Special Issue Preface Cite This: J. Phys. Chem. A 2018, 122, 2825−2828
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W. Lester S. Andrews Autobiography Published as part of The Journal of Physical Chemistry virtual special issue “W. Lester S. Andrews Festschrift”.
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research laboratories in Huntsville. His host was Dr. Charles Colburn, widely known for research in fluorine chemistry. After revealing to Dr. Colburn that he was going to Berkeley in the fall, Lester was again told that he should seek out Prof. Pimentel as his research director. On the next day Lester went to the TVA library and read several recent research articles from the Pimentel lab. Matrix isolation infrared spectroscopy presented a good mix of physical techniques, apparatus design, and new chemistry. Lester decided then to talk to Prof. Pimentel about his research as soon as possible, and ask to join his group. After two fruitful conversations with George, Lester became a part of the Pimentel group in mid September 1963. Pimentel passed the word on to new students to address him as “George,” and George personified the player-coach role with his research team. George was a great man, a great teacher, and a great research scientist. George held a stimulating group seminar and a one hour appointment with each graduate student every week. (The ACS Award in Chemical Education was renamed the George C. Pimentel Award in Chemical Education in his honor in 1989.) Lester went to this appointment every week with questions to ask and/or new research to discuss. After a group seminar in the spring of 1965 George announced that he was too busy for appointments that week, and Lester approached him on the way out and told him if he had a minute he could hear about the methyl radical: George replied “come back with me to my office.” Lester realized then, as he would more and more as the years rolled by, that Berkeley was an excellent choice and that Pimentel was an even better choice. The Pimentel group was very helpful to new students and always ready to answer questions. In particular, Dr. Bradley Moore, a Pimentel Ph.D., then a new Assistant Professor, provided excellent advice on research (Moore went on to a distinguished career, a member of the National Academy of Sciences and Dean of the College of Chemistry at Berkeley). Lester wrote his Ph.D. thesis in the summer of 1966 and designed a state-of-the-art double dewar cryostat for liquid nitrogen and hydrogen coolants to be constructed in the chemistry department machine shop. In September 1966, he began teaching and research in the Chemistry Department at the University of Virginia as an Assistant Professor and member of the Center for Advanced Studies in the Sciences. Lester was attracted to Prof. Paul Schatz as a senior spectroscopist and future colleague. Paul was particularly helpful with sound advice and encouragement for a younger faculty member. Asking questions about the possibility of making liquid hydrogen with a helium liquifier, Lester talked to Dr. Bascom Deaver, a lowtemperature physicist at UVA, and they learned about the closed-cycle “Cryodyne” refrigerator using helium under pressure that would reach 14 K. The decision was made to purchase this refrigerator and to assemble a new vacuum
utobiography of W. Lester S. Andrews [75th birthday year 2017] Lester Andrews was born January 31, 1942 in Lincolnton, North Carolina, to Clara Adele Self Andrews from that area and William Baker Andrews from central Mississippi. Lester grew up on the campus of Mississippi State University, where his father was a Professor of Agronomy (Ph.D. Michigan State University in 1936), known worldwide for developing the physical method for applying anhydrous ammonia (ammonia gas) under pressure directly into the ground as a fertilizer. His mother studied piano at Peabody Conservatory and participated in local classical music circles enabling her to provide music appreciation and education for her family. Lester balanced work in the local public schools with building toys, play houses, boats, work tables, etc., playing baseball and the clarinet (three years in the All-State Band), and Boy Scout activities leading to the Eagle Scout award. Lester enjoyed being a Little League baseball coach and manager for his two sons. One of the defining experiences of his growing up years was a ten-day Boy Scout canoe trip from the Boundary Waters of Minnesota into the Quetico Provincial Park in Canada, which made Lester an avid canoeist for life. In the summer of 1991 Lester as Scoutmaster led a crew of his older scouts, including a son, back along