Speciation of Copper(II)-Betaine Complexes as Starting Point for Electrochemical Copper Deposition from Ionic Liquids

The application of ionic liquids for the dissolution of metal oxides is a promising field for the development of more energy- and resource-efficient metallurgical processes. Using such solutions for the production of valuable chemicals or electrochemical metal deposition requires a detailed understanding of the chemical system and the factors influencing it. In the present work, several compounds are reported that crystallize after the dissolution of copper(II) oxide in the ionic liquid [Hbet][NTf2 ]. Dependent on the initial amount of chloride, the reaction temperature and the purity of the reagent, copper crystallizes in complexes with varying coordination geometries and ligands. Subsequently, the influence of these different complex species on electrochemical properties is shown. For the first time, copper is deposited from the ionic liquid [Hbet][NTf2 ], giving promising opportunities for more resource-efficient copper plating. The copper coatings were analyzed by SEM and EDX measurements. Furthermore, a mechanism for the decomposition of [Hbet][NTf2 ] in the presence of chloride is suggested and supported by experimental evidence.

Modified-amino acid/peptide pyrimidine analogs: synthesis, structural characterization and DFT studies of N-(pyrimidyl)gabapentine and N-(pyrimidyl)baclofen

H-Bonding networks and π–π and halogen bonding interactions in the crystal structures of N-modified amino acid pyrimidine analogs are investigated using DFT calculations and X-ray crystallography analysis.

Mechanochemical Preparation of Active Pharmaceutical Ingredients Monitored by In Situ Raman Spectroscopy

The mechanochemical preparation of silver sulfadiazine and dantrolene, two marketed active pharmaceutical ingredients, was investigated by in situ Raman spectroscopy. For the first time, the mechanochemical transformations involving highly fluorescent compounds could be studied in situ with a high-resolution Raman system combined with a unique suitable Raman probe. Moreover, the kinetic features of the mechanochemical process were examined by a mathematical model allowing to describe the chemical changes under mechanical stress. This approach is promising both to broaden the scope of Raman in situ investigations that would otherwise be impossible and for process optimization at any scale.

The affinity of copper(ii) ions towards l-amino acids in the solid-state: a simple route towards mixed complexes

Competitive milling was successfully employed to determine the relative affinity of Cu(ii) ions towards selected l-amino acids (Asn, Gln, His, Phe, Pro, and Trp). Described process opens a simple route towards mixed coordination compounds.

Tailoring the structures and transformations between copper complexes in gas–solid reactions and solid-state synthesis

A series of unusual structures and transformations between several copper salts and complexes induced in the solid–gas and solid-state reactions were investigated.

Alternative Technologies That Facilitate Access to Discrete Metal Complexes

Organometallic complexes: these two words jump to the mind of the chemist and are directly associated with their utility in catalysis or as a pharmaceutical. Nevertheless, to be able to use them, it is necessary to synthesize them, and it is not always a small matter. Typically, synthesis is via solution chemistry, using a round-bottom flask and a magnetic or mechanical stirrer. This review takes stock of alternative technologies currently available in laboratories that facilitate the synthesis of such complexes. We highlight five such technologies: mechanochemistry, also known as solvent-free chemistry, uses a mortar and pestle or a ball mill; microwave activation can drastically reduce reaction times; ultrasonic activation promotes chemical reactions because of cavitation phenomena; photochemistry, which uses light radiation to initiate reactions; and continuous flow chemistry, which is increasingly used to simplify scale-up. While facilitating the synthesis of organometallic compounds, these enabling technologies also allow access to compounds that cannot be obtained in any other way. This shows how the paradigm is changing and evolving toward new technologies, without necessarily abandoning the round-bottom flask. A bright future is ahead of the organometallic chemist, thanks to these novel technologies.

