Editorial Editorial TributeTribute to JosefJosef Michl Michl

IgorIgor Alabugin Alabugin 1,1,** andand Petr Petr Klán Klá n2,*2, *

1 1 Department of of Chemistry Chemistry and and Biochemistry, Biochemistry, Florida Florida State University,State University, Tallahassee, Tallahassee, Fl 32306, Fl USA 32306, USA 2 2 Department of of Chemistry Chemistry and and RECETOX, RECETOX, Faculty Faculty of Science, of Science, Masaryk Masa University,ryk University, Kamenice Kamenice 5, 5, 625 00 Brno,Brno, Czech Czech Republic Republic * Correspondence: [email protected] (I.A.); [email protected] (P.K.) * Correspondence: [email protected] (I.A.); [email protected] (P.K.)

It is our great pleasure to introduce the Festschrift of Chemistry to honor professor JosefIt Michl is our (Figure great pleasure 1) on the to o introduceccasion of the hisFestschrift 80th birthdayof Chemistry and toto recognize honor professor his exceptional Josefcontributions Michl (Figure to 1the) on fields the occasion of organic of his photoc 80th birthdayhemistry, and quantum to recognize chemis his exceptionaltry, biradicals and contributionsbiradicaloids, to electronic the fields of and organic vibrational photochemistry, spectroscopy, quantum magnetic chemistry, circular biradicals dichroism, and sili- biradicaloids,con and boron electronic chemistry, and vibrational supramolecular spectroscopy, chem magneticistry, singlet circular fission, dichroism, and molecular silicon ma- andchines. boron chemistry, supramolecular chemistry, singlet fission, and molecular machines.

 

Citation: Alabugin, I.; Klán, P. Tribute to Josef Michl. Chemistry 2021, Citation: Alabugin, I.; Klán, P. 3, 440–443. https://doi.org/10.3390/ Tribute to Josef Michl. Chemistry chemistry3010032 2021, 3, Firstpage–Lastpage. https://doi.org/10.3390/xxxxxReceived: 17 March 2021 Accepted: 17 March 2021 Received:Published: 17 March 22 March 2021 2021 Accepted: 17 March 2021 Published:Publisher’s 22 March Note: MDPI 2021 stays neutral with regard to jurisdictional claims in published maps and institutional affil- Publisher’s Note: MDPI stays neu- Figure 1. Josef Michl, credit from Neuron Foundation. iations. Figure 1. Josef Michl, credit from Neuron Foundation. tral with regard to jurisdictional claims in published maps and institu- JosefJosef Michl Michl was was born born in , in Prague, , Czechoslov in 1939,akia, just in at 1939, the beginning just at the of World beginning of tional affiliations. WarWorld II. Hard War times II. Hard for the times family for continued the family even continued after the war even when after the Communists the war when seized the Com- powermunists in 1948.seized Despite power all in that, 1948. Josef Despite received all an that, excellent Josef education.received an He excellent warmheartedly education. He Copyright: © 2021 by the authors. remembers his elementary- and high-school teachers whom he credits for his love of Licensee MDPI, Basel, Switzerland. warmheartedly remembers his elementary- and high-school teachers whom he credits for chemistry, as well as his very tolerant parents who allowed him to perform his first This article is an open access article his love of chemistry, as well as his very tolerant parents who allowed him to perform his Copyright: © 2021 by the authors. chemical experiments in the kitchen. He studied chemistry at in distributed under the terms and Praguefirst chemical and received experiments the M.S. degreein the inkitchen. 1961 with He physical studied organic chemistry at Charles Václav Hor Universityák in Submittedconditions for of possible the Creative open Commonsaccess andPrague electrochemist and received Petr the Zuman. M.S. degree He chose in 1961 Rudolf with Zahradn physicalík, an organic outstanding chemist physical Václav Horák publicationAttribution under (CC BY)the terms license and (https:// chemist,and electrochemist as his Ph.D. project Petr Zuman. supervisor He to chose work simultaneouslyRudolf Zahradník, on the an theory, outstanding electronic physical conditionscreativecommons.org/licenses/by/ of the Creative Commons π Attribution4.0/). (CC BY) license spectroscopy,chemist, as his and Ph.D. synthesis project of non-alternantsupervisor to -electronwork simultaneously systems. He was on introducedthe theory, to electronic (http://creativecommons.org/li- spectroscopy, and synthesis of non-alternant π-electron systems. He was introduced to censes/by/4.0/). photophysics during his postdoctoral studies with Ralph Becker at the University of Hou-

