Ömer Çelik

Syntheses, structural characterization and biological activities of spiro-ansa-spiro-cyclotriphosphazenes

The replacement reactions of the Cl-atoms in partly substituted spiro-ansa-spiro-cyclotriphosphazenes (7 and 8) with excess pyrrolidine, 4-(2-aminoethyl)morpholine, and 1,4-dioxa-8-azaspiro[4,5]decane in dry THF led to the formation of heterocyclic amine substituted cyclotriphosphazenes (9a–c and 10a–c). All cyclotriphosphazene derivatives were characterized by elemental analysis, FTIR, MS, 1D 1H, 13C and 31P NMR and 2D HSQC, and HMBC techniques, and the crystal structure of partly substituted cyclotriphosphazene 8 was verified by X-ray diffraction analysis. Cyclotriphosphazene derivatives (5–8, 9a–c, and 10a–c) were subjected to antimicrobial activity against seven clinic bacteria and one yeast strain, and the interactions of the phosphazenes with plasmid pBR322 DNA were investigated. Phosphazene derivatives [(5, 7, 8, 9b and 9c) and (10a and 10b)] caused a slight increase and substantial decrease in the mobility of form I DNA, respectively, while 9a caused retardation on gel. Cytotoxic, apoptotic and necrotic effects against L929 fibroblast and A549 lung cancer cells were also evaluated. While the highest toxic effect was obtained for 9a in L929 fibroblast cells and for 9c in A549 lung cancer cells at 100 μg mL−1 concentration, the highest apoptotic effect was determined for 10a in L929 fibroblast cells and for 9a in A549 lung cancer cells at the same concentration. It was found that 9a and 10b exhibited the most necrotic effects against L929 fibroblast and A549 lung cancer cells, respectively. The toxic and necrotic effects of the phosphazenes against A549 lung cancer cells were greater than those against L929 fibroblast cells, whereas, the apoptotic effect of the compounds was greater in L929 fibroblast cells than in A549 lung cancer cells.

Chemical fixation of CO2 into cyclic carbonates by azo-containing Schiff base metal complexes

Two new ligands containing a –NN– group, 4-((E)-(4-bromophenyl)diazenyl)-2-((E)-(phenylimino)methyl)phenol (L1H, 2), 4-((E)-(4-bromophenyl)diazenyl)-2-((E)-((4-ethylphenyl)imino)methyl)phenol (L2H, 3) and their metal complexes were synthesized. The synthesized metal complexes were used as catalysts for the chemical fixation of CO2 into cyclic carbonates using epoxides which were used as both substrate and solvent. According to analytical, UV-visible and IR data, the metal complexes are formed by coordination of the N and O atoms of the ligands and the metal : ligand ratio was found to be 1 : 2 for all the complexes. The TG and DTA results showed that these complexes had good thermal stability. The molecular structures of ligand 2 (L1H) and its ZnII complex 4 (Zn(L1)2) were determined by single crystal X-ray diffraction studies. After choosing the most active catalyst (Zn(L1)2, 4), optimization studies were performed by changing various parameters. Ionic liquids have been found to have a positive effect and showed the most active performance with (bmim)PF6 + Zn(L1)2 (4) as a binary catalytic system.

Synthesis of Lead(II) Minoxidil Coordination Polymer: A New Precursor for Lead(II) Oxide and Lead(II) Hydroxyl Bromide

A new lead(II) coordination polymer, [PbBr2(C9H15N5O)]n (1), where C9H15N5O is (2,4-diamino-6-piperidine-1-yl) pyrimidine N-oxide (minoxidil) is synthesized and characterized. Polymer 1 is synthesized in methanol by sonochemical and hydrothermal methods from lead(II) acetate, KBr and the minoxidil ligand. The crystal structure of [PbBr2(C9H15N5O)]n indicates a syndiotactic coordination polymer. The Pb(II) atom lies on a mirror plane; the mirror plane is perpendicular to the pyrimidine ring bisecting the piperidine ring. N–H···O intramolecular and C–H···Br, N–H···N strong intermolecular interactions were observed. Micro-rods of PbO and nano-plates of PbOHBr were prepared by thermal decomposition of the nano-structured [PbBr2(C9H15N5O)]n as a precursor. Characterization of the products was carried out using X-ray crystallography, elemental analysis, FTIR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis and thermal analysis. The sonochemical method resulted in a significant reduction of reaction time, reaction temperature and particle sizes of the products.

