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Matrix isolation infrared spectroscopy has been combined with MP2/aug′-cc-pVDZ calculations to characterize the 1:1 hydrogen-bonded complexes between H 2 O 2 and the hydrogen halides HF, HCl, and HBr. The infrared spectra of the these complexes are characterized by an intense, red-shifted H-X stretching band, as well as slight perturbations to several of the HOOH vibrational bands. For the HF complex, the intermolecular librational modes were also observed. The ab initio calculations identified two equilibrium structures on each surface, one an open structure, and the other cyclic. These two structures have similar binding energies. However, only the open structure appears to be present in argon and nitrogen matrices. This open structure is preferentially stabilized by interaction of its larger dipole moment with the matrix medium.

Each year, more than 30 million children and adolescents participate in organized sports in the United States (US), and more than 4.3 million nonfatal sports-and recreation-related injuries are treated in US hospital emergency departments. Two types of activity-related injuries, in particular, that we study in the Bone and Joint Injury Prevention and Rehabilitation Center at the University of Michigan are anterior cruciate ligament (ACL) injuries and head injury and concussion. Knee ACL injuries are occurring in epidemic-like proportions. In the US alone there are approximately 200,000 new ACL injuries at a total cost of over $1 billion per year. ACL-injured patients are at a significant risk of developing early onset osteoarthritis. Exacerbating the concern is the increase in ACL injury rates in youth and adolescents; particularly girls can experience ACL injury rates from two to five times greater than boys in the same sport. In addition, 3.8 million sports-and recreation-related concussions occur in the US each year. Significantly more research is needed, but intriguing findings are surfacing. For example, high school athletes' recovery times for a concussion are longer than college athletes' recovery times. Moreover, high school athletes who sustain a concussion are 3 times more likely to sustain a second concussion. Preliminary studies state suggest women have a higher risk for head injury and post concussion syndrome due to potentially weaker neck muscles, different muscle activation patterns, and hormone variations. Three key questions must be answered to understand these and other sports-related injuries: 1) What is the magnitude of the epidemic? 2) What are the causes of injury? and 3) What can we do to prevent injuries? Without a greater awareness of the injury risk and a better understanding of the injury mechanisms, the risk of sport-related injuries may escalate in the coming years.

The matrix-isolation technique has been combined with infrared spectroscopy to identify and characterize the products formed by irradiation of cage-paired CrCl(2)O(2) and a series of chloroethenes, C(2)H(x)()Cl(y)() (x + y = 4). For each system, oxygen-atom transfer occurred upon irradiation, yielding the corresponding acetyl chloride derivative and the Cl(2)CrO species. The products were formed in the same matrix cage and strongly interacted to form a distinct molecular complex after formation. Three different modes of interaction were explored computationally: eta(1) to the oxygen atom, eta(2) to the C=O bond, and eta(1) to the chlorine atom. In addition, a five-membered metallocycle and the chloroepoxide species were considered. No evidence was obtained for the chloroacetaldehyde derivative, indicating the occurrence of oxygen-atom attack at the more substituted carbon of the chloroethene. Evidence tentatively supporting the formation of the metallocycle was obtained as well. Theoretical calculations indicated that the acetyl chloride derivative was approximately 10 kcal/mol more stable than the corresponding chloroacetaldehyde species for each system at the B3LYP/6-311++g(d,2p) level of theory. The binding energy of each of the complexes was also found to be near 10 kcal/mol at this level of theory.

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