the same route. After an excellent high school chemistry course taught by Mr. Bill Foster, who later obtained a Ph.D. and became the head of Student Affairs at Mississippi State, and many discussions with his father about chemistry, Lester decided to major in Chemical Engineering at Mississippi State. He did this in spite of the fact that his father warned him that he would really prefer chemistry. After three years and a summer job at the Humble Oil Research and Development laboratories in Baytown, Texas, Lester realized that his father was right. While at Humble Lester talked to every staff member that he met about graduate schools in chemistry, asking where they studied and their opinions of the top three programs in the country. The dominant answers to the last question were California at Berkeley, Cal Tech, and Harvard. Dr. Joe Franklin, a distinguished senior scientist at Humble, particularly recommended a rising star at Berkeley, Prof. George Pimentel, as a research advisor. (Franklin went on to be a Welch Professor at Rice in 1963, and the ACS Frank H. Field and Joe L. Franklin Award for Outstanding Achievement in Mass Spectrometry is Named after him.) Lester applied for Ph.D. programs at Berkeley and Cal Tech and decided before Thanksgiving to go to Berkeley. During his senior year Lester took extra chemistry and physics courses to get ready for graduate school in Chemistry. He also won the Hamilton Watch Award for the Outstanding Senior in Engineering and graduated with Highest Honors in 1963. Lester continued with music and played principal clarinet in the concert band his last two years at Mississippi State. The following summer, while at the TVA research center in Wilson Dam, Alabama, Lester visited the Rohm and Haas © 2018 W. Lester S. Andrews
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thermally evaporated Pd atoms to compare with laser ablation. On a car trip up the Seine River, Lester learned how Laurent became such a master in a canoe: he was a backup for the French National kayak team. The Andrews research group progressed in different subject areas like charged species and HF-, DF-base complexes. Metal atom reactions were limited to alkali and alkaline earth metals (except for Be) using homemade nichrome wire heaters to evaporate these reactive metals from small stainless steel Knudsen cells. During a visit Dr. F. W. Froben from the Institut für Molekülphysik der Freie Universität Berlin suggested laser ablation experiments to produce more metal atoms. In 1988 a pulsed Nd:YAG laser was obtained to ablate metal atoms including boron, the most refractory ones like Ta and W, and all of the others including lanthanides that are not radioactive were also investigated. The YAG laser was used to investigate metal atom reactions with many important small molecules including O2, N2, H2, H2O, CO, O3, F2, OF2, Cl2, CH4, C2H2, H2O2, and (CN)2 over the years. Reactions with CO opened Lester’s eyes to the presence of metal cations and electrons in the ablation plume, since metal carbonyl cations, neutrals, and anions absorbed in different regions of the infrared spectrum, which was confirmed by DFT frequency calculations on all three species. (These investigations were done by Dr. Mingfei Zhou, who moved back home into a Professorial position at Fudan University in Shanghai. Dr. Charles Bauschlicher and Dr. Matthew Neurock also helped with many calculations involving transition metals.) The idea to add an electron-trapping molecule to the matrix as a charge diagnostic was borrowed from the radiation chemistry investigations of Dr. Tadamasa Shida working at Kyoto University in Japan. With a trace of CCl4 included in these matrix samples, the carbonyl cation absorptions increased while the anion bands decreased owing to the capture of most of the ablated free electrons by the CCl4 molecules to give CCl3 and Cl− in the matrix. This allowed for a higher survival of the cations produced by M+ reactions and a lower number of free electrons for capture by neutral metal carbonyls. Isolated anions were also observed from laser-ablated metal reactions with an electron-capturing molecule like ozone to form isolated O3−. A collaboration with the Oak Ridge National Laboratory and Dr. Rodney D. Hunt opened the group to Th and U atom reactions, where UO2+ was also observed. (Rodney earned his Ph. D. with Lester, and he returned to work in the lab in Charlottesville several times when he was visiting his parents in nearby Waynesboro.) Laser ablation and reactions of U atoms with O2 and with N2 produced the same oxides and nitrides including OUO and NUN previously investigated by infrared matrix