1,721,246 research outputs found
Crystal structures of salts of transition-metal halide clusters
No full textThe ion organization in crystalline salts formed by transition-metal carbonyl cluster anions containing
halide ligands has been investigated. It has been shown that the presence of the heteroligand(s) drives
either towards the 'trapping' of two halogen atoms within a cage of counter ions or towards the formation
of anion rows insulated by cation rows. The formation of either type of pattern appears to be due to the size
and mode of bonding of the halogen atoms, the first type being preferred with small terminal halogens or
with large halogens in bridging bonding mode, while the second is observed with large halogens in
terminal bonding mode
Carvedilol, a β adrenoceptor blocker with chelating properties: a copper ‘superdimer’ based on dimetal units
No full textCopper(II) complexes of carvedilol molecule, (carvH): 1-[carbazolyl-(4)-oxyl]-3-[(2-methoxyphenoxyethyl)-amino]-2-propanol, were synthesized and characterized with respect to their structural and spectroscopic properties. The crystal structure of [Cu(Carv)Cl(MeOH)]2•4MeOH complex revealed that the molecule chelates two Cu(II) ions via the N and O atoms belonging to the amino and propanol moiety, respectively. The coordination behaviour of carvedilol studied by 1H nuclear magnetic resonance (NMR, 1-D and 2-D-COSY) spectroscopy in dimethyl sulfoxide solution at room temperature, allowed us to obtain structural information and to identify the donor atoms involved in the coordination process in solution
From 0D-complex to 3D-MOF: changing the antimicrobial activity of zinc(II) via reaction with aminocinnamic acids
Full text linkCombining zinc nitrate with 3- and/or 4- aminocinnamic acid (3-ACA and 4-ACA, respectively) leads to the formation of the 0D complex [Zn(4-AC)2(H2O)2], the 1D coordination polymer [Zn(3-AC)(4-AC)], and the 2D and 3D MOFs [Zn(3-AC)2]∙2H2O and [Zn(4-AC)2]∙H2O, respectively. These compounds result from the deprotonation of the acid molecules, with the resulting 3- and 4-aminocinnamate anions serving as bidentate terminal or bridging ligands. All solids were fully characterized via single crystal and powder X-ray diffraction and thermal techniques. Given the mild antimicrobial properties of cinnamic acid derivatives and the antibacterial nature of the metal cation, these compounds were assessed and demonstrated very good planktonic cell killing as well as inhibition of biofilm growth against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus
Deriving kinetic insights from mechanochemically synthesized compounds using multivariate analysis (MCR-ALS) of powder X-ray diffraction data
Full text linkKinetics information on the progress of the mechanochemical reactions is key to their understanding and
subsequent scale-up. For crystalline materials, the most robust and tested method for obtaining kinetic data
is the Quantitative Phase Analysis (QPA) via Rietveld refinement. In this work, we tested the feasibility of the
Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) method on powder X-ray diffraction
(PXRD) data of mechanochemical processes by studying the system theophylline (TP) and malonic acid
(MA) in a 1 : 1 stoichiometric ratio at different milling conditions. We have highlighted the strengths and
weaknesses of the MCR-ALS method, and we demonstrated why it may be an alternative route to obtain
quantitative information on mechanochemical kinetics
Single crystal to single crystal [2+2] photoreactions in chloride and sulphate salts of 4-amino-cinnamic acid via solid-solution formation: A structural and kinetic study
Full text linkA set of molecular salts with general formula [1H]nA·xH2O (1 = 4-amino-cinnamic acid, An- = NO3-, BF4-, PF6-, SO42-, x = 0, 1) was prepared and structurally characterized. [1H]Cl and [1H]2SO4·H2O(ii) were found to undergo an SCSC stepwise [2+2] photodimerization, which was followed by X-ray diffraction; a kinetic analysis was performed on single crystals of both salts. In the case of [1H]Cl the photoreaction was also studied on polycrystalline materials
Organic-inorganic ionic co-crystals: A new class of multipurpose compounds
Full text linkIn this highlight, the reasons for the widespread interest generated by ionic co-crystals, namely those formed by a neutral molecule and a salt, are addressed. In particular, the class of compounds obtained by co-crystallization of neutral organic molecules and inorganic salts (e.g. alkali and alkaline earth halides, sulfates, phosphates etc.) is discussed with the focus on their applications in diverse areas, such as pharmaceuticals, food and fertilizers, and also in chiral resolution. It is argued that, in terms of structure and intermolecular bonding features, these compounds do not differ from classical coordination compounds (complexes) and that their popularity arises from the effectiveness of the organic-inorganic assembly to enhance thermal stability, improve particle size and morphology and change significantly the solubility and dissolution rate with respect to those of the pure active ingredients
The Relevance of Crystal Forms in the Pharmaceutical Field: Sword of Damocles or Innovation Tools?
