Direct observation of the intermediate in an ultrafast isomerization.

Using a combination of two-dimensional infrared (2D IR) and variable temperature Fourier transform infrared (FTIR) spectroscopies the rapid structural isomerization of a five-coordinate ruthenium complex is investigated. In methylene chloride, three exchanging isomers were observed: (1) square pyramidal equatorial, (1); (2) trigonal bipyramidal, (0); and (3) square pyramidal apical, (2). Exchange between 1 and 0 was found to be an endergonic process (ΔH = 0.84 (0.08) kcal mol-1, ΔS = 0.6 (0.4) eu) with an isomerization time constant of 4.3 (1.5) picoseconds (ps, 10-12 s). Exchange between 0 and 2 however was found to be exergonic (ΔH = -2.18 (0.06) kcal mol-1, ΔS = -5.3 (0.3) eu) and rate limiting with an isomerization time constant of 6.3 (1.6) ps. The trigonal bipyramidal complex was found to be an intermediate, with an activation barrier of 2.2 (0.2) kcal mol-1 and 2.4 (0.2) kcal mol-1 relative to the equatorial and apical square pyramidal isomers respectively. This study provides direct validation of the mechanism of Berry pseudorotation - the pairwise exchange of ligands in a five-coordinate complex - a process that was first described over fifty years ago. This study also clearly demonstrates that the rate of pseudorotation approaches the frequency of molecular vibrations

Assessing Psychological Well-Being: Self-Report Instruments for the NIH Toolbox

Objective— Psychological well-being (PWB) has a significant relationship with physical and mental health. As part of the NIH Toolbox for the Assessment of Neurological and Behavioral Function, we developed self-report item banks and short forms to assess PWB. Study Design and Setting— Expert feedback and literature review informed the selection of PWB concepts and the development of item pools for Positive Affect, Life Satisfaction, and Meaning and Purpose. Items were tested with a community-dwelling U.S. internet panel sample of adults aged 18 and above (N=552). Classical and item response theory (IRT) approaches were used to evaluate unidimensionality, fit of items to the overall measure, and calibrations of those items, including differential item function (DIF). Results— IRT-calibrated item banks were produced for Positive Affect (34 items), Life Satisfaction (16 items), and Meaning and Purpose (18 items). Their psychometric properties were supported based on results of factor analysis, fit statistics, and DIF evaluation. All banks measured the concepts precisely (reliability ≥0.90) for more than 98% of participants. Conclusion— These adult scales and item banks for PWB provide the flexibility, efficiency, and precision necessary to promote future epidemiological, observational, and intervention research on the relationship of PWB with physical and mental health