edited by
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ROBERT C.
BRASTED
University of Minnesota Minneapolis. MN 55455
Interview with Jannik Bjerrum and Christian Klixbull Jqirgensen George 6. Kauffman California State University, Fresno, CA 93740 Jannik Bierrum. Emeritus Professor of Chemistrv at the University of Copenhagen, is one of the world's leading authoritieson the stabilitiesofcom~lexions. Horn in Cooenhagen on April 5, 1909, he is th; author of more than 130 articles on coordination chemistry. He has been active for more than three decades in the promotion of international scientific contacts and in the training of young research workers. He is a member of several Danish and foreign academies and the recipient of numerous prestigious prizes and awards. Christian Klixbiill J$rgensen, born on April 18, 1931, in Aalbore. Denmark. received his cand. mae. and PhD deerees from ;t ~oiversit;of copenhagen in 195h and 1957, respectively. He is a former student of Bjerrum's and the author of seven books and almost 300 articles. He sewed as the Director of the Office of Scientific Advisor to NATO, Paris (1959-601, Director of the Theoretical Inorganic chemistry Group, Cyanamid European Research Institute, Geneva (1961-681, and Professor of Physical Chemistry at the University of Geneva (1969-74). Since 1974 he has been Professor of Inorganic Chemistry at Geneva. Kaullman: IWs a real pleasure to conduct this interview not only because llve known both of you gentlemen for more than two decades but also because, to the best of my knowledge. Mis is the first Impact joint interview with a professor and one of his former students. Since the majority of our readers are chemical educators. I hope that, among other things, we will be able to expiore the teacher-student relationship more thoroughly than usual. Professor Bjsrrum, I studied the life of your father', who passed away in 1958. He is well known as the oriainator of the canceot that strona electrolvtes arealmost comp elell alrsoclateo nto 100s n sol.tlon m o w mat hls Interest on scoence *as aroaed oy n ? paternal abn!. m e pnysrc$s!4 rstme Blerrum
I 1002 I
Christian Kiixbllil Jpgensen
Journal of Chemical Education
Meyw. Did anyone, other than the obvious example of yaur falher, have an influence on your choice of a career? Blerrum: Yes. I suppose that I was born and raised in a family of the best Danish scientific tradition. Not only my lamer but also my paternal grandfather. Jannik Petersen Bjerrum, was a university professor. In the gymnasium I toe was strongly influenced and insplred by my great-aunt and teacher in physics. Kirstine Meyer. A reform in Danish gymnasia requiring teachers and students alike to carry out experimental investigations in physics and chemistry and introduced at the turn of the centurv was mainlv due to her influence. Act- y. 1 was not especla y ,nteresteo n my school work untll tna age of 12 or 13 when Ibegan to st& physlcs oa~ghtme necessary eqLlpmenland began to carry out chemical experiments in my parents' home. i read chemical literature, for example. Benellus' "Stoichiomefrische Untersuchungen," horn my father's library. At the age of 15 1 was allowed to work in my father's laboratory where I took up more meaningful projects alter gaining some experience in qualitative and quantitative analysis. I verified some of BerzeIiw' ex~eriments.obtained reasonable atomic weiahts for more than ten elemels. and made comparat ue exper menral pnase diagram st~aieson hh.CI.MgC &O ,i and c a m llle (KC .MgCIr6H,0) My own persona stbdies and investigations gave me a firm basic understanding for later studies. KauHman: Christian, can you tell us a little about your early interest in science and your gymnasiumdays? Jflrgensen: When i was one year old, my parents moved to Copenhagen, where I lived until 1958. Two years later I moved to Geneva. The municipal libraries in Copenhagen were excellent. I borrowed 3.000 books on very diversified subjects. This extensive reading lell me with two lasting impressions: how rapidly accepted theories change and haw microscopically little we know compared to what is unknown. Beginning at the age of 12.1 had a small laboratory at home where i began observing colored flames and later carried out separations of rare eanhs by recrystallization. Sho!tly before that time, I met the astronomer Luplau C.
Jannik Bjerrum
Kauffman, G. B., J. CHEM.EOUC., 57, 779, 863 (1980).
