Supramolecular interactions in salts/cocrystals involving pyrimidine derivatives of sulfonate/carboxylic acid.

The crystal structures of three compounds involving aminopyrimidine derivatives are reported, namely, 5-fluorocytosinium sulfanilate-5-fluorocytosine-4-azaniumylbenzene-1-sulfonate (1/1/1), C4H5FN3O+·C6H6NO3S-·C4H4FN3O·C6H7NO3S, I, 5-fluorocytosine-indole-3-propionic acid (1/1), C4H4FN3O·C11H11NO2, II, and 2,4,6-triaminopyrimidinium 3-nitrobenzoate, C4H8N5+·C7H4NO4-, III, which have been synthesized and characterized by single-crystal X-ray diffraction. In I, there are two 5-fluorocytosine (5FC) molecules (5FC-A and 5FC-B) in the asymmetric unit, with one of the protons disordered between them. 5FC-A and 5FC-B are linked by triple hydrogen bonds, generating two fused rings [two R22(8) ring motifs]. The 5FC-A molecules form a self-complementary base pair [R22(8) ring motif] via a pair of N-H...O hydrogen bonds and the 5FC-B molecules form a similar complementary base pair [R22(8) ring motif]. The combination of these two types of pairing generates a supramolecular ribbon. The 5FC molecules are further hydrogen bonded to the sulfanilate anions and sulfanilic acid molecules via N-H...O hydrogen bonds, generating R44(22) and R66(36) ring motifs. In cocrystal II, two types of base pairs (homosynthons) are observed via a pair of N-H...O/N-H...N hydrogen bonds, generating R22(8) ring motifs. The first type of base pair is formed by the interaction of an N-H group and the carbonyl O atom of 5FC molecules through a couple of N-H...O hydrogen bonds. Another type of base pair is formed via the amino group and a pyrimidine ring N atom of the 5FC molecules through a pair of N-H...N hydrogen bonds. The base pairs (via N-H...N hydrogen bonds) are further bridged by the carboxyl OH group of indole-3-propionic acid and the O atom of 5FC through O-H...O hydrogen bonds on either side of the R22(8) motif. This leads to a DDAA array. In salt III, one of the N atoms of the pyrimidine ring is protonated and interacts with the carboxylate group of the anion through N-H...O hydrogen bonds, leading to the primary ring motif R22(8). Furthermore, the 2,4,6-triaminopyrimidinium (TAP) cations form base pairs [R22(8) homosynthon] via N-H...N hydrogen bonds. A carboxylate O atom of the 3-nitrobenzoate anion bridges two of the amino groups on either side of the paired TAP cations to form another ring [R32(8)]. This leads to the generation of a quadruple DADA array. The crystal structures are further stabilized by π-π stacking (I and III), C-H...π (I and II), C-F...π (I) and C-O...π (II) interactions.

Supramolecular architectures in metal(II) (Cd/Zn) halide/nitrate complexes of cytosine/5-fluorocytosine.

