Ponraj Prabakaran

Amino­pyrimidine–carboxyl­(ate) interactions in trimethoprim maleate, an antifolate drug

In the title cocrystal, trimethoprim maleate [2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium maleate], C(14)H(19)N(4)O(3)(+).C(4)H(3)O(4)(-), the trimethoprim molecule is protonated at N1. The carboxyl group of the maleate ion makes a specific double hydrogen bond of type N-H.O with the 2-amino group and the protonated N1 atom of the trimethoprim cation which is similar to the carboxylate-trimethoprim cation interaction observed in the complex of dihydrofolate reductase with trimethoprim. The pyrimidine moieties of trimethoprim cations are centrosymmetrically paired through a pair of N-H.N hydrogen bonds involving the 4-amino group and the pyridinium N3 atom of a symmetry-related molecule. One of the O atoms at the maleate carboxylate group bridges the 2-amino and 4-amino groups on either side of the paired trimethoprim cations. The other O atom of the carboxylate group forms an intramolecular O-H.O hydrogen bond with the carboxyl group. These characteristic hydrogen bonds result in infinite two-dimensional aggregation of rings into a supramolecular ladder, which is further crosslinked through weak C-H.O interactions with methoxy groups of neighbouring trimethoprim molecules to form a layered structure.

Conformational pseudo-polymorphism and hydrogen bonding: benzthiazide anhydrate and monohydrate, an antihypertensive drug

Crystal structures of benzthiazide [6-chloro-3-[[(phenylmethyl)thio]ethyl]4H-1,2,4-benzthiadiazine-7-sulfonamide-1,1,dioxide] in its anhydrate and monohydrate forms reveal, respectively, a J-like folded as well as extended type conformations that have critical torsional flexibility along the C–C–S–C bonds and novel H-bonded sulfonamide motifs.

A pseudo-quadruple hydrogen-bonding motif consisting of six N-H...O hydrogen bonds in trimethoprim formate

The title compound, trimethoprim (TMP) formate [systematic name: 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium formate], C(14)H(19)N(4)O(3)(+).CHO(2)(-), reveals a pseudo-quadruple hydrogen-bonding motif consisting of six N-H.O hydrogen bonds involving two unpaired TMP cations and two formate anions which are symmetrically disposed. The hydrogen-bonding motif is strikingly comparable with that observed in other TMP salts where the aminopyrimidine moieties of the TMP cations are centrosymmetrically paired. These conserved hydrogen-bonding motifs may serve as robust synthons in crystal engineering and design. The characteristic pseudo-quadruple hydrogen-bonding motif and other intermolecular hydrogen bonds operating in the crystal form a two-dimensional supramolecular sheet structure.

Hydrogen-bonded (H 2 O·X) 2 (X=Cl - , Br - ) clusters in 1-phenacyl-4-(dimethylamino)pyridinium halide monohydrates †

The synthesis, and X-ray crystal and molecular structures, of 1-phenacyl-4-(dimethylamino)pyridinium chloride and bromide monohydrates are described.

Thiabendazolium Nitrate, an Anthelmintic Compound

In the crystal structure of 2-(thiazol-4-yl)-1H-benzimidazolium nitrate, C 10 H 8 N 3 S + .NO - 3 , the benzimidazole moiety is protonated. The benzimidazole and thiazole systems are coplanar. Both N-H groups of the protonated benzimidazole are involved in N-H…O hydrogen bonds with the nitrate anion.

Comment on μ1,3-azido-di­azido­tetrakis(1,10-phenanthroline)­dicopper(II) azide tetrahydrate

The supramolecular structure of the title dimeric azido complex of copper(II), [Cu(2)(mu(1,3)-N(3))(N(3))(2)(phen)(4)](N(3)) x 4H(2)O (phen is 1,10-phenanthroline, C(12)H(8)N(2)) [Cheng, Hu, Wang & Ye (2002). Acta Cryst. C58, m12-m13], which was originally described in terms of hydrogen-bonded chains, has been re-interpreted as two-dimensional hydrogen-bonded sheets built from R(6)4(12) and R(10)10(28) rings, taking into account the complete hydogen-bonding pattern.