150th anniversary of the periodic table of chemical elements. Periodic table, Mendeleev and philately.

Russian chemist Dmitri I. Mendeleev (1834–1907) has formulated the periodic system of chemical elements (PSCE) in 1869. Frequently, this is considered as one of the greatest inventions in chemistry. The year 2019 marks the 150th anniversary of this discovery and has thus been proclaimed the “International Year of the Periodic Table of Chemical Elements (IYPT2019)” by the United Nations General Assembly and UNESCO.

Philately is my hobby and in the last years I have focused especially on chemical items. From time to time I prepare short articles for newspapers or journals on various topics and support them with philatelic materials (1-4). I have recently prepared a short contribution about the periodic table, Mendeleev and also about some lastly discovered chemical elements for Slovenian journal »Kemija v šoli in družbi« (Chemistry in school and society) (5). Therein I have involved selected philatelic items that are related to periodic table and some I present also below. I am sure that this year some new stamps, first day covers (FDC), seals, etc., will appear to celebrate IYPT 2019.

Figure 1-6 (from top to bottom):

It is understandable that most of stamps that show Mendeleev were issued in Russia (and previously in Soviet Union). To the best of my knowledge, the first stamps showing Mendeleev were issued in 1934 (100 years after his birth).

Fig. 1 shows one of these. The stamp issued to commemorate 100 years of periodic table of chemical elements discovery (1969) shows Mendeleev deep in thought (Fig. 2). Two chemical elements that represented some problems to Mendeleev are marked in red. Gallium was then not yet discovered but he has predicted its existence. It was discovered by French chemist Paul Emile Lecoq de Boisbaudran in 1875. In contrast, indium was already known but its relative atomic mass was not determined accurately. Non-accurately determined relative atomic masses were the reason that in the first versions of the periodic table some elements were placed in wrong positions which was later corrected in improved versions. Interestingly, also the available relative atomic mass of ruthenium, the most important element for our research group was not very precise at that time (104.4; correct value is 101.1).

A commemorative postcard (Fig. 3) showing the portrait of Mendeleev with a stamp and corresponding seal were issued in 1957 (50 years after his death).

A souvenir sheet from 1969 (100 years of PSCE discovery) shows the stamp with Mendeleev which is embedded in his signed and dated work paper (Fig. 4).

Spanish post has issued the first day cover in 2007 (hundred years after Mendeleev died) (Fig. 5). The corresponding stamp shows a colourful drawing of the periodic table which was inspired by the paintings of Piet Mondrian, the Dutch painter. Four smaller white squares in the periodic table represent elements that were predicted by Mendeleev (scandium, technetium, gallium, and germanium).

First day cover from Armenia shows Yuri Oganessian who is one of the leading nuclear physicists in the field of superheavy chemical elements (Fig. 6). He was involved in the preparation of several elements, among them is also the currently heaviest which is named oganesson (Og) in his honour. Artificial heavy elements are very unstable and the radioactive decay pathway of the isotope oganesson-294 is also shown on the stamp and cover. With the isolation of this element the 7th row of periodic table was completed (Z = 118). The methods of how to “synthesize” new chemical elements, how to verify and name them, as well as some speculations about possible new element discoveries in the coming years were nicely presented in the paper of Prof. J. Reedijk recently (5).


  1. I. Turel, Acta Chim. Slov., 59, p. S94-S96 (2012).
  2. I. Turel, Acta Chim. Slov., 60, S115-118 (2013).
  3. D. Rabinovich, I. Turel, Philatelia chimica et physica, 35, 171-173 (2014).
  4. I. Turel, Kemija v šoli in družbi, nr. 1, p. 1-4 (2019).
  5. J. Reedijk, Row 7 of the periodic table complete: Can we expect more new elements; and if so, when?, Polyhedron, 2018, vol. 141, str. 1–4.


