James A. Ibers (1930-2021)
Pioneer in structural inorganic chemistry, James A. Ibers, dies at age 91
by Mercouri G. Kanatzidis
Prof. James A. Ibers, a pioneer in the field of structural coordination and inorganic chemistry, and a long-time faculty member in the Department passed away on December 14, 2021. He was 91.
Jim brought the science and art of X-ray crystallography to inorganic chemistry, making the structural determination of molecular metal complexes a foundation of the field. By the mid-1960s, he was one of the very few who saw the unlimited potential of X-ray diffraction for characterizing the structure and bonding of inorganic compounds, even though it posed an intrinsically more difficult problem than many organic structures. Before the 1970s, the determination of molecular structures using X-ray crystallography was a niche specialty in physics and very few expert crystallographers. Chemistry was blind to structural details for most compounds that were being discovered at that time. The advent of structural determination using X-rays in chemistry, and particularly inorganic chemistry, coupled with advanced data collection and processing made it broadly accessible to chemists. It was a pivotal achievement that enabled the development and growth of our molecular understanding at an atomic level. It encouraged the synthesis of new compounds and led to powerful synthesis methodologies. In a sense, it democratized the field and opened the door for exponential growth and many technological achievements. X-ray crystallography was established as the primary tool for determining the atomic and molecular structure of a crystal. Jim played a central role in showing the path and leading the revolution in which powerful single-crystal X-ray diffraction techniques came to be routinely used to uncover the complexities of bonding in inorganic systems. These techniques are a cornerstone of modern chemistry and rest on the pioneering work done by Ibers. For his contributions, Ibers was recognized by the American Chemical Society Award in Inorganic Chemistry, the ACS Linus Pauling Award, and the American Crystallographic Association Martin J. Buerger Award. He was elected to the American Academy of Arts and Sciences and the U.S. National Academy of Sciences.
Born in Los Angeles, Ibers lived in California until he was 31, taking his first job as a chemist at Shell Development Company in Emeryville, California. In 1961 he moved to New York to work at the Brookhaven National Laboratory and then joined Northwestern University as a full professor in Evanston, Illinois in 1965. While at Shell he developed estimates of standard deviations of observed structure factors and of determining the electron density from intensity data, a variety of new atomic form factors, including relativistic ones, anharmonic oscillations of nuclei, and tables of atomic scattering amplitudes for electrons, which were made available in Volume 3 of International Tables for X-ray Crystallography. This much-needed collection of organized information had a high impact on the budding field of structural crystallography, which was only beginning to diffuse from the physics to the chemistry community. The rapid ascendance of inorganic chemistry and its enormous scientific and technological impact not only in chemistry but also in physics and beyond, in large part developed because we began to understand in detail the real structure and chemical bonding in crystalline compounds, regardless of composition and structural complexity. The moment inorganic chemists realized they could solve the structures of the compounds they were making, single crystal XRD became a Game Changer in the development of our field. And Jim played a big role in developing the rules of the Game. For example, as an Associate Editor in the early days of Inorganic Chemistry, he was instrumental in establishing the journal’s guidelines for publishing single-crystal data. Many of us remember the pre-electronic era when the infamous “Blue and Yellow” sheets were required when submitting a paper on a new structure. These were the precursors of the Crystallographic Information File (CIFs) and the vast number of organic, inorganic, organometallic, coordination, and solid-state compounds in the digital databases today.
His career was divided into three major areas over the decades. In the sixties and seventies, he focused on a fundamental understanding of the structures of coordination complexes, transition metal chemistry, and hydrogen bonding. The structures determined by Ibers and his research group, as well as his analysis of this information and his correlation with other information in hydrogen-bonded systems, made a major contribution to our understanding of this area. Because hydrogen bonding is ubiquitous in Nature, the impact this work has had on diverse fields of basic and applied science cannot be over-emphasized. The 1968 book by Hamilton and Ibers, Hydrogen Bonding in Solids (7), has become a classic in the field. Jim was one of the early users of neutron diffraction for chemical problems. He studied bifluoride containing compounds to differentiate between a symmetric F-H-F bond from the disordering of asymmetric bonds. He and Hamilton also reported the first structural characterization of any xenon compound XeF4. In the 1970s his main interests included the study of the structures of coordination and cluster compounds of direct interest to the budding area of bioinorganic chemistry. This included solving the first crystal structures of the class of Fe/S compounds synthesized by Richard H. Holm as models for the active sites of ferredoxins. In the 80s he transitioned into the study of porphyrin chemistry and made the key contributions to the discovery of solid-state chalcogenide compounds. The latter was a permanent incursion, and he stayed focused on this area until he retired in the early 2010s.
