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Full process of preparation of single crystals; powder patterns; IR spectra; molecular structures; hydrogen bonding system; and geometric parameters.

Penta-coordinated complexes of Ni(II) (S = 1) represent promising magnetically active materials. The synthetic strategy leading to penta-coordination may be based on using a combination of two- and three-donor voluminous ligands, e.g. N,N-donor chelating neoc (2,9-dimethyl-1,10-phenantroline), and O,N,O-donor pyridine-2,6-dicarboxylato(2-) (pdca) ligands. We have experimentally studied the aqueous-ethanolic systems formed of various Ni(II) salts, H2pdca and L being neoc, phen (1,10-phenantroline), bpy (2,2ˈ-bipyridine) and dtbpy (4,4ˈ-di-tert-butyl-2,2ˈ-bipyridine). We have isolated and characterized five different Ni(II) complexes, four of them being molecular and one ionic. All molecular complexes are built up of complex molecules with the general formula [Ni(pdca)(L)(H2O)]; however, all these complexes contain hexacoordinated Ni(II) atoms. In addition, the crystal structures of these four complexes comprise various solvate molecules. The fifth ionic complex also contains hexacoordinated Ni(II) atoms and is built up of [Ni(phen)2(H2O)2]2+ complex cations and [Ni(pdca)2]2- complex anions and solvate water molecules.

From methanolic solutions of Ni(NO3)2, 5,5ˈ-dimethyl-2,2ˈ-bipyridine and LiTCNQ (TCNQ = 7,7,8,8-tetracyanidoquinodimethane), complex [Ni(5,5ˈ-dmbpy)3](TCNQ)2 was isolated and its thermal properties were studied. The complex is stable in air atmosphere up to 208 ºC. The thermal decomposition consists in 3 consecutive steps in the temperature ranges 208-274 ºC (weight loss of 10.0 %), 274-401 ºC (17.5 %) and 401-495 ºC (64.2 %). The weight of the solid residue (8.3 %) corresponds to formation of NiO (calc. 7.3 %).KTCNQ was prepared reacting boiling acetonitrile solutions of TCNQ and KI. It is thermally stable up to 300 ºC. Its crystal structure at 200 ºC was determined. KTCNQ consists of one crystallographically independent TCNQ- anion and one potassium cation K+. Each K+ cation is octa-coordinated by eight nitrogen atoms from cyanide groups of TCNQ- anions. This crystal structure corresponds to the high-temperature phase of KTCNQ. As expected, the cell volume is by 1.5 % larger than the reported value measured at 140 ºC.

Commentary is given on a paper [Butler et al. (2022). IUCrJ, 9, 364–369] reporting the crystallization of two room-temperature liquids, water and 2,2,6,6-tetra­methyl­piperidine, to form a crystalline solid with a water-lined channel potentially capable of proton transport.

Isolable crystals of the cesium salt of an anionic Jahn-Teller-active Cu complex, initially formed by reaction in solution, are spontaneously consumed in a solvent-mediated crystal-to-crystal transformation that produces a final product with a four-coordinate Cu center. Depending on the size of the crystals of the intermediate and the evaporation rate of the solvent, the transformation from intermediate to final product occurs in a two-week time frame. The crystalline Jahn-Teller Cu intermediate presents a noteworthy difference in stability compared to its non-Jahn-Teller Ni-centered isomorph. It is proposed that a Jahn-Teller intermediate may precede the formation of other four-coordinate Cu complexes.

This educational review postulates the importance of maintaining an adequate level of crystallographic education among structure-dependent scientists whose interests are not primarily in crystallography, at a time when automation and validation have made it possible to obtain high-quality structure analyses in many cases with a minimum of crystallographic background. The topics addressed are intended to form a second round of crystallographic education for a novice user whose first round involved hands-on experience with structure solution and an introduction to elementary concepts. The specific topics, chosen for their relevance as basic knowledge and their lack of emphasis in many formal treatments, are (1) crystallographic reference frames and the utility of the reciprocal cell in geometrical calculations; (2) the relationship between the two concepts that constitute our model of the crystal, namely the unit cell and the lattice; (3) the manner in which an atom is represented in concept and in practice; (4) the importance of interleaved symmetry elements required by the presence of additional symmetry on a lattice; (5) the harnessing of the natural properties of the crystalline state for the potential manipulation of properties of synthetic crystals; and (6) useful terminology for navigating a crystal structure.