Three new metal(II)-cytosine (Cy)/5-fluorocytosine (5FC) complexes, namely bis(4-amino-1,2-dihydropyrimidin-2-one-κN3)diiodidocadmium(II) or bis(cytosine)diiodidocadmium(II), [CdI2(C4H5N3O)2], (I), bis(4-amino-1,2-dihydropyrimidin-2-one-κN3)bis(nitrato-κ2O,O')cadmium(II) or bis(cytosine)bis(nitrato)cadmium(II), [Cd(NO3)2(C4H5N3O)2], (II), and (6-amino-5-fluoro-1,2-dihydropyrimidin-2-one-κN3)aquadibromidozinc(II)-6-amino-5-fluoro-1,2-dihydropyrimidin-2-one (1/1) or (6-amino-5-fluorocytosine)aquadibromidozinc(II)-4-amino-5-fluorocytosine (1/1), [ZnBr2(C4H5FN3O)(H2O)]·C4H5FN3O, (III), have been synthesized and characterized by single-crystal X-ray diffraction. In complex (I), the CdII ion is coordinated to two iodide ions and the endocyclic N atoms of the two cytosine molecules, leading to a distorted tetrahedral geometry. The structure is isotypic with [CdBr2(C4H5N3O)2] [Muthiah et al. (2001). Acta Cryst. E57, m558-m560]. In compound (II), each of the two cytosine molecules coordinates to the CdII ion in a bidentate chelating mode via the endocyclic N atom and the O atom. Each of the two nitrate ions also coordinates in a bidentate chelating mode, forming a bicapped distorted octahedral geometry around cadmium. The typical interligand N-H...O hydrogen bond involving two cytosine molecules is also present. In compound (III), one zinc-coordinated 5FC ligand is cocrystallized with another uncoordinated 5FC molecule. The ZnII atom coordinates to the N(1) atom (systematic numbering) of 5FC, displacing the proton to the N(3) position. This N(3)-H tautomer of 5FC mimics N(3)-protonated cytosine in forming a base pair (via three hydrogen bonds) with 5FC in the lattice, generating two fused R22(8) motifs. The distorted tetrahedral geometry around zinc is completed by two bromide ions and a water molecule. The coordinated and nonccordinated 5FCs are stacked over one another along the a-axis direction, forming the rungs of a ladder motif, whereas Zn-Br bonds and N-H...Br hydrogen bonds form the rails of the ladder. The coordinated water molecules bridge the two types of 5FC molecules via O-H...O hydrogen bonds. The cytosine molecules are coordinated directly to the metal ion in each of the complexes and are hydrogen bonded to the bromide, iodide or nitrate ions. In compound (III), the uncoordinated 5FC molecule pairs with the coordinated 5FC ligand through three hydrogen bonds. The crystal structures are further stabilized by N-H...O, N-H...N, O-H...O, N-H...I and N-H...Br hydrogen bonds, and stacking interactions.

Supra-molecular inter-actions in 2,6-di-amino-4-chloro-pyrimidin-1-ium 5-chloro-salicylate and bis-(2,6-di-amino-4-chloro-pyrimidin-1-ium) naphthalene-1,5-di-sulfonate.

The crystals of two new salts, 2,6-di-amino-4-chloro-pyrimidin-1-ium 5-chloro-salicylate, C4H6ClN4+·C7H4ClO3-, (I), and bis-(2,6-di-amino-4-chloro-pyrimidin-1-ium) naphthalene-1,5-di-sulfonate, 2C4H6ClN4+·C10H6O6S22-, (II), have been synthesized and characterized by single-crystal X-ray diffraction. In both compounds, the N atom of the pyrimidine group in between the amino substituents is protonated and the pyrimidinium cation forms a pair of N-H⋯O hydrogen bonds with the carboxyl-ate/sulfonate ion, leading to a robust R22(8) motif (supra-molecular heterosynthon). In compound (I), a self-complementary base pairing involving the other pyrimidinium ring nitro-gen atom and one of the amino groups via a pair of N-H⋯N hydrogen bonds [R22(8) homosynthon] is also present. In compound (II), the crystallographic inversion centre coincides with the inversion centre of the naphthalene-1,5-di-sulfonate ion and all the sulfonate O atoms are hydrogen-bond acceptors, generating fused-ring motifs and a quadruple DDAA array. A halogen-bond (Cl⋯Cl) inter-action is present in (I) with a distance and angle of 3.3505 (12) Šand 151.37 (10)°, respectively. In addition, a C-Cl⋯π inter-action and a π-π inter-action in (I) and a π-π inter-action in (II) further stabilize these crystal structures.

Supramolecular hydrogen-bonding patterns in salts of the antifolate drugs trimethoprim and pyrimethamine.