Investigating the Mechanism of L-Valine in Improving the Stability of Gabapentin Combining Chemical Analysis Experiments with Computational Pharmacy

The mechanism of L-Val on how to improve the stability of gabapentin (GBP) was described by the combination of chemical analysis experiments and computer simulations. Scanning electron microscope (SEM), powder X-ray diffraction (PXRD), and differential scanning calorimeter (DSC), coupled with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), were used to identify β-GBP prepared by rapid solvent removal method. The reaction barriers on crystal planes, β-GBP (100) and β-GBP (10-1), are smaller than α-GBP and γ-GBP, reaching 276.65 kJ/mol and 299.57 kJ/mol, respectively. Thus, it was easier for β-GBP to form lactam, and the occurrence of β-GBP would lead the worse stability of α-GBP. The addition of neutral amino acids such as L-Val could improve the stability of α-GBP effectively. The adsorption energy of α-GBP (002) crystal plane with L-Val is larger than that of other crystal planes, reaching 42.17 kJ/mol. Hydrogen bond was the combination of L-Val and GBP main crystal planes, which could inhibit the crystal transformation of α-GBP. These results suggest that neutral amino acid protectants, such as L-Val, could improve the stability of α-GBP effectively, and inhibition of crystal transformation is one of the effective methods to improve the stability of polymorphic drugs.

Instant Detection of Hydrogen Cyanide Gas and Cyanide Salts in Solid Matrices and Water by using CuII and NiII Complexes of Intramolecularly Hydrogen Bonded Zwitterions

A series of intramolecularly hydrogen-bonded zwitterionic compartmental ligands HL1-HL4, containing a pendent diamine arm that is monoprotonated and an aldehyde functionality at two different ortho-positions of a 4-halophenoxide, is reported herein. Single-crystal X-ray diffraction (SXRD) provides persuasive evidence for the identification of this class of proton-transferred zwitterions at room temperature. The solid-state photoluminescent nature of these zwitterions remains intact in aqueous and organic solutions. Grinding of HL1 and HL2 with Cu²⁺ /Ni²⁺ salts develop turn-on probes 1-4. Compounds 1 and 4 are dinuclear Cu^II and Ni^II species, respectively. Compound 2 is a tetranuclear Cu^II complex. Interestingly, compound 3 is a mononuclear Ni^II species in which both nitrogen atoms in the pendant diamine arm are protonated and, therefore, not coordinated to the Ni^II center. All these probes (1-4) display an instant response to the poison gas hydrogen cyanide (HCN) and cyanide salts present in both solid matrices and aqueous (100 % water) solution. Selective and rapid sensing of HCN gas and cyanide salts in solid/soil/water phases, without any interference, by the mechanosynthesized complexes 1-4 can be perceived easily by the naked eye under a hand-held UV lamp.

Towards medicinal mechanochemistry: evolution of milling from pharmaceutical solid form screening to the synthesis of active pharmaceutical ingredients (APIs)

This overview highlights the emergent area of mechanochemical reactions for making active pharmaceutical ingredients (APIs), and covers the latest advances in the recently established area of mechanochemical screening and synthesis of pharmaceutical solid forms, specifically polymorphs, cocrystals, salts and salt cocrystals. We also provide an overview of the most recent developments in pharmaceutical uses of mechanochemistry, including real-time reaction monitoring, techniques for polymorph control and approaches for continuous manufacture using twin screw extrusion, and more. Most importantly, we show how the overlap of previously unrelated areas of mechanochemical screening for API solid forms, organic synthesis by milling, and mechanochemical screening for molecular recognition, enables the emergence of a new research discipline in which different aspects of pharmaceutical and medicinal chemistry are addressed through mechanochemistry rather than through conventional solution-based routes. The emergence of such medicinal mechanochemistry is likely to have a strong impact on future pharmaceutical and medicinal chemistry, as it offers not only access to materials and reactivity that are sometimes difficult or even impossible to access from solution, but can also provide a general answer to the demands of the pharmaceutical industry for cleaner, safer and efficient synthetic solutions.

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

Mechanochemistry is a powerful and environmentally friendly synthetic technique successfully employed in different fields of synthetic chemistry. Application spans from organic to inorganic chemistry including the synthesis of coordination compounds. Metal-organic frameworks (MOFs) are a class of compounds with numerous applications, from which we highlight herein their application in the pharmaceutical field (BioMOFs), whose importance has been growing and is now assuming a relevant and promising domain. The need to find cleaner, greener and more energy and material-efficient synthetic procedures led to the use of mechanochemistry into the synthesis of BioMOFs.

