Ibrahim Abdul Razak

The crystal structure, equilibrium and spectroscopic studies of bis(dialkyldithiocarbamate) copper(II) complexes [Cu2(R2dtc)4] (dtc=dithiocarbamate)

Abstract Four copper(II) complexes of bis(dialkyldithiocarbamate) [Cd(R2dtc)2] (R=Me, Et, Pr, i-Pr; dtc=dithiocarbamate) have been prepared and characterized by elemental analysis, IR and ESR spectra studies. Their equilibrium constants (K), determined by a UV–vis spectrometry in EtOH, were influenced by the alkyl groups in the following order: i-Pr>n-Pr≈Et>Me. The single crystal structures of complex [Cu2(R2dtc)4] have been determined using X-ray diffraction methods. The compounds [Cu2(Et2dtc)4] and [Cu2(Pr2dtc)4] are built of centrosymmetric neutral dimeric [Cu2(R2dtc)4] entities. The copper atom lies in a distorted square–pyramidal environment. The four equatorial donors are two bidentate chelate sulfur atoms from two dtc ligands. One of the sulfur atoms from the third dtc ligand acts as a bridging ligand occupying the apical position of the symmetry-related copper atom in the dimer structure, which is viewed as two edge-sharing distorted square–pyramids. The structure of [Cu2(i-Pr2dtc)4] is square planar with an exactly planar CuS4 unit and nearly planar NCS2 moieties. The Cu–S distances shows small decreases along the series n-Pr>Et>i-Pr, the biggest change being for the diisopropyl complex. The alkyl substituents at the nitrogen atom affect their coordination number and Cu⋯Cu distance. In the solid, [Cu2(n-Pr2dtc)4] has the shortest Cu⋯Cu distance and [Cu(i-Pr2dtc)2] has the longest one.

Sb-C Bond Cleavage Reaction on a Triruthenium Cluster and the Formation of a Bridging Phenylacyl Unit

Syntheses and single crystal X-ray structures of an open triruthenium acyl carbonyl cluster [(C6H5)2SbRu3(COC6H5)(CO)10] (1) and a simple triruthenium Ru3(CO)9[(C6H5)2PCH2P(C6H5)2]Sb(C6H5)3(2) are reported. Formation of compound (1) at room temperature from [Ru3(CO)12] and [Sb(C6H5)3] is unique, a similar reaction with Ru3(CO)10[(C6H5)2PCH2P(C6H5)2] under identical conditions results in compound (2), with Sb(C6H5)3 occupying an equatorial site. IR, 1H, 13C NMR spectra of the compounds are reported. The X-ray crystal structure of (1) consist of 2 crystallography distinct molecules and shows Ru–Sb distances in the range: 2.6361(6)–2.6273(7) Å and Ru–Ru distances in the range: 2.8236(7)–2.9855(7) Å. Ru–O distances in the bridging carbonyl are: 2.137(4), 2.158(4) Å. The Sb–Ru–Ru angles in the two molecules of the asymmetric unit are in the range of 73.78(2)–77.52° indicating the puckered nature. Compound (2) has bond parameters comparable to those of Ru3(CO)10[(C6H5)2PCH2P(C6H5)2]. The present study shows for the first time that the cleaving of Sb–C bond at room temperature is possible under non-ionic conditions, though there have been many instances of P–C and As–C bond cleavages reported previously.

Copper(I)–azoimidazoles: a comparative account on the structure and electronic properties of copper(I) complexes of 1-methyl-2-(phenylazo)imidazole and 1-alkyl-2-(naphthyl-(α/β)-azo)imidazoles

Abstract Bis-[1-alkyl-2-(naphthyl-(α/β)azo)imidazole]copper(I) perchlorate derivatives, [Cu(α-NaiR)2(ClO4)] and Cu(β-NaiR)2](ClO4), have been characterised by spectral and electrochemical studies. The single crystal X-ray structure of bis-[1-ethyl-2-(naphthyl-α-azo)imidazole]copper(I) perchlorate shows strong bonding with two imidazole-N atoms, two azo-N donors interact weakly and the structure is described as having a [2+2] distorted linear geometry. A structural comparison has been done with the X-ray structure of bis-[1-methyl-2-(phenylazo)imidazole]copper(I) perchlorate which is Td symmetric. Solution electronic spectra and redox properties are compared and have been correlated with EHMO calculation.

