1,721,002 research outputs found
Cocrystallization as a tool to stabilize liquid active ingredients
No full textCocrystallization is an extensively used method in Crystal Engineering for tuning the properties of target compounds by pairing them with ad-hoc selected molecular partners (i.e. coformers) in a stoichiometric ratio within the same crystal structure. The formation of a new intermolecular network significantly alters the physical–chemical properties of the final material, becoming crucial for target applications such as pharmaceutical, agrochemical and nuctraceutical where cocrystals are largely investigated. Although, the majority of the cocrystals reported in the literature so far are generally made of coformers which are solid at room temperature, there is no restriction in using liquid or low melting compounds as a coformer. This contribution aims at reviewing some significant cases and applications where cocrystallization is used to stabilize liquid ingredients, that are generally poorly stable and their manufacturing, transportation, and storage conditions present considerable environmental, logistical, and cost-related challenges
Polymorph and isomer conversion of complexes based on CuI and PPh 3 easily observed via luminescence
No full textReactions between copper(i) iodide and triphenylphosphine have been explored in solution and in the solid state and six luminescent coordination complexes have been obtained and characterized by X-ray diffraction and UV-vis spectroscopy and photophysics. Solid-state reactions of CuI with PPh 3 in different conditions (kneading, vapour digestion) and stoichiometries resulted in the formation of high ratio ligand:metal compounds while tetrameric structures could be obtained only by solution reactions. Crystal structures were determined by single crystal X-ray diffraction while purity of the bulk product was checked by powder diffraction (XRPD). Three different tetrameric structures with 1:1 stoichiometry have been synthesized: two closed cubane-type polymorphs [CuI(PPh 3)] 4 (form 1a) and [CuI(PPh 3)] 4 (form 1b) and an open step-like isomer [CuI(PPh 3)] 4 (form 2). The conversions between the polymorphs and isomers have been studied and characterized by XRPD. The most stable form [CuI(PPh 3)] 4 (form 1b) can convert into the open step-like isomer [CuI(PPh 3)] 4 (form 2) in a slurry experiment with EtOH or CH 2Cl 2 or AcCN and converts back into [CuI(PPh 3)] 41b when exposed to vapors of toluene. At room temperature all the tetrameric compounds exhibit luminescence in the solid state and, notably, the two polymorphs show a dissimilar dual emission at low temperature. The luminescence features in the solid state seem to be peculiarly related to the presence of the aromatic phosphine ligand and depend on the Cu-Cu distance in the cluster. © 2012 The Royal Society of Chemistry
Synthesis, crystal structure, structural phase transition and dielectric properties of new organic-inorganic hybrid compound: (C6H5CH2N(C2H5)3)CdCl3
Full text linkSingle crystal of new organic-inorganic hybrid compound, (C6H5CH2N(C2H5)3)CdCl3, was successfully synthesis by slow evaporation method at room temperature and characterized by divers techniques such as single X-ray diffraction, Infrared and Raman spectroscopy, Thermal analysis (TGA and DSC), Variable temperature X-ray powder diffraction (VT‒XRPD) and dielectric properties. The results of single X-ray studies demonstrated that the title compound crystallizes in the monoclinic system with the space group P21/n. The atomic arrangement of the crystal structure can be described as 1D polymeric inorganic chain CdCl5 along the a-axis between which the organic groups are located. It consists on isolated square-pyramidal [CdCl5]3− anions and triethylbenzylammonuim (C6H5CH2N(C2H5)3)+ cations, which are interconnected via C−H...Cl weak hydrogen bonds forming 3D network. Investigation of RT‒XRPD was carried out to identify the purity of the bulk material. Hirshfeld surface and fingerprint plots reveal that the structure is dominated by H...H and H...Cl/Cl...H contacts. It is found that the (C6H5CH2N(C2H5)3)CdCl3 material displays a irreversible structural phase transition at T = 413 K. This latter was confirmed by means of variable temperature X- ray powder diffraction and dielectric permittivity (ε′andε′)