Chemistry 2021, 3, 440–443. https://doi.org/10.3390/chemistry3010032 https://www.mdpi.com/journal/chemistry

Chemistry 2021, 3, Firstpage–Lastpage. https://doi.org/10.3390/xxxxx www.mdpi.com/journal/chemistry Chemistry 2021, 3, FOR PEER REVIEW 2 Chemistry 2021, 3 441

photophysicsston and Andy during Albrecht his postdoctoral at Cornell studiesand to 19 withF NMR Ralph spectroscopy Becker at the in Universitythe laboratory of of Mi- Houstonchael Dewar and Andy at the Albrecht University at Cornell of Texas, and Austin to 19F. NMR His short spectroscopy return to in Prague the laboratory was interrupted ofby Michael the Warsaw Dewar Pact at the invasion University of Czechoslovakia of Texas, Austin. in His 1968. short At returnthe time to Pragueof this attack, was while interruptedparticipating by thein the Warsaw Löwdin Pact summer invasion school of Czechoslovakia of quantum inchemistry 1968. At thein Norway, time of this he decided attack, while participating in the Löwdin summer school of quantum chemistry in Norway, to join a theoretical physicist Jan Linderberg in Aarhus, Denmark. In 1969, Josef married he decided to join a theoretical physicist Jan Linderberg in Aarhus, Denmark. In 1969, Josef marriedthe love the of love his oflife, his Sara, life, Sara, a political a political scientist. scientist. They They loved loved traveling traveling around around the the world, world, espe- especiallycially mountain mountain climbing climbing (Figure (Figure2 ),2), and and Josef Jose enjoysf enjoys telling telling of their of their adventures, adventures, such such as ascrossing crossing the the Andes as as they they walked walked from from Argentina Argentina to Chile to Chile or climbing or climbing Mt. Kilimanjaro, Mt. Kilimanjaro, Tanzania,Tanzania, when when Sara Sara was was pregnant pregna withnt with their firsttheir child. first Lifechild. inflicted Life inflicted severe wounds severe onwounds on JosefJosef when when two two of of their their three three children children succumbed succumbed to cancer, to cancer, and more and recently, more recently, when Sara when Sara passedpassed away away after after half half a century a century of blissful of blissful companionship. companionship.

FigureFigure 2. 2.Josef Josef Michl, Michl, credit credit from from Veronica Veronica Vaida. Vaida.