Our study on inhibition of cholinesterases and glutathione-S-transferases by organoruthenium complexes selected for cover feature in October 2018 edition of ChemMedChem

In this paper , a library of 17 organoruthenium compounds was screened for inhibitory activity against cholinesterases and glutathione-S-transferases of human and animal origins. The cover feature picture (see below) shows an organoruthenium-pyrithione complex which inhibits cholinesterases and glutathione-S-transferases at pharmaceutically relevant concentrations while we observed no undesirable physiological responses on the neuromuscular system as well as no toxicity against non-transformed cells. Combining these results with our previous study (Kljun et al.  Dalton Trans. 2016, 45, 11791-11800) which has shown the ability of this compound to inhibit enzymes involved in hormone-dependant breast cancer as well as high toxicity on MCF-7 breast cancer cell line it is supposed that the cover page compound can be an interesting candidate as a multi-target drug for the treatment of cancer or Alzheimer’s disease. In this multidisciplinary study we have joined the forces with our colleagues from different faculties of the University of Ljubljana (Biotechnical Faculty, Faculty of Medicine, Veterinary Faculty) and a student from University of Rijeka was also involved.

Cover page of paper:

S. Ristovski, M. Uzelac, J. Kljun, T. Lipec, M. Uršič, Š. Zemljič Jokhadar, M. C. Žužek, T. Trobec, R. Frangež, K. Sepcic, I. Turel, Organoruthenium prodrugs as a new class of cholinesterase and glutathione-S-transferase inhibitors, ChemMedChem, 13, 2166-2176 (2018).






Our study on concomittant polymorphism selected for cover page in June 2018 edition of Acta Crystallographica, Section C

Polymorphism is a well-known phenomenon and represents the ability of a solid material to exist in more than one form. It is not only important from the academic point of view but has also many practical applications or consequences. A typical example is the pharmaceutical industry where many drugs receive regulatory approval for only one polymorphic form. However, there are known examples where the patent was later obtained also for different form.

Sometimes the growth rates of polymorphic forms are sufficiently similar that such crystals coexist. In such case we call them concomitant polymorphs.

Concomitant polymorphism is rarely mentioned for ruthenium complexes and we have previously never observed it in any of previously synthesized compounds in our lab. However, during her Ph.D. study, Katja Traven has prepared several organometallic ruthenium(II) complexes, among other also with dimethyl 6-(pyridine-2-yl)pyridine-3,4-dicarboxylate ligand. In the latter system two types of crystals were observed in the reaction mixture and studied in cooperation with the Slovak group led by Prof. J. Kozisek. Crystal structures of both polymeric forms have shown that the most bond lengths are approximately the same but differences in the orientaion of methoxycarbonyl groups and p-cymene were found. These concomitant polymorphs also differ in melting point temperatures for cca. 10 °C.

Cover page of paper: K. Traven, I. Turel*, J. Koziskova, L. Bučinský, J. Kozisek*, Concomitant Polymorphism in Organometallic Ruthenium(II) Complex with N,N-donor Ligand, Acta Crystallogr. C74, 683-689 (2018).


Spring in Ru lab

Several interesting and important things have happened in our group during spring 2018.
During his short stay at our Faculty, Prof. Bostjan Kobe has shortly visited our labs. Bostjan and Iztok were classmates during their study of chemistry at the Univerity of Ljubljana. Bostjan later went to University of Texas Soutwestern America Medical Center at Dallas, USA, for his Ph.D. studies under the supervision of Nobel prize winner Johann Deisenhofer and he is now Professor of Structural Biology at the University of Queensland in Australia.
It is always nice to meet old friends to talk about the past, present and also future!

Professor Roger Alberto from the University of Zürich, Switzerland has visited our labs in May and held a lecture titled »Bioorganometallic Technetium and Rhenium Chemistry: Theranostics, Fundamentals and Applications« for the students of the FKKT doctoral study programme. Complexes of the radioactive element technetium are well established in diagnostic nuclear medicine, and various complexes of the gamma-emitting nuclide 99mTc are routinely used for organ imaging (heart, brain, etc). Professor Alberto was involved in the discovery of compound MIP 1405 which is on a good way to enter clinical use soon.

In spring 2018 two members of the group have finished their doctoral study. The Turel group thanks and congratulates to Matija Uršič on his successful defence of PhD thesis entitled »Synthesis and characterisation of ruthenium complexes with phosphine ligands« and to Katja Traven (nee Krančan) on her successful defence of PhD thesis with the title »Novel ruthenium coordination compounds with N,N-, N,O- and N,N,N-donor ligands«. We wish both of them all the best and continued success with new challenges.