George Kauffman
Janssen. who oermined me to look throuah his fine teiascooa and to borrow b o o ~ shom n r lmpresslve c a l l e n m Professor Enoe Rasmussen of the dongel ge Veter naer-og -andban# skok IRoya Veterinary and Agricultural College), of whlcn Jannlk s lamer wasolreclor, d scusseo stamlc spectra wlth meand allowed me to use a large spectroscope to observe the line spectrum of Cesium. I was baffled that the long series corresponding to excited ns, nd, and nf states were not even in the catalogs. Iattended me gymnasium in Denmark from 1947 to 1950. There were only 15 students in mv class. Iwas the worst in French. which is ironic. conriderim m e tan mat i row have to &cure n m e Geneva dm&t o i UNS language Perhaps tho3 w I1gove some comfort l o your student readers Kauifman: Prolessor B euum, born what yod ve sala. t appears as t you had decided upon your goal long before you entered the university. Bjerrum: ThaVs consct. Even long before I took my final r c h w l examination (studentereksamen)atMa age of 18.1 had opted for a career in chemistry. The question was only whether I should study to be a chemical engineer at Danmarks tekniske H6jskole (Technical University) or, as Christian did, study mathematics, physics, and chemistry at the University of Copenhagen in order to Obtain teachino in all three subiects. I chose vat a third - comoetenca . ~,~~ passibility-to be a "magister" (maglsler sclenliarium) in a free scientific study. In thiscasethestudy plan is individually arranged with the professors at the university. Such a plan has now bean discontinued. i entered the University of Copenhagen in 1927 and obtained my master's degree in chemistry in 1932, with a majw in physical chemistry, under Johannes Nicolaus BrAsted's direction. During my studies I profited by my contact not oniy with such outstanding teachers as Einar Biilmann and J. N. Br@nstedbut also with my father's friends, especially Ole Chiewitz and Niels Bohr, who helped to mold my scientitic development and to strengthen my Scientific instinct. Kaunman: Professw Bjemrm, what were your earliest research experiences at the university? Bjenum: Aner I quickly passed the obligatory courses in analysis and synthesis, my first research work was the preparation of anhydrous alcohols With my teacher Hakon Lund. which I carried out at the same timethat It w k up research at the Royal Veterinary Agricultural College. My interest in coordination chemistrv. which became mv most imoortant field of research. beam aurlng the qualotat ue analysts course haa nollced that copper-ammanm SOl.t~~ns~ S L P P O SI0 ~ ~Contam the letraammlne complex) .nderwenl a color mange trom vlo el to o l e on ncreaslng the ammon a concentrat on. and n my subsequent research I studied this phenomenon. I was able to show that the color change was caused by the formation of a pemaammine complex with a very small formation constant and with a spectrum clearly different trom that of the tetraammine. Kauffman: We'll go into more detail on "our metal-ammine studies shortlv. B L f~m t et s SL p a generatoon Cnrrst~an,can you snare wnn ~s your cno ces ~nyou m verstyeo.cat,on. on panmlar. yodr dec soon to wow wllh Professor Bierrum? Jprgensen: My first "real" job was as an instructor when I was about 22.1 W85 blessed with having tolerant and supportive parents. In the summer of 1950, it was my intention to attempt to be a cand mag.. preparing tor teaching in secondary school. Except far some anernom practical work, the cuniculum for asnonomers, chemists, mathematicians, and physicists was almost identical. Durina the anernaans. I became a national chamoion in dodoina oroanic svntnesw i mLst cmiess IM~ Chose chem shy as a mam subpct tor an apparently arbmary reason Every ahernoon in n s laoaratory at SBIvtorvet. a 0-old ng whlcn was then a can ot IheTecnnlcal Lnlversty .an0 k. my mentorto-be, was drinking tea for a few hours with his 12 assistams and two or three students (the yearly production of university candidates war 0.6). 1 found this egalitariantreatment of undergraduates so attractivethat Istayed. Ilearned not to Put less M a n 26 grams of tea in the Niter pot, and I acquired a marathonic rhetoric. Seriously, I've always respectedJannik's tolerance for young collaborators havina entirely different interests. I read Jannik's thesis even before entering hls research gmup. I must be a bad Scandinavian since I seem to lack respect for complex formation canstants. I certainly enjoyed transition-group complexes because they are colored. The compensation fund for the Marshall Plan was at that time providing Beckman DU spectrophotometers, those inexpensive but robust instruments which Over the years have resisted the onslaught ot even medlcal