Di­bromo­bis­(phthalazine‐κN2)­zinc(II)

In the title compound, [ZnBr2(C8H6N2)2], the Zn atom is coordinated by two Br atoms and two N atoms of two different phthalazine ligands in a distorted tetrahedral arrangement. The central bond angles, N—Zn—N and Br—Zn—Br, are 105.6 (2) and 115.59 (5)°, respectively.

Ring-expanded iridium and rhodium N-heterocyclic carbene complexes: a comparative DFT study of heterocycle ring size and metal center diversity

Abstract A new series of ring-expanded six- and seven-membered N-heterocyclic carbene precursors (re-NHCs) and their transition metal complexes were synthesized. The basic properties of the synthesized materials were investigated by density functional theory (DFT). The six- and seven-membered re-NHCs were synthesized in good yield via reaction of the corresponding alkyldibromides or alkyldiiodides with N,N′-bis-(2-phenylbenzene)formamidine in the presence of K2CO3 under aerobic conditions. Complexes, represented by the formula [ML1,2(COD)Cl] (where M = Ir or Rh and L is a ring-expanded N-heterocyclic carbene ligand), were synthesized in the presence of the corresponding free carbene and iridium or rhodium metal precursors in tetrahydrofuran. All new re-NHC complexes were characterized by different analytical techniques, including NMR spectroscopy, X-ray diffraction, UV spectroscopy and elemental analysis. According to molecular electrostatic potential calculations, the electrophilic properties of the complexes were aligned, from highest to lowest, as Ir-6-DiPh, Rh-6-DiPh and Ir-7-DiPh. The HOMO, LUMO and energy gaps of the complexes were calculated by DFT. On the basis of the DFT analysis, it can be predicted that Rh-6-DiPh is the most stable complex and Ir-7-DiPh is more reactive than Ir-6-DiPh.

Synthesis, characterization, crystal structure, and antimicrobial studies of novel thiourea derivative ligands and their platinum complexes

Abstract N,N-Di-R-N′-(4-chlorobenzoyl)thiourea (Di-R: diethyl, di-n-propyl, di-n-butyl and diphenyl) ligands (HL1–4) and their Pt(II) complexes (cis-[Pt(L1–4-S,O)2]) have been synthesized and structurally characterized by elemental analyses, FT-IR and NMR spectroscopy. HL2 ligand and cis-[Pt(L4-S,O)2] metal complex have been also characterized by a single-crystal X-ray diffraction study. HL2, C14H19ClN2OS, crystallizes in the monoclinic space group P21/n (no. 14), with Z = 4, and unit cell parameters, a = 11.1405(16) Å, b = 9.7015(12) Å, c = 14.790(2) Å, β = 106.547(7)°. The cis-[Pt(L4-S,O)2], C40H28Cl2N4O2PtS2: triclinic, space group P-1 (no. 2), a = 8.9919(3) Å, b = 14.7159(6) Å, c = 15.7954(6) Å, α = 113.9317(18)°, β = 97.4490(18)°, and γ = 105.0492(16)°. Single crystal analysis of complex, cis-[Pt(L1–4-S,O)2], revealed that a square planar coordination geometry is formed around the platinum atom by two sulfur and two oxygen atoms of the related ligands, which are in a cis configuration. In addition, the thiourea derivative ligands and their complexes were evaluated for both their in-vitro antibacterial and antifungal activity. The results have been reported, explained, and compared with fluconazole and ampicillin, used as reference drugs.

