Amit Delori

pKa‐Directed Host–Guest Assemblies: Rational Analysis of Molecular Adducts of 2,4‐Diamino‐6‐methyl‐1,3,5‐triazine with Various Aliphatic Dicarboxylic Acids

Molecular adducts of 2,4-diamino-6-methyl-1,3,5-triazine (1) have been prepared with various aliphatic dicarboxylic acids. The molecular complexes (1 a-1 i) thus formed by co-crystallizing 1 with oxalic, malonic, succinic, fumaric, acetylene dicarboxylic, glutaric, thiodiglycolic, diglycolic, and adipic acids have been found to give two types of host-guest assemblies that have voids or channels in a three-dimensional arrangement. The different types of host-guest arrangement appear to result from differences in the acidity of the dicarboxylic acids, that is, acids with pK(a)<3.0 give host networks that consist of 1 and the corresponding acid with water or solvent molecules of crystallization present as guests, whereas acids with pK(a)>3.0 exist as guests in voids in a host network formed by 1. The former arrangement is observed in adducts 1 a, 1 b, 1 e, and 1 h and the latter arrangement is found in adducts 1 c, 1 d, 1 f, 1 g, and 1 i.

Drug solid solutions – a method for tuning phase transformations

This paper describes a methodology for the modification of phase transition temperatures using (±)-4′-methylmethcathinone solid solutions as an exemplar. This method serves to show that by varying the composition of the halide ion one can systematically alter the temperatures at which phase transitions can occur in order to evade the possibility of interconversion between polymorphs during processing or storage of materials.

Supramolecular hair dyes: a new application of cocrystallization

The manuscript presents the first report of hair dyes of various colors formed by cocrystallization. Unlike the most popular oxidative hair dye (OHD) products, these dyes are NH3 free and do not require H2O2 as a color developer. The importance of these new hair dyes products is further enhanced by recent reports which indicate that some of the OHDs may be carcinogenic.

Polymorphism of a polymer precursor: metastable glycolide polymorph recovered via large scale high-pressure experiments

A novel polymorph of glycolide, the precursor to polyglycolic acid, has been observed at 0.6 GPa. Large scale high-pressure production has been performed and the seeds successfully used to aid crystallisation of the polymorph at ambient pressure. PIXEL calculations confirm the metastable nature of the polymorph. Subsequent experiments show that, whilst initially stable for 12 days, this may be a case of disappearing polymorphism.

Influence of molecular shape on the design and synthesis of supramolecular assemblies

Influence of shape of coformers on supramolecular assemblies has been demonstrated by synthesizing six new molecular adducts of 2,4-diamino-6-phenyl-1,3,5-triazine (1) with coformers of different shapes. A structural correlation has also been revealed between the molecular adducts and 1.

The ecstasy and the agony; compression studies of 3,4-methylenedioxymethamphetamine (MDMA)

MDMA (3,4-methylenedioxymethamphetamine) is a Class A substance that is usually found in a tableted form. It is only observed in one orthorhombic polymorph under ambient conditions. It shows slight positional disorder around the methlyenedioxy ring which persists during compression up to 6.66 GPa. The crystal quality deteriorates above 6.66 GPa where the hydrostatic limit of the pressure-transmitting medium is exceeded. The structure undergoes anisotropic compression with the a-axis compressing the greatest (12% cf. 4 and 10% for the b- and c-axes, respectively). This is due to the pattern of the hydrogen bonding which acts like a spring and allows the compression along this direction.

Using crystallography, topology and graph set analysis for the description of the hydrogen bond network of triamterene: a rational approach to solid form selection

This study has demonstrated the use of crystallography, topology and graph set analysis in the description and classification of the complex hydrogen bonded network of triamterene. The aim is to give a brief overview of the methodology used to discuss the crystal structure of triamterene with a view to extending the study to include the solvates, cocrystals and salts of this compound.Graphical abstractOne of the structurally significant dimers (supramolecular synthons) of triamterene identified by this study

Structural studies of crystalline forms of triamterene with carboxylic acid, GRAS and API molecules

This work discusses the preparation and characterization of crystalline forms of the drug triamterene with various carboxylic acids including Generally Regarded as Safe and Active Pharmaceutical Ingredients using liquid-assisted grinding and solvent-evaporative crystallization; a method of potential benefit to the pharmaceutical industry. Triamterene is selected as an appropriate model compound because it has poor water solubility which can have an impact on its bioavailability as a drug and it contains numerous hydrogen-bonding sites, thereby allowing a study of the competition between the different potential supramolecular synthons. Cambridge Structural Database studies show good agreement between this and previous studies using similar compounds.

Under pressure to react – acetylenedicarboxylic acid polymerisation

Organic polymers play an important role in our life and we use many such polymers on day to day basis such as polyethene, nylon, kevlar, PVC, bakelite, teflon etc. Solid state synthesis of polymers is of great interest, as the polymers synthesized by this route might have different properties as compared to those obtained via solution methods. This is possible due to the rigid position of the molecules with respect to each other; their orientation being a crucial component in the formation of the polymer backbones. Hence polymorphism in monomeric systems can play a significant role in the outcome of the polymerization. Such solid state syntheses of acetylene derivatives is of special interest as it may selectively form conducting polyacetylene polymers, which are much needed for applications such as solar cells and as organic light emitting diodes, which in turn are required in the manufacturing of displays for TV, mobile phones, cameras etc. Pressure is a powerful thermodynamic variable that can induce polymorphism as well as polymerization. Example of these reactions are ethylene,[1] butadiene,[2] and acrylic acid.[3] In this talk we will describe the polymerisation of acetylenedicarboxylic acid (ADCA) via the application of pressure. Traditional solid state polymerization of ADCA is marked by very low yields (around 5.5%) and long exposure times of γ-radiation (>10 days) whilst we will show that the chemical reaction can occur in a fraction of the time by applying pressure. Structural data has been collected on the system up to the reaction point using X-ray diffraction methods and shown that ADCA undergoes two polymorphic transitions before the reaction. Pixel calculations have been performed to provide information on intermolecular interactions as a function of pressure. Raman spectroscopy has been used to help identify the intramolecular changes over the chemical reaction.