[EN[ The present work is focused on the study of single-molecule magnets based on selected transition metals and lanthanides using a selected Schiff base ligand. The first part deals with the theoretical interpretation of the magnetic phenomenon of SMM as well as the coordination and magnetic properties of complexes containing central atoms Ni(II), Co(II)/(III), Ce(III), Gd(III) and Dy(III). In the experimental part, the method of preparation of the required complexes was determined in the first place - the so-called "self-assembly" method. According to the synthetic procedures thus determined, 21 compounds were prepared, which were physically and chemically characterized and their crystal structure was determined by X-ray structure analysis. One chapter is focused on the crystallographic study of polymorphism, where FIM methods and analysis of Hirshfeld surfaces were used for a more detailed examination of two polymorphs [CoIII 2(o-van-en)3]·4CH3CN. The work also includes a crystallographic study of a topotactic reaction of the SC-SC (Single Crystal-to-Single Crystal) type in which the complex [Ni(o-van-en)DyCl3(H2O)] dehydrates at a higher temperature and subsequently dimerizes to form a new complex [Ni2(o-van-en)2Dy2Cl6]. From the prepared substances, 4 complexes were selected and subjected to magnetic examination with respect to SMM properties. For all four substances, the slow relaxation of magnetization, typical for single-molecule magnets, was confirmed. The most significant result was the observation of slow magnetic relaxation in a Ni-Gd sample, where the Ni(II) central atom is diamagnetic and Gd(III) is generally magnetically isotropic. The geometry and the electron density of the coordination sites has been proved to exert a very important influence on the SMM behaviour of lanthanide ions which has contributed to the theoretical knowledge of SMMs., [SL] Predkladaná práca je zameraná na štúdium jednomolekulových magnetov na báze vybraných prechodných kovov a lantanoidov s použitím vybraného ligandu Schiffovej zásady. Prvá časť práce sa venuje teoretickému opisu jednomolekulového magnetizmu ako aj koordinačnej chémii a magnetickým vlastnostiam komplexov obsahujúcich centrálne atómy Ni(II), Co(II)/(III), Ce(III), Gd(III) a Dy(III). V rámci experimentálnej časti bola najprv vypracovaná metóda prípravy požadovaných komplexov – tzv. „self-assembly“ metóda. Podľa takto určených syntetických postupov bolo pripravených 21 látok, ktoré boli fyzikálne a chemicky charakterizované a pomocou rtg. štruktúrnej analýzy bola stanovená ich kryštálová štruktúra. Jedna kapitola práce je zameraná na kryštalografickú štúdiu polymorfie, kde sa použili metódy FIM a analýza Hirshfeldových povrchov na detailnejšie preskúmanie dvoch polymorfov [CoIII 2(o-van-en)3]·4CH3CN. Práca zahŕňa aj kryštalografické štúdium topotaktickej reakcie typu SC-SC (Single Crystal-to-Single Crystal), pri ktorej sa komplex [Ni(o-vanen)DyCl3(H2O)] pri vyššej teplote dehydratuje a v jej dôsledku dimerizuje za vzniku nového komplexu [Ni2(o-van-en)2Dy2Cl6]. Spomedzi pripravených látok boli vybrané 4 komplexy, u ktorých sa študovali ich magnetické vlastnosti s ohľadom na ich SMM charakter. U všetkých štyroch látkach bola potvrdená pomalá relaxácia magnetizácie, ktorá je typická pre jednomolekulové magnety. Najvýznamnejším výsledkom bolo pozorovanie pomalej magnetickej relaxácie v Ni-Gd vzorke, kde centrálny atóm Ni(II) je diamagnetický a Gd(III) je vo všeobecnosti magneticky izotropný. Ukázalo sa, že geometria a elektrónová hustota koordinačných miest majú veľmi dôležitý vplyv na SMM správanie lantanoidových iónov, čo porispelo k doplneniu teoretických poznatkov o SMMs., [ES] El presente trabajo se centra en el estudio de imanes monomoleculares (SMM) basados en metales de transición y lantánidos seleccionados utilizando un ligando base de Schiff seleccionado. La primera parte aborda la interpretación teórica del fenómeno magnético de SMMs, así como las propiedades de coordinación y magnetismo de los complejos que tienen como átomos centrales Ni(II), Co(II)/(III), Ce(III), Gd(III) y Dy(III). En la parte experimental, el método de preparación de los complejos se estableció en primer lugar, el llamado método de "autoensamblaje". De acuerdo con los procedimientos sintéticos así determinados, se prepararon 21 compuestos, que fueron caracterizados físicamente y químicamente mediante las técnicas habituales, mientras se analizaron sus estructuras cristalinas mediante la difracción de rayos X en monocristal. Un capítulo se centra en el estudio cristalográfico del polimorfismo, donde se utilizaron los métodos FIM (full interaction mapping) y el análisis de las superficies de Hirshfeld para una exploración detallada de dos polimorfos de [CoIII 2(o-van-en)3]·4CH3CN. El trabajo también incluye el estudio cristalográfico de una reacción topotáctica del tipo SC-SC (Single Crystal-to-Single Crystal) en el que el complejo [Ni(o-van-en)DyCl3(H2O)] se deshidrata a una temperatura elevada con dimerización concomitante para formar un nuevo complejo [Ni2(o-van-en)2Dy2Cl6]. Cuatro de los compuestos preparados sometidos a estudios magnéticos dirigidos a sus posibles propiedades de SMMs. Para todos los cuatro complejos, se confirmó la relajación lenta de la magnetización, típica de los SMMs. El resultado más significativo fue la observación de la relajación magnética lenta en una muestra de Ni-Gd, donde el átomo central de Ni(II) es diamagnético y Gd(III) es generalmente magnéticamente isotrópico. Se ha demostrado que la geometría y la densidad electrónica del entorno de coordinación ejercen una influencia muy importante en el comportamiento SMM de los ion

