Special Issue Preface pubs.acs.org/JPCA
2140 Bond Energies and Counting: A Tribute to Peter B. Armentrout [Int. J. Mass Spectrom. 2000, 200, 219]. This experimental effort has been accompanied by development of theoretical models using threshold collisional energy transfer models [J. Phys. Chem. 1984, 88, 5454], and statistical rate theory [J. Phys. Chem. A 2008, 112, 10071] to extract accurate thermochemical values. The hallmark of the experimental approach of the Armentrout research program has been to apply mass spectrometry and guided ion beam radio frequency trapping technology in a careful way to make precise and accurate thermochemical determinations. Custom design and construction of the ion sources and guided ion beam tandem mass spectrometers [J. Chem. Phys. 1985, 83, 166] affords precise control over the internal energy distributions of the ions and the kinetic energy distributions of the ion−molecule collisions, which is at best difficult to achieve with commercial mass spectrometers. The data analyses are performed rigorously and carefully to take into account all energy distributions and kinetic and competitive shifts, as required to determine accurate thermochemistry. The modeling of kinetic shifts involves sophisticated use of statistical rate theory (RRKM theory and phase space theory), including use of appropriate transition state models and full consideration of angular momentum effects, which is especially important for the wide range of available collision energies [J. Chem. Phys. 1997, 106, 4499; J. Chem. Phys. 1998, 109, 1787]. Peter’s recent extensions to these statistical rate theory modeling methods include handling sequential dissociation processes [J. Chem. Phys. 2007, 126, 234302] and ion association processes [J. Chem. Phys. 2003, 119, 12819]. Peter has regularly conducted experiments designed to test and validate these experimental methods, both by comparisons with independent thermochemical cycles and by direct measurement of product energy distributions [J. Chem. Phys. 2001, 115, 1213]. The Armentrout group has applied these methods to a variety of reaction systems ranging from reactions of atomic ions with molecular hydrogen to transition metal clusters to large biomolecular ions. Peter’s work on reactions of atomic ions, including selected electronic states for both transition metals and main-group elements, with hydrogen and simple hydrocarbon molecules has provided a wealth of information on periodic trends and on the importance of the electronic configuration on determining the reaction dynamics. Isotope effects, particularly among reactions of H2, D2, and HD, have been used to examine the kinematics of these reactions at elevated collision energies. Electronic-state effects have also been proved important in the intrinsic reactivity related to C−H and C−C bond activation. For instance, Peter and his research group have examined the details of the effects of electronic spin and spin−orbit states on ion−molecule reactions as a function of kinetic energy.
Photograph taken by Stephen Speckman
We are pleased to join the many colleagues who contributed to this special issue of The Journal of Physical Chemistry A (and those who could not) in dedicating it to Professor Peter B. Armentrout upon the occasion of his 60th birthday. As friends, collaborators, and former advisees, we are pleased to have this opportunity to share with you Peter’s major scientific and academic accomplishments. Peter is a leader in the field of ion− molecule reaction chemistry and the use of energy-resolved collisions of ion−molecule reactions to obtain thermochemical information. His prodigious body of scientific work is evident from the more than 2140 bond energies he has measured, the 430 publications he has authored or coauthored, listed herein, and his ranking among the most highly cited chemists. Peter began his education as an undergraduate at Case Western Reserve University, graduating with a B.Sc. in Chemistry with highest honors in 1975. At Case, Peter produced his first scientific publication working with Professor Robert C. Dunbar studying photodissociation of trapped gasphase ions. Peter moved on to the California Institute of Technology, where he earned his Ph.D. in 1980. Under the mentorship of Jack Beauchamp, Peter began developing ion beam instrumentation and data analysis techniques that have become the hallmark of his career. In addition to his efforts in instrument development, Peter produced 21 publications from his Ph.D. work, providing another early indicator of the high level of scientific productivity to come. Peter spent a year and a half as a Postdoctoral Member of Technical Staff at Bell Laboratories before he began his academic career as an Assistant Professor at the University of California, Berkeley in 1981. From Berkeley, Peter moved to the University of Utah in 1987, rapidly rose through the ranks, and is currently Distinguished Professor and Cannon Fellow in the Department of Chemistry. Peter is best known for experiments measuring precise energy thresholds for ion−molecule reactions using guided ion beam tandem mass spectrometry techniques. The measurement of absolute reaction cross sections for collisions from nearthermal energies to tens of electron volts allows exploration of the dynamics and energetics of these ion−molecule reactions © 2013 American Chemical Society
Special Issue: Peter B. Armentrout Festschrift Published: February 14, 2013 967
dx.doi.org/10.1021/jp401080r | J. Phys. Chem. A 2013, 117, 967−969
The Journal of Physical Chemistry A
Special Issue Preface
