Karna Wijaya

DNA binding of iron(II) complexes with 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline: salt effect, ligand substituent effect, base pair specificity and binding strength

The DNA binding of iron(II) mixed-ligand complexes containing 1,10-phenanthroline(phen) and 4,7-diphenyl-1,10-phenanthroline(dip), [Fe(phen)(3)](2+), [Fe(phen)(2)(dip)](2+) and [Fe(phen)(dip)(2)](2+) has been characterized by spectrophotometric titration and melting temperature measurements. The salt concentration dependence of the binding constant has allowed us to dissect the DNA-binding constant and free energy change of each iron(II) complex into the nonelectrostatic and polyelectrolyte contributions. A comparison of the nonelectrostatic components in the binding free energy changes among iron(II) complexes has made it possible to rigorously evaluate the contribution of the ligand substituents to the DNA-binding event. The peripheral substitution of phen by two phenyl groups increases the nonelectrostatic binding constant of the iron(II) complex more than 20 times, which is equivalent to approximately 7.5 kJ mol(-1) of more favorable contribution to the DNA binding. In general, the iron(II) complexes studied have higher affinity towards the more facile A-T sequence than the G-C sequence. This preferential binding may be attributed to the steric effect induced by the ancillary part of the ligands in the course of DNA binding. The binding of disubstituted iron(II) complex to DNA is quite strong as reflected in the modest increase in the denaturation temperature (T(m)) of double helical DNA upon the interaction with the iron(II) complex.

Polysulfonylamines. CI. 1,4,7,10-Tetraoxacyclododecane–Di(benzenesulfonyl)amine (1/2)

In the centrosymmetric formula unit of the title complex, C 8 H 16 O 4 .2C 12 H 11 NO 4 S 2 , the disulfonylamine molecules are linked to 12-crown-4 via a slightly bent N-H...O hydrogen bond [N…O 2.771(2)A]. The macrocycle adopts the [66] conformation and the (PhSO 2 ) 2 NH molecules have an open pseudo-C2 symmetric conformation with the phenyl groups lying on opposite sides of the S-N-S plane.

Polysulfonylamine, XCVI [1]. Homokonjugate aus Di(organosulfonyl)aminen und ihren konjugierten Anionen: Vier Kristallstrukturen mit asymmetrischen [N -H ··· N ]--Wasserstoffbrücken / Polysulfonylamines, XCVI [1]. Homoconjugates Formed from Di(organosulfonyl)amines and their Conjugate Anions: Four Crystal Structures Featuring A symmetric [ N - H ··· N ]- Hydrogen Bonds

The following compounds were prepared by cocrystallization of their components from MeOH or MeCN and structurally characterized by low-temperature X-ray diffraction: Na[N(SO2Me)2]·HN(SO2Me)2·2 (12-crown-4) (2, orthorhombic, space group Pna21). Na[N(SO2Me)·HN(SO2Me)·(15-crown-5) (3, monoclinic. P21/n), Na[N(SO2Ph)2] · HN(SO2Ph)2 · 2 (12-crown-4) (4. monoclinic. P21). (MeNH)2COHN(SO2Ph)2·0.5 MeCN (5, monoclinic. P21/n). The four structures exhibit [(RSO2)2N-H ··· N(SO2R)2]- anions as rare examples of intermolecular [N-H ···N]- homo- conjugates. The N ··· N distances of the asymmetric hydrogen bonds are. in order. 266.9(6). 276.0(3). 291.3(4) and 279.4(2) pm. the corresponding N-H···N angles amounting to 137(10), 176(3), 177(4) and 177(2)°. The asymmetry of the hydrogen bonds is clearly reflected in the geometry of the NS2 groups (amine moieties: N-S 162.3-165.2 pm. S-N-S 124.5-127.1°; amide moieties: N-S 159.7-161.8 pm. S-N-S 119.1-122.6°). The dihedral angles formed by the NS2 planes vary from 51.8° in 4 to 87.6° in 5. The crystal lattices of 2 and 4 consist of discrete ions, sandwich-type [Na(12-crown-4)2]+ complexes acting as the counter-ions. In 3. Na+ is coordinated in an out-of-cavity pattern by the five polyether oxygen atoms and further accepts two Na-O bonds from the amide moiety of the complex anion [Na-O(crown) 241.5(2)-249.9(2), Na-O(anion) 235.0(2) and 263.9(2) pm]. Thе surprising structure of 5 contains homoconjugated 1.3-dimethylurea cations [(MeNH)2C-O-H ··· O=C(NHMe)2]+, which are formed via a very strong asymmetric [O-H ···O]+ hydrogen bond [О···О 247.7(2) pm. O-H ··· O 172(3)°] and are associated with the amide moieties of the anions through a set of N-H···О bonds to form infinite chains: the MeCN molecules occupy lattice cavities.