Nine salts of the antifolate drugs trimethoprim and pyrimethamine, namely, trimethoprimium [or 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium] 2,5-dichlorothiophene-3-carboxylate monohydrate (TMPDCTPC, 1:1), C14H19N4O3+·C5HCl2O2S-, (I), trimethoprimium 3-bromothiophene-2-carboxylate monohydrate, (TMPBTPC, 1:1:1), C14H19N4O3+·C5H2BrO2S-·H2O, (II), trimethoprimium 3-chlorothiophene-2-carboxylate monohydrate (TMPCTPC, 1:1:1), C14H19N4O3+·C5H2ClO2S-·H2O, (III), trimethoprimium 5-methylthiophene-2-carboxylate monohydrate (TMPMTPC, 1:1:1), C14H19N4O3+·C6H5O2S-·H2O, (IV), trimethoprimium anthracene-9-carboxylate sesquihydrate (TMPAC, 2:2:3), C14H19N4O3+·C15H9O2-·1.5H2O, (V), pyrimethaminium [or 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium] 2,5-dichlorothiophene-3-carboxylate (PMNDCTPC, 1:1), C12H14ClN4+·C5HCl2O2S-, (VI), pyrimethaminium 5-bromothiophene-2-carboxylate (PMNBTPC, 1:1), C12H14ClN4+·C5H2BrO2S-, (VII), pyrimethaminium anthracene-9-carboxylate ethanol monosolvate monohydrate (PMNAC, 1:1:1:1), C12H14ClN4+·C15H9O2-·C2H5OH·H2O, (VIII), and bis(pyrimethaminium) naphthalene-1,5-disulfonate (PMNNSA, 2:1), 2C12H14ClN4+·C10H6O6S22-, (IX), have been prepared and characterized by single-crystal X-ray diffraction. In all the crystal structures, the pyrimidine N1 atom is protonated. In salts (I)-(III) and (VI)-(IX), the 2-aminopyrimidinium cation interacts with the corresponding anion via a pair of N-H...O hydrogen bonds, generating the robust R22(8) supramolecular heterosynthon. In salt (IV), instead of forming the R22(8) heterosynthon, the carboxylate group bridges two pyrimidinium cations via N-H...O hydrogen bonds. In salt (V), one of the carboxylate O atoms bridges the N1-H group and a 2-amino H atom of the pyrimidinium cation to form a smaller R21(6) ring instead of the R22(8) ring. In salt (IX), the sulfonate O atoms mimic the role of carboxylate O atoms in forming an R22(8) ring motif. In salts (II)-(IX), the pyrimidinium cation forms base pairs via a pair of N-H...N hydrogen bonds, generating a ring motif [R22(8) homosynthon]. Compounds (II) and (III) are isomorphous. The quadruple DDAA (D = hydrogen-bond donor and A = hydrogen-bond acceptor) array is observed in (I). In salts (II)-(IV) and (VI)-(IX), quadruple DADA arrays are present. In salts (VI) and (VII), both DADA and DDAA arrays co-exist. The crystal structures are further stabilized by π-π stacking interactions [in (I), (V) and (VII)-(IX)], C-H...π interactions [in (IV)-(V) and (VII)-(IX)], C-Br...π interactions [in (II)] and C-Cl...π interactions [in (I), (III) and (VI)]. Cl...O and Cl...Cl halogen-bond interactions are present in (I) and (VI), with distances and angles of 3.0020 (18) and 3.5159 (16) Å, and 165.56 (10) and 154.81 (11)°, respectively.

Supramolecular architectures in cytosinium 6-chloronicotinate monohydrate and 5-bromo-6-methylisocytosinium hydrogen sulfate.

Aminopyrimidine derivatives are biologically important as they are components of nucleic acids and drugs. The crystals of two new salts, namely cytosinium 6-chloronicotinate monohydrate, C4H6N3O+·C6H3ClNO2-·H2O, (I), and 5-bromo-6-methylisocytosinium hydrogen sulfate (or 2-amino-5-bromo-4-oxo-6-methylpyrimidinium hydrogen sulfate), C5H7BrN3O+·HSO4-, (II), have been prepared and characterized by single-crystal X-ray diffraction. The pyrimidine ring of both compounds is protonated at the imine N atom. In hydrated salt (I), the primary R22(8) ring motif (supramolecular heterosynthon) is formed via a pair of N-H...O(carboxylate) hydrogen bonds. The cations, anions and water molecule are hydrogen bonded through N-H...O, N-H...N, O-H...O and C-H...O hydrogen bonds, forming R22(8), R32(7) and R55(21) motifs, leading to a hydrogen-bonded supramolecular sheet structure. The supramolecular double sheet structure is formed via water-carboxylate O-H...O hydrogen bonds and π-π interactions between the anions and the cations. In salt (II), the hydrogen sulfate ions are linked via O-H...O hydrogen bonds to generate zigzag chains. The aminopyrimidinium cations are embedded between these zigzag chains. Each hydrogen sulfate ion bridges two cations via pairs of N-H...O hydrogen bonds and vice versa, generating two R22(8) ring motifs (supramolecular heterosynthon). The cations also interact with one another via halogen-halogen (Br...Br) and halogen-oxygen (Br...O) interactions.

