Antiferromagnetic complexes involving metalmetal bonds IV. Synthesis,molecular structure and magnetic properties of the heterotrinuclear cluster, (C5H5Cr)2(μ2-SCMe3)(μ3-S)2Fe(CO)3, with direct and indirect exchange between CrIII and FeI centers

The photochemical reaction between the antiferromagnetic complex (C₅H₅-CrSCMe₃)₂S (I) (containing a CrCr bond 2.689 Å long) and Fe(CO)₅ results in the elimination of two carbonyl groups and one tert-butyl radical to give (C₅H₅Cr)₂(μ²-SCMe₃)(μ³-S)₂ · Fe(CO)₃ (III). As determined by X-ray diffraction, III contains a CrCr bond of almost the same length as in I (2.707 Å), together with one thiolate and two sulphide bridges. The latter are also linked with the Fe atom of the Fe(CO)₃ moiety (average FeS bond length 2.300 Å). Fe also forms a direct bond, 2.726 Å long, with one of the Cr atoms, whereas its distance from the other Cr atom (3.110 Å) is characteristic for non-bonded interactions. Complex III is antiferromagnetic, the exchange parameter, ?2J, values for CrCr, Cr(1)Fe and Cr(2)…Fe are 380, 2600 and 170 cm^?1, respectively. The magnetic properties of III are discussed in terms of the “exchange channel model”. The contributions from indirect interactions through bridging ligands are shown to be insignificant compared with direct exchange involving metalmetal bonds. The effects of steric factors and of the nature of the M(CO)_n fragments on the chemical transformations of (C₅H₅CrSCMe₃)₂S · M(CO)_n are discussed.     

Antiferromagnetic complexes with a metal—metal bond: VIII. Synthesis and structure of the antiferromagnetic heteronuclear cluster, “butterfly” (or “metal-chain”), (Cp4Cr2Ni2)(μ3-S)2(μ4-S)

By heating the mixture of solutions of (CpCrSCMe₃)₂S (I) in benzene and [CpNi(CO)]₂ in pentane followed by chromatography on alumina, dark cherry-red needles of the heteronuclear cluster (Cp₄Cr₂Ni₂)(μ³-S)₂(μ⁴-S) (II) were obtained, whose structure was established on the basis of a complete X-ray analysis. The crystals are rhombic, spatial group Pbca; a = 12.07(1), b = 18.50(2), c = 17.36(1) Å, Z = 8. The metallic skeleton of II has the “butterfly” or “metal-chain” structure with a direct CrCr bond (2.62(1) Å) and inequivalent CrNi bonds, 2.86(1) and 2.64(1) Å, while the Ni·Ni distance is nonbonding (4.34(1) Å). The NiCr₂ triangle planes produce a dihedral angle of 127°. The two μ³-bridged sulfur atoms locate under these triangles whereas the third sulfur atom is μ⁴-bridging coordinating all four metal atoms in the cluster with mean NiS and CrS distances of 2.29(1) and 2.25(1) Å, respectively. The Ni₂S₃ group is planar and almost perpendicular to the CrCr axis. Complex II is anti-ferromagnetic and its exchange parameter — 2J (418 cm^-1) is close to that found for the initial binuclear complex I (— 2J = 430 cm^-1 with a CrCr bond length of 2.689(8) Å). The role of the Ni coordination number in the generation of II is discussed.     

Design,synthesis of novel quinazolin-4-one derivatives and biological evaluation against human MCF-7 breast cancer cell line

A new series of 6,8-dibromo-2-(4-chlorophenyl)quinazolin-4(3H)-one derivatives VI–XIII were synthesized. Their chemical structures were confirmed by spectral and elemental analysis. The cytotoxic effect of the newly synthesized compounds was tested in vitro against human breast cancer cell line (MCF-7). Most of the tested compounds have shown promising cytotoxic activity. Compounds X and XIIIb exerted a powerful cytotoxic effect against MCF-7 with a very low IC50 (0.0015 and 0.0047 µmol/ml), while compounds VI, VII, VIII, XIIb, XI, XIIIc and IX exerted a moderate cytotoxic effect (IC50 0.01523, 0.0213, 0.031, 0.0478, 0.049, 0.068 and 0.079 µmol/ml respectively), compared to doxorubicin (0.0025 µmol/ml). Exploring their apoptotic effect; interestingly,all compounds activated apoptotic cascade in MCF-7. Compounds VI, XIIIb, XIIb, XI, XIIa, VII, V and VIII showed potent effect even much more than doxorubicin by 12.87–5.91 folds, while compounds XIIIc, IX, XIIIa, XIIc and X showed moderate increase in CASP3 activity by 4.96–3.22 folds relative to untreated cells more or less similar to doxorubicin (5.57 folds).     

Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

Obliquely propagating altra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfvén mode propagating parallel to the external magnetic field and dustmagnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfvén mode these effects play no role, but in obliquely propagating dust-Alfvén mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays stabilizing role.     

