Dipjyoti Kalita

Formation of symmetry non-equivalent molecules in urea and carbamate derivatives: the role of anion

The perchlorate salts of the compounds 1-phenyl-3-(quinolin-5-yl) urea, 1-phenyl-3-(quinolin-8-yl) urea, and quinoline-8-yl phenylcarbamate, possess symmetry non-equivalent molecules in their unit cell. The role of anion in generating high Z′ is discussed by comparing the structures of the salts and the original compounds.

Five-coordinate dicarboxylate complexes of copper (+2) and zinc (+2)

A new dicarboxylic acid, LH2 , derived from 2-[(2-hydroxy-3,5-dimethylphenyl) (phenyl)methyl]-4,6-dimethylphenol (1) was prepared by reacting it with methyl bromoacetate followed by alkaline hydrolysis. Two five-coordinate mononuclear complexes of L with zinc (+2) and copper (+2), [Zn(L)(py)2(H2O)] · H2O · py (IV), and [Cu(L)(py)2(H2O)] (V), were prepared (py = pyridine) and characterized. The packing patterns of these two complexes are different and the H-bond interactions in their lattices are controlled by the presence or absence of water molecules. This difference arises from subtle change in the orientation of carbonyl groups of the carboxylates.

Different spatial orientations of amide derivatives on anion coordination

The N-[2-(4-methoxypheny)-ethyl]-2-(quinolin-8-yl-amino)acetamide is a stretched amide, whose protonated perchlorate salt has a tweezer-like geometry. The self assembly of the salt molecules through weak C–H⋯π and C–H⋯O interactions gives a channel like structure. The crystal structure of two salts of N-quinolin-8-yl-2-(quinolin-8-yloxy)acetamide (II) is determined. The corresponding perchlorate salt arises from di-protonatation of the parent amide derivative, whereas the tetrafluroborate salt formed is a mono-protonated species of the amide derivative II. The di-protonated species has a concave shape but mono-protonated species adopts an S-shaped geometry.

1-Phenyl-3-(quinolin-5-yl)urea as a host for distinction of phthalic acid and terephthalic acid

AbstractCo-crystals of 1-phenyl-3-(quinolin-5-yl)urea (1) with terephthalic acid, adipic acid; and salts of 1 with phthalic acid, p-toluenesulphonic acids are prepared and structurally characterized. The reaction of phthalic acid and p-toluenesulphonic acid resulted in protonation of the host 1, whereas the terephthalic acid and adipic acid interact with 1, led to cocrystals with the host 1 through hydrogen bond interactions. The hydrogen bonds that appears in the urea taps of the host molecules 1 are lost while formation of salts; in such cases anions interacts with the urea portion of the host, while in the co-crystals the hydrogen bonded urea taps are retained. The salts are yellow in colour while the co-crystals are colourless; thereby the positional isomer phthalic acid can be distinguished from the terephthalic acid. Graphical AbstractCo-crystals of 1-phenyl-3-(quinolin-5-yl)urea (1) with terephthalic acid, adipic acid; and salts of 1 with phthalic acid, p-toluenesulphonic acids are prepared and structurally characterized. The salts are yellow in colour while the cocrystals are colourless; thereby the positional isomer phthalic acid can be distinguished from terephthalic acid.

Solvatochromicity of 3-hydroxy-4-(1-(2,4-dihydroxyphenyl)-2-hydroxy-2,2-diphenylethylidene)cyclohexa-2,5-dienone for screening of solvents

The quinonic compound 3-hydroxy-4-(1-(2,4-dihydroxyphenyl)-2-hydroxy-2,2-diphenylethylidene)cyclohexa-2,5-dienone (I) is synthesised by the reaction of benzil with 1,3-dihydroxybenzene in basic medium. Solution of this compound shows visibly distinct colour differences in different solvents. From the different absorption maxima of the compound in visible spectra it can be used as an excellent analytical reagent to screen different solvents.