Conjugated organometallic materials containing tungsten centers

Our group is interested in the optical and electronic properties of organometallic analogues of conjugated organic compounds. Specifically, in this thesis we will discuss the properties of complexes in which W≡C moieties replace C≡C fragments within the framework of oligo(phenyleneethynylenes) and a C4-polyyne.; A family of derivatives of the type Ph(C≡CC6H4 )m(L)4W≡C(C6H 4C≡C)nPh (m = 0, 1; n = 0, 1, 2) have been prepared and characterized by X-ray crystallography, electronic-absorption spectroscopy, and electrochemistry. This substitution has allowed us to directly compare the electronic and optical properties of these organometallic complexes with those of their organic analogues. We found that while these systems exhibit redox and spectroscopic properties similar to those of their organic counterparts they also exhibit new characteristics that are due to the incorporation of the metal center. The design of these compounds has also allowed us to address how the position of the metal within the backbone affects the electronic and optical properties of these compounds. We found that the position of the metal is important in controlling the electronic structure of the material, thus suggesting that the properties of these compounds can be further tuned by changing the position of the metal within the conjugated carbon chain.; In addition, we have appended sulfur and isocyanide functionalities to oligo(phenyleneethynylene) analogues. A family of compounds of the type Cl(dppe) 2W(≡CC6H4-4-(C≡CC6H 4)m-4'-R) (m = l, 2; R = N≡C, SCH2CH 2Si(CH3)3) have been prepared and characterized by electronic-absorption spectroscopy and electrochemistry. Differences between the sulfur and isocyanide functionalities are examined, along with the effects of extending conjugation along the arylidyne chain. Evidence that the sulfur-containing arylidyne complexes form self-assembled monolayers on Au and Pt electrodes is presented. In addition, the electron-transfer rates for the sulfur-containing compounds are compared to those of analogous oligo(phenyleneethynylenes) and rationalization for the observed differences is offered.; Lastly, we have used electrochemistry to assess the extent of communication between the redox orbitals in a series of ditungsten alkylidyne complexes. The basic layout of each compound remained constant throughout-symmetric bimetallic complexes connected by a bridging ligand---however, variations were introduced so that the affect of these on the electronic interactions between the two metals could be probed. Specifically complexes of the type XL4W≡CC 6H4-4-C≡WL4X, XL4W≡CC 6H4-3-C≡WL4X, and XL4W≡C-C≡WL 4X were investigated. We found that the position of the metal within the backbone was important and that the observed electrochemical differences could be understood based on molecular orbital considerations and electrostatic interactions.