Under various experimental conditions seven complexes have been crystallized from the systems Ni(II) – HBz – bpy (HBz = benzoic acid, bpy = 2,2′-bipyridine). The use of freshly prepared Ni(OH)2 as starting reagent leads to isolation of [Ni(bpy)(Bz)2] (1) and [Ni(bpy)3](Bz)2·5H2O (2). On the other hand, the use of nickel(II) nitrate as starting salt yielded 1 and also resulted in the formation of additional complexes in which the nitrate group entered into the final compositions, namely [Ni(bpy)2(Bz)](NO3)·2HBz (3), [Ni(bpy)2(Bz)](NO3)·1.25H2O (4), [Ni(bpy)2(H2O)(NO3)](NO3)·0.5HBz (5), [Ni(bpy)2(NO3)](NO3) (6) and [Ni(bpy)3](NO3)2·nH2O (n = 4.25) (7). The newly prepared complexes were characterized chemically and spectroscopically. The results of X-ray structure analyses of 1, 3–6 have shown that in all complexes, the Ni(II) atoms are hexacoordinated. Complex 1 exhibits a mononuclear molecular structure, while the ionic structures of 3–6 are built up of mononuclear complex cations with a heteroleptic coordination sphere around the Ni(II) atoms and by nitrate anions. In addition, the structures of 3–5 contain HBz solvate molecules or water molecules. The magnetic properties of 1 were studied in the temperature range 1.8–300 K showing that 1 is characterized by the presence of single-ion anisotropy of the easy-axis type with a value of D/kB = −6.32 K and a strong rhombic term with E/D = 0.327. Theoretical calculations using the ORCA package also confirm a significant influence of rhombic anisotropy.

The reactions of [Re(N‐N)(CO)3(PMe3)]OTf (N‐N=2,2′‐bipyridine, bipy; 1,10‐phenanthroline, phen) compounds with tBuLi and with LiHBEt3 have been explored. Addition to the N‐N chelate took place with different site‐selectivity depending on both chelate and nucleophile. Thus, with tBuLi, an unprecedented addition to C5 of bipy, a regiochemistry not accessible for free bipy, was obtained, whereas coordinated phen underwent tBuLi addition to C2 and C4. Remarkably, when LiHBEt3 reacted with [Re(bipy)(CO)3(PMe3)]OTf, hydride addition to the 4 and 6 positions of bipy triggered an intermolecular cyclodimerization of two dearomatized pyridyl rings. In contrast, hydride addition to the phen analog resulted in partial reduction of one pyridine ring. The resulting neutral ReI products showed a varied reactivity with HOTf and with MeOTf to yield cationic complexes. These strategies rendered access to ReI complexes containing bipy‐ and phen‐derived chelates with several C(sp3) centers.

The involvement of silver in two-electron AgI/AgIII processes is currently emerging. However, the range of stability of the required and uncommon AgIII species is virtually unknown. Here, the stability of AgIII towards the whole set of halide ligands in the organosilver(III) complex frame [(CF3)3AgX]− (X=F, Cl, Br, I, At) is theoretically analyzed. The results obtained depend on a single factor: the nature of X. Even the softest and least electronegative halides (I and At) are found to form reasonably stable AgIII−X bonds. Our estimates were confirmed by experiment. The whole series of nonradiative halide complexes [PPh4][(CF3)3AgX] (X=F, Cl, Br, I) has been experimentally prepared and all its constituents have been isolated in pure form. The pseudohalides [PPh4][(CF3)3AgCN] and [PPh4][(CF3)3Ag(N3)] have also been isolated, the latter being the first silver(III) azido complex. Except for the iodo compound, all the crystal and molecular structures have been established by single-crystal X-ray diffraction methods. The decomposition paths of the [(CF3)3AgX]− entities at the unimolecular level have been examined in the gas phase by multistage mass spectrometry (MSn). The experimental detection of the two series of mixed complexes [CF3AgX]− and [FAgX]− arising from the corresponding parent species [(CF3)3AgX]− demonstrate that the Ag−X bond is particularly robust. Our experimental observations are rationalized with the aid of theoretical methods. Smooth variation with the electronegativity of X is also observed in the thermolyses of bulk samples. The thermal stability in the solid state gradually decreases from X=F (145 °C, dec.) to X=I (78 °C, dec.) The experimentally established compatibility of AgIII with the heaviest halides is of particular relevance to silver-mediated or silver-catalyzed processes.

The Schiff-base bis­(2-hydroxy-3-methoxybenzylidene)ethylenediamine, denoted H2(o-van-en), is a versatile two-compartment polydentate ligand that can bring different guests, such as a transition metal and a lanthanoid, into close proximity to produce novel complexes with potentially singular properties. The base, which is prepared by the condensation of o-vanillin with ethylenediamine, reacts with nickel(II) carbonate to yield a microcrystalline product which upon recrystallization from acetone, ethanol and isopropanol, yielded three solvatomorphs of [Ni(o-van-en)]. These products, the hydrate [Ni(o-van-en)]⋅nH2O (n = 1.17, 1), the ethanol–water solvate [Ni(o-van-en)]⋅H2O⋅EtOH (2) and the isopropanol-water solvate [Ni(o-van-en)]⋅H2O⋅iPrOH (3), all contain the molecular complex [Ni(o-van-en)], as characterized by single-crystal x-ray diffraction. The [Ni(o-van-en)] fragment, which has been developed as a metalloligand for the preparation of mixed-metal (Tr-Ln) complexes with novel magnetic properties, here forms solvatomorphs whose crystals display pronounced differences in morphology and stability. The Ni(II) center in each of the three solvatomorphs is coordinated by the (o-van-en)2- ligand in a square geometry with a cis-N2O2 donor set. Each solvatomorph contains water solvate molecules; and in addition, ethanol and isopropanol solvate molecules are present in 2 and 3, respectively. Full Interaction Maps were used for comparison of the intermolecular interactions, by way of understanding the factors leading to the different solvation behavior. A review of the known structures containing o-van-en fragments is used as a contextual backdrop for a discussion of the new solvatomorph structures. Calculations based on an energy-decomposition model are used to characterize the interactions within dimeric aggregates observed in the structures of 2 and 3.

