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U okviru ovog rada pripravljene su i u čvrstom stanju istražene tetraklorokupratne(II), tetrabromokupratne(II) i tetrakloromanganatne(II) soli izvedene iz monoamina, diamina i triamina različitih geometrijskih karakteristika i kemijskih funkcionalnosti. Poseban naglasak pri istraživnju posvećen je strukturnim karakteristikama priređenih spojeva, njihovim termičkim svojstvima, te odabranim magnetskim i električnim svojstvima. Iz difrakcijske strukturne analize priređenih spojeva, te simetrijske i statističke analize literaturno opisanih primjera, postavljena su geometrijska ograničenja i očekivanja za ovaj tip spojeva, koja su omogućila predlaganje smislenih strukturnih modela iz podataka difrakcije na prahu. Predložena je prava simetrija feroelektrične faze etilamonijevog tetraklorokuprata(II) iz podataka neutronske difrakcije, određene su strukture triju aperiodičnih kristala. Izučene su promjene u strukturi metilamonijevih halogenokuprata(II) uslijed supstitucijskog miješanja na položaju halogenidnog iona. Analizirana su magnetska svojstva slojevitih hibrida u ovisnosti o odabranim gradivnim ionima i dimenzionalnosti anorganske okosnice, te su kvantificirane modulacije u magnetskim svojstvima u supstitucijski miješanim kristalima. In this work, tetrachlorocuprate(II), tetrabromocuprate(II) and tetrachloromanganate(II) salts derived from monoamines, diamines and triamines with different geometric characteristics and chemical functionalities were prepared and investigated in the solid state. An emphasis was given to the structural characteristics, thermal properties, and selected magnetic and electrical properties of prepared compounds. Geometric limitations and expectations were derived for this type of materials from the diffraction structural analysis of prepared compounds, and the symmetry and statistical analysis of those described in the literature, which enabled the proposal of meaningful structural models from powder diffraction data. The true symmetry of the ferroelectric phase of ethylammonium tetrachlorocuprate was proposed from neutron diffraction data. Structures of three aperiodic crystals were determined. Changes in the structure of methylammonium tetrahalocuprates(II) due to substitutional mixing of halide ions were quantified. The magnetic properties of the layered hybrids were analyzed in relation to the selection of building ions and the dimensionality of the inorganic framework. Modulations of the magnetic properties in substitutionally mixed crystals were quantified.

Penicylone A is a naturally occurring polyketide compound containing a spiro[5.5]lactone moiety which was recently isolated from Penicillium sp. F23-2.1 Our motivation for the synthesis of penicyclone A, aside from its exotic structure, was its reported antibacterial activity (MIC = 0.3 µg/mL for S. Aureus). The variety of functional groups and chiral centers in a relatively small molecule presented a considerable synthetic challenge. We developed the first total synthesis of penicyclone A, which was accomplished in 10 steps starting from a known D-ribose derivative.2 The key step was a double Grignard reaction enabling the diastereoselective construction of a crucial tertiary alcohol intermediate. This new methodology was also tested on several other modal compounds to determine the scope of its applicability. The synthesis also featured a tandem oxidation/cyclization for the synthesis of the lactone moiety and a photooxygenation followed by an oxidative rearrangement to introduce the enone functionality. The synthetic penicyclone A was thoroughly characterized using NMR spectroscopy, mass spectrometry, circular dichroism and optical rotation measurements. Its absolute configuration was confirmed using single crystal X-ray diffraction. After reevaluation of the reported biological activity of penicyclone A the synthetic sample showed no antimicrobial activity. Discrepancies in the values of optical rotation between the natural and synthetic sample point to the possibility that the natural compound was isolated as an enantiomeric mixture which directed the research towards the synthesis of the other enantiomer.3

