Crystallography in Croatia

Introduction

Logo of CCA (abbr. in Croatian: hkz; colors of national flag: red, white, blue; author B. Gržeta, CCA).

Crystallography in Croatia began with courses in mineralogy in the last decades of the 19th century. M. Paić used powder diffraction in his PhD studies at the Sorbonne in Paris in the 1930s and in 1946 as the head of the Physics Dept. of Zagreb U. he continued research in crystallography. D. Grdeni&caute; studied crystal structures of mercury compounds by single-crystal XRD in Moscow from 1946 to 1948 with A. I. Kitaigorodskii. In 1948 he founded X-ray crystal structure analysis in Zagreb. Soon a group of talented younger crystallographers (K. Kranjc, S. Šćavnićar, A. Bonefačić, A. Bezjak, B. Kamenar, B. Matković, Z. Ban, M. Sikirica, M. Topić, B. Kojić-Prodić and S. Popović) began studying crystal structures and microstructures.

Drago Grdenić in the 1960s.

In 1966 the crystallographers in the former Yugoslavia established the Yugoslav Centre of Crystallography (YCCr), which acted under the auspices of the Yugoslav (now Croatian) Academy of Sciences and Arts in Zagreb. D. Grdenić was elected President and B. Kamenar Secretary. That same year, YCCr joined the IUCr (at the 7th Congress of IUCr in Moscow). Most of the members of YCCr performed their research in Croatia. From 1966 to 1991, annual crystallographic conferences were held in Yugoslavia, often organized by YCCr members from Croatia. The invited speakers at those conferences were eminent crystallographers from abroad [M. Nardelli, G. Allegra, M. Mammi, G. Gilli, C. Giacovazzo, D. Viterbo and L. Randaccio (Italy), A. Kálmán (Hungary), S. C. Abrahams (USA), I. Olovsson (Sweden), M. Porai Koshic and Y. Struchkov (USSR), J. Helliwell, C. K. Prout and Nobel laureate D. Hodgkin (UK)]. Six joint Italian-Yugoslav crystallographic conferences were organized in that period. Many crystallographers from Croatia were trained in prominent international laboratories. A number of scientists from other republics of the former Yugoslavia obtained MSc and PhD degrees in Zagreb.

In the seventies and eighties the laboratories in Zagreb were equipped with modern instruments for XRD, TEM and associated methods, enabling research of crystal structures of inorganic, organometallic and organic compounds, as well as microstructure at ambient and elevated temperature. YCCr published a journal, the Annual of the Yugoslav Centre of Crystallography, containing (in English) papers based on plenary lectures and abstracts of short contributions given at annual conferences, lists of publications of the YCCr members, titles of MSc and PhD theses of the YCCr members, and minutes of annual YCCr assembly meetings. YCCr was also a member of the European Crystallographic Committee (ECC); B. Kamenar was the Vice-President and President of ECC in the period 1978-1984. Due to the war in Yugoslavia the 13th European Crystallographic Meeting scheduled for Ljubljana, Slovenia, in 1991 was transferred to Trieste thanks to good relations among crystallographers in Italy (L. Randaccio), Croatia (B. Kamenar) and Slovenia (L. Golič). A plenary lecture was given by the Nobel laureate R. Huber (Germany), and a satellite meeting on synchrotron radiation was organized.

Boris Kamenar

After the disintegration of Yugoslavia and proclamation of independence of Croatia in 1991, the Presidency of the Croatian Academy of Sciences and Arts (CASA) dissolved the YCCr. With an advisory board composed of B. Kamenar, B. Kojić-Prodić, S. Popović and B. Gržeta and the unanimous support of crystallographers in Croatia, the Croatian Crystallographic Association (CCA) was founded on February 28, 1992. B. Kamenar was elected President and S. Popović Secretary. The CCA joined the European Crystallographic Association in 1992 (ECM14 Enschede) and the IUCr in 1993.