Polysulfonylamines. CX. Hydroxylammonium di(methanesulfonyl)amidate 1,4,7,10,13,16-hexaoxacyclooctadecane (1/1/1) and 2-aminopyridinium di(methanesulfonyl)amidate 1,4,7,10,13,16-hexaoxacyclooctadecane (1/1/1)

In the formula unit of hydroxylammonium di(methane-sulfonyl)amidate 1,4,7,10,13,16-hexaoxacyclooctadecane (1/1/1), H 3 NOH + .C 2 H 6 NO 4 S 2 - .C 12 H 24 O 6 , the 1,4,7,10,13,16-hexaoxacyclooctadecane ring adopts a pseudo-D 3d conformation. The hydroxylammonium cation forms an O-H...N - hydrogen bond to the anion [O…N 2.677(2) A and O-H…N 171 (3)°] and three well defined N + -H...O bonds to alternate polyether O atoms. The ammonium N atom is displaced by 0.981 (2) A from the best O 6 plane of the crown, in contrast to the analogous perchlorate hemihydrate [True-blood, Knobler, Lawrence & Stevens (1982). J. Am. Chem. Soc. 104, 1355-1362], where the corresponding distance is only 0.68 A and the H atoms of the NH 3 + group were found to be disordered (at 115 K). In the formula unit of 2-aminopyridinium di(methanesulfonyl)-amidate 1,4,7,10,13,16-hexaoxacyclooctadecane (1/1/1), C 5 H 7 N 2 + .C 2 H 6 NO 4 S 2 - .C 12 H 24 O 6 , the 18-crown-6 ring also adopts a pseudo-D 3d conformation. The pyridinium donor of the cation forms a markedly bent N.H...O hydrogen bond to the anion [N…O 2.868 (2) A and N-H...O 150 (2)°], whereas the exocyclic NH 2 group is connected to opposite pairs of crown O atoms via two three-centre N-H(...O) 2 interactions. The amino N atom is displaced by 1.531 (2) A from the best O 6 plane of the crown.

1,4,7,10-Tetraoxacyclododecane-acetone thiosemicarbazone (1/2)

In the centrosymmetric formula unit of the title complex, C 8 H 16 O 4 .2C 4 H 9 N 3 S, the 1,4,7,10-tetraoxacyclododecane molecule adopts the biangular [66] conformation and the thiosemicarbazone molecules are linked to the macrocycle via a long and appreciably bent N-N-H...O hydrogen bond [N...O 2.992 (2) A and N-H...O 158 (2)°]. These units are associated into sheets by two additional hydrogen bonds, N-H...O and N-H...S, originating from the NH2 group and utilizing the thioureido S atom or the second crystallographically independent ether O atom as acceptors.

Polysulfonylamine, XCVII [1] Di(organosulfonyl)amine und ihre konjugierten Anionen als simultane Baugruppen in zwei supramolekularen Strukturen / Polysulfonylamines, XCVII [1] Di(organosulfonyl)amines and their Conjugate Anions as Simultaneous Building Blocks in Two Supramolecular Structures

The complex compounds 4HN (SO2Me)2 · (diaza-18-crown-6) (1) and Na[N(SO2Ph)2] · 2HN(SO2Ph)2 · 2 (12-crown-4) · 2 MeOH (2) were obtained from their components and characterized by low-temperature X-ray diffraction. Structure 1 (monoclinic, space group P21/n) displays centrosymmetric formula units consisting of a biangular diazonia-18-crown-6 dication, two (MeSO2)2N− anions situated above and below the macrocycle and linked to the NH2+ groups via an N - H ··· O and N -H ··· N bond system, and finally two HN(SO2Me)2 molecules, each forming an N -H ··· O bond to one of the anions. The molecule-anion entity represents an iso form of the [(RSO2)2N -H ··· N (SO2R)2]− homoconjugates previously described. The crystal packing of 1 is stabilized by an extensive and highly organized [H2C -H ··· O(S)] hydrogen bond network. Structure 2 (monoclinic, space group P21/n) exhibits inconspicuous [Na(12-crown-4)2]+ cations and, as a striking feature, supramolecular anions assembled from a central (PhSO2)2N− ion, two MeOH molecules flanking the amide anion, and two HN (SO2Ph)2 molecules bonded to the MeOH moieties. The assembly is held together by two N -H ··· O(H )(Me) bonds, one MeO -H ··· N− bond and one MeO -H ··· O(anion) interaction. For both structures, conformational peculiarities of the N(SO2C)2 groups are discussed.