Chemical reactions in solid-state gained significant popularity in recent years1 due to their ability to expand the chemical space of organic synthesis, 2 which provides novel routes towards advanced materials for various applications.3 An important beneficial aspect of mechanochemistry is the fact that it requires environmentally acceptable conditions which includes the use of little or no organic solvent. Among the techniques for monitoring and characterization of solid-state reactions used so far (XRD methods, temperature and/or pressure monitoring, Raman, NMR and IR spectroscopy), 4 isothermal calorimetry (ITC) studies were scarcely applied, especially at ambient temperatures.5, 6 A lack of reaction enthalpy data for reactions in solid-state makes full thermodynamic characterization of these processes impossible without using thermodynamic cycles (requiring many different, long-lasting calorimetry experiments). Therefore, a crying need for direct detection of heat effect upon mixing of two or more solid reactants emerges in this reaserch area, the response to which, to the best of our knowledge, was not yet reported. In this work, a robust Calvet-type calorimeter (Setaram®), equipped with a cell originally designed for studies of dissolution processes, was used to directly measure the enthalpy of reactions between solid compounds at room temperature. Investigated reactions were complexation of KHSO4 with 18-crown-6 ether7 and proton transfer from salicylic acid to N, N-dimethylpyridin-4-amine combined with cocrystal formation. The reliability of the data was tested by comparing the directly obtained values of solid-state reaction enthalpies with the ones calculated using the appropriate thermodynamic cycles.

The coordination chemistry of molybdenum has been growing rapidly due to the rich biochemical and catalytical properties of the obtained complexes [1, 2]. Molybdenum Schiff’s base complexes are of particular interest because MoO2L type of complexes possess open coordination site that can be utilized for substrate binding properties [3]. Furthermore, hydrazone ligands are the most important pharmacophoric cores of several anti- inflammatory, antinociceptive, and antiplatelet drugs [4]. In light of the mentioned, two ligands obtained from nitrobenzaldehyde were prepared and coordinated to the MoO22+ core. If the reactions were performed in alcohols, mononuclear complexes, [MoO2(L1or2)(D)], D=donor molecule, were obateined. When acetonitrile was used as the solvent, the polynuclear [MoO2(L1)]n or mononuclear complex [MoO2(L2)(H2O)] was obtained. All the complexes were analysed and identified by IR-ATR, TG analysis, while molecular and crystal structure was determined by X-Ray diffraction. It has been noticed that grinding of [MoO2(L2)(D)] alters the crystal structure and obtained compounds correspond to [MoO2(L2)]n. After exposure to alcohol vapors, the starting compounds [MoO2(L2)(D)] were obtained. Further research perspective is to test the obtained complexes as the catalysts in the oxidation reactions following the principles of green chemistry.

International audience; Dinuclear and mononuclear molybdenum(VI) complexes with aroylhydrazonato ligands were studied as catalysts for cyclooctene and oct-1-ene epoxidation. Different isomers of the OH and NH2 functionalised aroylhydrazones led to four specific [MoO2L] units showing different catalytic activity. Three oxidants have been investigated: tert-butylhydroperoxide (TBHP) in water or in decane, and hydrogen peroxide (H2O2). Catalytic processes with TBHP in decane provided outstanding results in the case of cyclooctene epoxidation: TOF2.5 min > 9000 with 0.25 mol % [Mo] loading. DFT calculations confirmed the relationship between the ligand nature and reactivity with TBHP and H2O2 as oxidant agents. In the case of TBHP as oxidant, calculations considered the solvent in which the oxidant is delivered to the olefin. A plausible mechanism with H2O2 has been proposed after considering various pathways.

