Frontiers in coordination chemistry and its applications

There is a moment in a chemist's career when one reflects back in time to recollect what specific episode in their life made them chose such a unique profession. For a few of us this realization involves the process of natural selection or a naturally born instinct, whereas for most of us, such a decisive moment can stem from a single impression or experience collected from a chemistry textbook, a chemical reaction, a life changing event, or even chemical concepts applied by Bryan Cranston's role in the American drama series “Breaking Bad”. For me, this life changing episode took effect in the spring semester of 1993 at Michigan State University, where I nervously awaited the start of the introductory chemistry course 141. Like most freshmen in the audience I did not know what to expect from this course and was fearing the worst based on prior experiences suffered in high school. Soon enough, all the fear we generally associate with chemistry was about to fade away forever, and it was all due to a woman dressed in black giving an inspiring lecture on coordination chemistry. To me, Kim Dunbar was the quintessence of a chemistry professor and from that moment on I was hooked to inorganic chemistry for life!

Professors Michael Shatruk, Eric Schelter, and myself are honored and very proud to serve as guest editors for this special issue in Dalton Transactions honoring the many contributions of Prof. Kim R. Dunbar, the Davidson Chair of Science and Distinguished Professor of Chemistry at Texas A&M University in College Station, Texas. Kim is the first female faculty to hold Texas A&M's highest academic faculty rank. She has inspired and guided our careers as scientists and instilled in us a strong foundation of the beauty of synthetic inorganic chemistry. Kim's research efforts, developed over her independent career of over 30 years, encompass fundamental coordination chemistry but also have a much broader impact, given their implications in chemotherapeutic reagents, molecular magnetism, synthetic conductors, and the emerging field of anion–π interactions in supramolecular archetypes. Without question, her studies blend metal–metal bonds, supramolecular and mesoscopic chemistries with both fundamental and broad implications. At the core of many of these investigations are metal–metal bonds, which comes as no surprise given Kim's background with luminaries in the fields such as Professor Richard Walton (the John A. Leighty Distinguished Professorship and Emeritus as of 2001, Purdue University) and the late Professor F. Albert Cotton (W. T. Doherty-Welch Foundation Chair and Distinguished Professor of Chemistry at Texas A&M University). Her research program continues to unearth fascinating examples of coordination compounds relevant to the aforementioned research areas.

Another of Kim's qualities, well-known to many of her former and current students, postdocs, colleagues, and mentees, is her ability to instill excitement in those who work with her. Kim is one of the most productive chemists of her generation with over 400 research publications in peer-reviewed and high-profile chemistry journals (along with over 16 book chapters). She is also a dedicated teacher and mentor. We remember fondly her contagious enthusiasm for sharing knowledge with students in classrooms and for learning about new results at the infamous “Saturday morning Dunbar group meetings”. Kim is also an ardent promotor of diversity in chemistry, having served on a myriad of minority affairs committees and subcommittees at the American Chemical Society (ACS) and having volunteered as one of the first advisors for the ACS Scholars Program in the mid 1990s. Kim was therefore a natural choice to be awarded the ACS Distinguished Service award for the Advancement of Inorganic Chemistry, the second woman to be given such a distinction (the first being her colleague, Professor Marcetta Darensbourg) in its 54^th year as a top ACS award in inorganic chemistry. Consequently, given Kim's enthusiasm and dedication to diversity, her research program has provided the “tool box or sand box” for the training of students at the cutting edge of interdisciplinary science. Taking a moment to explore her research website, one notices how diverse her research group is and has been over her entire independent career. Speaking from personal experience, it was Kim who got me involved with the ACS and also the ACS Scholars Program. With a former graduate student and mentor, Dr Kemal Catalan, Kim introduced me to programs that supported underrepresented groups in the chemical sciences, namely the NOBCChE (National Organization of Black Chemists and Chemical Engineers) and the SACNAS (Society for the Advancement of Chicanos/Hispanics and Native Americans in Science).