Phenyltellurenyl halide complexes of ruthenium and rhenium (CO)2RuBr2(PhTeBr)2 and (CO)3Re(PhTeI)3(μ3-I): Synthesis and crystal and molecular structures

Reactions of Ru₃(CO)₁₂ with PhTeBr₃ and of Re(CO)₅Cl with PhTeI in benzene give the stable complexes (CO)₂RuBr₂(PhTeBr)₂ (I) and (CO)₃Re(PhTeI)₃(μ³-I) (II) containing two and three ligands PhTeX (X = Br or I), respectively. The bonds between these ligands and the central metal atom are fairly shortened (on average, Ru-Te, 2.608 ?; Re-Te, 2.7554(12)-2.7634(13) ?). The Te-X bonds in the ligands PhTeBr (2.5163(5) ?) and PhTeI (2.7893(15) ?) are not lengthened appreciably. In complex II, the iodide anion is not coordinated by rhenium, yet being attached through weak secondary bonds to three Te atoms of the three ligands PhTeI.     

The complex of dicarbonyl(methylcyclopentadienyl)molybdenum with carbonyl(cyclopentadienyl)nitrosyl[tris(phenylacetylenide)stannyl]manganese: Synthesis and molecular formula

A reaction of CpMn(CO)(NO)Sn(C=CPh)₃ (I) with [Cp′Mo(CO)₂]₂ (Cp′ = MeC₅H₄) gave CpMn(CO)(NO)Sn(C=CPh)₃[Cp′Mo(CO)₂]₂ (II) as dark red prismatic crystals. The molecular structure of complex II was determined by X-ray diffraction study. Complex II contains the Mo-Mo bond (2.9799(5) Å), which is perpendicular to the coordinated C=C bond. The latter is longer (1.371(5) Å) than free acetylenide fragments (1.190(5) and 1.198(5) Å). In addition, the angle Sn-C=C for the coordinated C=C bond is smaller (134.1(3)°) than that in free fragments (173.5(4)° and 171.9(4)°). The Mn-Sn bond length in complex II (2.5662(7) Å) is close to that in complexI (2.5328(17) Å) and is much shorter than the sum of the corresponding covalent radii (2.78 Å). The Sn-C bond (2.108(4) Å) in the acetylenide fragment π-bound to two Mo atoms (average Mo-C, 2.19 Å), as well as the other Sn-C bonds (2.119(4) and 2.135(4) Å), remains virtually the same as in complex I (average 2.105 Å).     

Non-local symmetries of first-order equations

It is shown how one can transform scalar first-order ordinarydifferential equations which admit non-local symmetries of theexponential type to integrable equations admitting canonicalexponential non-local symmetries. As examples we invoke theAbel equation of the second kind, the Riccati equation and naturalgeneralizations of these. Moreover, our method describes howa double reduction of order for a second-order ordinary differentialequation which admits a two-dimensional Lie algebra of generatorsof point symmetries can be affected if the second-order equationis first reduced in order once by a symmetry which does notspan an ideal of the two-dimensional Lie algebra.     

Stannylene complexes of manganese,iron, and platinum

A number of stannylene complexes with different M: Sn ratios were obtained using various metals and substituents at the tin atom. The structures of the complexes were examined. A reaction of CpMn(CO)₂THF with (Ph₄As)⁺(SnCl₃)^? gave the ionic complex [Ph₄As]⁺[CpMn(CO)₂SnCl₃]^? (I). The action of C₆F₅MgBr on the complex C₅H₅Mn(CO)(NO)SnCl₃ produced C₅H₅Mn(CO)(NO)Sn(C₆F₅)₃ (II). Replacement of the Cl ions in the complex [CpFe(CO)₂]₂SnCl₂ by phenylacetylenide groups gave rise to the neutral complex [CpFe(CO)₂]₂Sn(C≡CPh)₂ (III). A reaction of (Dppm)PtCl₂ (Dppm is 1,1-bis(diphenylphosphino)methane) with SnCl₂ · 2H₂O in the presence of diglyme yielded the ionic complex [η³-CH₃O(CH₂)₂O(CH₂)₂OCH₃)SnCl]⁺[(η ²-Dppm)Pt(SnCl₃)₃]^? (IV). Transmetalation in a reaction of [(Dppe)₂CoCl][SnCl₃] · PhBr (Dppe is 1,2-bis(diphenylphosphino)ethane) with (Dcpd)PtCl₂ (Dcpd is dicyclopentadiene) in the presence of SnCl₂ afforded the ionic complex [Pt(Dppe)₂]₃[Pt(SnCl₃)₅]₂ (V). Structures I–V were identified by X-ray diffraction. In these structures, the formally single bonds between the atoms of transition metals M (Mn, Fe, and Pt) and Main Group heavy elements (Sn and P) having vacant d orbitals are appreciably shortened. The M-Sn bond length in complexes II and III are virtually independent of the substituents at the tin atom and the Pt-Sn bond length in complexes IV and V is virtually independent of the Pt: Sn ratio.