isolation using sputtering sources for these early actinides. A particularly fruitful investigation involved U and CO, where the inserted CUO was the major product and isoelectronic with NUN. It turned out that the singlet ground-state CUO molecule was trapped in solid neon, but a slightly higher energy triplet state was formed in solid argon: the two states have very different infrared spectra. (This work was reinforced by theoretical calculations done by Drs. Jun Li and Bruce Bursten then at The Ohio State University.) Experimental investigations of CUO(Ng)n (Ng = Ar, Kr, Xe; n = 1, 2, 3, 4) complexes were performed by Binyong Liang, a Ph.D. student with Lester from Fudan University, who went on to do research in physical biochemistry at Virginia. Hydrogen reactions required colder substrate temperatures to hold the H2 molecule for reaction, and refrigerator
chamber, cold window mount, and radiation shield to do matrix isolation experiments. John Harvell, a cryogenic engineer at Cryogenic Technology, Inc. in Waltham, Massachusetts, helped with this new apparatus. The first matrix experiments with this new closed cycle refrigerator were performed in January 1967. This machine was retired in 1984 with over 56 000 h of operation and was replaced by a newer model that attained 10 K. Meanwhile Lester and several graduate students were doing alkali metal reactions to make halomethyl free radicals through halogen atom abstraction and to make ionic molecules (M+)(O2−) by addition reactions for infrared spectroscopic analysis. As expected the infrared spectra exhibited very strong interionic stretching modes. The Chemistry Department obtained a laser Raman instrument in 1971, and Dr. Douglas Hatzenbuhler and Lester observed the superoxide anion in (Li+)(O2−), which revealed a strong intraionic stretching mode. Drs. D. E. Milligan and M. E. Jacox invited Lester to visit them at the National Bureau of Standards, and they gave him a sample of OF2 to make the OF free radical by lithium atom abstraction of an F atom. The Raman spectrum of OF2 in solid argon also revealed OF signal at the same frequency shifted: the signal increased with time of exposure to 488 nm laser excitation owing to laser photodissociation of OF2. The next investigation of (M+)(Cl2−) by the group produced resonance Raman spectra with eight overtones and broadened the Andrews group research to include UV and visible spectroscopy of matrix-isolated species. These studies led to more spectra of ionic molecules such as (Na+)(HCl2−) and the first preparation of the trifluoride anion as (Cs+)(F3−) with both infrared and Raman spectra of the anion, which were done by Dr. Bruce Ault. (Bruce went on to a successful academic career at the University of Cincinnati.) Lester gratefully acknowledges the gift of 0.5 L stainless steel “cans” containing a few atmospheres of fluorine from Dr. W. B. Fox of the Naval Research Laboratory with the assurance that it was safe to use this quantity of fluorine in the lab outside of a hood. Dr. Niel Bartlett kindly provided a liter of fluorine during a Berkeley sabbatical in 1974. Years later Dr. Joe Thresher refilled some of these containers for us. The next investigations led to the development of open discharge tube vacuum ultraviolet light and matrix gas sources and the formation of the isolated CF3+ and HF2− ions. Confirmation for CF3+ required 13C substitution, and Dr. Helge Willner, Lester’s first research visitor, assisted with the synthesis of suitable precursors. Helge went on to be Professor of Inorganic Chemistry at the University of Wuppertal. Next the naphthalene cation was made by two-mercury-arc UV photon ionization, and matrix vibronic absorption spectra were obtained by Dr. Benuel Kelsall. To do gas-phase spectroscopy on halomethyl cations such as CH2Cl+, Lester spent a sabbatical leave year on the photoelectron spectroscopy of several halomethyl radicals at the University of Southampton with Dr. John Dyke and Prof. Neville Jonathan. Lester gladly played in goal for the research group 5-a-side “football” games at Christmas time. Dr. Laurent Manceron spent a two-year postdoctoral with Lester in Virginia in 1984−1986 working on several problems including Li atom complexes. During this period the research group made canoe trips on the James River near Charlottesville, and Laurent proved to be an expert canoe captain. In 2000 Lester returned the favor with a three-month sabbatical in the laboratory of Laurent at the Universite Pierre et Marie Curie, Paris working on the Pd(H2)1,2,3 complexes in solid argon using 2826