students. Shortly thereafter, the Cary 11 was received with great enthusiasm and used 23 hours a day for a long time. I should em~hasizsthat the almost invariant minure of the four " h.. ad' sciences-m~lhematics. chem stry. phys cs, and astronomy -was specific lor Scand.nau!a at tnat lime. n Csnhai Europe. on the otfw nand. there is a w de gu Ioelween chemistry ana phys cs. My mire-year exam n a t m had an almost medieval schalaslic character. For two full hours we disputed the qUeJtiOrI of whether scandium or gallium is most similar to aluminum. The representative (according to our plan) for lhe StudenVs Union, being among the hilarious public for defending me, went home taking half me lethal dose of acetylsalicylic acid. ~
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Kaullman: Those who have been privileged to associate with you over the years will appreciate what must have transpired during the exam. Professor Bjerrum, what is your recaliection of Christian at lhis time, as a student and as a budding scientist? Bjerrum: Even as a gymnasiumstudent. Christian wrote letters to me about chemical problems. As a university student in 1950 he looked me up in me laboratory, and, as he just said, I gave him a copy of my dissertation. "Metal Ammine Formation." He must have stayed upail nightreadingthe book, tor the next day I wasastonished that he had understood everwing so well. He started withresearch at the same time as he foilowed the normai plan for his study. He was sxtremelv. mod " in auaiitative analvsis and ,Dassed the course in one third 01 the normai Ume. At lnat time in Denmar* it was a very extensive course aea in9 w In nearly all the elements. On the other nand. ne had some trouble with qantmiveanalysis, n pan because01 cenar d sagreemsnts onana yi.. cal precision and accuracy. Christian was an extremely gifted student. In his research he had plenty of ideas, and it was a pleasure for me to work with him. However, in my opinion. he wanted to publish his results too quickly before they were sufficiently digested and put Into a proper form. I tried, with little effect, to improve his stvle. the last time beino at his defense of his doctoral dissertation in 1957. Chrman has a brdltsnl nt.11 on, an0 for thlr reason he nas made oniy a few metakes II h10 sc ent f c wow However, somelames tee mat hls very large and valuable scientitic production would have been easier to survey and mare accessible to readers if as a student he had listened more to my criticism. Kaufiman: This couid be a good time to change the subject. Professor Bjerrum, our guests in this column have all made multiple contributions to science. We are interested in finding out which one or ones they feel will have the oreatest immct on the chemical communitv. I doubt if mere's a chemist alive todav who hasn't heard of "our 1941 doctoral dis.enatian It's attained ~ ~ .. the 51at~s01 a lrde Chemlcai classnc is nfllence .sancsted to by the fact rnat has oeon cited in more lnan 955 p~olicatlonronce 1961 accoralng 10the Science Citation Index. It is thought by many to have revitalized the field of coordination chemistry. Am I correct in assuming that you consider it your greatest contribution and, if so,could you please tell us something about its genesis? Bjerrum: Yes. you're right. As I related previously. in 1927. when i was 18 wars old. I stated studvino the imenselv blue coaoer-ammonia solutions. I lornd Inat n the presence at an ammonodm salt n nlgn concentratoon I sas passsb e to make homogeneous Cu-Nh, sol~tlonseven at small ammon a COnCenwat~OnS I then oegan to study the equ llor um cond r ons in these ~Oiutionsby measuring the very small ammonia vapor pressures over the SOiUtion~of constant ionic strength, at that time NH,NO. being used. In this way Iobtained the average number of ammonia molecules bound per capper atom (now internationally well known as ;I) as a function of the free ammonia concentration. An analysis of the data showed the existence of all the intermediate comolexes uo to the oentaammine comolex and the consecutive tormallon constants T n e copom-ammnc m k was puo shed n German by the Dan sh Acaaemy of Scence ana Leners over the pernod 1931- 1934 and s lor In 5 reason not a5 we I known as my later worr mere 5 qu lea b Iof nestory that is pan of the 'Metal Ammme 'treat se StLaled 101 SIX montns in Germany-wnth Xarlmlr Fa,ans on Munlch ana w i n Gearges de Hevesy in Freiburg im Breisgau. In 1933, after completing a magisterdegree. Iobtaineda positionat the University of Copenhagen Institute for Medical Phvsioloov. . -. where I was accuoied with biochemicalstudies on the melmo jsm of copper in raobit o o w In 1934 1 obla nea a nockefeller Fe o w m p to st& with me biochem st DI -eonor Michae sat me Rocksteler lnslel~letor Medica. Research n Nee Yark and iuckl) uss promlsed oy Professor Biilmann a position as a teacher at the Chemical Institute when I returned to Copenhagen. At lhis time i realized that if I could measure pH in ammoniacal metal salt SOlUtion~ with a sufficiently high accuracy, it would be possible in a very easy way to extend my copper-ammonia studies to all ammine-forming metal ions. The electrodes which couid be considered tor such Studies at the time were: the hvdraoen aas electrode. the ouinhvdrone . .