Synthesis, spectral studies and structure of 2-hydroxyacetophenone nicotinic acid hydrazone

Abstract 2-Hydroxyacetophenone nicotinic acid hydrazone (H2ApNH) was synthesized as a part of our work, in search for non-linear optical crystal based on hydrazones, and studied spectroscopically. Complete NMR assignments for the hydrazone was made using COSY homonuclear and HMQC heteronuclear correlation techniques. Solid state reflectance was also studied in order to understand the electronic structure of the synthesized compound. The crystal and molecular structures of H2ApNH were determined. The compound crystallizes into an orthorhombic lattice with a non-centrosymmetric space group Pca21 with two crystallographically unique molecules of in an asymmetric unit. The geometry reveals quasi co planarity in the whole molecular skeleton with localization of the double bonds in the CN–N–CO with an E-configuration.

A facile chemo-, regio- and stereoselective synthesis and cholinesterase inhibitory activity of spirooxindole-pyrrolizine-piperidine hybrids.

A series of novel hybrid spiro heterocycles comprising pyrrolizine, spiroxindole and piperidine moieties was synthesized chemo-, regio- and stereoselectively in good yields from 1,3-dipolar cycloaddition reaction of a series of 1-acryloyl-3,5-bisarylmethylidenepiperidin-4-ones with azomethine ylides generated in situ from 5-choloroisatin and l-proline in methanol. These cycloadducts displayed significant cholinesterase inhibitory activity. Among the compounds screened, 8g and 8e, showed maximum inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinestrase (BChE) with IC50 values of 3.33 and 3.13μM, respectively.

Recognition of Dicarboxylic Acid by 6,6′-Dipivaloylamino-3,3′-bipyridine and the Supramolecular Solid State Locking of the Carboxyls in the anti Form

A new crystal-engineering motif has been developed where a ditopic receptor 1 having anti binding hindered pyridine pivaloylamide groups instead of normally used acetylamino groups shows a novel anti–anti hydrogen bonded polymeric supramolecular complex giving rise to hydrogen bonded stair like polymeric ribbon structure between the receptor pyridine amides and the carboxyl groups of the guest substrate (1,4-phenylenediacetic acid).

Coordination of Deprotonated Saccharin in Copper(II) Complexes. Structural Role of the Saccharinate Directed by the Ancillary N-heterocyclic Ligands

