Department of Chemistry
Professor of Chemistry
(Chemical Crystallography, Ph.D., Princeton University, 1988)
(206) 616-8195
kahr@chem.washington.edu
Research Group Website
Identifying mechanisms of crystal growth is a major challenge in solid state science and supramolecular chemistry. Motivated as well by a desire to understand the interactions of electromagnetic radiation and crystalline matter, we approach mechanistic studies of crystal growth with optical probes both chemical and physical: 1. We use optically responsive molecules to report what was happening on crystalline surfaces during growth, and 2. We use new methods in optical microscopy to reveal aspects of crystal growth mechanisms and crystal structure heretofore unknown.
Every civilization has invented technologies for dyeing textile fibers. The dyeing of growing crystals is likewise a general branch of supramolecular chemistry but one that never developed into an independent area of inquiry. We have been trying to put this chemistry on the foundation of specific non-covalent interactions. In order to determine the structure of mixed crystals we have been required to invent new microscopies and associated contrast mechanisms. In turn, we have discovered new crystal-optical phenomena.The generalization of single crystal matrix isolation in this way has provided materials that are excellent foci of single molecule studies of the nature of dark states and for the parsing of ensemble averages of energy and orientation (see Reid group). In turn, single molecule studies have revealed the important role of kinks in dyeing crystals. The dyeing of emergent growth structures has even been used to test theories of the origin of life on earth.
The science of crystal optics is surely not complete. For example, researchers have struggled to measure chiroptical properties of organized substances. Recent advances in polarimetry and polarimetric imaging allow us to determine the orientational dependence of optical rotation, circular dichroism, and circular scattering in crystals and molecules. Together with advances in quantum chemistry, it is now possible to provide structural interpretations of chiroptical phenomena. Current research is focused on the optical rotatory power of simple achiral substances, such as carbon compounds of the form CX4 and H2O. The dearth of information on the anisotropy of chiroptical properties represents an enormous hole in the science of molecular chirality that can now be filled after almost two centuries.
More recently, we have been trying to understand not only mechanisms of single crystal growth but also mechanisms that underlie polycrystalline pattern formation. Pattern formation is one of the great organizing principles among all of the sciences. For example, spherical crystalline aggregates are common in Alzheimer's disease, supercooled high polymers, and many simple molecular substances. These so-called spherulites commonly display supramolecular chirality. Here, new methods in polarimetric imaging are used to understand the mesoscale stereochemistry of complex, regular crystal aggregates.
K Claborn, C Isborn, W Kaminsky, B Kahr, Chiroptics of achiral compounds, Angew Chem Int Ed Engl, review in press.
T Bullard, J Freudenthal, S Avagyan, B Kahr, Test of Cairns-Smith’s crystals-as-genes hypothesis, Faraday Discussions, 2007, 136, 231-245.
D Cohen, JB Benedict, B Morland, D Chiu, B Kahr, Dyeing polymorphs: The MALDI host 2,5-dihydroxybenzoic acid, Cryst Growth Des, 2007, 7, 492-495.
C Isborn, K Claborn, B Kahr, The optical rotatory power of water, J Phys Chem A, 2007, 111, 7800-7804.
KL Wustholz, ED Bott, CM Isborn, X Li, B Kahr, PJ Reid, Dispersive kinetics from single molecules oriented in single crystals of potassium acid phthalate, J Phys Chem C, 2007, 111, 9146-9156.
B. Kahr, K. Claborn, The Lives of Malus and His Bicentennial Law, ChemPhysChem. 2007, DOI: 10.1002/cphc.200700173.
W Kaminsky, E Gunn, R Sours, B Kahr, Simultaneous false-color imaging of birefringence, extinction, and transmittance at camera speed, J Microscopy, 2007, 228, 153-164.
B Kahr, ed. Optically Anomalous Crystals. (English language edition of Nauka publication by A. Shtukenberg and Y. Punin), Springer Series in Solid State Science, 2007.
E Gunn, R Sours, W Kaminsky, B Kahr, Mesoscale chiroptics of rhythmic precipitates, J Am Chem Soc. 2006, 128, 14234-14235.
