Crystal and molecular structure of the 1:1 complex of 1-piperidineacetic acid with 2,6-dichloro-4-nitrophenol studied by X-ray diffraction and B3LYP calculation

Spectrophotometric study on the proton transfer reaction between 2-amino-4-methylpyridine with 2,6-dichloro-4-nitrophenol in methanol, acetonitrile and the binary mixture 50% methanol+50% acetonitrile

Proton transfer reaction between 2-amino-4-methylpyridine (2AMP) as the proton acceptor with 2,6-dichloro-4-nitrophenol (DCNP) as the proton donor has been investigated spectrophotometrically in methanol (MeOH), acetonitrile (AN) and a binary mixture composed of 50% MeOH and 50% AN (AN-Me). The composition of the complex has been investigated utilizing Job(')s and photometric titration methods to be 1:1. Minimum-maximum absorbance equation has been applied to estimate the formation constant of the proton transfer reaction (K(PT)) where it reached high values in the investigated solvent confirming its high stability. The formation constant recorded higher value in AN compared with MeOH and mixture of AN-Me. Based on the formation of stable proton transfer complex, a sensitive spectrophotometric method was suggested for quantitative determination of 2AMP. The Lambert-Beer(')s law was obeyed in the concentration range 0.5-8 μg mL(-1) with small values of limits of detection and quantification. The solid complex between 2AMP with DCNP has been synthesized and characterized by elemental analysis to be 1:1 in concordant with the molecular stoichiometry in solution. Further analysis of the solid complex was carried out using infrared and (1)H NMR spectroscopy.

Cocrystals of 2,6-dichloroaniline and 2,6-dichlorophenol plus three new pseudopolymorphs of their coformers

The structures of cocrystals of 2,6-dichlorophenol with 2,4-diamino-6-methyl-1,3,5-triazine, C6H4Cl2O·C4H7N5, (III), and 2,6-dichloroaniline with 2,6-diaminopyrimidin-4(3H)-one and N,N-dimethylacetamide, C6H5Cl2N·C4H6N4O·C4H9NO, (V), plus three new pseudopolymorphs of their coformers, namely 2,4-diamino-6-methyl-1,3,5-triazine-N,N-dimethylacetamide (1/1), C4H7N5·C4H9NO, (I), 2,4-diamino-6-methyl-1,3,5-triazine-N-methylpyrrolidin-2-one (1/1), C4H7N5·C5H9NO, (II), and 6-aminoisocytosine-N-methylpyrrolidin-2-one (1/1), C4H6N4O·C5H9NO, (IV), are reported. Both 2,6-dichlorophenol and 2,6-dichloroaniline are capable of forming definite synthon motifs, which usually lead to either two- or three-dimensional crystal-packing arrangements. Thus, the two isomorphous pseudopolymorphs of 2,4-diamino-6-methyl-1,3,5-triazine, i.e. (I) and (II), form a three-dimensional network, while the N-methylpyrrolidin-2-one solvate of 6-aminoisocytosine, i.e. (IV), displays two-dimensional layers. On the basis of these results, attempts to cocrystallize 2,6-dichlorophenol with 2,4-diamino-6-methyl-1,3,5-triazine, (III), and 2,6-dichloroaniline with 6-aminoisocytosine, (V), yielded two-dimensional networks, whereby in cocrystal (III) the overall structure is a consequence of the interaction between the two compounds. By comparison, cocrystal-solvate (V) is mainly built by 6-aminoisocytosine forming layers, with 2,6-dichloroaniline and the solvent molecules arranged between the layers.

Spectroscopic characterization of hydrogen-bonded proton transfer complex between 4-aminopyridine with 2,6-dichloro-4-nitrophenol in different solvents and solid state

Proton transfer reaction between the proton donor 2,6-dichloro-4-nitrophenol (DCNP) with the proton acceptor 4-aminopyridine (4APy) has been investigated spectrophotometrically in different solvents included the aprotic solvent acetonitrile (MeCN), the protic one methanol (MeOH) and a mixture consists of 50% acetonitrile+50% dichloroethane (ANDC). The proton transfer complex is produced instantaneously with deep yellow color and absorption maxima in the range 395-425nm. The composition of the complex was characterized spectrophotometrically to be 1:1 in all solvent proving that the solvent has no effect on the complex stoichiometry. The proton transfer formation constant has been estimated by using Benesi-Hildebrand equation where the highest value was recorded in the mixture ANDC. This proofs the high stability of the complex in less polar solvent as a result of the high stability of the complex ground state. The solid complex has been synthesized and characterized by elemental analysis to be 1:2 [(proton donor) (proton acceptor)2]. The obtained solid complex was analyzed by infrared spectroscopy where two broad band's at 3436 and 2500cm(-1) characterized for asymmetric NHN(+) hydrogen bond were identified. Molecular modeling utilizing GAMESS computations as a package of ChemBio3D Ultra12 program was carried out where asymmetric NHN(+) was explored with NN bond distance 2.77Å. The computations showed a difference in molecular geometry of the complex compared with reactants especially bond lengths, bond angles and distances of close contact.