Hydrothermal crystallization of hydrous hafnia at 90 and 120 DGC, was monitored at pH 3, 7, 9.5 and 13, using X-ray powder diffraction analyses. The obtained results showed that hydrothermal ...crystallization proceeded much more slowly in a neutral pH medium than in an acidic or alkaline medium. Phase analysis of the products of hydrothermal treatment showed that, regardless of pH, hydrous hafnia crystallized into m-HfO2. Stabilization of a metastable cubic or tetragonal HfO2 occurred upon adding a sufficient amount of stabilizing Na+ ions. Similarities and differences between the hydrothermal crystallization of HfO2 and the hydrothermal crystallization reported for ZrO2 were discussed. It was concluded that in both cases hydrothermal crystallization proceeds via a dissolution/precipitation mechanism in the whole pH range.
Stogodišnjica rendgenske kristalografije Kojić-Prodić, B; Molčanov, K
Kemija u industriji; časopis kemičara i tehnologa Jugoslavije,
07/2013, Volume:
62, Issue:
7-8
Journal Article
Peer reviewed
Open access
The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.
W. L. Bragg
Stogodišnjica rendgenske kristalografije veže se uz prvi pokus difrakcije ...rendgenskih zraka koji su s kristalom modre galice izveli njemački fizičari W. Friedrich i P. Knipping prema ideji i teorijskom predviđanju M. von Lauea 1912. Matematička formulacija pojave, kao i temeljne postavke znanosti o građi kristala - kristalografije, u to vrijeme vezane uz mineralogiju, pogodovale su razvitku metode za određivanje geometrijske strukture tvari na atomnoj razini. Već su 1913. otac i sin Bragg započeli stvarati temelje za primjenu rendgenske difrakcije u određivanju kristalnih struktura jednostavnih molekula. Povijesni primjeri određivanja struktura od kuhinjske soli do složenih, za život bitnih, (makro)molekula, kao globularnih proteina hemoglobina i mioglobina, DNA, vitamina B12, te novog otkrića ribozima, ilustriraju razvojni put rendgenske strukturne analize. Otkriće trodimenzijskih struktura tih molekula metodom rendgenske difrakcije pokrenulo je nove znanstvene discipline poput molekularne biofizike, molekularne genetike, strukturne molekularne biologije, bioanorganske kao i organometalne kemije i niza drugih disciplina. Otkriće i razvoj rendgenske kristalografije revolucioniralo je naše spoznaje u svim područjima prirodnih znanosti: fizici, kemiji, biologiji, geološkim znanostima i znanosti o materijalima. Znanstvena javnost prepoznala je ta temeljna znanstvena postignuća (uključujući i otkriće X-zraka) dodijelivši Nobelove nagrade tridesetdevetorici znanstvenika i dvjema znanstvenicama. Eksplozivan razvoj znanosti i tehnologije tijekom 20. i 21. stoljeća temelji se na spoznajama o detaljnoj trodimenzijskoj građi molekula i njome predviđenih i objašnjenih fizičkih, kemijskih, bioloških i farmakoloških svojstava molekula. Jedan od svježih primjera, koji je bilo teško predvidjeti, uspješna je i nedovršena priča o grafenima, koja puni naslovnice vodećih znanstvenih časopisa kao što su Science, Nature, Nature Materials, Nature Nanotechnology, Nature Chemistry i Nature Physics. Suvremena kristalografska istraživanja pokrivaju široko područje znanosti i veoma su inovativna, te nije uputno predviđati u kojim će se smjerovima nastaviti razvijati.