Since 1992, CCA and the Slovenian Crystallographic Society have organized annual joint Meetings with international participation, alternately in Slovenia and in Croatia. The reports on the meetings can be found in the IUCr Newsletter. Invited speakers at the meetings have included C. Giacovazzo, G. Zanotti (Italy), M. Kaftory (Israel), I. Hargittai (Hungary), M. Jaskólski (Poland), W. Duax (USA), H. Flack, N. Ban (Switzerland), P. Naumov (Japan), R. Dinnebier, H. Fuess (Germany), B. Kobe (Australia), E. and G. Dodson (UK), and E. Tillmanns (Austria). Papers based on plenary lectures are published in Croatica Chemica Acta (Croatian Meetings) and Acta Chimica Slovenica (Slovenian Meetings). Members of CCA edited a special issue of Croatica Chemica Acta, 82 (2009), a Festschrift dedicated to D. Grdenić on his 90th birthday. D. Balzar was a member of the IUCr Commission on Powder Diffraction, B. Kojić-Prodić is a Co-editor of Acta Cryst. C and S. Popović was a member of the EPDIC Committee.

The CCA has about one hundred members conducting research in at least ten laboratories in universities, scientific institutes and industry. The crystallographers study biologically active molecules, proteins, organometallic compounds, pharmaceuticals, microstructure of composites and its relation to properties. Short reports on research in several prominent laboratories in Croatia are given below.

The members of the Executive Committee of CCA (since January 12, 2006; reelected on May 5, 2009) are: M. Luić, Secretary, marija.luic@irb.hr; D. Matković-Čalogović, Vice Chair, dubravka@chem.pmf.hr; S. Popović, Chair, spopovic@phy.hr; D. Tibljaš, dtibljas@geol.pmf.hr; A. Tonejc, atonejc@phy.hr; A. Višnjevac, aleksandar.visnjevac@irb.hr; K. Vlahoviček, kristian@bioinfo.hr; B. Kamenar, Honorary Chair, bkamenar@chem.pmf.hr.

More details on CCA can be found at www.hazu.hr/kristalografi.

Laboratory of General and Inorganic Chemistry (LGIC), Dept. of Chemistry, Faculty of Science, Zagreb U.

Boris Kamenar with Dorothy Hodgkin during her visit to Zagreb in 1966.

In 1952 LGIC became the center of crystallography led by D. Grdenić when he published a paper in Acta Cryst. describing the electron density distribution on mercury diethylene oxide. In 1955/56 Grdenić worked on the structure of ferroverdin in the laboratory of D. Hodgkin. Upon returning to Zagreb he continued his research of mercury compounds. The Structural Chemistry of Mercury published in Quart. Rev. Chem. Soc. in 1965 is still one of the most cited papers of a Croatian chemist.

Milan Sikirica

Drago Grdenić inspecting the new diffractometer. Zoran Bojanić (technician in charge of the diffractometers) is in the back.

He had begun with a Unicam camera and three Weissenberg goniometers. Later the Laboratory was equipped with a General Electric powder diffractometer and the first four-circle single-crystal Philips diffractometer (1974).

Grdenić's students and co-workers at the Faculty of Science included: B. Kamenar, M. Sikirica (intermetallic and organomercury compounds), A. Nagl, M. Bruvo, A. Hergold-Brundić, Z. Popović, D. Matković-Čalogović (organomercury compounds), Z. Ban, M. Pušelj (powder diffraction of intermetallic compounds and metal peroxides).

Structure of the antibiotic azithromycin.

B. Kamenar was a visiting scientist in D. Hodgkin's Lab, in All Souls College, at Auckland U. and Massey U. in New Zealand. In Zagreb, he studied inorganic, organometallic and organic compounds, complexes of molybdenum and vanadium (M. Penavić, B. Kaitner, N. Strukan, B. Marković), and pharmaceuticals such as azithromycin and its derivatives (D. Mrvoš-Sermek). I. Vicković worked on computing in direct methods with D. Viterbo in Torino, C. Giacovazzo in Bari, and at Texas Christian U. In Groningen he developed protein data collection strategy. In his doctoral thesis (1977), he was among the first in Croatia to use direct methods for crystal structure analysis.

In 1981, M. Sikirica obtained a second Philips diffractometer (one for molybdenum and one for copper radiation). An Oxford Diffraction Xcalibur 3 with a CCD camera was purchased on the fiftieth anniversary of the Laboratory in 2002.