K Claborn, J Herreros Cedres, C Isborn, A Zoulay, E Weckert, W Kaminsky, B Kahr, Optical rotation of achiral pentaerythritol, J Am Chem Soc. 2006, 128, 14746-14747
W. Kaminsky, L.-W. Jin, S. Powell, I. Maezawa, K. Claborn, B. Kahr, “Polarimetric imaging of amyloid,” Micron, 2006, 37, 324-338
J.B. Benedict, D. Cohen, S. Lovell, A. Rohl, B. Kahr, “What is syncrystallization? States of pH indicator methyl red in single phthalic acid crystals,” J. Am. Chem. Soc. 2006, 128, 5548-5559
K. Claborn, A.-S. Chu, S.-H. Jang, F. Su, W. Kaminsky, B. Kahr, “Circular extinction imaging: Determination of the absolute orientation of embedded chromophores in enantiomorphously twinned LiKSO4 crystals,” Cryst. Growth Des. 2005, 5, 2117-2123
K. L. Wustholz, B. Kahr, P. J. Reid, “Single-molecule orientations in dyed salt crystalsJ Phys Chem A, 2005, 109, 16357-16362
B. Kahr, B. Chittenden, A. Rohl, “Robert Boyle’s Chiral Crystal Chemistry: Computational Reevaluation of Enantioselective Adsorption on Quartz,” Chirality, 2005, 18, 127-133
W. Kaminsky, K. Claborn, B. Kahr, "Polarization imaging of crystals," Chem. Soc. Rev., 2004, 33, 514-525. Click here to download a reprint of this article
A. Barbon, M. Bellinazzi, J. B. Benedict, M. Brustolon, S. D. Fleming, S.-H. Jang, B. Kahr, A. L. Rohl, "Luminescent probes of crystal growth: Surface charge and polar axis sense in dye-doped potassium hydrogen phthalate," Angew. Chem. Int. Ed. Engl., 2004, 43, 5278-5286. Click here to download a reprint of this article
B. Kahr, "Crystal Engineering in Kindergarten," Cryst. Growth Design, 2004, 4, 3-9. Click here to download a reprint of this article
L.-W. Jin, K. Claborn, M. Kurimoto, M. Estrada, W. Kaminsky, B. Kahr, "Imaging linear birefringence and dichroism imaging of amyloid plaques," Proc. Natl. Acad. Sci., 2003, 100, 15294-15298. Click here to download a reprint of this article
K. Claborn, E. Puklin-Faucher, M. Kurimoto, W. Kaminsky, B. Kahr, "Circular dichroism imaging microscopy: Application to enantiomorphous twinning in 1,8-dihydroxyanthrquinone," J. Am. Chem Soc. 2003, 125, 14825-14831. Click here to download a reprint of this article
J. B. Benedict, P. M. Wallace, P. J. Reid, S.-H. Jang, B. Kahr, "Up-conversion luminescence in dye-doped crystals of potassium hydrogen phthalate," Adv. Mat. 2003, 15, 1068-1070. Click here to download a reprint of this article
B. Kahr, L. Vasquez, "Painting Crystals,"Cryst. Eng. Comm, 2002, 514-516. Click here to download a reprint of this article
B. Kahr, R. W. Gurney, "Dyeing Crystals," Chem. Rev., 2001, 101, 893-951. Click here to download a reprint of this article
D. Hrovat, W. T. Borden, P. Eaton, B. Kahr, "A computational Study of the Interactions among the Nitro Groups in Octanitrocubane," J. Am. Chem. Soc., 2001, 123, 1289-1293. Click here to download a reprint of this article
R. W. Gurney, C. Mitchell, L. Bastin, S. Ham, B. Kahr, "Salting Benzenes," J. Phys. Chem. B, 2000, 104, 878-892. Click here to download a reprint of this article
M. Kurimoto, P. Subramony, R. Gurney, S. Lovell, J. A. Chmielewski, B. Kahr, "Kinetic Stabilization of Biopolymers in Single-Crystal Hosts: Green Fluorescent Protein in a-Lactose Monohydrate," J. Am. Chem. Soc., 1999, 121, 6952-6953. Click here to download a reprint of this article
B. Kahr, "Gibbs and Amistad," Chemical Intelligencer, 1999, April, 24-31. Click here to download a reprint of this article
National Science Foundation Young Investigator, 1994-99
National Science Foundation Creativity Extension, 2007-09