Why now? Experimental structure (what has changed?) determination in the undergraduate curriculum Status and Future Potential of Searching

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1 Experimental structure determination in the undergraduate curriculum Dean H. Johnston PDS/OVCS 2011 Creating data-rich integrated laboratory exercises Why now? (what has changed?) Access to crystallographic databases Computing power rapid structure solution / refinement high quality graphical displays Instrumentation low maintenance high level of automation Status and Future Potential of Crystallography (USNC/Cr 1976) Searching education and It seems apparent that the major use of crystallography in most undergraduate chemistry curricula is simply the dissemination of certain crystallographic results. In almost no case was there evidence that any information was given to students about how to evaluate the reliability of these results. Structural Data Continuum Most instruction in structural chemistry at the undergraduate level uses either idealized geometries (i.e. VSEPR) or selected bond distances and bond angles (average values) Students are disconnected from the experimental sources of structural data, and therefore unaware of the associated uncertainty in such measurements Crystallography in the Curriculum General Chemistry (1 st or 2 nd year) Inorganic Chemistry (2 nd or 3 rd year) Biochemistry (3 rd or 4 th year) Stand-alone crystallography course idealized experimental VSEPR Computed Textbook Database Laboratory 1

2 Crystallography in the Curriculum General Chemistry (1 st or 2 nd year) Inorganic Chemistry (2 nd or 3 rd year) Biochemistry (3 rd or 4 th year) Stand-alone crystallography course many contexts exist in which crystallography can be incorporated in undergraduate education with minimal disruption to current courses, and should be included in curricula of all undergraduate programs in the physical and life sciences Crystallography Education Policies for the Physical and Life Sciences, ACA & USNC/Cr Questions / Potential Issues Curriculum If we add (crystallography), what do we take out? What do we want to teach our students? What do we want our students to learn? Faculty time: insert favorite subject here data collection, data analysis, and data distribution is too time consuming can t babysit the instrument Our Context Otterbein University 3000 total students primarily undergraduate institution (PUI) Chemistry Department six full-time faculty in Chemistry / Biochemistry around ten majors per year General Chemistry enrollment of students diverse majors including chemistry, biology allied health, equine science, etc. General Chemistry General Chemistry Lab Goal to develop an integrated multi-week laboratory activity that reinforces concepts of molecular geometry, intermolecular forces, unit cells and crystal packing using experimental data (both databases and student-generated) General Chemistry Lab Student groups assigned an amino acid Cambridge Database VSEPR activity 1 Crystal packing / unit cell activity 2 Crystallization of amino acid (multi-week) (X-ray analysis of amino acid samples) Analysis of experimental X-ray data using Mercury and Mogul 1 Battle, G. M.; Allen, F. H.; Ferrence, G. M. J. Chem. Educ. 2010, 87, Otterbein: 2

3 Amino Acid List CSD VSEPR Tutorial Amino acids were chosen based on the number of entries in the Cambridge Database and availability / cost. L-alanine DL-alanine L-asparagine L-cysteine L-glutamine L-histidine L-methionine DL-methionine L-serine DL-serine L-threonine L-valine Figures from Battle, G. M.; Allen, F. H.; Ferrence, G. M. J. Chem. Educ. 2010, 87, Crystal Packing Crystallography All samples were mounted and run on a Bruker SMART X2S benchtop diffractometer Data Analysis Validation / Mogul Analysis Students used Mercury to analyze: overall structure (atoms, connectivity) geometry (compared to VSEPR predictions and physical model built using model kit) hydrogen bonding network unit cell packing and number of molecules per unit cell calculated density (compare to reference) structure validation (Mogul) 3

4 Questions / Potential Issues Curriculum: what do we take out? most of the material was already in place modified existing exercises to incorporate experimental data (CSD / student samples) Inorganic Chemistry Faculty time: level of automation of the SMART X2S allowed data collection, structure solution, and distribution (on CDs) with minimal intervention sophomore-level inorganic chemistry course with integrated laboratory enrollment between 10 and 20 students final three weeks of term select a synthetic procedure (Inorg. Synth.) determine equipment, reagent needs get approval, order reagents make compound(s), characterize tris(3-nitro-acetylacetonate) cobalt(iii) [Cu(tmhd) 2 ] (C 12 H 18 N 2 )[Mo 6 Cl 14 ] 1.5 C 3 H 6 O tricarbonyltris(pyridine)molybdenum(0) (C 6 H 10 N 2 )[Mo 6 Cl 14 ] 3 DMF 4

5 (C 12 H 18 N 2 )[Mo 6 Cl 14 ] 1.5 C 3 H 6 O Organic Chemistry (!) Acta Cryst. (2011). E67, o2735 Acta Cryst. (2011). E67, o2276 Conclusions Crystallography provides a rich source of data that we can use to teach fundamental concepts of chemical structure, bonding, intermolecular forces, crystal packing, and critical analysis at the undergraduate level Advances in single crystal XRD instrumentation have made experimental crystallography accessible and feasible for teaching (and research) at primarily undergraduate institutions Acknowledgements Allen Hunter (YSU) Otterbein Students Chem Department, Otterbein University Greg Ferrence (ISU) Matt Zeller (YSU) ACA 2010 Summer School faculty National Science Foundation (DUE # ) Web Resources All materials available online at: 5