The title hydrated mol­ecular salt (systematic name: tetra-n-butyl­ammonium 2,6-dioxo-1,2,3,6-tetra­hydro­pyrimidine-4-carboxyl­ate monohydrate), C16H36N+·C5H3N2O4 −·H2O, crystallizes with N—H⋯O and O—H⋯O hydrogen-bonded double-stranded anti­parallel ribbons consisting of the hydro­philic orotate monoanions and water mol­ecules, separated by the bulky hydro­phobic cations. The hydro­phobic and hydro­philic regions of the structure are joined by weaker non-classical C—H⋯O hydrogen bonds. An accurate structure analysis conducted at T = 100 K is compared to a lower-resolution less accurate determination using data measured at T = 295 K. The results of both analyses are evaluated using a knowledge-based approach, and it is found that the less accurate room-temperature structure analysis provides geometric data that are similar to those derived from the accurate low-temperature analysis, with both sets of results consistent with previously analyzed structures. A minor disorder of one methyl group in the cation at low temperature was found to be slightly more complex at room temperature; while still involving a minor fraction of the structure, the disorder at room temperature was found to require a non-routine treatment, which is described in detail.

The new organic–inorganic hybrid material [Zn(H2O)6][{(CH2)6N4}ZnCl3]2·0.5H2O, is the second hydrate in this system, the first having been the hexahydrate. The new solid was prepared by slow evaporation of a solution of the reactants at room temperature and was structurally characterized by X-ray crystallography. This compound crystallizes in the trigonal system, space group P-3c1 with a = 9.8303(2)Å, c = 17.5460(2)Å, V = 1468.38(4)Å3 and with Z = 2. The complex was characterized by FT-IR, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and with a detailed analysis of Hirshfeld surfaces and fingerprint plots. The structural unit of the title compound consists of a [ZnII(H2O)6]2+ cation, two [ZnIICl3(hmt)]- anions and half of a water molecule, partially occupied and disordered [hmt is hexamethylenetetramine, (CH2)6N4]. Crystal packing is mediated by OH⋯N and OH⋯Cl hydrogen bonds between the anions and cations, and to a lesser extent by OH⋯O contacts, which are present only part of the time as a consequence of the partial occupancy of the isolated water molecules. The relationship between the packing in the new structure and that of the previous hexahydrate is described.

Studies of phase transitions in molecular crystals are becoming more commonplace as improvements in instrumentation and technique enable more efficient exploration of the behavior of samples with varying external conditions, usually temperature. This scientific commentary provides contextual background on this type of study, with reference to an article on transformations in a ferrocenyl-acetylide-gold(I) complex [Makal (2018). Acta Cryst. B74, 427-435].

Trinuclear cobalt paddlewheel complexes, [Co3(dpa)4X2] (dpa = the anion of 2,2'-dipyridylamine, X = Cl-, Br-, -NCS-, -CN-, (NC)2N-), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T1/2) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T1/2 values follow the trend I- < Br- ≈ Cl- < F-; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl-, Br- and I- derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second example of an unsymmetric complex supports the observation that they display dramatically lower T1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found.

Schiff bases prepared from ortho-vanillin and various diamines are ligands in a rich diversity of complexes, from mononuclear species to polymers. The complexes have interesting properties in a variety of fields – among them magnetism, luminescence, chirality, and catalysis. We have used targeted synthesis to prepare discrete heterodinuclear complexes with 3d-4f metal centers connected by the Schiff base ligand (H2L), which is prepared by condensation of ortho-vanillin and ethylenediamine in molar ratio 2:1. In the first step of the synthesis we isolated two solid solvates of NiL, namely [NiL]·H2O·EtOH and [NiL]·H2O·iPrOH; and in a subsequent step we obtained the heteronuclear compounds [NiLGdCl3(H2O)] and [NiLGd(NO3)3]·4MeCN from the reaction system [NiL] – LnIII. We present the structures of all four products. Possible causes are presented for some noteworthy differences between the two solid forms of the [NiL] compound, including different stabilities and colors of their crystals.

The Lewis acidity of perfluorinated trimethylgold (CF3)3Au was assessed by theoretical and experimental methods. It was found that the (CF3)3Au unit is much more acidic than its nonfluorinated analogue (CH3)3Au, and probably sets the upper limit of the acidity scale for neutral organogold(III) species R3Au. The significant acidity increase on fluorination is in line with the CF3 group being more electron‐withdrawing than CH3. The solvate (CF3)3Au⋅OEt2 (1) is presented as a convenient synthon of the unsaturated, 14‐electron species (CF3)3Au. Thus, the weakly coordinated ether molecule in 1 is readily replaced by a variety of neutral ligands (L) to afford a wide range of (CF3)3Au⋅L compounds, which were isolated and characterized. Most of these mononuclear compounds exhibit marked thermal stability. This enhanced stabilization can be rationalized in terms of substantially stronger [Au]−L interactions with the (CF3)3Au unit. An affinity scale of this single‐site, highly acidic organogold(III) fragment was calculated by DFT methods and experimentally mapped for various neutral monodentate ligands. The high‐energy profile calculated for the fluorotropic [Au]−CF3⇌F−[Au]←CF2 process makes this potential decomposition path unfavorable and adds to the general stabilization of the fragment.