Multiferroic guanidinium copper(II) formate, [C(NH2)3][Cu(HCOO)3], belongs to the family of metal organic perovskites with the formula ABX3. It crystallizes in the orthorombic space group Pna21 and consists of copper – formate 3D framework with guanidinium cations in its nearly cubic cavities. Due to the Jahn-Teller effect of Cu2+ ion, the octahedral coordination is elongated, producing the framework of Cu-formate chains in the c direction, where Cu2+ ions inside the chain are linked with short bonds and Cu ions between the chains with the long bonds. We have studied magnetic properties of [C(NH2)3] [Cu(HCOO)3] using MPMS5 SQUID magnetometer. Temperature dependence of magnetization showed a broad peak centered at 45 K which can be ascribed to antiferromagnetic order in the Cu-formate chains. Below 4.6 K the sharp rise of magnetization indicated a formation of 3D spin canted antiferromagnetic long range order. Hysteresis loops at the temperatures below 4.6 K showed a sharp increase of magnetization for the fields lower than 50 Oe. Anisotropy could be seen in both M(T) and M(H) measurements. The effect of electric field on the magnetization was observed at temperatures below 4.6 K as a difference in magnetization curves measured with and without the applied electric field, pointing to the existence of substantial magnetoelectric coupling. Search for the explanations of observed magnetic and magnetoelectic behaviour is in progress considering the interesting crystal structure of this compound. Wishing for better understanding we are collaborating with other scientists doing the complementary research such as the ab-initio calculations and torque anisotropy measurements. It would also be interesting to do electron paramagnetic resonance experiments and optical measurements in order to see if there is magnetoelectric response at much higher frequencies making it possible choice for the application as a fast magnetoelectric.

Dioxomolybdenum(VI) complexes based on dihydrazone scaffolds have proved well their coordination and supramolecular prospects for the design of materials ranging from discrete multinuclear complexes to polyoxometalates.1 In contrast to their rigid benzhydrazones and carbohydrazone congeners, alkyl (di)hydrazones offer entirely new scenarios when considering materials framework topology. As we show, the extreme topological richness can be achieved by combining flexible alkyl (di)hydrazones with rigid bis(pyridyl) linkers, while relying on the coordinatively predictable MoO22+ core. A detailed structural analysis unveils that the geometrical features and topology of the polymers are dictated by the conformational flexibility of the alkyl chain of the ligand, as well as hydrogen-bonding propensities of peripheral functional groups.

The development of novel synthetic routes to achieve polyoxometalate (POM) architectures is an attractive research field because POMs are, among others, materials with catalytic, magnetic, bioactive, and energy storage properties. There are two ways of functionalizing inorganic-organic hybrid POMs, one being by the formation of polyoxometalate salt with organic or metal-organic cation and the other one by the substitution of the oxo atoms [1, 2]. Bearing in mind previously stated facts, the tendency of dioxobis(pentane-2, 4- dionato)molybdenum(VI) towards hydrolysis in wet acetonitrile solutions, as well as the solubility of hydrazones [3] we hypothesized the possible formation of hexamolybdate and octamolybdate hybrides functionalised by the hydrazonato complexes. All hybrides were achieved by using aroylhydrazone ligands derived from (iso)nicotinoylhydrazide and differently substituted salicylaldehydes. Structurally diverse POMs with cations of various protonation states were obtained. Characteristic bands in the IR spectra showed facile differentiation of POMs with different nuclearities whereas crystal and molecular structures were unambiguously determined by single-crystal X-ray diffraction.

Hydrazones serve as a valuable platform for exploring fundamental aspects of soft material engineering, owing to their straightforward preparation and chemical robustness. Naturally, insight into their behaviour propels the development of novel chemosensors, biologically active materials and catalysts. Dihydrazones, while seldom explored, offer a plethora of compelling chemical and structural scenarios. Within this study, aryl dihydrazones derived from succinic and adipic acid dihydrazide were synthesized and thoroughly investigated in the solid-state and solution. The potential of the prepared ligands for the development of coordination polymers based on molybdenum(VI) species was investigated under various reaction conditions. The isolated compounds were characterized in the solid-state and solution by appropriate spectroscopic and diffraction methods and compared with the relevant data for neutral dihydrazones. The results unveil that while neutral dihydrazones demonstrate substantial conformational flexibility in solution, crystallization or chelation effectively lodges the dihydrazone framework in a robust anti conformation.

