Tenured and Tenure-Track Faculty

Research in the Szczepura group involves exploring the chemistry of supraoctahedral clusters with the basic formula [M₆(μ₃-X)₈L₆]ⁿ where M = Mo or Re, and X = halide or chalcogenide.  We are particularly interested in developing synthetic methodologies which will enable us to design new cluster complexes.  We are also interested in conducting fundamental studies which will allow us to understand ligand effects on the physical properties and reactivity of these new cluster complexes.  This knowledge is essential for the deliberate application of supraoctahedral clusters towards specific applications such as catalysis.

Students conducting research in the Szczepura group synthesize and characterize new transition metal cluster complexes, and are trained to work with air sensitive compounds (glove box and Schlenk line techniques).  Common characterization techniques include NMR (¹H,¹³C and ³¹P), IR and UV-vis spectroscopies, X-ray crystallography and cyclic voltammetry.  In addition, our laboratory is equipped with a state-of-the-art rapid scanning spectrophotometer with a stopped flow device. This instrument enables us to conduct detailed analyses of very fast reactions.

Activation of Small Molecules:  Recently, we demonstrated that the hexanuclear [Re₆Se₈]²⁺ cluster core activates organonitriles to undergo a [2+3] dipolar cycloaddition reaction with NaN₃ (Chem. Commun. 2007, 4617-4619).  Specifically, [Re₆Se₈(PEt₃)₅(MeCN)]²⁺ and N₃^- react to form [Re₆Se₈(PEt₃)₅(1,5-methyltetrazolate)]⁺ within minutes at room temperature.  Our findings mark the first time rhenium has activated an organonitrile to undergo a cycloaddition reaction, and the first hexanuclear cluster complex to contain this type of N-donor ligand.  There is a great deal of interest in tetrazoles because they have such varied uses, in addition to their use in synthetic organic chemistry.  We are currently exploring the scope and mechanism of small molecule activation by the [Re₆Se₈]²⁺ cluster core.

Luminescent Properties of Hexanuclear Clusters: It is well known that both the hexanuclear molybdenum halide and rhenium chalcogenide cluster complexes display interesting photophysical properties.  In fact, [Mo­₆(μ₃-Cl)₈Cl₆]^2- is known to have one of the longest excited state lifetimes for a transition metal complex.  In the process of characterizing a new series of [Mo­₆Cl₈(SR)₆]^2- (R = Et, Bu, benzyl, Ph, 3-indolyl) clusters, we investigated their luminescent properties.  Shown here are emission spectra of (Bu₄N)₂[Mo₆Cl₈(SEt)₆] in MeCN at three different excitation wavelengths.  (These studies were done in collaboration with Prof. D. Cedeño.)  In a manuscript published in the Journal of Cluster Science (2009, 20, 105-112) we provide the excited state lifetimes and quantum yields of these thiolate complexes.  Notably, we found that the [Mo₆Cl₈(SR)₆]^2- complexes exhibit long excited state lifetimes.  Although the emission maximum does not vary with a change in the substituent on the thiolate ligand, there is a correlation between the substituents and the excited state lifetime and quantum yield.  We have also collaborated with Prof. Cedeño on a study investigating a family of [Re₆S₈(PEt₃)_nCl_6-n]^4-n (n = 1 – 4) clusters (Inorg. Chem. 2010, 49, 11386-11394).

Scholarship of Teaching and Learning: The educational component of my NSF CAREER award (2003-08) resulted in the development and implementation of a program aimed at improving the success rate of underrepresented minorities majoring in the sciences at Illinois State University (ISU).  The program, titled the Enrichment Workshop Program (EWP), offered a small group of incoming students a unique opportunity to become part of a support group where they could network with faculty and other minority students.  The development and preliminary assessment of this program are detailed in a manuscript published in The Chemical Educator (2010, 15, 126-133).