~~ e ectrode. and tne glass eleclrws. Of lhese tne hydrogon gar electrode s of imlted Jse, and m e qu nhydrone e ecwode can only measereme hydrogen ,on conceotration in m i d o n s rith @ < 7 The glass e ectroae 9, ol co.rse. of far more universalapplication. i learned that in Duncan Anhur Maclnnes' labarataryat the Rockefeller Institute in New York they hadsucceeded in making glass ektrades of Cwningghss 015. They were both reliabieandaccwateand had the theoretical pH dependence. For these and oher reasons this electrode would be ideal for complex chemical studies. After I had published a short mu own studies .m m . r with Michaelis. he was kind enauah to let me continue~, w i n this glass electrwe At fvsl works0 on y late at mgn. s i n g his personal off ce laboratory electrode i cont ndea there complex cnemical slaies after my return to Denmark, and m e res~ltsafths worn. Mela Ammme Formatoon
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2 Bjerrum, J., "Metal Ammine Formation in Aqueous Solution: Theory of the Reversible Step Reactions," P.Haase and Son. Copenhagen, 1941.
Volume 62
Number 11
November 1985
1003
in Aqueous Solution: Theory of the Reversible Step Reactions," were published as my doctoral dissertation in eariy 1941 during the German occupation of Denmark. I succeeded in sendino about 50 eooies to the Unled States oetore the 1941 oomomg of Pearl Harbor so it was known n America durmg WOWWar I1 It was abstractedat length n Chamrcal Abrfracls, wn cn wnam y must have contributed to its being rapidly recognized asan important publication. As you. Christian, William Brock, and K. A. Jensen have recently pointed out. It contributed to chemical terminology by making the word ligand, coined in 1916 by Aihed Stock and flrst used in English en passant by Tsuchida in 1938. a household word among Engiish-speakingchemists. KauHman: Christian. what do vou consider vow most imoortant contribw tons to science? What was the state of the an" on yow fleld when you fwsl OmOBrked on your research. and what nas been yoLr suosequem fled of interest? Jflgensen: Iam happy that i don't have to write my own necrology. Sublects ramify when I look at them. At least chronologically. there is one plausible answer to your question: explaining why Send f-group compounds ere colored and have excited states In the 1 to 6 eV range. However, the explanation deveio~edinto arouo-theoretical enoineerino " , " " and the anauiar over la^ model elaborated with my comrade Ciaus E. Schaffer, who is now Jannik's successor. Also, the electron transfer bands (due to transfer of one electron from reducing to oxidizing atoms) provided optical eiechonegativitieswhich turned out lo be llnear functions of the molecular orbital ionization energies later determined fram photoelectron spectra. There is a second field, for which iam grateful to have lived long enough to see the beginningofa rationalization. Just as the "element" concept was elaborated during the century between Bayle and Lavoisler. SO the constitution ol matter by quarks and leptons recently has beoun to clarifv. , I do not feel frustrated bv workino - .oart-time as a "tame gemhemst" trylng to predict chemca propenier of systems contamng 4nSaturated quarks. I mink that oy their indbct vs approach chemlsls a00 something that Is needed by deductive physicists. I believe that it is very rare that huifful resulh come from a committee deciding "Let's try to do something useful." Rather, the academic conclusions are some day applied to problems that could not be solved otherwise. For instance. I have a very fortunate collaboration with Professor Renata Reisfeld of the Hebrew University in Jerusalem regarding excited levels and energy transfer in lanthanides lasoeeiallv in olassesl used far lasers and more recent. . " y n urnmescent solar concentrators, oased on me total nternai retlectm in glass platso. mss laea can a so os sxterded to fluorescent materfalsthat do not tolerate Me heat of molten glass. For example. Professor Reisfeld has soaked a solution into Vycor' glass with pores so narrow that Rayieigh scattering is minimal. The exceptionally weak electron transfer bands of the uranyi Ion also have relations to exploiting