AfterAfter the the stay stay in Aarhus,in Aarhus, Josef Josef accepted accepted a postdoctoral a postdoctoral position position with Frank with Harris Frank at Harris at thethe University University of Utahof Utah to learn to learn ab initio ab calculationsinitio calculations and, in 1970, and, a in research 1970, a faculty research position faculty posi- attion the sameat the institution. same institution. At this time, At this he joined time, the hecommunity joined the ofcommunity organic photochemists of organic andphotochem- started a long-term cooperation with many prominent physical and organic . Josef ists and started a long-term cooperation with many prominent physical and organic chem- quickly attained the rank of full professor and later served as chairman of the Department ofists. Chemistry. Josef quickly Then, attained he moved the to therank University of full professor of Texas atand Austin later asserved the M. as K. chairman Collie- of the WelchDepartment Regents Chairof Chemistry. in Chemistry Then, (1986) he andmoved finally to toth thee University University of Colorado,Texas at Austin Boulder as the M. (1991),K. Collie-Welch where he still Regents works Chair and teaches. in Chemistry When Czechoslovakia(1986) and finally became to the a democraticUniversity of Colo- countryrado, Boulder again in 1989,(1991), Josef where was freehe still to travel works back an tod histeaches. homeland, When and Czechoslovakia since 2006, he has became a helddemocratic the position country of head again of the in research1989, Josef team was at fr theee Institute to travel of back Organic to his Chemistry homeland, and and since Biochemistry,2006, he has Academy held the of position Sciences ofof thehead Czech of the Republic, research Prague. team He at likes the to Institute say that heof Organic isChemistry delocalized and between Biochemistry, Boulder and Academy Prague. of Sciences of the Czech Republic, Prague. He Josef has made a significant impact in many fields of chemistry. His independent likes to say that he is delocalized between Boulder and Prague. career at Utah started with the analysis of electronic states of fundamentally important π- systems.Josef This has work made revealed a significant to the world impact some ofin Josef’smany classicfields “penof chemistry. and pencil” His analysis independent ofcareer intriguing at Utah puzzles started which with now the can analysis be found of in electronic textbooks, states such as of how fundamentally two hydrocarbons important π- withsystems. identical This ionization work revealed potentials to the and world electron some affinities of Josef’s can have classic dramatically “pen and different pencil” analysis colors.of intriguing If pen and puzzles pencil werewhich insufficient, now can Josef be foun appliedd in advanced textbooks, spectroscopic such as how techniques two hydrocar- andbons did with it with identical remarkable ionization insight potentials and proficiency. and electron affinities can have dramatically dif- ferent colors. If pen and pencil were insufficient, Josef applied advanced spectroscopic techniques and did it with remarkable insight and proficiency. This work was a stepping stone for the next large research area—organic photochem- istry. Josef was one of the most important early contributors to the development of this field as he introduced the notion of excited-state potential energy surfaces that explained

Chemistry 2021, 3 442

This work was a stepping stone for the next large research area—organic photochem- istry. Josef was one of the most important early contributors to the development of this field as he introduced the notion of excited-state potential energy surfaces that explained the role of “funnels” (or “conical intersections”) as a way for the excited molecules to escape to the ground state. Perhaps it can be said that Josef’s unique advantage of spending a large part of his life traversing mountainous landscapes guided him in defining his famous models for organic photochemistry and showing how correlation diagrams can be used to deduce qualitative shapes of such surfaces. This work introduced important paradigms that have shaped the field, connected photochemistry with photophysics, and led to the famous book that he co-authored with Martin Klessinger. It is widely considered to be a masterpiece. Josef has applied his knowledge of photochemistry and spectroscopy to the prepa- ration and characterization of many reactive intermediates. This work afforded the first glimpses of the structure of many unusual species, including a highly reactive non-alternant hydrocarbon pleiadene (a molecule with rich chemistry and unusual photophysics), quin- odimethanes, biradicaloids, strongly twisted alkenes (such as adamantene), and pyrami- dalized alkenes, to name just a few. It also provided important early measurements for the structures of benzyne and cyclobutadiene. In the latter case, the double labeling with 13C al- lowed the measurement of bond lengths and provided evidence for heavy-atom tunneling. The scope of this work ranged from frozen glasses to cluster ions in mass spectrometers. A logical connection for a very curious man would be to expand these studies to other elements. In his search for the molecules with a Si=Si double bond (in collaboration with Robert West), Josef and his graduate students prepared many silicon structures that had never been directly observed before, including species with divalent or multiply bonded silicon atom. This pioneering work launched a new chapter in silicon chemistry. Another important insight in silicon chemistry involved the nature of sigma electron delocalization in oligo- and polysilanes, i.e., the silicon analogs of linear hydrocarbons. The electronic states of these molecules are remarkably complicated and are strongly affected by chain conformation. Josef’s work provided a simple, intuitive and general model that explains the origin of the conformational dependence of σ-electron delocalization in saturated chains of carbon and silicon. In the mid-1980s, Josef developed rigid molecules (“staffanes”) that can serve as elements of a molecular construction kit. These molecules were used to construct arrays of dipolar molecular rotors and propellers in search of surface ferroelectric behavior. Another very interesting direction of Josef’s research was his work on carboranes. His lab developed a practical synthesis of the key members of this family and investigated − • the redox couple consisting of the CB11Me12 anion and the isolable CB11Me12 . These species are highly unusual. For example, despite having an almost naked lithium cation, LiCB11Me12 is highly soluble in benzene and toluene. This anion was surprisingly hard to oxidize. Not satisfied with that Josef and his talented students prepared CsCB11(CF3)12, a species that is even more remarkably resistant to oxidation, resisting also strong acids and bases, and all other conditions (although scratching with a spatula would occasionally − bring it to a violent explosion). The salts of HCB11F5(CF3)6 are safer and with the reversible redox potential of more than 4 V above that of ferrocene, the isolable blue radical • HCB11F5(CF3)6 is a candidate for the strongest known neutral oxidant. The latest new chapter in Josef’s research is singlet fission, a process in which a singlet exciton splits into two triplet excitons. Although this process has the potential to improve the efficiency of a solar cell by nearly one-half, very few known materials supported singlet fission before Josef applied his insights and creativity. Josef’s work has greatly improved the understanding of the complexity of singlet fission and outlined the general design ideas of organic chromophores that may lead to practical materials in the future. It would be challenging to provide a complete list of Josef’s achievements, titles, and awards in this text. To name a few, he is a member of the U.S. National Academy of Sci- ences, the American Academy of Arts and Sciences, and an honorary member of the Czech Chemistry 2021, 3 443

