journal menu
abstracts
The interactions experimented by multiple phenyl or other aromatic groups in crystals have been described as ``embraces'' since 1995, when Dance and co-workers developed the embrace paradigm as an important and widespread tool of supramolecular chemistry. There are three main classes of Multiple Phenyl Embraces (MPE) depending on the total number of phenyl rings (Ph) located in the interaction domain: sextuple (6PE), quadruple (4PE), and double phenyl embrace (2PE) [1]. Recently, an accurate theoretical evaluation of the MPE motifs between PPh4+ was presented by Novoa et al [2]. In our laboratory we demonstrated that by changing the counterion of the [IrCl5(NO)]- salts from K+ to PPh4+, it was possible to stabilize an excited state of the metal complex anion. The electronic distribution of the IrNO moiety in K[IrCl5(NO)] can be depicted as the closed-shell electronic structure IrIII-NO+. However, in PPh4[IrCl5(NO)] an unprecedented electronic perturbation takes place favouring the open-shell electronic structure IrIv-NO* [3]. These results together with the interesting systematic studies on MPE, encouraged us to explore the synthesis of new phosphonium salts. In this work we report new phosphonium ions of the type Ph3PR+ and five new Ph3PR[IrCl5(NO)] salts (R = aryl, methylaryl). Structural analyses of these compounds were done in the context of the multiple embraces motifs. For the new unsymmetrical [IrCl5(NO)]- salts, the supramolecular arrangements are different from the one observed for the PPh4+ one. In the last one, the 4PE infinite chains run parallel to the columns described by the anions [3] and for the others, the presence of bulkier substituents give place to symmetries that favours other kinds of aryl embraces resulting in a side by side location of the anions. Finally, DFT calculations were performed to evaluate the theoretical concerns regarding the structural behaviour, as well as the electronic distribution along the family of compounds.
abstracts
Over the last decade the design and synthesis of metal-organic compounds with fascinating structural properties and potential applications as functional materials has been a major challenge in various fields of research.1 Strategies for preparing these compounds are based on the careful selection of the constituent building blocks. 4'-(substituted)-4,2':6',4''-terpyridine ligands are considered versatile building blocks for the assembly of coordination polymers and networks with useful solid-state properties, such as magnetism, luminescence, redox activity, etc.2 The divergent arrangements of N-donor atoms and the attachment of aryl substituents into the 4'-position of 4,2':6',4''-terpyridine allow to bridge two or more metal centers, giving rise to molecular assemblies of 1, 2 or 3 dimensions.3 Our line of interest is the obtainment of compounds with emergent magnetic properties. Herein we present a copper complex surveying the new 4'-(quinolin-4-yl)-4,2':6',4''-terpyridine ligand (L), and formulated as [Cu(C5H1F6O2)2(C25H16N4·CHCl3)]n which was produced from the reaction of two equivalents of L with Cu(hfac)2, (hfac=hexafluoroacetylacetonate). The copper ion in trans-{CuN2(hfac)2} has an octahedral environment. The nitrogen atoms of the terminal pyridine rings coordinate to the paramagnetic centres, while the central ring remains uncoordinated. The linkage of the resulting polyhedra gives raise to an undulating 1D polymeric structure. Within these chains there are two main non-covalent interactions: π-stacking between the quinoline substituents and the pyridine rings and CH···F interactions due to CF3 group of the hfac ligand. There are also weak CH···N, CH···π and π-π intermolecular interactions linking the L and CHCl3 groups, which give stability to the crystal structure. Finally, we performed magnetic measurements, in order to determine the magnetic behaviour of our system. Acknowledgments: FONDECYT 1130433 project, CIPA of University of Concepción, LIA-MIF 836
abstracts
To celebrate the International Year of Crystallography 2014, the Argentinian Crystallography Association ("Asociación Argentina de Cristalografía", AACr) [1] has launched the Crystal Growing Competition to be held June-October 2014 among Argentinean high school students. This activity is sponsored by the IUCr, CONICET (Argentinean Science Council) and MinCyT (Argentinean Ministry of Science, Innovation and Technology). Based on IUCr suggestion [2] and successful previous experiences in other countries [3], we planned the program of the activity. Before the contest, a five hours course including the basic concepts of crystal growing and crystallization experiences demonstrations will be offer for the teachers of the interested schools. They will take place at different regions of the country during April. The information of the contest together with the instructions on how to grow crystals and guidelines for the teachers will be provided on the web. After the students sign up, they will growth their crystals and create a slideshow presentation or a video to show their work to the evaluation committee before the end of August 2014. Winners will be announced on September 15th, they will be invited to show their work at the X Annual Meeting of the Argentinean Crystallographic Association, Mar del Plata, Argentine, 28-31 October 2014. A special session will be held as a satellite activity of the meeting on October 27th and the awards ceremony of the Crystal Growing Competition will be during the opening ceremony. Besides this, everyone participating of the Argentinean contest has a chance to compete in the International Crystal Growing Competition. Trough this exciting, funny and hands-on scientific experience, crystallography and other related scientific fields will be promoted along the high school community across the country being also, a way to encourage youth to continue exploring science and developing their scientific skills.