The first doctoral thesis on protein crystallography was that of D. Matak-Vinković. M. Vinković determined structures of pharmaceuticals and worked at the pharmaceutical company Pliva in Zagreb. Later both Dijana and Mladen Vinković went to Cambridge. A. Nagl led a group at the Faculty of Textile Technology, Zagreb U., with G. Pavlović and M. Cetina. E. Meštrović formed a crystallography group at Pliva (N. Košutić-Hulita, M. Devčić).

Crystallographers in the Laboratory of General and Inorganic Chemistry, Dept. of Chemistry, Faculty of Science, University of Zagreb: (in front, from left to right) Marijana Đaković, Marina Tašner, Nenad Judaš, Zoran Bojanić, (sitting) Dubravka Matković-Čalogović, (back, from left to right) Dominik Cinčić, Biserka Prugovečki, Draginja Mrvoš-Sermek, Zora Popović, Marija Zbačnik, Vladimir Stilinović, Branko Kaitner.

Part of the protein crystallography group in Elettra, Trieste (left to right): Ivica Đilović, Dubravka Matković-Čalogović and Dalibor Milić.

Today four groups are active at LGIC. B. Kaitner's group studies intra- and intermolecular interactions and their effect on structures and properties using synthesis, crystal structure determination and solid-state analytical methods. Materials being studied include organic salts, triacylmethanes, Schiff bases, β-diketones and coordination compounds of transition metals. Zora Popović's group is focused on preparation and structure determination of metal complexes of the late 3d-block and group 12 metals with molecules of biological importance to elucidate their role on the formation of polymorphic forms. M. Cindrić's group studies anion-directed self-assembly of flexible ligands into highly symmetrical organic solids, complex compounds, coordination polymers and polyoxometalates of vanadium, molybdenum and tungsten, and their interactions with amino acids, pyridoxal derivatives and thiosemicarbazones. They are investigating the catalytic role of vanadium and molybdenum in biologically active molecules. D. Matković-Čalogović's group works on small molecules and protein crystallography (with G. Za, G. Dodson and A. Antson in York). She had a Fulbright fellowship at the U. of Kansas Medical Center. Her group studies modified insulin structures (B. Prugovečki), native and mutated forms of tyrosine phenol-lyase (TPL) in complexes with the substrate analogues and bovine 3,4-dioxygenase, as well as small molecule model systems of enzymes and supramolecular architectures (N. Judaš). Courses on crystallography are taught at the Dept. of Chemistry.

Dept. of Physics, Faculty of Science, Zagreb U.

Department of Physics, Faculty of Science, University of Zagreb.

The earliest crystallographic activity at the Dept. of Physics of the Faculty of Science, Zagreb U., began in 1954 with the PhD work of K. Kranjc (1915-1989), Investigation of poly-dispersive systems with small-angle X-ray diffraction. Her supervisor, M. Paić (1905-1997), initiated crystallography in the Dept. after using the Debye-Scherrer technique at the Sorbonne in Paris. When he was appointed head of the Dept. of Physics in 1946 only a Unicam-25 camera was available. K. Kranjc continued to use SAX and Berg-Barrett X-ray diffraction microscopy to investigate the domain structure and Moiré fringes in electron micrographs. Kranjc worked in the laboratory of A. Guinier in Paris and A. Mackay at Birkbeck College. She was a friend of Rosalind Franklin who visited Zagreb in 1953.

Slo-Cro Cryst Meeting 2010: on the left Antun and Anđelka Tonejc, on the right Stanko Popović.

52Al-48Zn alloy: difference in microstructure between the quenched (WQ) and slowly cooled (SC) alloys from the solid-solution temperature to RT (Croat. Chem. Acta 82 (2009) 405-420).

62Al-38Zn alloy: a gradual transition of the quenched alloy, during ageing at RT, from a metastable system, α+Guinier-Preston zones, into a more stable system, α+β (Croat. Chem. Acta 82 (2009) 405-420).