Jim loved exploratory synthesis and the discovery of new compounds. He and his students were very skilled and successful in uncovering such new compounds as the excitonic Ta2NiSe5 narrow-gap semiconductor that many physicists love so much today. Jim, like Linus Pauling, whom he met as a graduate student, was a "chemical" solid-state chemist. By thinking of solid-state structures in terms of their coordination chemistry, he contributed to the development of a conceptually powerful approach and on the experimental side was an early developer of the “reactive flux method” used worldwide to discover a wide variety of new solid-state compounds, many with interesting physical properties of considerable importance. In the last decade of his very productive career, Jim concentrated on the solid-state chemistry of uranium and neptunium compounds of the chalcogenides and pnictides. This work has involved the development of new procedures for handling these materials. It has encompassed syntheses and structures, as well as experimental physical properties and theoretical electronic structure properties. Here, again, Ibers recognized an area of chemistry that was largely neglected, especially that of neptunium and other actinides. Jim published about 870 articles mainly in ACS journals. Jim’s continued publishing beautiful and new structures, with the most recent in 2020.
In addition to remembering Jim for pioneering work on the structural chemistry of inorganic substances, his unwavering dedication to excellence, and his service to the chemistry enterprise, he will be remembered for BIP. Shortly after Jim joined the Department in the mid-1960s, Fred Basolo, Ralph G. Pearson, and Jim began group meetings which later expanded to include all inorganic chemistry groups and became large enough to fill a conference room. No one at the time anticipated that this meeting, which was referred to as BIP (for Basolo-Ibers-Pearson), would become the time-honored tradition that continues today. BIP began as a nine o’clock event on lazy Saturday mornings. For more than the next 50 years, inorganic chemistry students at Northwestern gathered on Saturday mornings to hold BIP. It is well known not only at Northwestern but also in national and international inorganic chemistry circles, despite Pearson’s having left Northwestern in the late 70s. During early BIPs the Professors would call upon a student to give a research progress report - without warning. Later, they were warned ahead of time when it would be their turn to talk about their work, but the impromptu nature was upheld by the ground rule that banned visual aids such as transparencies. Only chalk and a blackboard were allowed. TBIP has moved to Friday afternoons in the last decade and is still as vibrant as ever. Jim was a strong supporter of BIP and attended almost every meeting until very near his retirement.
Jim had a tremendous influence in building the Chemistry Department and the Inorganic Division over the past five decades to become top-ranked in the world. Jim cared deeply about the welfare of the Chemistry Department and was involved in all important aspects of its operations, including serving on key committees and recruiting. He retired at the age of 83 but even after he became emeritus, he attended and contributed his time and wisdom in helping to make good departmental decisions. While Jim didn't sugarcoat the things he cared about, his honest appraisals were always in line with what was best for his department. He had a legendary dry wit and humor, and colleagues could count on his direct and frank advice. “Personally, I can attest to how supportive Jim could be,” said colleague Mercouri Kanatzidis “He supported my move to Northwestern and in a way took me under his wing”. He used his hard-earned experience and wisdom to mentor more junior colleagues. Many of the inorganic faculty remember his communication style as a type of “tough love”, and, in hindsight came to understand it as a unique form of management and inspiration. Younger coworkers benefited from his mentorship as he demonstrated, explained, and modeled. Legend has it that he once advised a young ambitious assistant professor on how to successfully navigate the tenure process to achieve a successful, illustrious career. He said “I know how you and your friends are impressed with your work so far, but what counts is what me and my friends think, and we are not that impressed yet! Here is some advice on how to prioritize what's important in your research for maximum impact”. His mentorship went well beyond insistence on high standards. Jim and Joyce regularly hosted dinner parties where the tough love melted away and Jim shared his deep knowledge and passion for the Lyric Opera, the Chicago Symphony Orchestra, and an abiding respect for California wines.
In 2005 Jim and Joyce moved to downtown Chicago to enjoy the cultural scene. He would shuttle bus into Northwestern every day rather than walk the few blocks from his old Evanston house. And he continued to do so long after he retired. He was a disciplined and avid athlete he ran every morning, and he loved a delicious steak and conversation with plenty of impact. This advice was well received by the younger colleague, who continued on to a very productive career. Jim cared deeply about the welfare of the department even up to his retirement at 83, and even beyond that, as shown by attending all the important faculty meetings and contributing his advice and wisdom to the discussion.
To learn more about Ibers and how to memorialize his life and career, you can read his own story, as captured by the American Crystallographic Association: https://history.amercrystalassn.org/jim-ibers