Multiferroic guanidinium copper(II) formate, [C(NH2)3][Cu(HCOO)3], belongs to the family of metal organic perovskites with the formula ABX3. It crystallizes in the orthorombic space group Pna21 and consists of copper – formate 3D framework with guanidinium cations in its nearly cubic cavities. Due to the Jahn-Teller effect of Cu2+ ion, the octahedral coordination is elongated, producing the framework of Cu-formate chains in the c direction, where Cu2+ ions inside the chain are linked with short bonds and Cu ions between the chains with the long bonds. We have studied magnetic properties of [C(NH2)3] [Cu(HCOO)3] using MPMS5 SQUID magnetometer. Temperature dependence of magnetization showed a broad peak centered at 45 K which can be ascribed to antiferromagnetic order in the Cu-formate chains. Below 4.6 K the sharp rise of magnetization indicated a formation of 3D spin canted antiferromagnetic long range order. Hysteresis loops at the temperatures below 4.6 K showed a sharp increase of magnetization for the fields lower than 50 Oe. Anisotropy could be seen in both M(T) and M(H) measurements. The effect of electric field on the magnetization was observed at temperatures below 4.6 K as a difference in magnetization curves measured with and without the applied electric field, pointing to the existence of substantial magnetoelectric coupling. Search for the explanations of observed magnetic and magnetoelectic behaviour is in progress considering the interesting crystal structure of this compound. Wishing for better understanding we are collaborating with other scientists doing the complementary research such as the ab-initio calculations and torque anisotropy measurements. It would also be interesting to do electron paramagnetic resonance experiments and optical measurements in order to see if there is magnetoelectric response at much higher frequencies making it possible choice for the application as a fast magnetoelectric.

Hydrazones, as structurally adaptable and functionally diverse systems, assume a number of practical roles as e.g. cytotoxic agents, molecular switches and anion receptors [1]. Moreover, hydrazones and their complexes are a versatile tool for investigating intermolecular interactions due to their tautomeric and conformational flexibility [2]. In this wide class of compounds, carbohydrazones have a special place, since they can be realized as mono- and disubstituted derivatives [3]. The possibility of tailoring them in asymmetric fashion, producing compounds with two structurally and chemically distinct subunits, offers a rich platform for testing them as supramolecular building blocks. To investigate carbohydrazones in this context, multifunctional asymmetric compounds bearing hydroxyaryl and pyridyl moieties, representing acidic and basic subunits, respectively, were prepared and structurally characterized. Title compounds were synthesized by stepwise functionalization of carbohydrazide. Depending on crystallization conditions, multiple polymorphs and/or solvates of the same compound could be isolated. Despite the expected supramolecular diversity, solid-state geometric features of those molecules are quite robust: all compounds crystallize as keto-imino tautomers in an anti conformation, with strong intramolecular OHaryl···Nimino hydrogen bond dictating the orientation of hydroxyaryl subunit. Pyridyl moiety is invariably taking part in interactions with hydrogen bond donors, while packing in whole is defined by delicate competition between carbamide homosynthon and carbonyl-hydroxyl heterosynthon.