Supramolecular architectures in the salt trimethoprimium ferrocene-1-carboxylate and the cocrystal 4-amino-5-chloro-2,6-dimethylpyrimidine-ferrocene-1-carboxylic acid (1/1).

In the salt trimethoprimium ferrocenecarboxylate [systematic name: 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium ferrocene-1-carboxylate], (C14H19N4O3)[Fe(C5H5)(C6H4O2)], (I), of the antibacterial compound trimethoprim, the carboxylate group interacts with the protonated aminopyrimidine group of trimethoprim via two N-H...O hydrogen bonds, generating a robust R22(8) ring motif (heterosynthon). However, in the cocrystal 4-amino-5-chloro-2,6-dimethylpyrimidine-ferrocene-1-carboxylic acid (1/1), [Fe(C5H5)(C6H5O2)]·C6H8ClN3, (II), the carboxyl-aminopyrimidine interaction [R22(8) motif] is absent. The carboxyl group interacts with the pyrimidine ring via a single O-H...N hydrogen bond. The pyrimidine rings, however, form base pairs via a pair of N-H...N hydrogen bonds, generating an R22(8) supramolecular homosynthon. In salt (I), the unsubstituted cyclopentadienyl ring is disordered over two positions, with a refined site-occupation ratio of 0.573 (10):0.427 (10). In this study, the two five-membered cyclopentadienyl (Cp) rings of ferrocene are in a staggered conformation, as is evident from the C...Cg...Cg...C pseudo-torsion angles, which are in the range 36.13-37.53° for (I) and 22.58-23.46° for (II). Regarding the Cp ring of the minor component in salt (I), the geometry of the ferrocene ring is in an eclipsed conformation, as is evident from the C...Cg...Cg...C pseudo-torsion angles, which are in the range 79.26-80.94°. Both crystal structures are further stabilized by weak π-π interactions.

Supramolecular interactions in carboxylate and sulfonate salts of 2,6-diamino-4-chloropyrimidinium.

Two new salts, namely 2,6-diamino-4-chloropyrimidinium 2-carboxy-3-nitrobenzoate, C4H6ClN4+·C8H4NO6-, (I), and 2,6-diamino-4-chloropyrimidinium p-toluenesulfonate monohydrate, C4H6ClN4+·C7H7O3S-·H2O, (II), have been synthesized and characterized by single-crystal X-ray diffraction. In both crystal structures, the N atom in the 1-position of the pyrimidine ring is protonated. In salt (I), the protonated N atom and the amino group of the pyrimidinium cation interact with the carboxylate group of the anion through N-H...O hydrogen bonds to form a heterosynthon with an R22(8) ring motif. In hydrated salt (II), the presence of the water molecule prevents the formation of the familiar R22(8) ring motif. Instead, an expanded ring [i.e. R32(8)] is formed involving the sulfonate group, the pyrimidinium cation and the water molecule. Both salts form a supramolecular homosynthon [R22(8) ring motif] through N-H...N hydrogen bonds. The molecular structures are further stabilized by π-π stacking, and C=O...π, C-H...O and C-H...Cl interactions.

Supramolecular architectures in two 1:1 cocrystals of 5-fluorouracil with 5-bromothiophene-2-carboxylic acid and thiophene-2-carboxylic acid.