crown ether-alkali metal cation host−guest interactions mentioned above was carried out in collaboration with Douglas Ray and co-workers, and more recently followed up in efforts with Mary Rodgers and co-workers. Work on cis-platin and related complexes was carried out with Richard O’Hair and coworkers. With Mary Rodgers, Jos Oomens, Jeffrey Steill, and Mathias Schäfer, he has recently collaborated on using IRMPD techniques at the free electron laser for infrared experiments (FELIX) facility to study complexes of amino acids and other biological molecules with metal ions. Ongoing collaborations with Joost Bakker and co-workers using the free electron laser for intracavity experiments (FELICE) make use of related IRMPD techniques to examine the structures of products formed by C−C and C−H bond activation by transition metal cations, many for the first time. The two of us continue to collaborate with Peter on improvements and upgrades to the powerful CRUNCH data analysis program, which has been developed by Peter and his co-workers over many years and which implements the modeling of reaction cross section thresholds and statistical rate theory for collision-induced dissociation processes. Early in his career, Peter profitably relied on efforts of various theoreticians for enhanced interpretation of his experimental data and to further elucidate periodic trends among related systems. As electronic structure codes became available to the scientific layman, Peter began to support and enhance his threshold measurements with complementary computational efforts. As time has progressed, the level of theoretical investigation that Peter and his students have included in their work has significantly increased. Indeed, virtually all of Peter’s recent publications interpret experimental data and compare measured and computed values at several levels of theory. These comprehensive comparisons have established relative accuracies of various theoretical models and basis sets for describing metal−ligand and noncovalent interactions in a whole host of systems and should prove useful for advancing the accuracy of computational models. We would be remiss in giving a full picture of Peter’s approach to and passion for science if we failed to mention his unremittingly vigorous defense of ion beam methods for thermochemical determinations and his sometimes highly vocal critiques of methods deemed less rigorous. He is not prone to mincing words. This is a side of Peter’s persona that is more commonly seen by conference-goers than by his co-workers, actually. Despite his stated reservations about analyzing threshold energies from instruments less well optimized for the task than a guided ion beam apparatus, however, Peter has freely distributed and helped many groups use the CRUNCH program to analyze energy thresholds measured using a variety of tandem mass spectrometer instruments. Peter’s ubiquitous contributions to discussions at scientific meetings, with comments, questions, and answers that educate both students and colleagues alike, not to mention his excellent speaking skills, make Peter highly sought after as an invited speaker at national and international conferences. Peter’s ultimate dedication to science and the pursuit of knowledge engenders high respect among his potential “competitors” in the field and results in them becoming his collaborators and friends in many cases. For example, Peter has been critical of some applications of the so-called extended version of the Cooks kinetic method for determination of relative ion affinities. However, despite not being a practitioner himself, he proposed data analysis methods to overcome some deficiencies of the method and has recently
In the area of inorganic and organometallic chemistry, Peter and his students have produced some of the most reliable bond energies for metal−metal and metal−ligand interactions. These quantitative bond energies provide valuable fundamental information for those studying organometallic reactivity, and also provide essential benchmarks for computational chemistry methods for these theoretically challenging systems. In continuing work, the Armentrout group has explored transition metal cluster ion chemistry, probing the transition between atomic metal ion characteristics and bulk metal behavior. Another theme in Peter’s research has been the investigation of intrinsic reactivity and energetics in the absence of solvent and how solvent interactions mediate reactivity. In a series of experiments, Peter and co-workers have studied the stepwise binding energies of electrostatically bound molecules in microsolvated ions. These studies have afforded insights into the nature of the interactions of ions with small molecules and critical comparisons with other experimental methods and with theory. Extending the investigation of noncovalent interactions further, Peter and his students have measured absolute binding energies of host−guest complexes, for example, of crown ethers interacting with metal ions. Because extreme kinetic shifts raise the apparent threshold energies for collision-induced dissociation of large ion−molecule complexes (resulting from slow unimolecular dissociation as compared to the detection time window), the statistical rate modeling of the dissociation process becomes paramount. Thus, these studies test the limits of energy-resolved threshold collision-induced dissociation to measure bond dissociation energies, and have enabled the statistical models employed to evolve for increasingly complex systems. More recently, the Armentrout group’s guided ion beam methods have been profitably applied to elucidating the interactions between metal ions and biological moieties. Collision-induced dissociation experiments on the binding between metal centers and ligands of biological significance, including nucleobases, amino acids, and small peptides, have afforded a thermochemical “vocabulary” for understanding