Metal-organic compounds with perovskite crystal structure provide a fertile playground for design of the multifunctional materials. Some properties can be mutually dependent, and some orders mutually coupled, paving the way to design of the magnetoelectric multiferroics. Interesting example of the hybrid layered perovskite multiferroic is ethylammonium tetrachlorocuprate, which consists of the ferromagnetic layers of corner sharing [CuCl4]2− octahedra connected by two layers of polarizable organic ions of C2H5NH3+. Besides the known ferroelectric transition around 245 K, it shows rich magnetic behaviour below 10.5 K, including magnetic anisotropy and transitions between different magnetic states. Although the search for magnetoelectric effect was not successful, a slight change of magnetization with the structural changes above 300 K was observed. Composition of this metal- organic perovskite was changed and the accompanied changes of the crystal structure and magnetic properties were studied. Up to now, magnetization is measured in DC regime using SQUID magnetometer in temperature range 2–300 K at different magnetic fields up to 5 T. Large impact of geometric and electronic changes of the organic cation structure on magnetic properties was observed in following two groups. Novel series of the solid-state architectures consisting of tetrachlorocuprate units and ortho-, meta- and para-anisidinium were prepared and in their crystal structure considerable change of geometry was observed: from the discrete square planar tetrachlorocuprate anions in the ortho- anisidinium compound to the Ruddlesden-Popper perovskite phase with slightly distorted layers built from CuCl6 octahedra in the para- anisidinium compound. Spins 1/2 per Cu2+ ion remain in the paramagnetic state down to the lowest temperatures in the ortho-anisidinium tetrachlorocuprate. However, there are transitions to the ferromagnetic state measured at 4.2 K and 9.5 K for the meta-anisidinium and para-anisidinium tetrachlorocuprates, respectively. Their ferromagnetic-like hysteresis loops are very soft, without the observable coercivity. Surprise happens in difference between the chloroethylammonium tetrachlorocuprate and bromoethylammonium tetrabromocuprate: the first one has antiferromagnetic transition at 7.8 K with metamagnetic transition in fields above 150 Oe, while the second one has ferromagnetic transition at 11 K and broad hysteresis loop with coercivity around 100 Oe at 2 K. Polar order is predicted in theoretical calculations, and magnetoelectric experiments could be challenging. This research showed that a small change in structure has drastic influence on the geometry and magnetism of the cuprate units. At the moment it seems to us that the 3D metal-organic perovskites have brighter perspective for magnetoelectric coupling than the 2D. If having on mind wide possibility of combining the building blocks with different physical properties like elastic, (super)conducting, optical, polar, magnetic, the rich field of applications can be foreseen for 2D perovskites, including also influence of the the light on the magnetic and electric response. Some of those will be of our future interest.

Hydrazones, as structurally adaptable and functionally diverse systems, assume a number of practical roles as e.g. cytotoxic agents [1] or anion receptors [2], while their Mo(VI) complexes have demonstrated their value as effective epoxidation (pre)catalysts [3]. In this wide class of compounds, carbohydrazones have a special place, owing to the structural versatility of their mono‐ and disubstituted derivatives [4]. The possibility of tailoring them in asymmetric fashion, creating in return systems with two different subunits, varying in chelating behaviour and acid‐base properties, offers a versatile platform for testing them as metalloorganic and supramolecular building blocks. To investigate carbohydrazones in this context, multifunctional asymmetric compounds bearing hydroxyaryl and pyridyl moieties were derived and tested for their chelating and anion receptor behaviour. Dioxomolybdenum(VI) complexes and carbohydrazonium polyoxomolybdates (POMs) were prepared by crystallization from solution and by mechanochemical synthesis. To explore alternative routes towards corresponding POM salts, dioxomolybdenum(IV) complex decomposition and salt metathesis reactions were explored as well. The results evidence that different reaction conditions, in particular solvent choice and water content, along with the starting carbohydrazone structure affect the reaction outcome and the structure of the products obtained. Whereas dioxomolybdenum(VI) complexes have their structures determined by strongly chelating hydroxyaryl subunit, structures of POM salts are shaped by delicate competition between CONH∙∙∙OPOM, NH+py∙∙∙OPOM and OHar∙∙∙OPOM intermolecular hydrogen bonds (Figure 1).

Pressure is an important, but often overlooked variable in soft solid-state science. Even though static[1] and shock[2] phase behavior is known for some pure compounds, knowledge about pressure dependence of solid-state reactions is practically non-existent. In this work, theoretical pressure dependence for formation of binary cocrystals from its components is explored, using Cambridge Structural Database[3] as a data source. Interestingly, distribution of reaction molar volume is not quite symmetrical, with more entries having molar volume greater than sum of molar volumes of its components. This suggests that higher pressure would usually work against cocrystallization. Structural correlation, extreme cases and potential of “pressure-only” synthesis are presented.