In solid-state engineering, cocrystallization is a strategy actively pursued for pharmaceuticals. Two 1:1 cocrystals of 5-fluorouracil (5FU; systematic name: 5-fluoro-1,3-dihydropyrimidine-2,4-dione), namely 5-fluorouracil-5-bromothiophene-2-carboxylic acid (1/1), C5H3BrO2S·C4H3FN2O2, (I), and 5-fluorouracil-thiophene-2-carboxylic acid (1/1), C4H3FN2O2·C5H4O2S, (II), have been synthesized and characterized by single-crystal X-ray diffraction studies. In both cocrystals, carboxylic acid molecules are linked through an acid-acid R22(8) homosynthon (O-H...O) to form a carboxylic acid dimer and 5FU molecules are connected through two types of base pairs [homosynthon, R22(8) motif] via a pair of N-H...O hydrogen bonds. The crystal structures are further stabilized by C-H...O interactions in (II) and C-Br...O interactions in (I). In both crystal structures, π-π stacking and C-F...π interactions are also observed.

Crystal structure and hydrogen-bonding patterns in 5-fluoro-cytosinium picrate.

In the crystal structure of the title compound, 5-fluoro-cytosinium picrate, C4H5FN3O+·C6H2N3O7-, one N heteroatom of the 5-fluoro-cytosine (5FC) ring is protonated. The 5FC ring forms a dihedral angle of 19.97 (11)° with the ring of the picrate (PA-) anion. In the crystal, the 5FC+ cation inter-acts with the PA- anion through three-centre N-H⋯O hydrogen bonds, forming two conjoined rings having R21(6) and R12(6) motifs, and is extended by N-H⋯O hydrogen bonds and C-H⋯O inter-actions into a two-dimensional sheet structure lying parallel to (001). Also present in the crystal structure are weak C-F⋯π inter-actions.

Supra-molecular hydrogen-bonding patterns in a 1:1 co-crystal of the N(7)-H tautomeric form of N6-benzoyl-adenine with 4-hy-droxy-benzoic acid.

The asymmetric unit of the title co-crystal, C12H9N5O·C7H6O3, contains one mol-ecule of N6-benzoyl-adenine (BA) and one mol-ecule of 4-hy-droxy-benzoic acid (HBA). The N6-benzoyl-adenine (BA) has an N(7)-H tautomeric form with nonprotonated N-1 and N-3 atoms. This tautomeric form is stabilized by a typical intra-molecular N-H⋯O hydrogen bond between the carbonyl (C=O) group and the N(7)-H hydrogen on the Hoogsteen face of the purine ring, forming a graph-set S(7) ring motif. The primary robust R22(8) ring motif is formed in the Watson-Crick face via N-H⋯O and O-H⋯N hydrogen bonds (involving N1, N6-H and the carboxyl group of HBA). Weak inter-actions, such as, C-H⋯π and π-π are also observed in this crystal structure.

Supra-molecular inter-actions in the 1:2 co-crystal of 4,4'-bipyridine and 3-chloro-thio-phene-2-carb-oxy-lic acid.

The asymmetric unit of the title compound, 2C5H3ClO2S·C10H8N2, is comprised of a mol-ecule of 3-chloro-thio-phene-2-carb-oxy-lic acid (3TPC) and half of a mol-ecule of 4,4'-bi-pyridine (BPY). A distinctive O-H⋯N-based synthon is present. Cl⋯Cl and π-π stacking inter-actions further stabilize the crystal structure, forming a two-dimensional network parallel to the bc plane.

Crystal structure of 4-amino-5-chloro-2,6-di-methyl-pyrimidinium thio-phene-2,5-di-carboxyl-ate.

In the title salt, C6H9ClN3 (+)·C6H3O4S(-), the cations and anions are linked via O-H⋯O and N-H⋯O hydrogen bonds, forming R 6 (6)(37) ring motifs that are inter-connected with each other, producing sheets. Separate parallel inversion-related sheets are linked through N-H⋯N and π-π stacking inter-actions [centroid-centroid distance = 3.5414 (13) Å], forming double layers parallel to (101). Weak C-H⋯O and C-H⋯S hydrogen bonds, as well as C-H⋯π inter-actions, connect the double layers into a three-dimensional network.

Supra-molecular inter-actions in a 1:1 co-crystal of acridine and 3-chloro-thio-phene-2-carb-oxy-lic acid.