Dynamic microporous mixed-ligand MOFs as adaptive crystalline containers for guest encapsulation and release*
No full textA series of Zn-based Mixed-Ligand Metal-Organic-Frameworks (ML-MOFs) containing a bis-isonicotinoyl and a dicarboxylate linker have been solvothermally synthesized. The structural analyses evidence two types of framework entanglements, interpenetrated and polycatenated, that lead to materials featured by different porosity. The host-guest propensity of the materials toward different organic molecules is highlighted, with particular emphasis to the supramolecular organization adopted by the included guest molecules, as inferred by single-crystal X-ray diffraction analysi
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Synthesis, spectroscopic and structural characterization and solution stability of ruthenium sandwich complexes containing 1,8-naphthalimide ligands
No full textTwo different N-substituted naphthalimide ligands 1 (bearing a phenyl on the imide nitrogen) and 2 (bearing a benzyl on the imide nitrogen) have been synthesized and reacted with the cationic organometallic fragment [Cp*Ru(ACN)3]PF6. Ligand 1 brings to the formation of a sandwich complex (3Naph) where Ru is positioned on the naphthalene platform, while the N-imide phenyl substituent is not involved in coordination. This has been proven by single-crystal X-ray diffraction analysis conducted on crystals of 3Naph, revealing the first sandwich complex structurally characterized containing a naphthaleneimide ligand η6-coordinated to a metal. Ligand 2 shows instead a different behavior, leading to the formation of two isomeric complexes (4Naph and 4Bz), where Ru is placed on the naphthalene platform and on the N-imide benzyl substituent, in a rough 1:1 ratio. Complex 3Naph results very labile in coordinating solvents, such as acetonitrile, where it undergoes a fast and quantitative ligand solvolysis, with formation of free 1 and [Cp*Ru(ACN)3]PF6. In the cases of complexes 4, only complex 4Naph undergoes a fast and quantitative ligand solvolysis once dissolved in acetonitrile, whereas complex 4Bz results more stable
Mechanochemical Preparation of Dipyridyl-Naphthalenediimide Cocrystals: Relative Role of Halogen-Bond and π-πInteractions
Full text linkNaphthalenediimide derivates are a class of π-conjugated molecules largely investigated in the literature and used as building blocks for metal-organic frameworks or coformers for hydrogen-bond-based cocrystals. However, their tendency to establish halogen-bond interactions remains unexplored. By using a crystalline engineering approach, we report here four new cocrystals with N,N′-di(4-pyrydyl)-naphthalene-1,4,5,8-tetracarboxidiimide and diiodo-substituted coformers, easily obtained via a mechanochemical protocol. Cocrystals were characterized via NMR, electron ionization mass spectrometry, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Crystallographic structures were then finely examined and correlated with energy framework calculations to understand the relative contribution of halogen-bond and π-πinteractions toward framework stabilization
Solvent-free preparation of co-crystals of phenazine and acridine with vanillin
No full textCo-crystals of phenazine and acridine with vanillin have been obtained by solvent-free reaction or thermal treatment of the solid reactants: their structures, thermal behaviour and eutectic formation have been investigated via single crystal X-ray diffraction, differential scanning calorimetry (DSC), variable temperature X-ray powder diffraction and hot-stage microscopy (HSM). Polymorph screening of the reagents has also been carried out. © 2010 Elsevier B.V
Dual luminescence in solid Cui(piperazine): Hypothesis of an emissive 1-D delocalized excited state
No full textSolid [CuI(piperazine)0.5]∞, characterized by a structure with an infinite double chain of CuI, presents an unexpected dual luminescence. The short copper-copper distances allow the existence of both cluster-centered and 1-D delocalized electronic transitions, as emerged from theoretical calculations. Beyond the more common cluster-centered emission a higher energy band, which differs in lifetime and in temperature dependence, is observed
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