Kim R. Dunbar is a native of Pennsylvania and obtained her B.S. in Chemistry from Westminster College, one of the leading liberal arts colleges located in New Wilmington, PA. Kim was inspired to become an inorganic chemist when she took a group theory course (as independent study) during her senior year. Not only did she read the Cotton group theory book from cover to cover but she also did all of the exercises. Kim became fascinated by the beauty of symmetry and its implications to chemistry, structure and spectroscopy. She then learned of the research of Al Cotton and Dick Walton in metal–metal bond chemistry and applied to both Purdue and Texas A&M and was accepted at both schools. Due to her Pennsylvanian roots, she succumbed to pressure from her family to go to Purdue since Indiana was a short drive away. As fate would have it, Kim got the opportunity to work for both chemists. She completed her Ph.D. degree under the guidance of Professor Richard Walton in the Chemistry Department at Purdue University, investigating the coordination and redox properties of multiply bonded dirhenium complexes. Her achievements as a PhD student and excitement about metal–metal multiple bonds earned her a postdoctoral research associate position in the laboratories of the late Professor F. Albert Cotton at Texas A&M University. The two years at Texas A&M helped Kim shape her future in terms of being certain that she wanted to pursue an academic career. After her postdoctoral stint, she commenced her independent career at Michigan State University, a place for luminaries in inorganic chemistry such as James Dye, Robert Grubbs, Gerald Babcock, Daniel Nocera and Mercouri Kanatzidis, among many other notable figures. Notably, it was at Michigan State where the discovery of the anticancer activity of cisplatin in 1965 by biophysicist Barnett Rosenberg and colleagues Loretta Van Camp and Thomas Krigas contributed to the birth of bioinorganic chemistry. It was therefore fitting that Kim, in her independent career, decided to explore the use of metal–metal bond chemistry in bioinorganic applications. At Michigan State, Kim's innovative research on metal–metal bonds led to the original syntheses of various dirhodium complexes and to the discovery of their binding to DNA. Soon thereafter she demonstrated their biological activity and photodynamic therapeutic effects. In related studies, Kim also demonstrated the use of these complexes as building blocks for the assembly of coordination polymers and supramolecular structures. In recognition of her excellent scholarship, Kim quickly rose through the ranks at Michigan State University to ultimately hold a University Distinguished Professor Chair from 1998–1999, before moving to her present institution.

At Texas A&M, Kim has expanded her research efforts and tackled new directions such as anion–π interactions, which have remained overlooked for quite some time compared to the prototypical cation–π interactions that essentially started the field of supramolecular chemistry. Kim was one of the first chemists to recognize the importance of anion–π interactions in various supramolecular and coordination crystal structures, and she expanded the study of these interactions from the solution phase to the solid state by demonstrating that anion–π contacts can serve as directing elements in supramolecular assembly.

Kim's research on molecular magnets was started at Michigan State, but she took these studies to an entirely new level at Texas A&M to become one of the world's leading experts in magnetochemistry and conducting materials. She carried out pioneering work on the design and synthesis of cyano-bridged multinuclear complexes that showed single-molecule magnetism and spin-crossover behavior. Her innovative use of various multidentate ligands has afforded fascinating molecular structures with controlled magnetic anisotropies and superexchange pathways. These coordination compounds also have a substantial inter-disciplinary impact as they provide excellent models for testing theories and advanced experimental techniques in condensed matter physics. Just as important were Kim's contributions to the areas of synthetic conductors and hybrid molecule-based magnets, where she made extensive use of the redox and magnetic properties of stable organonitrile radicals. Her group was the first to crystallize CuTCNQ and elucidate its crystal structure, explaining the nature of the widely researched semiconductor–insulator transition in this material. Her work on hybrid inorganic–organic magnetic conductors is an exemplary study in the application of various physical methods to solve highly challenging problems in inorganic and materials chemistry.

Kim's accolades are numerous, including recognition not only for her research but also for her continuously supportive mentorship. Among these awards are the Camille and Henry Dreyfus Teacher-Scholar Award, the Michigan State University Teaching Award, a Fellowship from the Alfred P. Sloan Foundation, the Sigma Xi Research Award, the Distinguished Alumni Award from Westminster College, Fellow of the American Association for the Advancement of Science, the Purdue University Department of Chemistry Distinguished Alumna Award, the Association of Former Students Inaugural Distinguished Achievement Award in Graduate Mentoring, Fellow of the American Chemical Society, Wilsmore Fellow, the Distinguished Achievement Award in Research from the Association of Former Students, an Honorary Degree from Westminster College, the Inaugural Eminent Scholar Award from Texas A&M University Women Former Students’ Network, the ACS Award for Distinguished Service in the Advancement of Inorganic Chemistry, and the Presidential Award for Service to the NOBCChE and the STEM Community. In addition, Kim has been Plenary and Keynote lecturer at numerous institutions and conferences worldwide and was a visiting professor at the Université de Strasbourg and the University of Melbourne. She was also an Associate Editor for the ACS journal Inorganic Chemistry, and has held numerous ACS roles at both local and national levels. Her productivity is not only reflected by her awards and scientific publications, but also by her commitment to producing chemists in multifaceted areas of science. Over her career, Kim has produced ∼60 doctoral students and hosted ∼20 postdoctoral associates, along with numerous undergraduates and visiting scholars.

We are thrilled to see the many, varied contributions to this special issue that reflect the range of Kim's contributions to the field of chemistry and the impact of her science on her friends, colleagues, former students and postdocs. Kim’s respected promotion of scientific advancement and international acclaim are also evident through her mentoring of many talented undergraduates, Ph.D. students and postdocs who have gone on to carve out illustrious careers of their own. We offer our sincere congratulations to Kim on the exceptional body of work amassed through her distinguished career and we look forward to her many years of creative discoveries yet to come. We are thankful to Kim for her unfailing support over our own careers. Lastly, we wish to thank Jessica Moon and Mike Andrews for their dedication and efforts in the development of this special issue.

---