A. Bonefačić earned his PhD (X-ray structural analysis of some Ag-II sulfates) with M. Paić as the supervisor. He worked on diffuse scattering in the Guinier lab. In 1966 he became the head of the research group in physics of metals, and in 1971 received the Croatian National Science Award for Physics (CNSAP) for his scientific research on crystallographic properties of metastable alloys. In 1967 Bonefačić and his colleagues (D. Kunstelj, M. Stubičar and Anđelka and Antun Tonejc) initiated structural studies of metastable metallic alloys obtained by rapid quenching from the melt using a Siemens diffractometer and Philips 120 kV transmission electron microscope EM300. Anđelka Tonejc was a postdoctoral student in the Guinier Lab in Orsay from 1974 to 1976, where she worked on rapidly quenched alloys using powder diffraction and TEM. In 1991 Antun Tonejc established the Laboratory for Microstructural Investigation of Materials with a new Philips powder diffractometer and JEOL 200 kV high-resolution transmission electron microscope. In 1995, Antun Tonejc became head of the laboratory and the staff expanded to include S. Popović (full professor) I. Đerđ, Ž. Skoko and I. Lončarek.

Anđelka Tonejc focused on high-resolution electron microscopy investigations and, with I. Đerđ, was one of the first researchers to use the Rietveld method for electron diffraction analysis. Antun Tonejc initiated structural examination of mechanically alloyed materials using high-energy ball milling and received the Science Award of Croatian Academy of Sciences and Arts (SACASA) in 2008 for investigations on phase transitions in nanostructural materials.

S. Popović concentrated on X-ray diffraction line profile analysis, microstructural investigations of Al-Zn and Al-Ag-Zn alloys, and mixed metal oxides in collaboration with the Dept. of Materials Chemistry, Ruđer Bošković Inst. Popović received the CNSAP in 2001 and became Fellow of CASA in 2004. Department courses are taught in solid state physics and crystallography.

Institute of Mineralogy and Petrology, Faculty of Science, Zagreb U.

The early days of crystallography in Croatia were linked to minerology. The Chair of Mineralogy and Geology (CMG) was established in 1874, by decree of the Emperor of the Austro-Hungarian Empire. Dj. Pilar started teaching there in the spring of 1875 and crystallography has remained one of its primary activities. After Dj. Pilar, the CMG was headed by eminent professors, and members of the Academy of Sciences and Arts. The first mineralogists from Bulgaria, G. Bončev and L. Vankov, obtained their doctors degrees under the supervision of Dj. Pilar.

Early research activities involved morphological studies of crystals and symmetry determinations by microscopic methods which are often neglected now. Optical crystallographic methods were developed and applied to minerals and other crystalline substances. Lj. Barić contributed to the development and teaching of these methods. Equipment for X-ray analysis consisted of reflexion goniometers, polarizing microscopes, X-ray diffraction cameras, modern diffractometers and electron microscopes.

From 1955 S. Šćavničar headed crystallographic research at the Inst. determining the structures of natural and synthetic compounds. In the 1950s he achieved the first successful hydrothermal synthesis of beryl. He taught generations of masters and doctoral students how to use powder and single-crystal diffractometry, electron microscopy, methods of thermal analysis, Raman and IR spectrometry and microanalysis to determine new mineral structures and improve characterisation of known ones. More than 10 new minerals were identified in the Inst. of Mineralogy and Petrology. The research involves complex investigative methods and precise determination of crystal morphology, optical constants, specific gravity, hardness, cleavage, electric and magnetic properties, chemical composition and genetic information. Crystallographers collaborate closely with investigators in associated fields. New areas of research include experimental mineralogy, biomineralization processes and environmental mineralogy. V. Bermanec and D. Tibljaš are training younger colleagues at the Inst. and collaborating with researchers in Croatia, Macedonia, Slovenia, Bosnia and Hercegovina, Austria, Hungary, Canada, Brazil and Russia.

Dept. of Mineralogy, Faculty of Mining, Geology and Petroleum Engineering, Zagreb U.

Weissenberg pattern of a biotite polytype with 17 single mica layers.

Microstructures of phyllosilicates, biotites and muscovites, taken from the Papuk Mts, have been studied by single-crystal and powder diffraction methods and related to physical and chemical properties. Polytypes of variable complexity up to 20 single mica layers were detected in biotite. In a number of cases an epitactic overgrowth of ordered and partially ordered polytypes were observed. The parameters of the 1M sub-cell of biotite, deduced from zero-layer rotation patterns, depended on the chemical composition and not on the particular polytype.

Lab of Chemical and Biological Crystallography, Ruđer Bošković Institute (RBI), Zagreb

Staff of the Laboratory of Chemical and Biological Crystallography, Ruđer Bošković Institute, Zagreb.