Schiff bases are often used as ligands for the coordination of cobalt due to their multi-donor properties and consequent versatility. In our quest for Co(II) complexes as magnetically active materials we have isolated two polymorphs of [Co2(o-van-en)3]×4CH3CN (1 and 2) based on the Schiff base ligand o-van-en synthesized by the reaction of ethylenediamine with o-vanillin in 1:2 molar ratio. The triclinic (P-1) polymorph 1 was obtained after room temperature crystallization of the acetonitrile solution of the reaction product of the Schiff base with cobalt hydroxide in air. Differences in reaction and crystallization conditions produced the monoclinic form 2 (space group P21/c). Both polymorphs were chemically and spectroscopically characterized, and the results indicated spontaneous oxidation of Co(II) to Co(III). The crystal structures of both 1 and 2 are built up of molecules of the centrosymmetric dinuclear complex [Co2(o-van-en)3], in which each Co(III) atom is coordinated by one tetradentate o-van-en ligand in an uncommon bent fashion. The pseudooctahedral coordination of the Co(III) atom is completed by one phenolato O and one amidic N atom of the same arm of the bridging o-van-en ligand. In addition, the asymmetric units of both polymorphs contain two acetonitrile solvate molecules. In polymorph 2, consistent with the symmetry of the space group, the dinuclear {Co2} units are arranged in an alternating ABABAB fashion, in contrast to the AAA arrangement of the dinuclear units in polymorph 1. As a consequence, both polymorphs differ in the positions of the acetonitrile solvate molecules and in the pattern of intermolecular interactions. Differences of some geometrical parameters, e.g., torsion angles were observed, too.

A newly prepared 3-D polymer of cobalt citrate cubanes bridged by high-spin Co(ii) centres displays both single-molecule magnet (SMM) behaviour and magnetic ordering. Triple interpenetration of the 3-D diamondoid polymers yields a crystalline solid with channels that host cations and free water molecules, with the SMM behaviour of the CoO cores preserved. The octahedrally coordinated Co(ii) bridges are implicated in the onset of magnetic order at an experimentally accessible temperature.

[ES]: La parte experimental de la tesis se dedica a la preparación de nuevos compuestos de lantánidos Ce(III), Gd(III) y Dy(III) elegidos por sus propriedades magnéticas y tres tipos de ligandos (PDOA, orotato y bapen). Dado que las sistemas heterobimetálicas 3d-4f atraen mucha atención, métales de transición Ni(II), Cu(II) y Co(III) han sido elegidos para la preparación de nuevos compuestos tipo 3d-4f. Se han sintetizado 15 compuestos en la forma de monocristales; las reacciónes del ligando PDOA conducen a la formacción de 7 compuestos, con el ligando orotato han sido preparado 6 compuestos a las reaccíones del sistema con ligando bapen han salido dos compuestos. Se han determinado por difracción de rayos X las estructuras de todos los complejos preparados y estosse han caracterizado mediante espectroscopia infraroja, análisis elementar, si fue possible. En algunos casos la análisis térmica y análisis de polvo con difracción de rayos X han sido aplicadas. A partir del estudio de sus estructuras cristalinas se puede decir que ocho compuestos tiene la estructura polimérica, tres son iónicos y cuatro tienen la estrucutura molecular. En el empaquetamiento final se han estudiados los enlaceds de hidrogeno y las interacciones tipo pi-pi. Las medidas magnéticas se han realizado en cinco muestras. Los compuestos 1 y 2 tienen unas interacciones atiferomagnéticas débiles entre los pares de ionos de lantánidos. El compuesto 3 está bajo de los estúdios; presenta un tipo de SMM. En el caso de compuesto 5 se han observado las interacciones débiles entre los centros de Ce(III) y resultados parecidos fueron obtenidos por las medidas del magnetismo del 14.

Following a previous report of proton transport in a channel-free molecular solid possessing a complex set of water wires, the mechanisms implied by the available neutron diffraction measurements are further developed. Three specific proton transfer pathways along an experimentally observed water wire are proposed. The first is proton transfer involving two aqua ligands coordinated to the same Mn(II) unit and one free water acting as a shuttle. The second mechanism consists of proton transfer between coordinated aqua ligands of distinct molecules, with no shuttle. The third mechanism involves a component of vehicle transport, involving a water molecule that changes position during the process. Geometric parameters of the proposed mechanisms are given.

The citratobis(aqua)gadolinium compound with empírical formula [Gd(Hcitr)(H20)2] [Hcitr = citrate (3-, C6H5O7(3-)] has been reportad previously as a 1D polymer which in the solid is a stoichiometric monohydrate, [Gd(Hcitr)(H20)2]n·nH20, prepared hydrothermally at a temperatura of 100 ºC (10 days). (For present naming purposes the aqua ligand is treated as distinct from the unligated water, which we call water of hydration.) We describe here the preparation, by wet chemistry means, of the stoichiometric dihydrate, [Gd(Hcitr)(H20)2]n·2nH20, whose basic building block in the crystal is a two-dimensional polymer of the complex. The anhydrous form, also a two-dimensional polymer, is preparad from the dihydrate at 77 'C (several hours) in a single-crystal to single-crystal transformation. This transformation, in the course of which no evidence of a monohydrate is observad, is fully reversible, with the same single-crystal sample having been used for the characterization of the initial dihydrate, the form with no free water, and the restored dihydrate. The evolution of the SCSC transformation can be followed neatly by means of axial photographs. The initial citratobis(aqua)complex dihydrate and the dehydrated citratobis(aqua) complex possess the same two-dimensional layer structure, but with significant layer slippage occurring between the two forms.

