Muhammed Ismail

Coordination behavior of chromone Schiff bases towards the [ReVO]3+ and [ReI(CO)3]+ cores

Herein, we describe the coordination behavior of chromone Schiff bases towards [ReVO]3+ and [ReI(CO)3]+. The reaction between 2-(2-thiolphenyliminomethyl)-4H-chromen-4-one (Htch) and [Re(CO)5Cl] led to fac-[Re(CO)3(bsch)Cl] (1) (bsch = 2-benzothiazole-4H-chromen-4-one). The square pyramidal [ReO(Hns)] (2) {H2ns=bis-[(2-phenylthiolate)iminomethyl]-methyl-1-(2-hydroxyphenyl)prop-2-en-1-one} and octahedral [ReO(OCH3)(PPh3)(Huch)] (3) complexes were isolated from reactions of trans-[ReVOBr3(PPh3)2] with Htch and H3uch [(5Z)-5-((4-hydroxy-2-methoxy-2H-chromen-3-yl)methyleneamino)-6-amino-1,3-dimethylpyrimidine-2,4(1H, 3H)-dione], respectively. The chromone Schiff bases and their metal complexes were fully characterized via NMR-, IR- and UV–Vis spectroscopy, single crystal XRD analysis and conductivity measurements. In addition, DFT studies were conducted to compare selected optimized and experimental parameters of the complexes.

(E)-6-Amino-1,3-dimethyl-5-[(pyridin-2-yl­methyl­idene)amino]­pyrimidine-2,4(1H,3H)-dione

In the title compound, C12H13N5O2, a Schiff-base-derived chelate ligand, the non-aromatic heterocycle and its substituents essentially occupy one common plane (r.m.s. of fitted non-H atoms = 0.0503 Å). The N=C bond is E-configured. Intracyclic angles in the pyridine moiety cover the range 117.6 (2)–124.1 (2)°. Intra- and intermolecular N—H⋯N and N—H⋯O hydrogen bonds are observed in the crystal structure, as are intra- and intermolecular C—H⋯O contacts which, in total, connect the molecules into a three-dimensional network. The shortest ring-centroid-to-ring-centroid distance of 3.5831 (14) Å is between the two different types of six-membered rings.

Oxorhenium(V) complexes with bidentate carbohydrazide Schiff bases: synthesis, characterization and DNA interaction studies

The respective coordination reactions of trans-[ReOCl3(PPh3)2] with N-[(4-oxo-4H-chromen-3-yl)methylidene]thiophene-2-carbohydrazide (Hchrtc) and N-[1,3-benzothiazol-2-ylmethylidene]thiophene-2-carbohydrazide (Hbztc) afforded two novel oxorhenium(V) complexes, cis-[ReOCl2(chrtc)(PPh3)] (1) and cis-[ReOCl2(bztc)(PPh3)] (2). These metal compounds were elucidated spectroscopically and their solid-state structures determined by single-crystal X-ray diffraction. The redox properties of the metal complexes were probed using cyclic and square wave voltammetry. The DNA interaction capabilities of 1 and 2 were gauged via UV/Vis spectroscopy DNA titrations and gel electrophoresis studies. A correlation is identified between the DNA cleavage observations and the redox potentials of the metal complexes.

N-[(E)-Thio­phen-2-yl­methyl­idene]-1,3-benzothia­zol-2-amine

In the title thiophene-derived Schiff base compound, C12H8N2S2, the thiophene ring is slighty rotated from the benzothiazole group mean plane, giving a dihedral angle of 12.87 (6)°. The largest displacement of an atom in the molecule from the nine-atom mean plane defined by the non-H atoms of the benzothiazole ring system is 0.572 (1) Å, exhibited by the C atom at the 3-position of the thiophene ring. In the crystal, weak C—H⋯S hydrogen bonds involving the thiophene group S atom and the 4-position thiophene C—H group of a symmetry-related molecule lead to an infinite one-dimensional chain colinear with the c axis. The structure is further stabilized by π–π interactions; the distance between the thiazole ring centroid and the centroid of an adjacent benzene ring is 3.686 (1) Å. The crystal studied was an inversion twin with the ratio of components 0.73 (3):0.27 (3).

6-Amino-1,3-dimethyl-5-[(E)-2-(methyl­sulfan­yl)benzyl­idene­amino]­pyrimidine-2,4(1H,3H)-dione–1,3,7,9-tetra­methyl­pyrimido[5,4-g]pteridine-2,4,6,8-tetrone (1/1)

In the title co-crystal, C12H12N6O4·C14H16N4O2S, both molecules are essentially planar [maximum deviations = 0.129 (1) and 0.097 (1) Å, respectively]. The tricyclic and Schiff base molecules are alternately stacked along the a axis and are linked by π–π interactions with centroid–centroid distances of 3.5170 (16) and 3.6576 (17) Å. An intramolecular C—H⋯O hydrogen bond and a C—H⋯S contact occur in the Schiff base molecule. In the crystal, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds lead to the formation of a three-dimensional network.

8-(2-Hy­droxy­phen­yl)-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione

The title compound, C13H12N4O3, is an imidazole derivative featuring an annealed purine ring system. The benzimidazole-inspired moiety is essentially planar (r.m.s. of all fitted non-H atoms = 0.0205 Å). An intramolecular O—H⋯N hydrogen bond occurs. In the crystal, intermolecular N—H⋯O and C—H⋯O hydrogen bonds are observed, which connect the molecules into chains along [110]. The shortest centroid–centroid distance between two aromatic systems is 3.7771 (11) Å.

2-[(E)-(6-Amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetra­hydro­pyrimidin-5-yl)imino­meth­yl]pyridinium chloride monohydrate

The title compound, C12H14N5O2 +·Cl−·H2O, is the monohydrate of the hydrochloride of an oxopurine-derived Schiff base in which protonation took place at the pyridine N atom. The organic cation is essentially planar (r.m.s. of all fitted non-H atoms = 0.0373 Å). In the crystal, N—H⋯O and N—H⋯Cl hydrogen bonds as well as C—H⋯O and C—H⋯Cl contacts connect the different entities into a three-dimensional network. The shortest centroid–centroid distance between two pyrimidine rings is 3.6364 (9) Å.

2-[(E)-(6-Amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetra-hydro-pyrimidin-5-yl)imino-meth-yl]pyridinium bromide.

The title compound, C12H14N5O2 +·Br−, is the hydrobromide salt of a Schiff base in which protonation has taken place at the pyridine N atom. This organic cation is essentially planar (r.m.s. of all fitted non-H atoms = 0.0448 Å). In the crystal, N—H⋯Br hydrogen bonds as well as C—H⋯O and C–H⋯Br interactions connect the molecules, forming a three-dimensional network.