solar energy. More generally, the photochemical interpretations by Adamson, Baizani, and others are to a great extent derived fram me identification of ilgand fieid and electron transfer bands. Slnce i t l r r t ~ e g a n research, anumber of beilefs have ossnasmolirhsa For examp s,the trwaisnt ianltenlder have ssrsntlaily .Llevdr ilks a gaseoLs lon in spherical symmetry. In practice, only P F and Yb3+ have been compared with 4 f 2 Pr(ii1) and 4f '3 Yb(ll1) in condensed matter. Intermediate coupling works far M(I1) and M(iII), using Racah's parameters of interelectronic repulsion. in 1968 Carnail and his group almost completely identified ail +levels up to 4 eV. assisted by a parameterized theory far band lntenslties. The &groups show a VBN different behavior. rationalized between 1952 and 1965. The hqpothes s that the c-grodp energy levels are delermined oy the qu le t ny. nonspher ca pan of the olherw se huge Made ung polenlm was shown to be untenable in 1956. A new approach was necessary because water and hydroxide, oxalate, and maionate anions show very similar perturbations, somewhat smaller than those induced by ammonia. The same reasoning was eaended in 1963 with the 4f-and Sfgoups. As in many other moleeuiesand polyatomic ions, the &group transitions are normally due to transitions from roughly nonbonding to snongly antibanding diike orbitals. Kadlman: Professor Bierrum. durino the more than four decades since "our d ~ s e n a l ~ oyod n ve continued to enrch the chemlcal l!teralure w th nUmer0t.s COnlrlOUl ens Would yo6 care to d SCLSS some of these? Blerrum: I'd be glao to 00, ge, but wlth tne mderstandmg !ha! in M dolng i must necessarily neglect many of my numerous capable co-workers fram a number of countries. After my dissertation my scientific work continued in the field of solution chemistry, in particular, the thermodynamic, kinetic, and opticai properties of metal complexes. In 1944 1 introduced a new method for the investigation of Stepwise equilibria by means of the principle of corresponding solutions and showed how it is possible to treat semiquantitatively weak complex formation, such as that of copper(l1) chloride (and later of cabalt(ii) chloride) in a solvent with high and varying concentration of the complex-forming elecboiyte. During the period 1947-51 1 was occupied with the discrepancy between the Brmsted and Lewis definltions of acids and bases. While thelr base definitions agree well with each other, such Is not the case with thelr acid definitions. For historical reasons i felt that the acid name should be resewed
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Journal o f Chemical Education
for the protonic acids, and I pointed out that h pmon lsaif cannot be acid considered as an acid. Therefore. instead of wino " two different - . -daflnitfons. i proposed for L e w s acoco ~ u c as h BF,. SO2,and the proton itself the term anllbasc, expressing lherr ao ty to neutralize bases w lnout being acids. However. tnis nomenclat~rehas famd mited use only in Denmark and Germany. Christiandrew my attentianto the fact m a t h s h a r p band of the necdymium ion at 427.5 nm in aqueaus solution shined lo 429.5 nm in ethanol. We used this ObSeNation in following me formation of the neadymium aqua ion in alcoholic solution. My co-worker K. G. Pouisen and I noted with surprise that equilibrium in such complex systems as Fe(ll1kSCN and Ni(1i)-amlne is not reached instantaneously. In fact, the complexes in the first system do not form at ail at Cod*) temperatures. Omer reactionsof the transition metal ions could be similarly followed by ciasslcal methods at temperatures down to -IOO°C using methanol as solvent. These experiments showed for the first time the Conne~tionbetween rates of complex formation and valency and eiechon Configurations of the metals in the transition series. By estimating half-lives of dissociation d the complexes in acid solution at two temperatures we caicuiated the activation eneroies. The values of the activation eneroies for the format on and atssoclat on of ins n~cksi(likand capper(ii)sthylened amme comp exes that we obta ned in tn1s way were m fair agreement w In reslits obla ned later oy the re axallan memoas developed oy E gsn and co-workers This pioneering work has not achieved the recognition it deserves. and i have Often regrenedthat the experiments were not continuedand published in more detall in an international journal. in 1951 ilse and Hartmann were the first to repwt on the application of crystal field theory to explain the absorption spectrum ofa transltlonmetal Ion. Their .oaDer . had a decisive influence on the research in mv laboratwv. In collaoorat on wnth Ballha-sen and .Drgsnsen the theory was appi ed la me specha of