This article is dedicated to the memory of Dr. F. H. Allen and the 50th anniversary of the Cambridge Crystallographic Data Centre (CCDC); the world-renowned centre for deposition and control of ...crystallographic data including atomic coordinates that define the three-dimensional structures of organic molecules and metal complexes containing organic ligands. The mission exposed at the web site (http://www.ccdc.cam.ac.uk) is clearly stated: “The Cambridge Crystallographic Data Centre (CCDC) is dedicated to the advancement of chemistry and crystallography for the public benefit through providing high quality information, software and services.” The Cambridge Structural Database (CSD), one among the first established electronic databases, nowadays is one of the most significant crystallographic databases in the world. In the International Year of Crystallography 2014, the CSD announced in December over 750,000 deposited structures. The use of the extensive and rapidly growing database needs support of sophisticated and efficient software for checking, searching, analysing, and visualising structural data. The seminal role of the CSD in researches related to crystallography, chemistry, materials science, solid state physics and chemistry, (bio)technology, life sciences, and pharmacology is widely known. The important issues of the CCDC are the accuracy of deposited data and development of software for checking the data. Therefore, the Crystallographic Information File (CIF) is introduced as the standard text file format for representing crystallographic information. Among the most important software for users is ConQuest, which enables searching all the CSD information fields, and the web implementation WebCSD software. Mercury is available for visualisation of crystal structures and crystal morphology including intra- and intermolecular interactions with graph-set notations of hydrogen bonds, and analysis of geometrical parameters. The CCDC gives even more options to the users developing sophisticated software such as GOLD, IsoStar and SuperStar, DASH, and extensive knowledge electronic libraries such as Mogul and Relibase. The CCDC released the new facility – Mercury’s Solid Form module. Such demanding projects require a highly competent team of experts with a scientific approach based on the long tradition in crystallography, modelling and informatics. The Cambridge Structural Database and diversified software and searching engines are useful tools in research and teaching. The use of electronic media and computer graphics makes “data mining” very efficient and useful, but also aesthetically appealing due to the molecular architecture. One can expect even more advanced approaches using cloud computing and ‘Big Data’ management; merging data from related databases will enable to recognize hidden molecular and crystal properties and information that could bring new important knowledge. Since 1985, the CSD has been available to users in Croatia. The use of the CSD in Croatia is illustrated by a few examples performed and published by the presenting authors and colleagues.
In the title compound, (C(13)H(11)N(2))(2)Zn(C(7)H(3)NO(4))(2)·3H(2)O, the Zn(II) ion is six-coordinated with the N(4)O(2) donor set being a distorted octa-hedron through two almost perpendicular ...(r.m.s. deviation of ligand atoms from the mean plane is 0.057 Å) tridentate pyridine-2,6-dicarboxyl-ate ligands dihedral angle between the ligands = 86.06 (4)°. The charge is compensated by two 9-amino-acridinium cations protonated on the ring N atom. A variety of inter-molecular contacts, such as ion-ion, N-H⋯O and O-H⋯O hydrogen bonds, and π-π stacking centroid-centroid distances = 3.4907 (9)-4.1128 (8) Å, between cations and between anions, play important roles in the formation of the three-dimensional network.
High field electron spin resonance (HF-ESR) study of three 3D oxalate-based coordination polymers, supported by crystallographic, photoluminescence (PL), elemental (EDX) and X-band ESR analysis. ...Display omitted
The detailed high field electron spin resonance (HF-ESR) study of three 3D oxalate-based coordination polymers with antiferromagnetic ordering below 13K, supported by crystallographic, photoluminescence (PL), elemental (EDX) and X-band ESR analysis, is presented. Two of the investigated compounds are described by the same chemical formula {Cu(bpy)3Mn2(C2O4)3·H2O}n, both exhibit PL but have different colors: green–blue and red–pink (CuMn2-Green and CuMn2-Red, respectively) while {Co(bpy)3Mn2(C2O4)3·H2O}n is yellow (CoMn2-Yellow) without PL. Despite different colors of CuMn2-Green and CuMn2-Red, X-ray diffraction, EDX, as well as X-band ESR, could not reveal any difference between these compounds. Therefore, detailed temperature dependent multifrequency HF-ESR experiments were performed. Owing to very high resolution of HF-ESR, two different Mn(II) centers in CuMn2-Green and CoMn2-Yellow compounds could be resolved, while in CuMn2-Red only one Mn(II) center is detected. A possible difference in the ligand coordination of Mn(II) ions in the oxalate-networks of CuMn2-Green and CuMn2-Red, that gives rise to slightly different g-factors, is discussed with respect to the different colors of these compounds.