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arranged by Dr. Pekka Pyykkö. (Björn and Colin Marsden did calculations on the nitride and phosphide products NUF3 and PUF3.) Lester spent sabbatical time in Toulouse working with Colin, and was awarded an honorary doctorate (D. h. c.) from the Toulouse Universite Paul Sabatier in 2004. Lester officially retired from the University of Virginia and moved into Emeritus status in May, 2008, while continuing research with Department of Energy support for the first four years. Laser-ablated and excited uranium atoms were reacted with N2 to form NUN and UN, and these new spectra exhibited additional satellite absorptions for five dinitrogen complexes of NUN and six for UN: DFT calculations showed that five NN molecules were bound equatorially with NUN and likewise for UN, with one more axially to the U center in UN. (Calculations to support these structures were performed by Drs. Bess Vlaisavljevich and Laura Gagliardi.) Photolysis of cold samples showed that U excited in the near-ultraviolet inserted into the triple bond of NN to form the NUN dinitride. Laser ablation of carbon-rich uranium/carbon alloys into a condensing argon matrix gave absorptions for UC and C UC. The alloys were produced by the group of Joaquim Marçalo at the Instituto Tecnologico e Nuclear, Sacavem, Lisbon, Portugal. Lester won the Distinguished Scientist Award from the University of Virginia in 2008 followed by the Plyler Prize from the American Physical Society in 2009 for extensive work involving the vibrational spectroscopy of interesting new molecules. Work in the Andrews laboratory during the decade since “retirement” continued with reactions of H2O2, OF2, HF, and (CN)2. Obviously hydrogen peroxide is a good source of two OH radicals, and laser-ablated metal atom reactions provided clean sources of many M(OH)2 and M(OH)4 molecules. The OF2 molecule yielded both F atoms and OF radicals, just as 488 nm laser photolysis did some 40 years ago, and group 4 metal atoms took advantage of both F and OF to form OMF2 molecules. Mercury is the only metal that could not be ablated in pure form owing to its liquid phase. However, both dental fillings and sodium amalgam were laser-ablated into argon along with the OF2 reagent, and the first oxyfluoride of mercury, OHgF, and also FOHgF and HgF2 were obtained. Lester began work on HUF and DUF at Virginia himself. He was awarded a Deutcher Akademischer Austauschdienst faculty research visit grant at the University of Freiburg, Germany, in 2011 to work with Dr. Sebastian Riedel, where HUF and DUF were also investigated. Calculations on these compounds were performed by Thomas Vent-Schmidt, a Ph. D. student with Riedel. Seb has now moved on to a Professorship at the Freie Universität Berlin, where he continues to do innovative experimental halogen chemistry and theoretical calculations. Lester worked with Seb’s group again in the laboratory during October and November 2017. The cyanogen reagent provides CN radicals, which can form metal cyanides or isocyanides depending on their stability for bonding with a particular metal atom. Uranium was his first reaction with cyanogen, and new absorptions were observed for UNC, U(NC)2, and U(NC)4, which were calculated to be more stable than their cyanide analogues. The cyanides are calculated to have much weaker absorptions ∼100 cm−1 higher than the stronger isocyanides. Both 13C- and 14N-enriched precursors were prepared, and the observed isotopic frequencies and their ratios were in good agreement with the calculated values for the isocyanides. In fact comparison of the 12/13 and 14/15
technology kept providing lower temperatures, next 7 K and then 4 K. The Al + H2 reaction is a noteworthy investigation. Several groups were involved in the hunt for the dialane molecule Al2H6, which was predicted from theory by the Schaefer group to have the diborane structure. The first reactions to form AlH and AlH3 were straightforward, and these products were trapped using H2 in argon in the 2% range at 10 K. Lester even observed weak absorptions that could be assigned to the strongest absorptions of dialane, two bridged H stretching bands, but this molecule has eight infrared active modes. His group was able to manage 10% H2 in argon at 7 K, but still could not observe all of the infrared absorptions that were predicted by the calculations. The answer for this problem was to use pure hydrogen with freezing at 4 K, which is clearly an ideal medium to produce and preserve the higher hydrides. The AlH molecule was trapped in high yield, and UV photolysis markedly increased the AlH3 absorptions at the expense of AlH. Five more bands that correlated with the calculations for Al2H6 