these interactions in biological systems [Acc. Chem. Res. 2004, 37, 989; Mass Spectrom. Rev. 2000, 19, 215]. Recently, Peter has become involved in spectroscopic studies for determining the structures of these metal−ligand complexes, employing infrared multiple photon dissociation (IRMPD) techniques. These spectroscopic studies combine with his guided ion beam work to provide an enhanced framework for understanding how noncovalent interactions influence molecular structure and energetics. Beyond his own group of graduate and undergraduate student and postdoctoral researchers, Peter has collaborated with several of his colleagues at the University of Utah, and many other scientists worldwide. We highlight several examples here. Peter collaborated with his colleagues, Chuck Wight and Michael Morse, to study metal-containing ions by photodissociation spectroscopy methods. An important advance in understanding the nature of thresholds for heterolytic bond cleavage resulted from work between Peter and his colleague Jack Simons. A fruitful collaboration with Tomas Baer, Balint Sztáray, and co-workers compares thermochemistry obtained by ion beam methods and photoionization methods. Extensive collaboration with Helmut Schwarz, Detlef Schröder, Ilona Kretzchmar, and their co-workers have examined catalytic reactions of transition metal ions. Much of the early work on 968
dx.doi.org/10.1021/jp401080r | J. Phys. Chem. A 2013, 117, 967−969
The Journal of Physical Chemistry A
Special Issue Preface
thereby enabling electronic-state and conformer specific thermochemistry to be measured. We are privileged to have this opportunity to publically thank a friend, collaborator, and mentor. We were lucky to have worked with one of the best and are pleased to continue to call Peter our friend. We join with Peter’s many other friends and colleagues in wishing him a wonderful 60th birthday, and many more years of scientific research and productivity. With Peter’s current energy and dedication to science, 5000 bond energies as a measure of his career is certainly within reach.
collaborated with Jean Claude Tabet and co-workers to experimentally study the origins of nonlinear effects in kinetic method determinations. Throughout his career, Peter has been a willing and effective leader in the enterprise of academic science, having served as Chemistry Department chair for 6 1/2 years at the University of Utah, among many other service activities, and on a variety of editorial and association boards, review panels, award committees, and as journal guest editor. Peter has been particularly active in the fundamental ion chemistry section of the American Society for Mass Spectrometry. Peter has organized a large number of scientific conferences and symposia, including a stint as chair of the Gordon Research Conference on Gaseous Ions: Structures, Energetics and Reactions. Peter has always taken highly active and hands-on interest in the research of his students at all levels. Peter’s students receive rigorous training as scientists and are held to high standards. The successes of Peter’s former students and postdoctoral associates in their careers in academia, national laboratories, and industry are a testament to his mentoring of young scientists. As just two of his former advisees, we are proud to share Peter’s passion for excellence in science. Peter is among the best and most dedicated teachers we have known. Peter has contributed to teaching and curriculum development at both the undergraduate and graduate levels, teaching undergraduate courses in General Chemistry, Physical Chemistry I and II, and graduate courses in Statistical Thermodynamics, Kinetics, Dynamics, and Spectroscopy. Peter has been recognized for his teaching excellence with several awards, as noted on his Curriculum Vitae (CV). Peter’s prodigious career and important contributions to science have been recognized by a vast number of awards over the years in addition to the citation and teaching recognition mentioned above. His CV published here provides a comprehensive list of these many awards, and includes a Camille and Henry Dreyfus Grant for Newly Appointed Faculty in Chemistry in 1981, Presidential Young Investigator Award, National Science Foundation in 1984, an Alfred P. Sloan Research Fellow in 1986, Fellow of the American Association for the Advancement of Science in 1992, Fellow of the American Physical Society in 1994, Distinguished Research Award at the University of Utah in 1994, the Biemann Medal of the American Society of Mass Spectrometry in 2001, the Utah Award of Chemistry given by the American Chemical Society in 2002, the Field and Franklin Award for Outstanding Achievement in Mass Spectrometry given by the American Chemical Society in 2009, the Utah Governor’s Medal for Science and Technology Award in 2010, and the Rosenblatt Prize for Excellence at the University of Utah in 2011. Peter’s research continues unabated. Present interests include the examination of solvation energies of multiply charged metal cations, where his group has recently measured the first complete inner-shell hydration energies for any such system. These systems also exhibit an interesting charge fission process, for which the energetics had never previously been elucidated. His work in biological systems is expanding to larger and more complex systems and, hearkening back to his graduate roots, he is actively studying the chemistry of actinide elements. Peter’s interest in advancing instrumentation for improved thermochemical determinations continues with current efforts to couple ion mobility with guided ion beam mass spectrometry,
Kent M. Ervin, Guest Editor Mary T. Rodgers, Guest Editor
969
dx.doi.org/10.1021/jp401080r | J. Phys. Chem. A 2013, 117, 967−969