X-ray structure analysis was initiated in Croatia by D. Grdenić after his doctoral studies in Moscow. His first rotation photograph was taken on New Year's Eve 1948 in the Physics Dept. of the Faculty of Science. A Goverment Decree established the Ruđer Bošković Inst. (RBI) for fundamental research in physics and chemistry. The institute was founded by I. Supek to foster collaborative research with scientists from Zagreb U. In 1951 the first Weissenberg goniometer was purchased, data were collected on film and a subscription to Acta Crystallographica was started. D. Grdenić was the founder and first head of the Dept. of Structural and Inorganic Chemistry, and supervised the work of A. Bezjak, S. Šćavničar and B. Matković. Scientific results included determinations of structures of organic molecules, phthalylurea and mellitic acid solved by original direct methods designed by Bezjak. Structures were solved from projections. The existence of a novel mercurated oxonium species, as a part of PhD thesis of Šćavničar, was published in Nature (1953). The structure of thorium(IV) acetylacetonate, solved by Matković, revealed an Archimedean antiprism as the coordination polyhedron around thorium.

Two views of the single-stranded DNA-binding protein from Streptomyces coelicolor, the first X-ray structure of an SSB protein from a member of the genus Streptomyces (Z. Štefanić, D. Vujaklija and M. Luić, Acta Cryst. D65 (2009), 974-979).

Co-crystals of cholic acid (CA) with n-alkylammonia (n = 10, 12, 14, 16) represent first examples of CA's co-crystals with molecules of comparable size. In one of the compounds a completely new type of bilayer arrangement was found (upper right). (V. Tomašić, Z. Štefanić, CrystEngComm 9 (2007) 1124-1128).

Solid-state tubular assemblies of thiolactones(I. Vujasinović, J. Veljković, K. Mlinarić-Majerski,K. Molčanov, B. Kojić-Prodić, Tetrahedron 62 (2006) 2868-2876).

π-Stacking of quinoid rings, described for the first time, in crystals of ammonium hydrogen chloranilate dihydrate (K. Molčanov, B. Kojić-Prodić, A. Meden, CrystEngComm 11 (2009) 1407-1415).

Since the founding of the laboratory in the 1950s two research lines have been maintained: the development of experimental techniques and numerical methods of analysis. Subjects of study included synthesis of heavy metal alkaline phosphates by a melt technique and transition metal complexes. A new type of ferroelectric without hydrogen bond was discovered. When direct method programs, such as Multan, became available, biologically active molecules became the targets of research. These included the plant growth hormone auxin and its analogues, peptides, sugars, and pharmaceutically active compounds (i.e. cimetidine, ranidine and diltiazem). Since 1985 the Cambridge Structural Database has been available in Croatia via the National Affiliation Centre of Cambridge Crystallographic Data Centre. In 1989 the first diffractometer was purchased. For over forty years chemical crystallography has been combined with spectroscopic methods, bio-assays and molecular modelling to understand intramolecular and intermolecular interactions, the topology of hydrogen bonds and the physical properties of chemical and biologically active molecules and their relation to functions. As the activities were more and more concentrated on biologically active molecules and their interactions, the Laboratory for Chemical and Biological Crystallography was founded in 1997 for research with protein crystallography. Structures of enzymes complexed with substrates and inhibitors are revealing catalytic mechanisms at the molecular level by combining structural, biochemical and genetic methods of analysis.

Powder Diffraction at RBI, Zagreb

Powder diffraction is used in the laboratory for analysis of micro- and nanocrystalline materials. New methods for accurate unit-cell parameter measurement have been developed based on the separation of adjacent diffraction lines and by combining single-crystal zero-layer rotation and Weissenberg patterns with powder diffraction patterns. Techniques for quantitative phase analysis of multicomponent samples are being developed. Phase diagrams of semiconductors are related to electrical properties. New high-temperature phases are characterized. Microstructure and phase diagrams of a series of mixed metal oxides (e.g. ferrites, orthoferrites, alumina, zirconia, titania) were systematically studied by X-ray powder diffraction, Raman, FT-IR and Mössbauer spectroscopies, in collaboration with the Dept. of Materials Chemistry (RBI). The processes of biomineralization of bivalvia have been studied in detail in collaboration with the Center for Marine Research (RBI).

