2-Pyridylmetallocenes: Part I. Electrophilic halogenation of 2-pyridylferrocene. Molecular structures of 2-pyridylferrocene and its α-brominated and -fluorinated derivatives. Synthesis of 2-pyridylruthenocene and 2-pyridylcymantrene

A new high-yield synthesis of 2-pyridylferrocene (1) without formation of the 1,1′-disubstituted product has been developed. Also the corresponding ruthenocene and cymantrene derivatives [C₅H₄(2-C₅H₄N)]ML_n (ML_n = Ru(C₅H₅) (2), Mn(CO)₃ (3)) were prepared and fully characterized. Ortho-lithiation of 1 followed by electrophilic halogenation yielded [C₅H₃X(2-C₅H₄N)]Fe(C₅H₅) [X = F (4), Cl (5), Br (6), I (7)], with 4 only being the second reported and first fully characterized fluoroferrocene. The molecular structures of 1, 4 and 6 have been determined by X-ray crystallography.     

Spectroscopic studies of metal complexes containing π-delocalized sulfur ligands. The pre-resonance Raman spectra of the antitumor agent 2-formylpyridine thiosemicarbazone and its Cu(II) and Zn(II) complexes

The pre-resonance Raman spectra of 2-formylpyridine thiosemicarbazone have been measured at three pH values corresponding to the fully protonated (H₂FPT⁺), half protonated (HFPT) and deprotonated (FPT⁻) forms of the ligand. Assignments of the vibrations coupled with the π→π^* transition have been made by comparison with the spectrum of the deuterated form (DFPT). The pre-resonance Raman spectra of the Zn(II) and Cu(II) complexes, [ZnFPT]⁺, [CuFPT]⁺ and [CuHFPT]²⁺, have also been measured. The spectral pattern of the Cu(II) complexes shows resonance enhancement of vibrations coupled with the π→π^*, as well as with the ligand to metal charge transfer transitions. In addition, it is consistent with coordination through thiolate sulfur in [CuFPT]⁺ and thione sulfur in [CuHFPT]²⁺.     

Binuclear metal complexes. 59. Synthesis and magnetism of dicopper(II) and copper(II)-nickel(II) complexes with N,N′-ethylenedisalicylamidatocuprate(II)

The complexes [Cu(samen)Cu(L)] and [Cu(samen)Ni(L)₂] (Lbpy, phen) have been synthesized by the reaction of sodium N,N′-ethylenedisalicylamidatocuprate(II) pentahydrate (Na₂- [Cu(samen)]·5H₂O), a divalent metal ion, and 2,2′- dipyridyl or 1,10-phenanthroline. Cryomagnetic data for the CuCu complexes did not fit the Bleaney- Bowers equation; but the data did fit a modified Bleaney-Bowers equation

with a large negative J and a significant negative θ, suggesting that a considerable magnetic interaction operates between essentially planar [Cu(samen)Cu(L)] molecules. The magnetisms of the CuNi complexes were well interpreted in terms of the susceptibility equation based on the Heisenberg model. An antiferromagnetic spin-exchange interaction (J= −13∼−14 cm⁻¹) was suggested between the metal ions.     

Synthesis and characterization of η-cyclopentadienyl-silylallyl niobium and tantalum complexes

Reaction of the disilylcyclopentadiene 1,1-[SiMe₂(CH₂CHCH₂)]₂C₅H₄ with NbCl₅ gave the new allylsilyl-substituted monocyclopentadienyl niobium complex [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}Cl₄]. This compound was reacted with LiNHtBu or NH₂tBu to give the imido derivative [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)Cl₂], which was further alkylated to the imido alkyl complexes [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)R₂] (R = Me, CH₂Ph) and [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)Cl (CH₂Ph)]. Reaction of the imido complexes with the corresponding lithium cyclopentadienides gave the dicyclopentadienyl-imido complexes [M(η⁵-C₅R₅){η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)Cl] (M = Nb, Ta; R = H, Me). Metallocene dichlorides [M(η⁵-C₅R₅){η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}Cl₂] (M = Nb, Ta; R = H, Me) were easily prepared by reduction with Na/Hg and simultaneous transmetallation of [Ta(η⁵-C₅R₅)Cl₄] with Li[C₅H₄SiMe₂(CH₂CHCH₂)] and of [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}Cl₄] with Li(C₅R₅). All of the new compounds have been characterized by elemental analysis, and IR and NMR spectroscopy.     