In the title co-crystal, C5H3ClO2S·C13H9N, the components inter-act with each other via an O-H⋯N hydrogen bond. Acridine-acridine stacking, thio-phene-thio-phene stacking and acridine-thio-phene C-H⋯π inter-actions also occur in the crystal.

Supra-molecular architecture in a co-crystal of the N(7)-H tautomeric form of N (6)-benzoyl-adenine with adipic acid (1/0.5).

The asymmetric unit of the title co-crystal, C12H9N5O·0.5C6H10O4, consists of one mol-ecule of N (6)-benzoyl-adenine (BA) and one half-mol-ecule of adipic acid (AA), the other half being generated by inversion symmetry. The dihedral angle between the adenine and phenyl ring planes is 26.71 (7)°. The N (6)-benzoyl-adenine mol-ecule crystallizes in the N(7)-H tautomeric form with three non-protonated N atoms. This tautomeric form is stabilized by intra-molecular N-H⋯O hydrogen bonding between the carbonyl (C=O) group and the N(7)-H hydrogen atom on the Hoogsteen face of the purine ring, forming an S(7) ring motif. The two carboxyl groups of adipic acid inter-act with the Watson-Crick face of the BA mol-ecules through O-H⋯N and N-H⋯O hydrogen bonds, generating an R 2 (2)(8) ring motif. The latter units are linked by N-H⋯N hydrogen bonds, forming layers parallel to (10-5). A weak C-H⋯O hydrogen bond is also present, linking adipic acid mol-ecules in neighbouring layers, enclosing R (2) 2(10) ring motifs and forming a three-dimensional structure. C=O⋯π and C-H⋯π inter-actions are also present in the structure.

Supramolecular architectures in Co(II) and Cu(II) complexes with thiophene-2-carboxylate and 2-amino-4,6-dimethoxypyrimidine ligands.

The coordination chemistry of mixed-ligand complexes continues to be an active area of research since these compounds have a wide range of applications. Many coordination polymers and metal-organic framworks are emerging as novel functional materials. Aminopyrimidine and its derivatives are flexible ligands with versatile binding and coordination modes which have been proven to be useful in the construction of organic-inorganic hybrid materials and coordination polymers. Thiophenecarboxylic acid, its derivatives and their complexes exhibit pharmacological properties. Cobalt(II) and copper(II) complexes of thiophenecarboxylate have many biological applications, for example, as antifungal and antitumor agents. Two new cobalt(II) and copper(II) complexes incorporating thiophene-2-carboxylate (2-TPC) and 2-amino-4,6-dimethoxypyrimidine (OMP) ligands have been synthesized and characterized by X-ray diffraction studies, namely (2-amino-4,6-dimethoxypyrimidine-κN)aquachlorido(thiophene-2-carboxylato-κO)cobalt(II) monohydrate, [Co(C5H3O2S)Cl(C6H9N3O2)(H2O)]·H2O, (I), and catena-poly[copper(II)-tetrakis(µ-thiophene-2-carboxylato-κ(2)O:O')-copper(II)-(µ-2-amino-4,6-dimethoxypyrimidine-κ(2)N(1):N(3))], [Cu2(C5H3O2S)4(C6H9N3O2)]n, (II). In (I), the Co(II) ion has a distorted tetrahedral coordination environment involving one O atom from a monodentate 2-TPC ligand, one N atom from an OMP ligand, one chloride ligand and one O atom of a water molecule. An additional water molecule is present in the asymmetric unit. The amino group of the coordinated OMP molecule and the coordinated carboxylate O atom of the 2-TPC ligand form an interligand N-H...O hydrogen bond, generating an S(6) ring motif. The pyrimidine molecules also form a base pair [R2(2)(8) motif] via a pair of N-H...N hydrogen bonds. These interactions, together with O-H...O and O-H...Cl hydrogen bonds and π-π stacking interactions, generate a three-dimensional supramolecular architecture. The one-dimensional coordination polymer (II) contains the classical paddle-wheel [Cu2(CH3COO)4(H2O)2] unit, where each carboxylate group of four 2-TPC ligands bridges two square-pyramidally coordinated Cu(II) ions and the apically coordinated OMP ligands bridge the dinuclear copper units. Each dinuclear copper unit has a crystallographic inversion centre, whereas the bridging OMP ligand has crystallographic twofold symmetry. The one-dimensional polymeric chains self-assemble via N-H...O, π-π and C-H...π interactions, generating a three-dimensional supramolecular architecture.