Prikaz je posvećen uspomeni na dr. F. H. Allena i obilježavanju 50-godišnjice The Cambridge Crystallographic Data Centre (CCDC), svjetski poznatog centra, koji pohranjuje i provjerava kristalografske ...podatke, uključujući koordinate atoma koje određuju trodimenzijsku strukturu organskih molekula i metalnih kompleksa s organskim ligandima. Misija institucije istaknuta na njezinim web-stranicama je jasna: “Centar za kristalografske podatke u Cambridgeu (CCDC) potpomaže napredak kemije i kristalografije za sveopću dobrobit pružajući kvalitetne informacije, softver i podršku.” Baza strukturnih podataka u Cambridgeu (CSD), jedna je od prvih elektroničkih i najznačajnijih baza u svijetu. U Međunarodnoj godini kristalografije 2014., u prosincu, Centar je obznanio 750.000. pohranjenu strukturu. Upotreba opsežne baze podataka, koja se brzo povećava, zahtijeva podršku u dobro osmišljenom i učinkovitom softveru za provjeru, pretraživanje, analizu i vizualizaciju strukturnih podataka. Prestižna je uloga te baze u istraživanjima povezanim s kristalografijom, kemijom, znanošću o materijalima, fizikom i kemijom krutog stanja, (bio)tehnologijom, znanošću o životu, te farmakologijom, posebno u oblikovanju lijekova. CCDC posvećuje posebnu pažnju točnosti pohranjenih podataka i razvoju softvera za tu namjenu (CIF). Jedan od najvažnijih softvera za korisnike je ConQuest, koji omogućava pretraživanje svih informacija u bazi CSD-a, te njegovo postavljanje na mreži u interaktivnom obliku pod imenom WebCSD. Za vizualizaciju kristalnih struktura i morfologije kristala, uključujući analizu intramolekularnih i intermolekularnih interakcija te topološke oznake vodikovih veza, kao i svih geometrijskih podataka, na raspolaganju je Mercury. Centar (CCDC) pruža još veće mogućnosti korisnicima razvijajući kompleksne softvere poput GOLD, IsoStar i SuperStar te DASH, kao i opsežne elektroničke biblioteke poput Mogula i Relibase. CCDC je pružio novu mogućnost korištenjem Mercuryjeva modula Solid Form. Takvi složeni i zahtjevni projekti mogu se ostvarivati samo s veoma kvalitetnim timom stručnjaka sa znanstvenim pristupom, temeljeći se na dugogodišnjoj tradiciji u kristalografiji, modeliranju i informatici. Sama baza, raznolik softver i alati za pretraživanje afirmirali su se u istraživanju, nastavi i stručnoj izobrazbi. Primjena elektroničkih medija i računalne grafike čini “data mining” učinkovitima i korisnima, ali i estetski privlačnim zbog molekularne arhitekture. Možemo očekivati još više unapređenja zbog uporabe “računarstva u oblacima” (cloud computing) i rukovanja opsežnim podacima (Big Data); umrežavanje podataka iz srodnih baza pomoći će da prepoznamo sakrivena svojstva molekula i kristala i informacija koje mogu otkriti nove važne spoznaje. Od 1985. Strukturna baza podataka u Cambridgeu (CSD) dostupna je korisnicima u Hrvatskoj. Upotreba te baze u Hrvatskoj ilustrirana je s nekoliko primjera autora ovog prikaza i nekih korisnika.
