Self-assembling properties of (arylimido)vanadium(V) compounds

Vanadium complexes derived from oxacalix[6]arenes: structural studies and use in the ring opening homo-/co-polymerization of ε-caprolactone/δ-valerolactone and ethylene polymerization

Oxacalix[6]arene vanadium complexes have been employed for the ROP of cyclic esters and ethylene polymerization.

Thirty years through vanadium chemistry

The relevance of vanadium in biological systems is known for many years and vanadium-based catalysts have important industrial applications, however, till the beginning of the 80s research on vanadium chemistry and biochemistry did not receive much attention from the scientific community. The understanding of the broad bioinorganic implications resulting from the similarities between phosphate and vanadate(V) and the discovery of vanadium dependent enzymes gave rise to an enormous increase in interest in the chemistry and biological relevance of vanadium. Thereupon the last 30years corresponded to a period of enormous research effort in these fields, as well as in medicinal applications of vanadium and in the development of catalysts for use in fine-chemical synthesis, some of these inspired by enzymatic active sites. Since the 80s my group in collaboration with others made contributions, described throughout this text, namely in the understanding of the speciation of vanadium compounds in aqueous solution and in biological fluids, and to the transport of vanadium compounds in blood plasma and their uptake by cells. Several new types of vanadium compounds were also synthesized and characterized, with applications either as prospective therapeutic drugs or as homogeneous or heterogenized catalysts for the production of fine chemicals. The developments made are described also considering the international context of the evolution of the knowledge in the chemistry and bioinorganic chemistry of vanadium compounds during the last 30years. This article was compiled based on the Vanadis Award presentation at the 9th International Vanadium Symposium.

Design and redox function of conjugated complexes with polyanilines or quinonediimines

Because of their potential application as new electrical materials that depend on their redox properties, π-conjugated polymers and oligomers have attracted much attention. Polyanilines, which are chemically stable, are one of the promising classes of conducting π-conjugated polymers. Polyanilines exist in three different discrete redox forms, which include the fully reduced leucoemeraldine, the semioxidized emeraldine, and the fully oxidized pernigraniline base form. The redox-active 1,4-phenylenediamine (PD) and 1,4-benzoquinonediimine, unit molecules of the emeraldine base form, can bind to transition metals to afford novel conjugated complexes. The introduction of metal centers into π-conjugated polymers is expected to dramatically change their functions. In this Account, we describe our ongoing research into the construction of conjugated complexes with redox-active π-conjugated polyanilines and 1,4-benzoquinonediimines. These systems can form architecturally controlled functionalized systems that depend on their dynamic redox properties, resulting in highly selective and versatile electron-transfer reactions and functionalized materials. Complexation with metals (Pd, V, Cu, etc.) occurred via the two nitrogen atoms of the quinonediimine moiety of the emeraldine base form of poly(o-toluidine) to afford the single-strand or cross-linked network conjugated complexes with d,π-conjugation. The complexation of the redox-active π-conjugated 1,4-benzoquinonediimines, unit molecules of the emeraldine base form, with palladium(II) compounds yielded a variety of conjugated complexes. Through regulation of the coordination mode of the quinonediimine moiety, we were able to architecturally control the formation of conjugated bimetallic, polymeric, or macrocyclic complexes. Complexation modulated the redox function of the quinonediimine moiety. Introduced metals act as a metallic dopant, and the complexed quinonediimine is stabilized as an electron sink. Furthermore, chirality could be induced into a π-conjugated backbone through complexation with optically active transition compounds, resulting in chiral d,π-conjugated complexes. We could also modulate the functional properties of conjugated complexes based on the redox states of the redox-active π-conjugated moieties. We also demonstrated how complexes with redox-active π-conjugated molecules can control the architecture of redox-functionalized systems through the metal imido bonds of these systems. Using the one-pot preparation of (arylimido)vanadium(V) compounds from the corresponding anilines, we synthesized binuclear complexes with axial chirality and trinuclear complexes with a tridendritic centrosymmetric structural motif. Such structures showed a strong tendency to self-assemble.