Crystal structure of 2-[4-(4-chloro­phen­yl)-1-(4-meth­oxy­phen­yl)-2-oxoazetidin-3-yl]benzo[de]iso­quinoline-1,3-dione dimethyl sulfoxide monosolvate

In the title solvated compound, C28H19N2O4·C2H6OS, the central β-lactam ring is almost planar (r.m.s. deviation = 0.002 Å). It makes dihedral angles of 1.92 (11), 83.23 (12) and 74.90 (10)° with the methoxy- and chlorophenyl rings and the ring plane of the 1H-benzo[de]isoquinoline-1,3(2H)-dione group [maximum deviation = 0.089 (1)], respectively. An intramolecular C—H⋯O hydrogen bond closes an S(6) ring and helps to establish the near coplanarity of the β-lactam and methoxybenzene rings. In the crystal, the components are linked by C—H⋯O hydrogen bonds, C—H⋯π interactions and aromatic π–π stacking interactions [centroid-to-centroid distances = 3.6166 (10) and 3.7159 (10) Å], resulting in a three-dimensional network, The dimethyl sulfoxide solvent molecule is disordered over two sets of sites in a 0.847 (2):0.153 (2) ratio.

2,4-Di-tert-butyl-6-[(2,5-difluorophenyl)iminomethyl]phenol

In the title Schiff base, C21H25F2NO, the dihedral angle between the aromatic rings is 27.90(5)° and an intramolecular O—H⋯N hydrogen bond occurs. In the crystal, the molecules are linked by C—H⋯O, C—H⋯N and C—H⋯F interactions.

Crystal structure of 2-[(3S,4S)-4-(anthracen-9-yl)-1-(4-meth-oxy-phen-yl)-2-oxoazetidin-3-yl]-2-aza-2H-phenalene-1,3-dione unknown solvate.

The central β-lactam ring of the title compound, C36H24N2O4, is almost planar (r.m.s. deviation = 0.003 Å) and makes dihedral angles of 17.17 (19), 89.76 (17) and 78.44 (17)° with the benzene ring, the anthracene ring (r.m.s. deviation = 0.003 Å) and the 1H-benzo[de]isoquinoline-1,3(2H)-dione moiety, which is nearly planar [maximum deviation = 0.098 (2) Å], respectively. The molecular structure is stabilized by an intramolecular C—H⋯N hydrogen bond. In the crystal, molecules are linked via C—H⋯π and π–π stacking interactions [centroid–centroid distances = 3.5270 (19) and 3.779 (2) Å], forming a three-dimensional structure. A region of disordered electron density, probably disordered solvent molecules, was treated with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9–18], which indicated a solvent cavity of 322 Å3 containing approximately 91 electrons. Their formula mass and unit-cell characteristics were not taken into account during the refinement.

Synthesis and X-ray crystal structures of three new terpyridine-based Pb(II) complexes, cytotoxicity studies of {[Pb(ttpy)(μ-AcO)]2}(SCN)2

Synthesis and X-ray crystal structures of three new terpyridine-based Pb(II) complexes, {[Pb(ttpy)(μ-AcO)]2}(SCN)2 (1) (ttpy = 4′-tolyl-2,2′:6′,2″-terpyridine), [Pb(Clphtpy)(AcO)(ClO4)] (2), and [Pb(Clphtpy)(SCN)2] (3) (Clphtpy = 4′-(4-chlorophenyl)-2,2′:6′,2″-terpyridine), are described. The synthesized materials have been characterized, also, by CHN elemental analysis, 1H NMR, and IR spectroscopy. The structural analyses showed that, in the solid state, the coordination number of Pb(II) in 1, 2, and 3 are six, seven, and five, respectively. In the complexes, the lone-pair electrons of Pb(II) are stereochemically active and the coordination geometry of Pb(II) is hemidirected. The structures of the three complexes were compared and the effect of counter ion is described. The antibacterial activity of 1 and previously reported {[Pb(ttpy)(μ-AcO)]2}(PF6)2 (1A) and {[Pb(ttpy)(μ-AcO)I]2} (1B) were tested by minimum inhibitory concentration method to investigate the effect of counter ions on biological activity of the compounds. Also, cytotoxicity test was assessed using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay to determine the maximum non-toxic concentration of ttpy, Pb(II), and their complexes to HepG2 cells. Effective lead detoxification was observed for 1, 1A, and 1B. Graphical Abstract