Metal-organic compounds with perovskite crystal structure provide a fertile playground for design of the multifunctional materials. Due to wide possibilities of combining the building blocks in such crystals, different physical properties can be tuned, such as elastic, conducting, optical, polar, magnetic. Some properties can be mutually dependent, and some orders mutually coupled, paving the way to design of the magnetoelectric multiferroics. One interesting example of the hybrid layered perovskite multiferroic is the ethylammonium tetrachlorocuprate, which consists of the ferromagnetic layers of corner sharing [CuCl4]2− octahedra connected by two layers of polarizable organic ions of C2H5NH3+. Motivated by its ferroelectricity and rich magnetic behaviour below 10.5 K, including magnetic anisotropy and transitions between different magnetic states, as well as recently observed change of magnetization with the structural changes above 300 K, we changed the composition of this metal-organic perovskite and studied the accompanied changes of the crystal structure and magnetic properties. Here we explored the novel series of the solid- state architectures consisting of the tetrachlorocuprate units and different anisidine isomers. Ortho-anisidinium, meta-anisidinium and para-anisidinium tetrachlorocuprates were prepared by crystallization from the mixed organic-aqueous solutions. In the crystal structure considerable change of geometry was observed: from the discrete square planar tetrachlorocuprate anions in the ortho-anisidinium compound to the Ruddlesden- Popper perovskite phase with slightly distorted layers built from CuCl 6 octahedra in the para- anisidinium compound. It seems that in the meta- anisidine compound structure resembles the para- compound, but with more distorted anionic layers. Up to now, we studied the temperature dependence of magnetization of the pure powder samples using SQUID magnetometer in temperature range 2–300 K at different magnetic fields and magnetic hysteresis loops in the ordered state. Large impact of geometric and electronic changes of the organic cation structure on magnetic properties was observed. Magnetic susceptibility in the paramagnetic state as well as the saturation magnetization are in agreement with spin 1/2 per Cu2+ ion. These spins remain in the paramagnetic state down to the lowest temperatures in the ortho-anisidinium tetrachlorocuprate showing that there are no magnetic interactions between the discrete planar [CuCl4]2- units. However, there are transitions to the ferromagnetic state measured at 4.2 K and 9.5 K for the meta- anisidinium and para-anisidinium tetrachlorocuprates, respectively. Their ferromagnetic-like hysteresis loops are very soft, without the observable coercivity, gaining very easily the saturation. Higher transition temperature is observed for larger separation between the cuprate plains, showing that packing of the isomers play an important role in transfering the interaction between the planes. Moreover, in the meta- compound magnetic transition is not so clearly ferromagnetic, that might be influenced with bigger canting of the tetrachlorocuprate octahedra and higher possibility for disorder in interlayer packing. This research showed that a small change in structure of the cation connecting the magnetic layers has drastic influence on the geometry and magnetism of the cuprate units within the structure, thus motivating us for further studies of such compounds with similar composition and structure. Authors acknowledge financial support of Croatian Science Foundation under the installation research project Multiferroic and Magnetoelectric Systems UIP-2014-09-8276.

Ispitane su mogućnosti visokotlačne statičke i udarne kompresije kao metode za pripravu kokristala lamotrigina, te uspoređene s mogućnostima uobičajenih metoda supramolekulske sinteze. Provedeno je pretraživanje kokristala lamotrigina kristalizacijom iz otopine, kristalizacijom iz taline te mehanokemijskom sintezom. Uzorci fizičke smjese lamotrigina i koformera obrađeni su statičkom kompresijom pri dva tlaka, te sporom i brzom udarnom kompresijom pri četiri različite brzine projektila. Dobiveni uzorci izučavani su metodom difrakcije rentgenskih zraka na praškastom uzorku, razlikovnom pretražnom kalorimetrijom te skenirajućom elektronskom mikroskopijom. Riješene su kristalne strukture za tri solvata i jedan kokristal lamotrigina metodom difrakcije rentgenskog zračenja na jediničnom kristalu. Visokotlačna sinteza i uobičajene metode sinteze uspoređene su prema broju uspješnih priprava, morfologiji i mehanizmu nastanka kokristala. High-pressure static and shock compression was studied and compared with common methods used for supramolecular synthesis. Cocrystal screening of lamotrigine was done by crystallization from solution, crystallization from melt and mechanochemical synthesis. Physical mixture of lamotrigine and coformer was subjected to static compression at two pressures, as well as slow and fast shock compression at four different projectile speeds. Obtained samples were analysed with powder X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. Crystal structure was solved for three solvates and one cocrystal of lamotrigine using single-crystal X-ray diffraction. High-pressure supramolecular synthesis and common methods of cocrystal preparation were compared by number of hits, morphology and formation mechanism of cocrystals.