Advances in Solid-State Transformations of Coordination Bonds: From the Ball Mill to the Aging Chamber

Controlling the formation of coordination bonds is pivotal to the development of a plethora of functional metal-organic materials, ranging from coordination polymers, metal-organic frameworks (MOFs) to metallodrugs. The interest in and commercialization of such materials has created a need for more efficient, environmentally-friendly routes for making coordination bonds. Solid-state coordination chemistry is a versatile greener alternative to conventional synthesis, offering quantitative yields, enhanced stoichiometric and topological selectivity, access to a wider range of precursors, as well as to molecules and materials not readily accessible in solution or solvothermally. With a focus on mechanochemical, thermochemical and “accelerated aging” approaches to coordination polymers, including pharmaceutically-relevant materials and microporous MOFs, this review highlights the recent advances in solid-state coordination chemistry and techniques for understanding the underlying reaction mechanisms.

Mechanochemistry for facilitated access to N,N-diaryl NHC metal complexes

A solvent-free synthesis of NHC–silver, gold, copper and palladium complexes in a ball-mill was achieved.

Controllable assembly of Cu(ii) coordination compounds based on a flexible zwitterionic benzimidazole–dicarboxylate ligand: synthesis, structural diversity, reversible SCSC transformation and magnetic properties

The reversible SCSC transformation of a paddle-wheel cluster to a 1D linear polymer could be accomplished.

New forms of old drugs: improving without changing

OBJECTIVES

In a short approach, we want to present the improvements that have recently been done in the world of new solid forms of known active pharmaceutical ingredients (APIs). The different strategies will be addressed, and successful examples will be given.

KEY FINDINGS

This overview presents a possible step to overcome the 10-15 years of hard work involved in launching a new drug in the market: the use of new forms of well-known APIs, and improve their efficiency by enhancing their bioavailability and pharmacokinetics. It discusses some of the latest progresses.

SUMMARY

We want to present, in a brief overview, what recently has been done to improve the discovery of innovative methods of using well-known APIs, and improve their efficiency. Multicomponent crystal forms have shown to be the most promising achievements to accomplish these aims, by altering API physico-chemical properties, such as solubility, thermal stability, shelf life, dissolution rate and compressibility. API-ionic liquids (ILs) and their advantages will be briefly referred. An outline of what has recently been achieved in metal drug coordination and in drug storage and delivery using bio-inspired metal-organic frameworks (BioMOFs) will also be addressed.

Tetraaqua-tetrakis-{μ(2)-[1-(carb-oxylato-meth-yl)cyclo-hex-yl]methanaminium}bis(μ(3)-hydroxido)bis(nitrato-κO,O')tetrazinc(II)

As the title gabapentin complex, [Zn₄(OH)₂(NO₃)₂(C₉H₁₇NO₂)₄(H₂O)₄](NO₃)₄ is located about a centre of inversion, the asymmetric unit contains two disordered nitrate ions and half a complex mol­ecule. The two zinc ions have different coordination environments: one is slightly distorted octa­hedral and the other is trigonal–pyramidal. The conformation of the gabapentin mol­ecule is defined by the formation of two intra­molecular O—H⋯O hydrogen bonds. Furthermore, the ammonium H atoms are involved in numerous hydrogen bonds with the disordered nitrate anions.

Crystal structures of a new polymorphic form of gabapentin monohydrate and the e and z isomers of 4-tertiarybutylgabapentin

Gabapentin, a widely used antiepileptic drug, crystallizes in multiple polymorphic forms. A new crystal form of gabapentin monohydrate in the space group Pbca is reported and the packing arrangement compared with that of a previously reported polymorph in the space group P2(1)/c [Ibers, J.A. (2001) Acta Crystallogr; C57:641]. Gabapentin polymorphs can also occur from a selection of one of the two distinct chair forms of the 1,1-disubstituted cyclohexane. Crystal structures of the E and Z isomers of 4-tert-butylgabapentin provide models for analyzing anticipated packing modes in the conformational isomers of gabapentin. The E isomer crystallized in the space group Pca2(1), while the Z isomer crystallized in the space group P2(1)/c. The crystal structure of E-4-tert-butylgabapentin provides the only example of a structure in a non-centrosymmetric space group. Crystal structures of the hydrochloride and hydrobromide salts of 4-tert-butyl derivatives are reported. The results suggest that for gabapentin, a large 'polymorph-space' may be anticipated, in view of the multiple conformational states that are accessible to the molecule.