Complex impedance measurements on single crystals and pellets of a CuCo-orotate coordination polymer, as a function of relative humidity and temperature, reveal proton conduction with a relatively high thermal activation energy, a negligible isotope effect, a large pre-exponential factor in the conductivity model, and a strong dependence on humidity, all of which are consistent with a vehicle mechanism. The proton conductivity found for this polymer compares favorably with that of MOFs and related porous materials even though it has no framework with pores and channels to provide proton-conduction pathways.

La tesis, titulada "Cubanos Metálicos con el Ligando Citrato: Obtención, Caracterización y Propiedades," se basa en el estudio de compuestos conocidos comúnmente como cubanos, formados por el ligando citrato (tetra anión del ácido cítrico) y cobalto o manganeso. El trabajo se ha dividido en tres partes para una exposición más clara de los resultados obtenidos. En la primera parte se ha llevado a cabo un completo estudio de la unidad cubano. En él, aspectos importantes de dicha unidad tales como su estructura, quiralidad y topología de su periferia han sido descritos y comparados. Así mismo, se ha propuesto un sistema de nomenclatura para el sistema cubano con el objetivo de simplificar futuras descripciones de su estructura y coordinación y de unificar los resultados. Finalmente, se ha revisado y clasificado los modos de coordinación de las diferentes unidades cubano obtenidas así como los de los ejemplos previamente publicados. La segunda parte de la tesis se centra en el estudio de los cubanos de citrato y cobalto. Se ha comprobado que estos compuestos son capaces de comportarse como ¿Single Molecule Magnets¿ (SMMs), exhibiendo interesantes propiedades magnéticas. Se ha logrado la síntesis de una familia de compuestos relacionados entre sí que presentan diferentes dimensionalidades. El primer capítulo de esta parte es una introducción al magnetismo y a los SMMs desde una aproximación química. El capítulo 3 está dedicado al estudio de una pareja de compuestos relacionados a través de una trasformación reversible de monocristal a monocristal (SC-SC, por sus siglas en inglés). Ambas especies son moléculas discretas. Una de ellas presenta una estructura cristalina modulada. Los capítulos 4 y 5 constan de un conjunto de citrato-cubanos de cobalto con estructuras 2-D y 3-D respectivamente. Finalmente, la tercera y última parte de la tesis se centra en los compuestos de citrato y manganeso cuya unidad básica es el cubano. Estos compuestos, a pesar del evidente parecido e

El movimiento de protones en el interior de espacios reducidos es un tema de gran interés en numerosas áreas de investigación. A pesar de que la mayoría de materiales empleados para el transporte y almacenaje de moléculas e iones suelen ser materiales porosos, se ha logrado obtener sustancias sintéticas no porosas capaces de ceder y capturar pequeñas moléculas, entre las cuales se encuentra el agua. Por otro lado, el transporte de protones implica la ruptura y formación de enlaces dentro del sólido, convirtiéndolo en algo más que un simple espectador. Este proceso, conocido como alambre de protones, se explica en base al mecanismo de Grotthuss. A pasar de su simplicidad conceptual, la mayoria de resultados se basan o necesitan el apoyo de cálculos teóricos. En este trabajo se presenta un polímero 1-D basado en manganeso y citrato. El ploímero esta formado por unidades [Mn4(citrato)4] propagadas a traves de unidades [Mn4(H2O)6]2+. La carga negativa de la cadena polimérica está compensada con unidades [Mn(H2O)5]2+ que cuelgan de ella y [Mn4(H2oO)6]2+ que se localizan entre las cadenas poliméricas. Asi pues el complejo consta, por monómero, de 21 moléculas de agua coordinadas y 9 libres alojadas entre las cadenas poliméricas. Este compuesto experimenta una pérdida de 3 moleculas de agua cuando se deja al aire a pesar de no presentar canales o poros en su estnructura. Cuando el cristal se expone a una atmósfera húmeda, estas tres moléculas de agua son reabsorbidas regenerando completamente la estructura inicial. Sin embargo, al llevar a cabo la rehidratación bajo atmósfera de D2O se ha observado un intercambio total de todos los H de las moléculas de agua (coordinadas y libres) por deuterio. Las estructuras antes y después del intercambio fueron caracterizadas por difracción de neutrones. Esto se explica gracias a la observación de cadenas de moléculas de agua unidas por puentes de hidrógeno que atraviesan la estructura completa. El desorden observado en los átomos de h

The transition-metal citrate cubane is a symmetrical, anionic molecular fragment that possesses twelve partially negatively charged oxygen atoms around its periphery. The cobalt variants have proved to be single molecule magnets (SMM), as demonstrated in studies by Murrie and by others. All of the negatively charged points on the surface of the fragment are potential linkage positions for metal atoms, and extended products of from zero- to three dimensions have been synthesized and characterized. In this presentation we describe products with five different combinations of linkage points for cobalt or manganese. A one-dimensional Co-containing cubane polymer has been found to undergo reversible cross-linking in the crystal to produce a two-dimensional polymer. A second Co-containg product, a discrete molecular solid with SMM behavior, undergoes reversible reaction in the crystal to produce an unsymmetrical product, also with SMM behavior -- a switchable SMM pair. A third product, a symmetrical two-dimensional Co-containing polymer, is an SMM with two blocking processes. A one-dimensional polymer of manganese citrate cubanes has been demonstrated to conduct protons via the Grotthuss mechanism. All of these products have different patterns of peripheral metal-atom linkage to the twelve surface-resident oxygen atoms of the cubane fragment. A systematic naming scheme for the citrate cubane topology is used to provide simple descriptions of the diverse linkage geometries found to date.