In the past twenty years the halogen bonding has investigated as a useful tool for synthesis of the new materials in solid state chemistry and crystal engineering. The most common building blocks in halogen bonded systems are perfluorinated halogenated hydrocarbons as halogen bond donors (for example 1, 4- and 1, 2-diiodotetrafluorobenzene) and Lewis bases as halogen bond acceptors (pyridines, amines and carbonyl compounds). On the other side, the potential of halogen atom coordinated to metal centre to act as halogen bond donor have not been extensively studied to date. For this purpose, we have prepared ten cobaloximes ([CoX(Hdmg)2L], where X = Cl, Br, I ; Hdmg = hydrogendimethylglyoximate anion and L is a Lewis base). In spite of the fact that all synthesized compounds have atoms which may act as a halogen bond acceptor (O atoms at Hdmg and in some cases additional O or N atoms on L), no halogen bonding between these atoms and halogen coordinated to metal centre has been observed in any of the investigated compounds. Quite the opposite, in all crystal structures the halogen atoms are at considerable distances from all the potential acceptor atoms. Such behaviour is explained by the ab-initio calculation which have shown that halogen atom coordinated at the metal centre does not have a positive σ-hole and consequently, cannot act as halogen bond donor. This result, as well as several similar cases reported in the literature, indicated that the cobaloxime halogen atoms may be good halogen bond acceptors. This prompted us to attempt cocrystallization of the prepared cobaloximes with halogen bond donors (1, 2- and 1, 4-diiodotetrafluorobenzene) rather than halogen bond acceptors. These experiments have resulted with corresponding halogen bonded co-crystals. All obtained compounds exhibit I∙∙∙X contacts (X = Br, Cl), while in some of them I∙∙∙O and I∙∙∙pi halogen bonds have found.

Aperiodic crystals are crystals which do not possess 3D translation symmetry. An incommensurately modulated structure can be considered a perturbed periodic crystal. Urotropine (hexamethylenetetramine) is a quasi-spherical molecule that is known for forming co-crystals of modulated superstructures with long linear coformers such as aliphatic diacids, of wich cocrystal with azelaic acid was found to have an invommensurately modulated superstructure. Here we present a halogen bonded cocrystal of urotropine and a linear halogen bond donor, octafluoro-1, 4-diiodobutane (ofib). The cocrystal was prepared by means of LAG (liquid-assisted grinding) and from solution. X-ray diffraction at room temperature has shown that the structure of the cocrystal is incommensurately modulated with a monoclinic sublattice (a = 5.976 Å, b = 24.82 Å, c = 6.015 Å, β = 105.82°, Z = 2) and the modulation vector q(298 K) = (0.0808, 0, 0.2063). Repeated measurement at 150K has shown only minor changes in the sublattice parameters (a = 5.911 Å, b = 24.21 Å, c = 5.947 Å, β = 103.94°, Z = 2) and a considerable change in the modulation vector q(150 K) = (0.0824, 0, 0.1907). Interestingly, it was possible to solve and refine both the room temperature and low temperature structures as periodic approximates – the room temperature one can be modeled as a centrosymmetric monoclinic structure with Z = 20, and the low temperature as an acentric monoclinic one with Z = 22 (Figure 1). Subsequent measurements oft he unit cell parameters and the modulation vector have shown that the change occurs relatively abruptly between 0 °C and the room temperature. There was, however, no corresponding thermal event discernable in the DSC curve bellow the room temperature, but a reversible phase transition at 35-40 °C has been detected, which has prompted us to remeasure the crystal at 325 K. The crystal structure of the high temperature phase was found to be a non-modulated orthorhombic structure with severe disorder in difluoromethylene groups of the ofib molecules.