Four different coordination patterns were observed following the partial or complete thermodynamically-controlled ligand substitution of the hydrated tetraaquabis(o-sulfobenzimidato-N)copper(II) complex with heterocyclic bases as examined by X-ray diffraction. The N-heterocycle directs the o-sulfobenzimidate (saccharinate) anion into the immediate coordination polyhedron of the metal by any of the imido, carbonyl or sulfonyl functionalities, or as a lattice counter-ion in the crystal lattice. Aqua(o-sulfobenzimidato-O)tetrakis(4-methylpyridine)copper(II) o-sulfobenzimidate hemihydrate (1) crystallizes in the monoclinic space group P21/n [a = 14.7858(2), b = 16.9090(1), c = 26.2350(2)A; β = 92.861(1)°], aquadi(o-sulfobenzimidato-N)bis(4-propylpyridine)copper(II) (2) in the tetragonal space group P42/n [a = 15.4127(1), c = 13.4604(1)A], diaquatetrakis(3-(2-propenyl)imidazole)copper(II) di-o-sulfobenzimidate (3b) in the monoclinic space group P21/c [a = 9.3959(5), b = 28.029(2), c = 8.8763(3)A; β = 111.175(1)°] and di(o-sulfobenzimidato)tetra(isoquinoline)copper(II) (4b) in the orthorhombic space group Pna21 [a = 23.2132(6), b = 11.5760(2), c = 17.6297(4)A]. The copper atom in 1 is six-coordinate in a distorted trans-N4O2Cu octahedron with elongated copper—oxygen bonds [Cu—Owater = 2.462(3), Cu—Osulfonyl = 2.567(3)A]. This adduct represents the first example of a combined Osulfonyl/ionic coordination of the o-sulfobenzimidate ion in the same crystal. The copper atom in 2 is five-coordinate in the form of a N4OCu square pyramid [Cu—Owater = 2.238(5)A]. In 3, the o-sulfobenzimidate anions are linked to the copper atom through the coordinated water molecule forming a distorted octahedral N4O2Cu environment. In 4, the copper atom is nearly octahedrally coordinated by four nitrogen atoms and a pair of o-sulfobenzimidate carbonyl oxygen atoms. The structural details of the o-sulfobenzimidate coordination pattern correspond well with the 298 and 77 K FT IR spectra of the adducts. The structures of two other solid adducts, tris(3-(2-propenyl)imidazole)copper(II) di-o-sulfobenzimidate trihydrate (3a) and diaquabis(o-sulfobenzimidato-N)bis(isoquinoline)copper(II) (4a) have been predicted by their spectral features. Alteration of the o-sulfobenzimidate coordination mode upon changing the heterocycle ligand shows that this moiety is as a convenient polyfunctional structural tool for the construction of functional solids. Koordination von deprotoniertem Saccharin in Kupfer(II)-Komplexen. Die strukturelle Rolle des durch N-heterocyclische Liganden gelenkten Saccharinat Vier verschiedene Koordinationsmuster wurden durch teilweise oder vollstandig thermodynamisch kontrollierte Ligandensubstitution des hydratisierten Tetraaquobis(o-sulfobenzimidato-N)-kupfer(II)-Komplexes mit Heterocyclenbasen erhalten und durch Rontgenbeugung untersucht. Die N-Heterocyclen lenken das o-Sulfobenzimidat (Saccharinat) entweder uber seine Imido-, Carbonyl- oder Sulfonylgruppe unmittelbar in das Koordinationspolyeder des Metalls oder als Gegenion in das Kristallgitter. Das Halbhydrat des Aquo(o-sulfobenzimidato-O)tetrakis(4-methylpyridin)kupfer(II)-o-sulfobenzimidats (1) kristallisiert in der monoklinen Raumgruppe P21/n [a = 14.7858(2), b = 16.9090(1), c = 26.2350(2) A; β = 92.861(1)°], Aquodi(o-sulfobenzimidato-N)bis(4-propylpyridin)kupfer(II) (2) in der tetragonalen Raumgruppe P42/n [a = 15.4127(1), c = 13.4604(1) A], Diaquotetrakis(3-(2-propenyl)imidazol)kupfer(II) di-o-sulfobenzimidat (3b) in der monoklinen Raumgruppe P21/c [a = 9.3959(5), b = 28.029(2), c = 8.8763(3) A; β = 111.175(1)°] und Di(o-sulfobenzimidato)tetra(isoquinolin)kupfer(II) (4b) in der orthorhombischen Raumgruppe Pna21 [a = 23.2132(6), b = 11.5760(2), c = 17.6297(4) A]. Das Kupferatom in 1 ist in Form eines trans-N4O2Cu-Oktaeders mit verlangerten Kupfer-Sauerstoffbindungen [Cu—OWasser = 2.462(3), Cu—OSulfonyl = 2.567(3) A] sechsfach koordiniert. Dieses Addukt reprasentiert das erste Beispiel eines Komplexes, in dem der o-Sulfobenzimidat-Ligand in einem einzigen Kristall einmal als Ion und ein weiteres Mal uber die Sulfonylgruppe gebunden ist. Das Kupferatom in 2 ist funffach in Form einer quadratischen N4OCu-Pyramide [Cu—OWasser = 2.238(5) A] koordiniert. In 3 sind die o-Sulfobenzimidat-Anionen uber koordinierende Wassermolekule an das in einer oktraedrischen N4O2Cu-Umgebung befindliche Kupferatom gebunden. In 4 ist das Kupferatomoktaedrisch durch vier Stickstoffatome und die Sauerstoffatome der Carbonylgruppen von zwei o-Sulfobenzimidat-Ionen koordiniert. Die strukturellen Details der o-Sulfobenzimidat-Koordinationsmuster stimmen gut mit den bei 298 und 77 K aufgenommenen FT IR-Spektren uberein. Anhand ihrer spektralen Eigenschaften wurden die Strukturen von zwei weiteren Addukten, namlich Tris(3-(2-propenyl)imidazol)kupfer(II)-di-o-sulfobenzimidat trihydrat (3a) und Diaquobis(o-sulfobenzimidato-N)bis(isoquinolin)kupfer(II) (4a) vorhergesagt. Die λnderung des Koordinationsverhaltens der Sulfobenzimidat-Einheit unter Austausch durch Heterocyclen zeigt, das diese Einheit ein geeignetes Werkzeug fur die Konstruktion funktioneller Festkorper ist.