Prikaz o kiralnosti posvećen je 100. godišnjici rođenja Nobelovca Vladimira Preloga i predstojećoj 160. godišnjici Pasteurovog otkrića kiralnosti soli vinske kiseline. Pojavu kiralnosti u prirodi ...prepoznali su umjetnici i graditelji koristeći je u svojim djelima što je ilustrirano primjerima u uvodu. Napretkom znanosti kroz povijest do danas šire se spoznaje o kiralnosti i gotovo je nemoguće obuhvatiti sve njezine aspekte i primjene. Opisana su ključna povijesna otkrića vezana uz pojavu zakretanja ravnine polariziranog svjetla kao posljedicu kiralnosti te otkrića Pasteura i lorda Kelvina. Kiralnost se susreće u fizici elementarnih čestica kao i u svim područjima kemije: analitičkoj i organskoj kemiji, kemiji prirodnih spojeva, medicinskoj i farmaceutskoj kemiji, biokemiji i biotehnologiji, kao i molekularnoj biologiji. Kratko je opisano širenje spoznaja o kiralnosti i fizikalne osnove molekularne kiralnosti. Sustavno su definirane: geometrijska, topološka i konformacijska
kiralnost. Povezanost simetrije i kiralnosti dolazi do izražaja i u kristalografiji. Kako je rendgenska strukturna analiza metoda kojom se jednoznačno određuje molekularna arhitektura, neosporno je da se pri tome utvrđuje i apsolutna konfiguracija molekula Bijvoetovim pristupom. Sažeto su opisane dvije metode za određivanje apsolutne konfiguracije: metoda rendgenske difrakcije i kružnog dikroizma. U skladu s obilježavanjem značajnog jubileja, prikaz je orijentiran na ulogu kiralnosti u (stereo)kemiji. To je u skladu s E. L. Elielovim pristupom koji stereokemiju smatra načinom
gledanja na kemiju, a ne granom kemije. Taj pristup omogućava sagledavanje različitih aspekata kiralnosti i usuglašavanje postojećih nepotpunih definicija o kiralnosti molekula, što zacijelo otvara nove primjene. Budućnost nam nudi da više saznamo o kiralnosti u službi komunikacije molekula koje upravljaju našim životnim procesima. U tijeku su eksperimenti priprave raznorodnih dinamičkih kiralnih supramolekula iz akiralnih molekula i predstoji istražiti kako se to korisno može upotrijebiti. Istraživanje izotopne kiralnosti kvantno-kemijskim metodama omogućit će razumijevanje odstupanja od zakona pariteta i rasvijetliti fizikalne osnovice molekularne kiralnosti.
The 100th Anniversary of X-Ray Crystallography Kojić-Prodić, B.; Molčanov, K.
Kemija u industriji; časopis kemičara i tehnologa Jugoslavije,
07/2013, Volume:
62, Issue:
7-08
Journal Article
Peer reviewed
Open access
The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.W. L. BraggThe 100th anniversary of X-ray crystallography dates back to the first ...X-ray diffraction experiment on a crystal of copper sulphate pentahydrate. Max von Laue designed the theoretical background of the experiment, which was performed by German physicists W. Friedrich and P. Knipping in 1912. At that time, the mathematical formulation of the phenomenon and the fundamental concepts of crystallography were subjects of mineralogy. Altogether, they facilitated the development of methods for determination of the structure of matter at the atomic level. In 1913, father and son Bragg started to develop X-ray structure analysis for determination of crystal structures of simple molecules. Historic examples of structure determination starting from rock salt to complex, biologically important (macro)molecules, such as globular proteins haemoglobin and myoglobin, DNA, vitamin B12 and the recent discovery of ribozyme, illustrate the development of X-ray structural analysis. The determination of 3D structures of these molecules by X-ray diffraction had opened new areas of scientific research, such as molecular biophysics, molecular genetics, structural molecular biology, bioinorganic chemistry, organometallic chemistry, and many others. The discovery and development of X-ray crystallography revolutionised our understanding of natural sciences – physics, chemistry, biology, and also science of materials. The scientific community recognised these fundamental achievements (including the discovery of X-rays) by awarding twenty-eight Nobel prizes to thirty-nine men and two women. The explosive growth of science and technology in the 20th and 21st centuries had been founded on the detailed knowledge of the three-dimensional structure of molecules, which was the basis for explaining and predicting the physical, chemical, biological and pharmacological properties of molecules. A most recent and striking example is the still unfinished story of graphenes, occupying the front pages of leading scientific journals, such as Science, Nature, Nature Materials, Nature Nanotechnology, Nature Chemistry and Nature Physics. Contemporary crystallographic research covers numerous scientific domains, and it is a very innovative area of science. Who would dare to be a prophet and foresee future findings?
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