The discovery of Single Molecule Magnets (SMMs) has represented a revolution in the field of molecular magnetism. Many research groups have focused their efforts on the development of new SMMs. For applications, including putative technological applications, however, the further step of arranging those compounds into well-ordered structures still is a pending issue. Coordination chemistry is proving to be a powerful tool for the preparation of polymeric nets of SMMs. As described in a recent review by Clerac, there are very few examples of SMMs arranged in networks. As we propose in this presentation, the number and functional possibilities of SMM networks can readily be increased in the case of citrate cubanes. The transition-metal citrate cubane [M4citrate4]8- is a symmetrical, anionic molecular fragment that possesses twelve partially negatively charged oxygen atoms (and twelve coordinated but reactive oxygen centers) around its periphery. The cobalt variants have proved to be SMMs, as demonstrated by Murrie et al. and by others. Interestingly, all of the negatively charged points on the fragment surface are potential linkage positions for metal atoms whose adhesion can give extended networks with dimensionalities ranging from zero- to three. In this presentation we apply this viewpoint to the previously reported [M4citrate4]8- cubanes with transition metal centres and to new ones, giving compounds with more than 10 different combinations of linkage points. Some of these products present an unexpected variety of magnetic and dynamic phase behaviour, including chemical reactions, phase transitions and proton transport. All of these products have different patterns of peripheral metal-atom linkage to the 12 surface-resident and 12 encrusted oxygen atoms of the cubane fragment. These results show that transition metal citrate cubanes are excellent synthons for the preparation of a potentially boundless family of networks of ordered SMMs with a high probability of fi

The neutral cluster [MnII 8(citrate) 4(H2O)18] is formed by the [M 4(citrate)4]8- fragment, with an Mn 4O4 cubane core, which bonds four peripheral aquomanganese units-two [Mn(H2O)4]2+ and two [Mn(H 2O)5]2+-through a total of six metal-ligand bonds, giving a discrete neutral compound. The compound presents a unique coordination mode in which the citrate cubane acts as a chelate to each of the two peripheral [Mn(H2O)4]2+ (tetra-aquo) units. A detailed analysis of the central and peripheral geometries is given in terms of the tetrahedral distortions of key structural features. A reversible dehydration-rehydration process has been observed in a polycrystalline sample of the complex, whose structure lacks pores or channels. © 2014 the Partner Organisations.

{[Ln2(PDOA)3(H2O)6]2H 2O}n (Ln = Gd, 1; Ln = Ce, 2; H2PDOA = o-phenylenedioxydiacetic acid) has been synthesized and characterized by chemical analyses, IR spectroscopy, and thermal analyses. Single-crystal X-ray structure analyses revealed that both 1 and 2 are polymeric and built up of a ladder-like arrangement of Ln(III) ions linked by short syn-anti carboxylate bridges and long bridges (legs of the ladder) formed by a second crystallographically independent PDOA. Ln(III) in both 1 and 2 is nine-coordinate with an O9 donor set formed by one chelating/bridging and one bridging PDOA, and an additional three waters. In the asymmetric unit, there is one crystallographically independent water of crystallization, which is involved in a rich system of hydrogen bonds of the O-H···O type. The identities of the bulk and single crystal phases were corroborated by powder X-ray diffraction. Variable temperature (2-300 K) magnetic studies indicate the presence of only weak antiferromagnetic interactions between pairs of paramagnetic Ln(III) ions with J/hc = -0.004 and -0.13 cm-1, for 1 and 2. © 2014 © 2014 Taylor & Francis.

Working without pores: In non-porous, channel-free crystals of a manganese citrate coordination polymer, neutron diffraction reveals that the water molecules, both metal-bound and co-crystallized, undergo full hydrogen/deuterium exchange. Neutron diffraction analyses show a pattern of hydrogen disorder that can be interpreted in terms of the Grotthuss proton-cascade mechanism (see scheme). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The reaction of N1,N1′-(ethane-1,2-diyl) bis(propane-1,3-diamine) (bapen), K2[Ni(CN)4] ·H2O and dimethylformamide in the presence of Gd(NO 3)3·6H2O under solvothermal conditions yielded yellow crystals of dicyanido(2,3,4,6,7,9,-10,11-octahydropyrimido[2′, 1′:3,4]pyrazino[1,2-a]pyrimidine)-rimidine)nickel(II) hemihydrate, [Ni(CN)2(C10H16N4)]·-0. 5H2O, (I), the crystal structure of which is composed of [Ni(CN) 2(pdpm)] molecules (pdpm is 2,3,4,6,7,9,10,11- octahydropyrimido[2′,1′:3,4]pyrazino[1,2-a]pyrimidine) on general positions linked by O-H⋯N hydrogen bonds to water molecules located on twofold axes. This structural unit is further linked by nonclassical C-H⋯N interactions to form a warped two-dimensional net perpendicular to the unit-cell b axis. The nets are stacked, with C-H⋯O contacts joining successive units. The NiII cation is coordinated with squareplanar geometry by a chelating pdpm ligand and two cyanide ligands in mutually cis positions. Complex (I) is stable up to 360 K, at which point dehydration takes place; the ligands start to decompose at 558 K. © 2013 International Union of Crystallography.

