EPR study of spin-labels in aqueous inclusions within macrosteps of KHP and phthalic acid single crystals

CHED 980

Lev Ryzhkov, lryzhkov@towson.edu, Chemistry, Towson University, 8000 York Rd, Towson, MD 21252-0001, Paul C. Norris, pcnorris@catawba.edu, Department of Chemistry, Catawba College, 2300 West Innes St., Salisbury, NC 28144, and Tanyka Young, Thurgood Marshall High School, 5000 Truesdale Ave, Baltimore, MD 21206.
Crystals containing liquid inclusions were grown from aqueous solutions of potassium hydrogen phthalate containing trace amounts of two different spin-labels. These crystals were studied by electron paramagnetic resonance spectroscopy (EPR) to examine their effectiveness as low dimensional “sample holders”. They were grown from heated solutions, grown in Petri dishes at room temperature before being removed, dried, and placed into a TE101 cavity of a 9.3GHz EPR spectrometer. The low dimensional nature of liquid inclusions minimized effects of dielectric loss and aided in the resolution of spin probe signals. Rotation studies indicated that the spin-labels are somewhat oriented, and EPR spectra of frozen and thawed crystals were interconvertible. Signal from two different spin labels in solution inclusions of KHP single crystals exhibited well-resolved low-field lines. Single crystals containing liquid inclusions may provide a cheaper alternative to EPR aqueous cells for studies of samples in salt-saturated aqueous solutions of high dielectric constant.