abstracts
"The history of Crystallography in Argentina is very rich, probably starting with the pioneer work of Prof. Ernesto Galloni in the decade of the `40s. Thanks to Prof. Galloni, the National Committee of Crystallography was founded in 1958 and recognized by the IUCr in 1960. This committee organized several scientific meetings and was in good contact with the Ibero American Crystallography Group during about 35 years. After some crisis in the late `90s, some young crystallographers decided to reorganize the activities and form the Argentinian Association of Crystallography (AACr), which was finally founded on October 30th, 2004, on the occasion of the ""National Workshop on Crystallography"" held in Villa Giardino, Province of Córdoba. Therefore, in the International Year of Crystallography, the AACr is also celebrating its tenth anniversary. The regular annual events of the AACr are a scientific meeting, a school on Crystallography and a workshop. This year, they will be held in Mar del Plata (Province of Buenos Aires) in the period of October 27th-Novembre 7th. In addition, many other academic activities such workshops or postgraduate courses are being organized in the whole country. It is worth to remark the School on Fundamental Crystallography to be held in La Plata, followed by an Agilent-UNESCO-IUCr OpenLab in La Plata and Buenos Aires, in April-May. Moreover, taking into account that Crystallography is a field that needs more promotion in our country, the AACr decided to propitiate several educational and dissemination activities. They include a national crystal growing contest, promotion of Crystallography in high and primary schools through the National Fairs of Science of the Ministry of Education, dissemination talks for different audiences, exhibitions, etc. Acknowledgements: The AACr thanks all the crystallographers that are working hard in these activities: G. Echeverría, O. Piro, S. Suárez, M. Saleta, D. Tobía, R. Carbonio, G. Aurelio, J. Pedregosa, F. Doctorovich, S. Conconi, L. Baqué, F. Napolitano, S. Alconchel, C. Alvarez, A. Ares, C. Bernini, S. Brühl, M. Dailoff, M.A. Foi, M. Harvey, M.S. Lassa, S. Montoro, E. Pannunzio Miner, etc."
abstracts
"Otilonium bromide (C29H43 N2 O4+.Br-) is a quaternary ammonium derivative which has been proven a potent spasmolytic drug with a good tolerability profile, used in the treatment of irritable bowel syndrome. We present herein the structural analysis of an unreported polymorphic form (I), comparing with the only one known so far and already reported [1] polymorphic form of the compound (II). The data set for I was obtained from a twinned specimen. The poor quality of the data thus available did not pose any problem in the structure resolution, but it did instead in refinement: the alkyloxy chains and ethyl branches in the quaternary ammonium groups needed some continuity restraints in their anisotropic displacement factors. In form II this effect appeared enhanced, ending up in unusually large anisotropic displacement parameters for most atoms in the chain. The main points of molecular disagreement reside in the torsion angles where the alkyloxy chains and quaternary ammonium groups leave the planar mainframe. The only notorious intermolecular contacts in both structures appear to be a number of rather weak C-H···Br ones involving the quaternary ammonium groups somehow ""wrapping"" the bromide counterion. There are a few C-H···O contacts interlinking molecules to each other. The phase transformation occurs at 124(2)°C and can be followed by DSC and XRPD. A detailed analysis shows some features in common, viz., in both structures packing stability is mainly due to the ionic interaction between the N+ and the Br-, with the latter ion being evenly surrounded by a number of ammonium groups in a way that they define regular 2D arrays "sandwiching" the neutral part of the molecules, which thus act as spacers. These similarities allow giving a plausibility argument about the way in which the transition may take place."