were observed: annealing the solid H2 to 6 K increased the seven dialane bands in our spectral range. Deuterium gas has a slightly higher freezing point, and these experiments provided appropriate isotopic counterparts. To confirm the overall chemistry, warming the hydrogen sample to 7 K allowed the unreacted hydrogen to evaporate and the trapped molecules to diffuse and associate. Thus, all sharp bands disappeared, and two new broad absorptions appeared, which agreed with the reported spectrum for solid (AlH3)n. Warming the deuterium sample to 10 K allowed the excess deuterium to evaporate and produced a new broad band for solid (AlD3)n [the other one was below our Fourier transform infrared (FTIR) limit]. Unlike diborane, dialane spontaneously forms a covalent network solid, so it appears to be impossible to prepare neat molecular dialane Al2H6, but solid hydrogen can isolate and preserve the dialane molecules. Our experimental work on dialane was done by Dr. Xuefeng Wang from Fudan University in Shanghai, China. Reactions with CH4 and the F- and Cl-substituted methanes opened the door to a wide variety of organometallic molecules where carbon−metal multiple bonds were formed and investigated with DFT. His group first attempted Ti reacting with CH4, but the anticipated CH2TiH2 product absorptions were weak. Dr. H.-G. Cho working in the Andrews lab suggested that fluorine substitution might enhance the reactivity with Ti, and the reaction with CH3F was highly successful. The CH3−Ti−F insertion complex and the methylidene CH2TiHF were prepared and found to undergo reversible visible and ultraviolet photochemical α-H transfer rearrangement. DFT structure calculations revealed an agostic distortion for the methylidene. (Dr. Cho was a sabbatical visitor from Incheon University in Korea, who returned to work with Lester several three-month periods and another year for many very fruitful collaborations.) Similar reactions with Th and U produced the first actinide carbon double bonds (CH2ThH2, CH2UHF, and CH2UH2), which also exhibited agostic distortion. Reactions of U atoms with fluoroform and chloroform produced the first uranium−carbon triple-bonded molecules HCUX3 (X = F, Cl, Br), and similar reactions with NF3 resulted in NUF3. (The former works were done by Jon Lyon, a Ph. D. student, who went on to teach at Clayton State University in Georgia, and Xuefeng Wang, who returned to Shanghai as a Full Professor at Tongji University.) The latter molecule came to mind during a lecture by Dr. Björn Roos at the Winter School for Quantum Chemistry in Helsinki in 2007 2827
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isotopic frequency ratios with those observed for the diatomic CN radical as a reference can determine which atom is bound to the metal. This is because the C−N stretching mode acquires antisymmetric character for the bound atom, which increases the central atom’s participation in the vibration and its isotopic frequency ratio. The important spectral pattern of isotopic mixtures ((12CN)2 + (13CN)2) and mixed isotopic molecules ((12CN)2 + (12CN13CN) +(13CN)2) reveals the CN stoichiometry for the product molecule. (Experimental work on these molecules was done by Dr. Yu Gong, now a Professor at the Radio-Chemistry Institute in Shanghai, and theoretical work by Dr. David Dixon and his group at the University of Alabama.) Finally, Lester investigated laser-ablated beryllium reactions with halogen molecules himself in his lab at Virginia. The simple molecules and complexes Lester has investigated in solid matrices are physically stable, but many are chemically reactive, hence the role for matrix isolation in keeping them safe and sound. It may be possible to preserve some of these functional groups (such as UC, NUN, CH2UHF, HCUCl3, and NUF3, for example) with ancillary ligands perhaps even up to room temperature. After moving to the University of Virginia, Lester played principal clarinet in the UVA orchestra for three years. Later he joined the Charlottesville Municipal Band, where he now plays Eb and Bb soprano clarinets. He has also played in the pit for 10 local musicals (including Fiddler on the Roof twice with 14 shows) and with the UVA Klezmer Ensemble for seven years. Lester also enjoys attending operas with his wife. Lester gratefully acknowledges the contributions from all of his collaborators and the support of his family during this research. Without all of you 865 publications would not have been possible in the first 54 years. Working with you in the laboratory has led to many lifetime friendships!
W. Lester S. Andrews
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