
3), CH=CH
2 (
4), (
E)-CH=CH-CH=CH
2(
5)) have also been prepared for comparison to the molecules in which there are linked Mo
2 units. Theprecursors [Mo
2(DAniF)
3(MeCN)
2](BPh
4), [
1]BPh
4, and Mo
2(DAniF)
3Cl(MeCN) (
2) have also been isolatedand characterized. The structures of all new molecules have been established by X-ray crystallography,including the methyl esters of various carboxylates used as ligands. All of the linked molecules have beenexamined by cyclic and differential pulse voltammetry, and
E1/2 values, the separation between successiveMo
24+/Mo
25+ oxidations, have been determined. Those compounds with highly unsaturated, fully conjugatedlinkers demonstrate electrochemical communication from end-to-end that is more persistent over distancethan is accounted for by an electrostatic interaction alone, implying that the
![](/images/gifchars/pi.gif)
system of these dicarboxylatelinkers is mediating communication. In the series [Mo
2(DAniF)
3](O
2C(CH=CH)
nCO
2)[Mo
2(DAniF)
3] (
n = 0-4),the first oxidation potential shifts progressively to less positive values due to an increasing contribution ofthe polyolefinic
![](/images/gifchars/alpha.gif)
,
![](/images/gifchars/omega.gif)
-dicarboxylate to the molecular orbital undergoing oxidation. This first oxidation potentialapproaches a limiting value of 63 mV (vs Ag/AgCl) as
n becomes infinitely long. Compound
11 can bephotoisomerized to
12 in a process that is affected by the presence of the Mo
24+ units, as the analogousrearrangement of dimethyl
cis,cis-muconate is faster.