Learned Society. He served as the President of the International Academy of Quantum Molecular Science, as the chair of the Photochemistry Commission of the IUPAC, as an edi- tor of Theoretica Chimica Acta, and especially noteworthy being his 31 yearlong service as editor-in-chief of Chemical Reviews. He has been a Sloan, a Guggenheim, a Fulbright, and a University of Colorado Faculty Fellow; he received many awards, such as the Cope Scholar, James Flack Norris ACS, Inter-American Photochemical Society, Wichterle, Hammond, and Neuron Foundation Awards, the Schrödinger and Porter Medals, the J. Heyrovský and Charles University Gold Medals, and the Patria Award from the Czech government. He holds honorary degrees from , the University of Pardubice, and the , Brno. He held close to a hundred visiting professorships and named lectureships, delivered hundreds of invited lectures at various institutions and conferences, has served on many professional and editorial boards, advisory councils, and committees, and has organized several international meetings. He has co-authored five books on photochemistry and polarization spectroscopy, and approximately 700 scientific papers in the fields of organic, inorganic, theoretical, and physical chemistry. Josef is a polymath, knowledgeable not only in chemistry but also, for example, in history. One of us witnessed an extraordinary situation during a tour of the castle Kokoˇrín in central Bohemia. A professional guide was late, therefore, Josef guided us himself, providing exciting, memorable details. We know Josef as an exceptionally brilliant chemist, a kind, warm and friendly person on whom one can always rely for a lucid explanation of a difficult concept. This Festschrift is a fitting tribute to the great impact he has had on the development of many branches of chemistry. The final part of this tribute is sealed with a special coda, a poem written by Kathleen F. (Kay) Edwards and Joel F. Liebman solely for this occasion. Ode to Josef Michl So many chemists’ contribution is about a nickel For their studies on latter day parchment and quill By contrast, consider a high denomination dollar bill Is what we ascribe to . . . Josef Michl So many chemists are moored, like a dock-bound boat Others resemble Johnny and Joannie One-Note By playing one chord. A few are diverse, but are fickle Very few are multiply productive. Here be . . . Josef Michl So many chemists are bland, and provide a slice of dill Others’ food is better approximated by an entire pickle Almost no others offer a meal that is as nutritious Far more than smorgasbord, elegant, scrumptious, For this “essen”, too, here be . . . Josef Michl Born 80 years ago in Prague Never content to be a cog Or just provide a # for a table (log?) He sought to scale the cliff, ignore the chaff. span the clef As a postdoc, he left home, where to stay? Wandered the globe, Now, U Colorado (Boulder), USA We celebrate a chemist of the world . . . our friend Josef Kathleen F. (Kay) Edwards and Joel F. Liebman, Maryland, March 2021

Acknowledgments: We are grateful to Professor Jack Saltiel (FSU) for the helpful comments on this tribute. Conflicts of Interest: The authors declare no conflict of interest.