Synthesis, molecular structure and fluorescence of an organic-inorganic hybrid complex [Eu(NO3)6][(Hphen)6(NO3)2]NO3 (phen=1,10-phenanthroline)

Abstract A new europium (III) complex, [Eu(NO3)6]{[(Hphen)6·2NO3]·NO3} (1) was prepared and structurally characterized in which Eu3+ is 12-coordinated to six bidentate nitrates. The coordination polyhedron around Eu3+ was described as a slightly distorted icosahedron. The six mono-protonated 1,10-phenanthrolines do not coordinate to the Eu3+ directively due to the formation of hydrogen bonds in form of O⋯H–N with two nitrates and also the formation of two face-to-face trigonal plates within which one free nitrate is sandwiched. 1 exhibits strong red and blue fluorescence when it was irradiated by UV light.

2-Aminopyrimidine-fumaric acid cocrystal

In crystals of the title compound, 2-aminopyrimidin-1-ium hemifumarate hemifumaric acid, C 4 H 6 N 3 + -0.5C 4 H 2 O 4 2- .0.5C 4 H 4 O 4 , the asymmetric unit contains one 2-aminopyrimidine cation, C 4 H 6 N 3 + , protonated at a pyrimidine ring-N atom, one half-molecule of fumaric acid, C 4 H 4 O 4 , and one half of a fumarate ion, C 4 H 2 O 4 2- . These are linked by N-H...O, O-H...O and relatively strong C-H...O bonds, resulting in eight- and nine-membered hydrogen-bonded rings and an extended supramolecular structure.

A new chalcone structure of (E)-1-(4-Bromophenyl)-3-(napthalen-2-yl)prop-2-en-1-one: Synthesis, structural characterizations, quantum chemical investigations and biological evaluations.

The structure of (E)-1-(4-Bromophenyl)-3-(napthalen-2-yl)prop-2-en-1-one (C19H13BrO) crystallized in the triclinic system of P-1 space group. The unit cell dimensions are: a=5.8944 (9)Å, b=7.8190 (12)Å, c=16.320 (2)Å, α=102.4364 (19)°, β=95.943 (2)°, γ=96.274 (2)° and Z=2. The physical properties of this compound was determined by the spectroscopic methods (FTIR and (1)H and (13)C NMR). Quantum chemical investigations have been employed to investigate the structural and spectral properties. The molecular structure, vibrational assignments, (1)H and (13)C NMR chemical shift values, non-linear optical (NLO) effect, HOMO-LUMO analysis and natural bonding orbital (NBO) analysis were calculated using HF and DFT/B3LYP methods with 6-311++G(d,p) basis set in the ground state. The results show that the theoretical calculation of the geometrical parameters, vibrational frequencies and chemical shifts are comparable with the experimental data. The crystal structure is influenced and stabilized by weak C-H⋯π interactions connecting the molecules into infinite supramolecular one dimensional ladder-like arrangement. Additionally, this compound is evaluated for their antibacterial activities against gram positive and gram negative strains using a micro dilution procedure and shows activities against a panel of microorganisms.