the copper( Ikammama camplexsr and provided an explanation for the so-called pentaammineeffect discovered in my first paperon the subject. I participatedIn theresearch in this field until 1956. Bailhawen and JFrgensan, together with Ciaus Schdffer, made important experimental and theoretical con hi but ion^ to the development of ligand field thewy during the following years. My students and i have malntained an interest in the unidantate behavior of ethvienediamine over the "ears since 1948 when I oubiished a oaoer on the trlstethy ened amlnel capper(ll1ion wlth E. Juhi N elsen One of the en I gands is Indeed manodentate. Other shaiss have incided platinum(ll,. chromun(I I, and slCer(.r in fact, as lateas 1978 Schwarzenoach ded cams a paper l o me at the time of a celebration of my 70th birthday lhat suggested a dimeric form ofthe silver manoethyienediaminecomplex. This paper actually followed very shortly Professor Schwarzenbach's death. Eva Bang and I feel that the complex is more than a dimer. However, it Is one of those unresolved orablems. In thedecade of 1962-72 we carried out numerous invsstioations. "~ ~. svstsm at ca ly cover ng the comp ax-tom ng ability of the water-solbb e phosphfne Ilgand, olphenylphosphinoben2ene-m5~IIonate.Tns wow of Ahrlana. Cnan. and others was used as a basis in this study. This work was coordinated with Pearson's hard and softacid-base theory slnce the phosphlnes function in his categorization as soft ligands. The physical chemistry of electrolyte solutions has always been of great interest to me. i have contributed to soivlng the problems connected with a c t i ~ i t ~ c o s f f i ~ i the e n tusefulnessand ~. iimltatlonsof a constant ionic medium. an0 the proolem of d st ngu sn ng oetween on par formation (outer spnere asocial on) an0 chemcal complex lormation (nner sphere association). Though most of my work has been performed wlth amine systems. i have also worked with other ligands such as chloride, cyanide, thiocyanate, and perchlorate. Kaunman: -t's quite a recital of accomplishments, but you failed to mention your compilation of stability constants, which has been of such utility 10 chemists. How did this come about, and what was your role in the compllatian? Blerrum: For a number of years i had collecteddataan complex formation in solution, and as early as 1947 1 published apaper In Danish "On the Tendency of Metal Ions Towards Complex Formation." This wwk led I. M. Kolthoff (then President of the Commission of Physicc-Chemical Data of Analytical interest) to invite me in 1951 to coilaborate on a publication of "Tables of Stability Constants." Iundertwk this task, but it was soon obvious that it was more than I could manage owing to the almost explosive development of the field during the 'tlnies. I am indebted lo the late Lars Gunner Sillen of Stockholm and the late Gerald Schwarzenbachof Zurich for their helo in comollino data for both morgan c and orgamc llgands Obr comolnedenons res~lted in m e p ~ icstnon o of the tables Others nave continued In s wow Kauffrnan: The resurgence of inorganic chemistry in large measure is related to developments in caardinatlon chemistry. I was aware of this as I started my graduate education in the very eariy '50's. An important factor in this growth was the series of Conferences that developed into Me biennial international Conferences on Coordination~Chemlstry, In fact. I first met you ~
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and Christian and coincidentally the editor of mis series, Pmfssor Brasted, at the 6th iCCC held in 1961 at Detroit. I understand mat you played a prominent role in the brganiration of the ICCC. Bjerrum: You may not know that the first of these conferenw was organized as "A Discussion on Coordination Chemistry" by Joseph Chan and held at Welwyn. Hertfordshire. England, in Septembei of 1950. The second conference, held at Copenhagen in August of 1953, was organized by Professors R. W. Asmussen, K. A. Jensen, and me. This w s the first truly international Conference tin coordination chemistry, and It was here that the faundatlons were laid for the series of congresse. which have become an imernationai institution and which are anended regularly by hundreds of chemists. So I suppose that I have played a small part in furthering international scientific contacts. Kauttman: You've aiso played a great part in furthering international chemlcal contacts, coordination chemistry, and training of young research wohers. Could you please mention a few dl the many chemists who have been attracted by your reputation and who have came from far and wideto work with YO"? Bjerrum: in 1948 i became Professor at the University of Copenhagen and Director of the Laboratory of Inorganic