Supramolecular hydrogen-bonding patterns in the organic-inorganic hybrid compound bis(4-amino-5-chloro-2,6-dimethylpyrimidinium) tetrathiocyanatozinc(II)-4-amino-5-chloro-2,6-dimethylpyrimidine-water (1/2/2).

Zinc thiocyanate complexes have been found to be biologically active compounds. Zinc is also an essential element for the normal function of most organisms and is the main constituent in a number of metalloenzyme proteins. Pyrimidine and aminopyrimidine derivatives are biologically very important as they are components of nucleic acids. Thiocyanate ions can bridge metal ions by employing both their N and S atoms for coordination. They can play an important role in assembling different coordination structures and yield an interesting variety of one-, two- and three-dimensional polymeric metal-thiocyanate supramolecular frameworks. The structure of a new zinc thiocyanate-aminopyrimidine organic-inorganic compound, (C6H9ClN3)2[Zn(NCS)4]·2C6H8ClN3·2H2O, is reported. The asymmetric unit consist of half a tetrathiocyanatozinc(II) dianion, an uncoordinated 4-amino-5-chloro-2,6-dimethylpyrimidinium cation, a 4-amino-5-chloro-2,6-dimethylpyrimidine molecule and a water molecule. The Zn(II) atom adopts a distorted tetrahedral coordination geometry and is coordinated by four N atoms from the thiocyanate anions. The Zn(II) atom is located on a special position (twofold axis of symmetry). The pyrimidinium cation and the pyrimidine molecule are not coordinated to the Zn(II) atom, but are hydrogen bonded to the uncoordinated water molecules and the metal-coordinated thiocyanate ligands. The pyrimidine molecules and pyrimidinium cations also form base-pair-like structures with an R2(2)(8) ring motif via N-H...N hydrogen bonds. The crystal structure is further stabilized by intermolecular N-H...O, O-H...S, N-H...S and O-H...N hydrogen bonds, by intramolecular N-H...Cl and C-H...Cl hydrogen bonds, and also by π-π stacking interactions.

Supra-molecular hydrogen-bonding patterns in the N(9)-H protonated and N(7)-H tautomeric form of an N(6) -benzoyl-adenine salt: N (6)-benzoyl-adeninium nitrate.

In the title molecular salt, C12H10N5O(+)·NO3 (-), the adenine unit has an N (9)-protonated N(7)-H tautomeric form with non-protonated N(1) and N(3) atoms. The dihedral angle between the adenine ring system and the phenyl ring is 51.10 (10)°. The typical intra-molecular N(7)-H⋯O hydrogen bond with an S(7) graph-set motif is also present. The benzoyl-adeninium cations also form base pairs through N-H⋯O and C-H⋯N hydrogen bonds involving the Watson-Crick face of the adenine ring and the C and O atoms of the benzoyl ring of an adjacent cation, forming a supra-molecular ribbon with R 2 (2)(9) rings. Benzoyl-adeninum cations are also bridged by one of the oxygen atoms of the nitrate anion, which acts as a double acceptor, forming a pair of N-H⋯O hydrogen bonds to generate a second ribbon motif. These ribbons together with π-π stacking inter-actions between the phenyl ring and the five- and six-membered adenine rings of adjacent mol-ecules generate a three-dimensional supra-molecular architecture.

Supramolecular hydrogen-bonding patterns in two cocrystals of the N(7)-H tautomeric form of N(6)-benzoyladenine: N(6)-benzoyladenine-3-hydroxypyridinium-2-carboxylate (1/1) and N(6)-benzoyladenine-DL-tartaric acid (1/1).

