Currently, my research interests lie with vanadium coordination chemistry, with one project focused on materials and catalysis and another involving bio-mimetic activity of vanadium complexes. These topics have been chosen with student interests and education in mind in that they each expose students to a variety of synthetic and characterization techniques while pursuing some intriguing chemical problems. A brief summary of each project follows. For more information, please feel free to browse the group website (http://about.illinoisstate.edu/ccmclau/) or contact me directly.
Open Framework Vanadium-Phosphonates as Catalysts Vanadium is used quite extensively for oxidation catalysis-- specifically for sulfuric acid production. Recently, it has been demonstrated that a vanadyl phosphate catalyst transforms C4H10 to maleic anhydride. Can simple reactions be used to make vanadium phosphates and phosphonates for catalytic use? It has been shown that reactions of phosphonic acids with metal alkyl reagents leads to the formation of cage structures. Metal -oxy and -amino complexes have also been reacted with phosphonic acids to create these open frameworks. The work in this area has, thus far, been limited to gallium and aluminum alkyl species. Other metal systems could be explored and, perhaps, expose new structures with unusual properties. With an open framework like a zeolite, vanadium species such as these could possess high surface areas conducive to effective catalysis. It is the goal of this work to produce new vanadium-phosphate or -phosphonate complexes that possess open frameworks and to study their catalytic properties. Lately, we have been working with tris-pyrazolylmethanesulfonate or cyclopentadienylphosphonate complexes bridged by a series of phosphonates. (ICA 2009, IC 2012, ICA 2014)
Biomimetic Uses of Vanadium: Insulin-Enhancing V Complexes
Over the past 30 years, a number of vanadium complexes have been shown to be "insulin mimetic", that is, to diminish blood glucose levels, when administered as therapeutic agents to diabetics. More recent studies have shown that these complexes do not actually mimic insulin, but merely enhance the effects of the small quantities of insulin that are present. A variety of coordination complexes containing combinations of N/S/O donor sets all seem effective in reducing blood glucose levels regardless of which donor set is employed. Complexes with ligand systems including dithiolenes (S/S), cysteine-amines (S/N), picolinates (N/O), catecholates (O/O), salen (N/O), and guanidine (N/N) have all been employed, all almost exclusively with V4+ and V5+ systems. The disparate nature of the ligands suggests that it is the metal center and not the ligand that is playing the dominant role in therapy. To date, bis(picolinato)oxovanadium(IV) (VO(pico)2) is one of the most effective coordination complex being investigated for use in diabetic therapy. Although initial studies were with VO43-, a V5+ complex, subsequent studies have shown that V complexes, whether administered as V3+, V4+, or V5+ complexes, all seem to be effective in reducing blood glucose levels. One of the dangers of using V complexes for diabetic therapies is the accumulation of V in the body, especially in the bone with, as yet, unknown physiological consequences. With appropriate ligand choice, the required dose may be minimized. We synthesize and characterize new vanadium complexes with varying oxidation states and examine their efficacy in inhibiting enzymes. We then implement the acquired knowledge in the synthesis of vanadium coordination complexes to be studied for bio-mimetic insulin-enhancing properties. Lately we have been using the ligands picolinate, anthranilate, and imidazolylcarboxylate with vanadium as V3+, V4+, or V5+ complexes or with decavanadate, V10O286-. (JIB 2010, JIB 2012)