and Analytical Chemistry of Danmarks tekniske Hpjskole in Copenhagen. Until then Ihad had to do ail my experimental work myself, This new situation made It possible far me to continue my studies with the help of students, many of whom have become internationally well-known chemists. From 1948 to 1960 they have worked in Chemistry Laboratory A at Danmarks tekniske H$jskole, and since 1960 they have worked in Chemical Laboratory I of the H.C. a s t e d Institute. Six of my Danish students are now full professors in inorganic or physical chemistry: Svend Erik Rasmussen in Aarhus: Carl J. Ballhaus6n and Claw E. Schaffer at this university. Fiemming Woldbye is at Danmerks tekniske H$jskoie, and Erik Larsen at the Royal Veterinary and Agricultural College, all in Copenhagen. Christian, of course, is in Geneva. They have ail made valuable contributions to cwrdination chemistry, as have many of me foreign visitors who have worked with me suchas Arthur W. Adamson. Fred Basoio. Clifford S. Garner, Gilbert P. Haight, and Robert L. Pecsok fromlhe United States, and Miheiy T. Beck from Hungary. The 1973 Nobel laureate, Geoffrey Wilkinsonof imperial College, London, assisted by F. Albert Cotton also worked in our laboratories. Kaunman: What do either of you look for in a young person who wishes to carry out research with you? Bjerrum: When a Danish chemistry student o r e guest t o m another country wants to work under my guidance. I find out what he stands for, and I arrange a research program so that both of us benefit from me cooperation. I strongly believe in maintaining a very flexible attitude with regard to both my coileagues' and my pupils' choice of their research problems. Jbrgensen: IWs not anen that young scientists come to work with me. I am much more of a generalist consultant than I am a research director selecting a staff. However. I would defend the opinion that two difficulties are as strong impediments to being a chemist as are for a locomotive engineer to be colorblind or compulsorily always wearing dark sunglasses. One of them is a bad memow. , . which mav be relatedto adisinterest in facts. Another lsa lack of tno~gntassociatans beween otnerwire perfectly rememoeredfacts For the r own sakes, persons w intheseoefeets shou d lmda career i n a f elaolner lhan chemistry. Kauffman: Professor Bjerrum. you've been involved in chemical education for more than three decades. Have you noticed any changes in the quality of students? HOWdo you feei about the present educational system? Bjerrum: The general quality of students in science is definitely lower than in the past, but the relatively few who succeed in passing all the necessary examinations with m o d results have never been better than thev are todav. -~ Personally. i thank that m r present edxationai system works we out the author toescampla n mat so few of thestan ng srudenlsget m e r finaiaegrees. Tne aulnor lies want more lor lne money they spend, out unfortmately Inns cannot be done without lowering the standards for the candidates. Along with other countries. we had a studentrevolution in 1968. Many responsibilities and duties were taken away from the full professors after that period. They have lost much influence, and they no longer have the power to direct their teaching and the researchof the scientific staff in the same way as previously. Also, in my opinion, the students and the technical staff have gained too much influence an me administration of the universities. Since my retirement in 1979. 1 enjoy working with my own hands in the laboratory. It makes me feel like a student again. Kaunman: Christian, I know that most of your research is theoretical and that consequently you have no problems obtaining equipmem. But Professor Bjerrum, have you had difficulties with funding? Bjerrum: My research has always been rather cheap, and I haven't had any great difficulties in obtaining the necessary funds for myself and my coworkers. at least not after the end of the 'fifties. but the near tuture i w k s vew ~. ~.~~ bad. In order to improve the Danish economy our present government has cut down an everything, unfortunately aiso on science, and many scientists at the ~~~
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universities are in dangercf losing their positions. Kaullman: in what area of your field do either of you feel that the greatest contributions will be made in the future? Bjarrum: In my opinion, the future of condination chemistry lies in the bioinorganic field. J6rgensen: I feei that inductive and comparative investigations of related compounds wlil become increasingly important. lWs not always realized the1 the structure of atomic soectra was undarstwd before ouantum mechanics w a ~ a p plea to monatom'c enltiss with several electrons By the s a w M e n . qbantum cnemmry nar oeen most s~ccessfuin lreatmg "venicai' problem obe)mg Fmnck amcondon s princpie, sucn as opt ca trans t onssna pnatoelectron ionization. In my opinion, quantum chemistry has contributed much less to describing me motlon of N (at least three) nuclei on (3N 5) dimensional potential swiaces. In many areas of chemistry, an ounce of ObSewationS is worth more than a pound of theory or a ton of computer output. ~~