Two novel cocrystals of the N(7)-H tautomeric form of N(6)-benzoyladenine (BA), namely N(6)-benzoyladenine-3-hydroxypyridinium-2-carboxylate (3HPA) (1/1), C12H9N5O·C6H5NO3, (I), and N(6)-benzoyladenine-DL-tartaric acid (TA) (1/1), C12H9N5O·C4H6O6, (II), are reported. In both cocrystals, the N(6)-benzoyladenine molecule exists as the N(7)-H tautomer, and this tautomeric form is stabilized by intramolecular N-H···O hydrogen bonding between the benzoyl C=O group and the N(7)-H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson-Crick face of BA (N6-H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N-H···O and O-H···N hydrogen bonds, generating a ring-motif heterosynthon [graph set R2(2)(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N-H···O and O-H···O hydrogen bonds, generating a different heterosynthon [graph set R2(2)(4)]. Both crystal structures are further stabilized by π-π stacking interactions.

Crystal structure of 4-amino-5-fluoro-2-oxo-2,3-di-hydro-pyrimidin-1-ium 3-hy-droxy-pyridine-2-carboxyl-ate.

The asymmetric unit of the title salt, C4H5FN3O(+)·C6H4NO3 (-), contains one 4-amino-5-fluoro-2-oxo-2,3-di-hydro-pyrimidin-1-ium (5-fluoro-cytosinium, 5FC) cation and a 3-hy-droxy-picolinate (3HAP) anion. The 4-amino-5-fluoro-2-oxo-2,3-di-hydro-pyrimidine mol-ecule is protonated at one of the pyrimidine N atoms. The typical intra-molecular N-H⋯F and O-H⋯O S(5) and S(6) hydrogen-bond ring motifs are observed in the cations and anions. The protonated N atom and 2-amine group of the 5FC cation inter-act with the 3HPA anion through a pair of nearly parallel N-H⋯O hydrogen bonds, forming a robust R 2 (2)(8) ring motif. The ions are further linked by N-H⋯N, O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, generating R 2 (2)(7), R 3 (3)(12) and R 6 (5)(18) ring motifs, respectively, leading to supra-molecular wave-like sheets parallel to (010). The crystal structure is further stabilized by C-H⋯π inter-actions, generating a three-dimensional architecture.

Importance of halide involving interactions at Hoogsteen sites in supramolecular architectures of some coordination metal complexes of N(6)-benzyl/furfuryl adenine.

BACKGROUND: Most of the benzyladenine and furfuryladenine derivatives inhibit tumor/cancer cell growth; their toxicity is lesser than the compounds used for the treatment of cancer now-a-days. Many cytokinin derivatives are tested for anticancer activity. RESULTS: A series of transition metal complexes containing N(6)-benzyl/furfuryl aminopurines of formula [Mn(FAH)2(H2O)(Cl3)]2.Cl2 (1), [Co(FAH)2(H2O)(Cl3)]2.Cl2 (2), [Co(FAH)2(Cl4)]2 .[Co(FAH)2(H3O)(Cl3)].Cl2 (3), [Ni(FAH)2(H2O)(Cl3)]2.Cl2. (H2O) (4), [Zn(BAH)Br3] (5) and [Cd2(BAH)2(µ-Br)4Br2]n (6) (where BAH and FAH benzyladeninium and furfuryladeninium cations respectively) have been synthesized and characterized. Crystal structures of (1-4) have similar distorted octahedral coordination geometry, while (5) and (6) have distorted tetrahedral geometry and octahedral geometries respectively. In (1-4) two halide ions and two cytokinin cations (BAH(+)/FAH(+)) are laterally coordinated to the metal ion. A water molecule and a halide ion are axially coordinated. But the coordination sphere of (5) consists of N7 coordinated benzyladeninium ion and three halide ions. The complex (6) is a coordination polymer bridged by bromide anions. A common notable feature in (1-4) is the presence of one or more lattice chloride anions. They help in a chain formation by N-H…Cl halide involving hydrogen bonding interactions in between the Hoogsteen site hydrogen. CONCLUSIONS: The observed crystal structures emphasize the role of the halide ions in developing the supramolecular architectures by halide involving hydrogen bonding interactions. Also most of the reported cobalt cytokinin complexes possess tetrahedral coordination geometry, but some cobalt complexes have distorted octahedral coordination geometry, which are discussed and compared. Graphical AbstractSupramolecular architectures of some coordination metal complexes of N6-benzyl/furfuryl adenine.