Laboratory of Solid State Chemistry, RBI

The ThM₂Ge₂ structure type published in Acta Crystallographica.

Germanium single crystals prepared by float zone crystal growth technique.

Crystallographic analysis began in the Lab for Solid State Chemistry (formerly High Temperature Materials) at RBI in the 1950s with studies of the crystal morphology and (di)electric properties of Rochelle salt (M. Topić). Subsequently, float zone crystal growth, uranium and thorium ternary silicides and germanides containing transition metals were analyzed with neutron and X-ray powder diffraction methods (M. Tudja). Chemical vapour transport technique was used for preparation of ternary uranium compounds of composition UNTe, UNAs and UAsSb. Powder diffraction analysis revealed that they crystallized in the tetragonal structure of the PbFCl type (Z. Despotović, R. Trojko). The technique of isothermal transport reaction between metals in molten alkali chloride mixtures was developed and applied to systems containing combinations of Cu, Ni, Ag, Pt, Cr and Fe metals (M. Paljević). Research on multicomponent intermetallic compounds started in the 1970s. A systematic study of phase equilibrium was carried out on selected rare earth-iridium systems. Substitution of one or both components in binary intermetallic compounds of the general composition AB₂ and AB₅ with other metals or metalloids has been used as a standard method for tailoring materials suitable for hydrogen storage purposes. Thermodynamic properties of the corresponding intermetallic compound-hydrogen systems were determined from pressure composition isotherms at various temperatures obtained by tensimetric methods (Ž. Blažina, A. Drašner, B. Šorgić). The crystal structures of fifty intermetallic compounds have been deposited in Pearson's Handbook of Lattice Spacings and Structures of Metals, the Powder Diffraction File Search Manual of Inorganic Compounds and the Metal Hydride Reference List of Sandia National Laboratories. Recent intensive investigations concern theoretical studies of intermetallic compounds based on electronic structure calculations designed to parametrize the structural basis for the thermodynamic, electrical, chemical and magnetic properties of these materials (G. Miletić).

Dept. of Materials Chemistry, RBI

Two interconnected cupolas of α-Fe₂O₃ precipitated from dense α-FeOOH suspension with added ammonium amidosulfonate (M. Žic, M. Ristić, S. Musić, J. Mol. Struct. 235 (2009) 924-926).

Almost four decades ago S. Musić initiated research in chemistry of metal oxides at the RBI. He prepared metal oxide carriers labelled with cyclotron radioisotopes for applications in nuclear medicine and investigated hydrolytic processes and precipitation of iron oxides. A research group was formed and started systematic investigations of other metal oxide systems such as ZrO₂, TiO₂, ZnO, Ga₂O₃, Nb₂O₅ and WO₃. The goals were to determine the relationship between the synthesis route and specific properties of metal oxide particles and the kinetics and mechanisms of precipitation of metal oxides. The formation and properties of ferrites with spinel-, perovskite- or garnet-type structures were investigated. The application of powder diffraction in combination with other techniques (Mössbauer, FT-IR, Raman, electron microscopy) made it possible to study the structure, phase composition, phase diagrams and chemical bonds, as well as the size and morphology of the particles of metal oxides.

The Glass Laboratory, RBI

Easy conductive pathways in partially crystallized 40Fe₂O₃-60P₂O₅ (mol%) glass through a) glass matrix and b) grain boundaries.

The Glass Laboratory at RBI (A. Moguš-Milanković, A. Šantić, L. Pavić) employs crystallography in conjunction with electrical characterization to study the relationship between the composition, structural and electrical properties of various materials. Principal techniques in electrical characterization include Impedance Spectroscopy (IS) and Thermally Stimulated Polarisation Current (TSDC/TSPC) measurements combined with Raman spectroscopy and XRD techniques. Research programs cover transition metal oxide glasses, bioactive materials and ionic liquid composites. Special interest is focused on the mechanism of crystallization of amorphous systems (phosphate, silicate, bioactive glasses), determination of crystalline phases, particle size and volume fractions, and their influence on electrical properties. Part of the research considers a surface activity of the electrically polarized bioactive materials.