Transition metal complexes of polyfunctional ligands -- ligands with multiple functional groups -- form molecular solids which change in unpredictable ways when their environments are modified. A cobalt orotate complex has been found to undergo an arrested phase transition that produces a crystalline sample with both triclinic and monoclinic phases present at the same time. The >single-crystal> characterization of this double phase is described, with special attention to the separation of the diffraction patterns of the two phases. Citrate complexes present a rich variety of behaviors in their molecular solids, from chemical reaction to modulation to solvent transport, all non-destructive, which have been studied by single-crystal diffraction. These transformations can be provoked by temperature and dehydration, or other modifications of ambiant conditions. The factors that give rise to this behavior are related to the nature of the structural building blocks of the crystals formed by these complexes.

The modulation of the magnetic properties of SMMs and their organization in extended magnetic arrays are, at the present, some of the top areas in the field of molecular magnetism for the implication in the improvement of the physical properties of the SMM and the potential use in devices such as for data storage. Few polymers of SMM have been structurally characterized in spite of the number of known SMM. [Co4citrate4]8- cubanes can behave as SMM. We have reported recently the union of these cubanes through “Co(H2O)2ETG” (ETG=ethylene glycol) bridges and the formation of anionic 2D layers. These layers crystallize in the tetragonal system, P-421c space group, with counterions (Cs+ or Rb+), water and ETG molecules connecting the layers though electrostatic interactions and hydrogen bridges. The magnetic studies show the co-existence of two magnetic nets: the SMM net and the one formed by the bridged cobalt atoms and also shows the influence of the counterions in the layer magnetic properties. Two intriguing relaxation processes with different characteristics timescales are observed. Moreover, [Co4citrate4]8- cubanes can also organize in 3D, diamond-like structural arrays showing SMM magnetic behaviour below 6K with an enegry barrier of 54K and magnetic ordering below 2.7K.

Transition metals (M) and quadruply deprotonated citrate (citr4-) form complexes with [M4(citr)4](8-) structural building blocks that have at their cores an M4O4 unit with cubane topology. At the periphery of the [M4(citr)4](8-) unit is an icosahedron formed by twelve oxygen atoms with partial negative charges, to which metal atoms can bind in a number of ways to give products with discrete molecular structures or with 1-, 2-, and 3-D polymers in the crystalline state. In addition to geometrically regular and irregular shapes, some of these products also display reactivity in the solid state, with reversible chemical processes having been observed to change the dimension of the polymer or to produce ion transfer with structual modulation. The geometries of the products reported to date are analyzed systematically in this presentation, and the geometrical relationships between reactants and products in a topotactic solid-state reaction are explored in detail. Unusual solvent uptake and loss in some of these solids is described, with reference to the structural features which enable this behavior.

Star gazing: The six-coordinate organoniobium(V) compound [NBu 4] 2[NbO(C 6F 5) 5] has been found to exhibit a pentagonal-pyramidal (PPY-6) structure, which is unprecedented in organotransition-metal chemistry (see picture: complex as viewed down the O-Nb axis; C in gray, O in red, F in yellow, and Nb in blue). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Un grupo de investigadores del Instituto de Ciencia de Materiales de Aragón (ICMA) ha conseguido ordenar moléculas con cobalto formando una red, de tal forma que cada unidad se comporta como un imán molecular. El estudio, que es portada de la revista Chemistry: A European Journal, puede tener un uso potencial en la fabricación de memorias masivas de información.

The counterion makes a difference: A square 2D array of cobalt citrate cubanes linked by bridging six-coordinate cobalt atoms (see graphic) displays collective magnetic behavior, which changes with subtle differences in the crystalline surroundings. The magnetic properties of two solid modifications, both synthesized by using wet chemistry techniques, reveal two different relaxation processes in each system at low temperatures, each with its own timescale.

The structure of the title complex, poly[dicaesium(I) hexaaquacobalt(II) [octaaquatetra--citrato-hexacobalt(II)] dodecahydrate], {Cs2[Co(H2O)6][Co6(C6H4O7)4(H2O)8]·12H2O}n, at 100 (1) K is formed by layers of a square two-dimensional polymer composed of CoII citrate cubanes bridged by magnetically active six-coordinate CoII cations. The polymer has plane symmetry p4mm in the c-axis projection. The cubanes reside on sites of crystallographic symmetry , while the bridging CoII centres lie on twofold axes. The basic polymeric unit has a charge of 4-, balanced by two Cs+ and a [Co(H2O)6]2+ (symmetry ) cation, which lie in channels between the polymeric layers. Unligated water molecules, of which there are 12 per cubane, enter into an extended intralayer and layer-bridging hydrogen-bond pattern, which can be described in detail even though not all of the H atoms of the water molecules were located.

The understanding of the hydrogen bond, an interaction that appears in diverse environments and exercises widely varying functions, continues to expand with the report of a neutron diffraction analysis of a complex displaying an OH⋅⋅⋅Pt hydrogen bond with unligated water as the donor. What is known about hydrogen bonding so far provides a broad context for this new result.