Viva Voce examination at Royal College of Surgeons in Ireland

In mid March Prof. I. Turel was invited to act as external reviewer of Ph.D. thesis and Viva Voce examiner at Royal College of Surgeons in Ireland (RCSI). In this thesis D. Keogan has studied metallohydroxamates as novel anti-bacterial and anti-leishmanial agents under supervision of Dr. D. Griffith (Department of Pharmaceutical & Medicinal Chemistry).
It was a very nice experience and also a possibility to compare Ph.D. procedures at various institutions. Prof. Turel has up to now acted as external reviewer at academic institutions in Slovenia and abroad: Spain (University of Granada); Serbia (University of Belgrade); Italy (University of Cagliari) and Canada (University of British Columbia, Vancouver).
Photo shows: D. Keogan, D. Griffith, Prof. I. Turel and Prof. Emeritus K. Nolan (from left to right) at lunch after examination.

Chapter in book »Ruthenium Complexes: Photochemical and Biomedical Applications«

A book entitled »Ruthenium Complexes: Photochemical and Biomedical Applications« (ISBN: 978-3-527-33957-0) was recently published by Wiley-VCH (Weinheim). The book consists of 15 chapters (344 pages). The content of book is covering many interesting properties of this popular element and spans from coordination chemisty of ruthenium to photochemical and photophysical properties of its compounds. The book mainly covers the application of ruthenium complexes in medicine (anticancer and other potential ruthenium drugs; photodynamic therapy; binding to DNA; diagnostics; etc.). Few chapters are also dedicated to applications of ruthenium complexes in artifical photosynthesis, production of hydrogen and oxidation of water. One of the chapters (»Biological Activity of Ruthenium Complexes With Quinoline Antibacterial and Antimalarial Drugs«) was written by senior group members assist. prof. Jakob Kljun and prof. Iztok Turel.

More information about the book is available at the webpage of the Publisher.

Visit by prof. Lee Cronin

5976-1Professor Lee Cronin from the University of Glasgow, UK has visited our labs in May and held a lecture ‘Towards a general theory of chemical evolution’ for the students of the FKKT doctoral study programme. The national newspaper Delo has at this occasion published an interview with prof. Cronin. You can read it (in Slovenian) here.



Prolific 2017 for former postdoc Božidar

During his one-year postdoc in our labs Božidar Čobeljić introduced Schiff base ligands to our research group. Fruitful cooperation with Belgrade group in last years results in several recent papers which focus on the systemic synthesis and studies of heterocyclic Schiff base ligands of Girard’s reagents and their 3d metal complexes. Further papers are in preparation.

  1. Journal of Inorganic Biochemistry (IF 2016 = 3.348): Synthesis, characterization and crystal structures of two pentagonal-bipyramidal Fe(III) complexes with dihydrazone of 2,6-diacetylpyridine and Girard’s T reagent. Anticancer properties of various metal complexes of the same ligand.bož
  2. Polyhedron (IF 2016 = 1.926): Synthesis, crystal structure, magnetic properties and DFT study of dinuclear Ni(II) complex with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent
  3. Journal of Coordination Chemistry (IF 2016 = 1.795): Synthesis, crystal structures and antimicrobial activity of azido and isocyanato Zn(II) complexes with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent

Congratulations to Božidar for the great publications and a big ‘’thank you’’ to all other co-authors for all the hard work.

New article in RSC journal Inorganic Chemistry Frontiers

Check out the newest publication of the Turel group in the RSC journal Inorganic Chemistry Frontiers (IF 2016 = 4.036) in collaboration with our Serbian colleagues from Kragujevac, Niš and Belgrade:

A new class of platinum(II) complexes with the phosphine ligand pta which show potent anticancer activity


This paper is the result of the research visit of postdoc Marija D. Živković in our labs in 2014/2015 and describes the synthesis, physico-chemical characterization and biological evaluation of two classes of platinum(II) complexes with halogen-substituted hydroxyquinoline ligands (hq) with the general formula [Pt(hq)(X)Cl] where X = S-dmso, pta. Congratulations to Marija for the great publication and to all other co-authors.

A visit from Serbia

Within the bilateral Slovenian-Serbian project our lab welcomed a visit from member of the Serbian Academy of Sciences and Arts prof. Miloš Djuran and former postdoc dr. Marija Živković. The meeting was instrumental in working out the final details of the manuscript revision of our upcoming article (stay tuned for news!). Prof. Djuran also had a lively discussion with the junior team members which was followed by an excursion to the Caves of Škocjan and a work lunch discussing future collaborations.

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