Full text linkThis review is aimed to provide to an “educated but non-expert” readership and an overview of the scientific, commercial, and ethical importance of investigating the crystalline forms (polymorphs, hydrates, and co-crystals) of active pharmaceutical ingredients (API). The existence of multiple crystal forms of an API is relevant not only for the selection of the best solid material to carry through the various stages of drug development, including the choice of dosage and of excipients suitable for drug development and marketing, but also in terms of intellectual property protection and/or extension. This is because the physico-chemical properties, such as solubility, dissolution rate, thermal stability, processability, etc., of the solid API may depend, sometimes dramatically, on the crystal form, with important implications on the drug’s ultimate efficacy. This review will recount how the scientific community and the pharmaceutical industry learned from the catastrophic consequences of the appearance of new, more stable, and unsuspected crystal forms. The relevant aspects of hydrates, the most common pharmaceutical solid solvates, and of co-crystals, the association of two or more solid components in the same crystalline materials, will also be discussed. Examples will be provided of how to tackle multiple crystal forms with screening protocols and theoretical approaches, and ultimately how to turn into discovery and innovation the purposed preparation of new crystalline forms of an API
Making crystals with a purpose; a journey in crystal engineering at the University of Bologna
Full text linkThe conceptual relationship between crystal reactivity, stability and metastability, solubility and morphology on the one hand and shape, charge distribution, chirality and distribution of functional groups over the molecular surfaces on the other hand is discussed, via a number of examples coming from three decades of research in the field of crystal engineering at the University of Bologna. The bottom-up preparation of mixed crystals, co-crystals and photoreactive materials starting from molecular building blocks across the borders of organic, organometallic and metalorganic chemistry is recounted
Designing Solid Solutions of Enantiomers: Lack of Enantioselectivity of Chiral Naphthalimide Derivatives in the Solid State
No full textThe enantiomers of a previously reported
naphthalimide derivative are shown in this study to form a
solid solution; furthermore, on the basis of the knowledge of
solid solution structural aspects other naphthalimide derivatives
have been synthesized and shown to lack the
enantioselectivity in the solid state. The structural origin of
solid solution formation is the same as observed in most of the
cases in the literaturequasi-centrosymmetric structures form
at nonracemic compositions where the most abundant
enantiomer adjusts its conformation to mimic the absent
one. Such solid solutions belong to the type showing some
enantioselectivity. An extended single crystal X-ray diffraction
study of the crystals of different enantiomeric compositions
reveals the nature of the disorder in studied solid solutions. Intermolecular interactions are analyzed in terms of Hirshfeld
surfaces and by means of density functional theory calculations to explore the differences of isostructural quasi-centrosymmetric
(enantiopure) and genuine centrosymmetric (racemic) packings to shed light on the energetic aspects of solid solution formation
as well as to explain the origin of partial enantioselectivity. Furthermore, lattice energy calculations explain why two structurally
distinct solid solutions (around the racemic and near the pure enantiomer regions) form as found for one of the studied
compounds
Re: “Crystal Engineering in the Regulatory and Patent Literature of Pharmaceutical Solid Forms”
No full textThis contribution was prompted in response to the recent
Perspective by Desiraju and Nangia (hereafter DN).1 The
somewhat unconventional format used here is consistent with
scientific discourse in general and the nature of an Editorial
comment. Following an initial exchange of views the four authors
opted on adopting a format historically employed in written
discourse−namely, presenting the views of various commentators
together in the same textual offering. Likewise, each of the
authors of this contribution wishes to comment individually on
the DN Perspective, but we wish to contain the comments in one
publication to be read, considered, and cited together rather than
individually. As a result, each comment is self-contained, with its
own text and references cited at the end
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