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Kaunman: Do either of you feei that there is any conflict between me demands of teaching and those of research? Bjerrum: No. Ithink that teaching and research go well together. Jprgensen: Yes, but teaching is not nearly as much fun. KauHman: Have either of you at any time felt any constraint in your research because of teaching obligations? Bjerrum: Yes, as a young professor at both the Universityand at Danmarks tekniske Hojskala before the separation of the two institutions in 1960. It e n felt that Ihad too many duties and too littie time for research. For this reason I hdd stomach troubles during most of the 'fifties. Kauflman: TOask a personal question. what are some major nonprofessio~ a1 activities that have helped to enrich your lives? Bjerrum: My different hobbies and especially my happy family life with my wife Grethe (nee Ehiers) have brought me a great deal of contentment. Jllrgenren: Religion has been of great importan- in my life. Being born In Denmark, I was a Lutheran. But, like G. K. Chesterton, i began to ask myself what the Protestantswere orotestino aaainst todav. and in 1959 1 was acceot" ea oy the Roman Mthal c C n ~ r c has a tang bie proof for its ndsstrdctnb ty (Accoramgto George Bernard Shaw. I s oener lo be a bad example tlwn 10 be 01 no u ~ e lhowever, ph4osopnmliy i am qu le c me to me Eastern Orthodox Churches. This is a very difficult topic to discuss with most people, because they tend to extrapolate that their denomination was created when they r a e four years old. However, we actually have to contemplate a 1950-year-old organism. Amona formal laaic. science fiction " mv. favorite hobbies are ashoohvsics. . . lmaloc 01s people argue that i wr le thns myse fr and banmole coilectlng i LOto coilect Stamps. out I abanooned ph lale ). wheneven thamorr vlrt.0~ count, es oeQm ssu ng stamps oslenslo y mended for coiieclaa n Geneva. a lotapatienceandamemoryfartiny detailsallow collecting minw banknotes rich in information. Kauffman: Professor Bjerrum, since you come horn a "sciemific" family. haven't your interests and accomplishments, as well as mose of your father. had an effect on the career choices of vaur own children? Bjerrum: Yes. i in nr so Eacn of my aoven chiiaren has taken a dn;verslty degree, an0 four of my sons are active sciem rts. N e s .an" hoe" Berrum, m ?"organc salt me I cneminry: Ois arm k B,errum. on prolem chernstry: Pod1 Jannik Bjenum, in membrane chemistry, and my youngest son, Morten Jannik Bjerrum, in coordination chemistry. Kaullman: Would either of you care to make any predictions about the future of chemistry?
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Jbreenren: Chemistry is not the preservation hall of old jazz that it some times looks like. We cannot know what may happen tomorrow. Someone may oxidize mercury(l1). francium(i), or radium(ii). A mineral in Nova Scotia may contain an unsaturated qvark per 10'' nucleons. (This is still 6000 per gam.) We may pick up an extraterrestrial edition of Chemical Abstracts. The universe may be a 4dlmensional soap bubble in an lldimensional space, as some supersymmktry theorists argued in May of 1993. Who knows? Kaullman: Have you noticed that the lines of demarcation between disciplines are disappearing? Do you find this trend desirable and how would you encourage it? J6rgenren: I haven't noticed it. We have journals on fluorine and on lanthanides: if one on thulium were started. I would even subscribe to it. interdisciplinaritywbuid indeed be desirable. How should we encourage it? Try to give secondary school teachers higher salaries than garbage collectors and try to interest children in books. Kaunman: Assumino that vou were a . vouna universitv. araduate again. what field would you chwse for graduate study? Bjerrum: I would most likely take up resoarch in the field of bioinorganic chemistry.
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Jprgensen: i would became a postgrad~alestudent m a oarder area b e tween chem stry and pnysics wodd never spem any time on comminws. Each evenlng woud say !not loo lodly, to myselt what think aood t h Establishment. As Paul Bergs$e sald, "Time resolves ail problems."
Volume 62
Number 11
November 1985
1005
