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The past year of funding has been very productive even though our single crystal X-ray diffractometer had ceased operation.  Service visits from Bruker have deemed the circa 1980 instrument unrepairable.  Under these conditions, we have used powder x-ray diffraction at Princeton University for initial phase characterization and have spent considerable time at George Washington University to use their single crystal x-ray diffractometer.  Over the period of the last year, four visits to GWU were made for two to three days at a time.

We have spent time preparing our ternary building blocks.  We were able to successfully prepare the polymer-like K₂P₂Se₆ compound with linear chains of ethane-like P₂Se₆ and expanded our research to include K₁₀Ge₄S_10, which contains the adamantane-like Ge4S10 supertetrahedra.  In our synthetic strategies, we have attempted to react these building blocks in solvothermal bombs with methanol, ethylenediamine, water, and acetonitrile under a variety of temperatures.  In our initial studies, we have produced black crystals through the reaction of LaCl₃ with K₂P₂Se₆ in acetonitrile at 150 C for three days.  We are eagerly awaiting powder and single crystal x-ray diffraction results.  This project has finally produced crystalline products.  In most experiments, amorphous powders or unreacted materials were found by powder X-ray diffraction.

In addition to our building block method, we have attempted to react LaCl₃ with Ge, K₂S₂, and additional S in water, methanol, ethylene diamine, and acetonitrile under solvothermal conditions between 100 C and 200 C.  After washing with a methanol/water mixture to remove KCl, we have discovered yellowish clear crystalline blocks in reactions that used ethylene diamine as the solvent.  Powder X-ray diffraction patterns could not be matched to any known phases in the powder diffraction data bases.  Unfortunately, single crystal x-ray diffraction could not be performed as the crystals slowly decomposed to form a powdered sample.  We believe that our compound contained ethylene diamine that was slowly evaporating from our crystals during transportation to Washington, DC.

With our moderate success of our solvothermal reactions and difficulty with single crystal data acquisition, we used more traditional methods to attempt to make a variety of high quality single crystal compounds that could be easily brought to GWU.  We began using reactive alkali chalcogenide fluxes (A₂Q_n where A=Na, K, Cs, Rb; Q=S, Se; and n=1-5).  In a series of reactions, we have studied the A-Nb-Q phase space, where A=K and Cs.  We have discovered two new compounds Cs₆Nb₄Se₂₂, and K₁₂Nb₆Se₃₅.  Both compounds are isostructural to Ta compounds; however, the literature has not related the two structures.  The compounds form similar dimers of NbSe₇ trigonal prisms.  In the Cs compound, the dimers are connected via a Se-Se chain; however, the dimers in the K compound are connected through a longer selenium chain, Se-Se-Se.  The structures are closely related to each other and we plan to write an Acta Crystallographica Communication to report the results and the novel structural relationship between the structures within the next month.

We are also using molten flux methods to study composition space that is related to the Cs-Bi-Te thermoelectric materials discovered by Kanatzidis.  We have begun to explore the A-La-Bi-Se composition space for novel compounds.  We believe the La will force a change in the structure due to the higher coordination numbers for lanthanum chalcogenides.  We have made single crystalline samples, but have been limited by XRD time at GWU.  We believe this composition space will be fruitful for novel compounds and we will test for thermoelectric properties at Princeton University as samples are structurally characterized.

The trips to GWU have also allowed collaboration with TCNJ organic chemist, Dr. David Hunt.  His student was able to grow single crystals of N-methylisatoic anhydride.  The compound was characterized by single crystal x-ray diffraction and the result will be published in Acta Crystallographica Structure Reports within the next month.  This work was partially funded by PRF through the travel funds to use the GWU instrument.

Impacts of the PRF Grant

After the diffractometer could not be repaired, I began to write the grant.  The PRF-funded trips to GWU have produced enough preliminary data for an NSF-MRI grant.  We have been funded this year (NSF-MRI-0922931) for $242,200 to purchase a new single crystal X-ray diffractometer.  Through additional PRF money ($15,000) and support from TCNJ ($47,000), we will also be purchasing a powder X-ray diffractometer.  We have chosen to purchase a Bruker Apex 2 and a Bruker D8 Focus and are eagerly waiting for the instruments to arrive in December 2009 or January 2010.  The productivity for these projects will be greatly enhanced, especially the solvothermal reactions.

The PRF grant has greatly impacted the students at TCNJ.  Two recent graduates have worked on projects related to the PRF grant, Sergio Pulido (2009, UMDNJ School of Osteopathic Medicine), Peter Davis (2009, Oregon State, Food Science). The PRF grant has funded one student, Sarah Wehrhan (2011), for the summer of 2009 for an intensive 10 weeks of research plus a portion of her housing.  Her primary focus was the solvothermal strategies which are now becoming successful.  She has continued her research during the academic year.

The SUMR grant funded Valisha Edwards for 10 weeks of summer research in 2009 ($3250 stipend, $1380 for housing stipend, and $370 for research expense).  When I first approached Valisha, she was quite timid and shy.  After her 10 weeks of summer research, I saw her confidence increase dramatically.  She became integrated into the department socially and academically.  This opportunity has truly changed her attitudes towards chemistry.  She has elected to do independent study in my laboratory during the academic year.  She already has an offer to do another 10 weeks of PRF funded research this summer when I will train her crystallography.  Valisha is now considering graduate school as a possibility when she graduates.  The SUMR award had tremendous impact on her life.