DNA-Binding Properties of Iron(II) Mixed-Ligand Complexes Containing 1,10-Phenanthroline and Dipyrido(3,2-a:2',3'-c)phenazine

An iron(II) mixed-ligand complex with 1,10-phenanthroline (phen) and dipyrido[3,2-a:2’,3’- c]phenazine (dppz), [Fe(phen)2(dppz)]2+, has been synthesized. The DNA-binding properties of the mixed-ligand complex have been studied in terms of equilibrium binding constant, thermodynamic parameter, thermal denaturation as well as Pfeiffer effect upon binding to DNA. The spectrophotometric titration of [Fe(phen)2(dppz)]2+ with calf thymus DNA (ct-DNA) has shown that the iron(II) mixed-ligand complex binds effectively to ct-DNA in an intercalation mode as indicated by remarkable hypochromicity (ca. 36%) and moderate bathochromic shift (8 nm) of the absorption spectra. This intercalative mode is supported by a significant increase (Δ Tm = 21 °C) in the melting temperature (Tm) of ct-DNA at R([complex]/[ct-DNA]) = 1.5. The binding of [Fe(phen)2(dppz)]2+ to ct-DNA is entropically driven as characterized by a positive enthalpy change and a large negative TΔ S term. An intense CD signal in the UV and visible region develops upon addition of ct-DNA to the racemate solution of [Fe(phen)2(dppz)]2+. This has revealed that a shift in diastereomeric inversion equilibrium takes place in the solution to yield an excess of one enantiomer of the DNA-iron(II) complex (Pfeiffer effect). The striking resemblance of the CD spectral profiles to those of the corresponding Δ -enantiomer indicates that Δ -[Fe(phen)2(dppz)]2+ is preferentially bound to ct-DNA

Polysulfonylamines. CIX. 1,2,4-Triazolium di(methanesulfonyl)amidate

The first accurate crystal structure involving the discrete unsubstituted 1,2,4-triazolium cation is reported. In the title salt, C 2 H 4 N + 3 .C 2 H 6 NO 4 S - 2 , the cation is linked to five adjacent anions by a set of N-H…N/O hydrogen bonds and C-H…O interactions, one of the latter being remarkably short and acceptably linear [H…O 2.26 (2), C…O 3.046 (2) A, C-H…O 161 (2)°]. We suggest on the basis of bond lengths, hydrogen bonding and U values that the X-ray structure of C 2 H 4 N + 3 .Sb 2 F - 7 [Udovenko, Gorbunova, Zemnukhova, Mikhailov & Davidovich (1998). Koord. Khim. 24, 655-657; Russ. J. Coord. Chem. 24, 611-613] contains an incorrectly refined cation in which both C atoms have been assigned as N and two N atoms as C.

Effect of Sulfuric Acid Treatment and Calcination on Commercial Zirconia Nanopowder

The modification of commercial zirconia nanopowder by sulfuric acid and heat treatment was conducted. The aim of this present research was to obtain a stable modified zirconia nanopowder chemically and thermally by studying the effect of sulfuric acid treatment and calcination temperature on commercial zirconia nanopowder. The material was prepared by dispersing the commercial zirconia nanopowder into 0.2, 0.5 and 0.8 M sulfuric acid solutions, followed by calcination at varied temperatures, i.e. 600, 700, 800 and 900 °C. The so called sulfated zirconias then were characterized their physicochemical properties using FT-IR, XRD and SEM-EDX analysis methods. The optimized condition for that modification was obtained by using sulfuric acid of 0.8 M and calcination temperature of 600 °C. The characterization results also revealed that using ammonia adsorption method, the acidity of the catalyst was found to be 1.06 mmol/g.

PREPARATION AND CATALYTIC ACTIVITY FOR ISOPROPYL BENZENE CRACKING OF Co, Mo AND Co/Mo-Al 2 O 3 -PILLARED MONTMORILLONITE CATALYSTS

It has been prepared Co, Mo and Co/Mo-Al2O3-pillared montmorillonite catalysts using montmorillonite clay as raw material. The structure and porosity of the catalysts were determined using N2 adsorptiondesorption and FT-IR spectroscopy analysis methods. Isopropyl benzene cracking using these catalysts were used to test the catalytic activity and performance of Co, Mo and Co/Mo-Al2O3-pillared montmorillonites. Characterization results showed that pillarization resulted in the increase of the total pore volume and specific surface area of the clay. Meanwhile, transition metals (Co, Mo and Co/Mo) loaded on Al2O3-pillared monmorillonites could increase the catalytic activity of the catalysts for isopropyl benzene cracking significantly.