A single β adaptin contributes to AP1 and AP2 complexes and clathrin function in Dictyostelium

The assembly of clathrin-coated vesicles is important for numerous cellular processes, including nutrient uptake and membrane organization. Important contributors to clathrin assembly are four tetrameric assembly proteins, also called adaptor proteins (APs), each of which contains a β subunit. We identified a single β subunit, named β1/2, that contributes to both the AP1 and AP2 complexes of Dictyostelium. Disruption of the gene encoding β1/2 resulted in severe defects in growth, cytokinesis and development. Additionally, cells lacking β1/2 displayed profound osmoregulatory defects including the absence of contractile vacuoles and mislocalization of contractile vacuole markers. The phenotypes of β1/2 null cells were most similar to previously described phenotypes of clathrin and AP1 mutants, supporting a particularly important contribution of AP1 to clathrin pathways in Dictyostelium cells. The absence of β1/2 in cells led to significant reductions in the protein amounts of the medium-sized subunits of the AP1 and AP2 complexes, establishing a role for the β subunit in the stability of the medium subunits. Dictyostelium β1/2 could resemble a common ancestor of the more specialized β1 and β2 subunits of the vertebrate AP complexes. Our results support the essential contribution of a single β subunit to the stability and function of AP1 and AP2 in a simple eukaryote.     

Substitution, cooperative, and solvent effects on π pnicogen bonds in the FH2P and FH2As complexes

Ab initio calculations have been carried out to study the substitution effect on the π pnicogen bond in ZH(2)P-C(2)HM (Z?=?H, H(3)C, NC, F; M?=?H, CH(3), Li) dimer, cooperative effect of the π pnicogen bond and hydrogen bond in XH-FH(2)Y-C(2)H(4) (X?=?HO, NC, F; Y?=?P and As) trimer, and solvent effect on the π pnicogen bond in FH(2)P-C(2)H(2), FH(2)P-C(2)H(4), FH(2)As-C(2)H(2), and FH(2)As-C(2)H(4) dimers. The interaction energy of π pnicogen bond increases in magnitude from -1.51?kcal?mol(-1) in H(3)P-C(2)H(2) dimer to -7.53?kcal?mol(-1) in FH(2)P-C(2)HLi dimer at the MP2/aug-cc-pVTZ level. The π pnicogen bond is enhanced by 12-30?% due to the presence of hydrogen bond in the trimer. The π pnicogen bond is also enhanced in solvents. The natural bond orbital analysis and symmetry adapted perturbation theory (SAPT) were used to unveil the source of substitution, cooperative, and solvent effects.     

Synthesis,stereochemistry and inhibition of tumor cell transplantability by the iron and copper complexes of 2-aminomethyl- and 2-(2′-aminoethyl)pyridine

Complex formation between transition metal chlorides and the ligands 2-aminomethylpyridine (AMP) and 2-(2′-aminoethyl)pyridine (AEP) has been investigated. The complexes were characterized on the basis of elemental analysis, magnetic measurements and spectral studies. The cytotoxicity of the iron and copper complexes of AMP and AEP against Ehrlich ascites tumor cells has been measured. Brief incubation of cells and drugs was followed by implantation into the host mice; subsequent development of tumor cells was a measure of cytotoxicity.     

f-Element/crown ether complexes. 26. Crystallization of two hydrated forms of hydrogen bonded complexes of NdCl3·nH2O and 15-crown-5. Crystal structures of [Nd(OH2)9]Cl3·15-crown-5·H2O and [NdCl2(OH2)6]Cl·15-crown-5

When slowly evaporated, the reaction of NdCl₃· nH₂O with 15-crown-5 in a 3:1 mixture of acetonitrile:methanol produces two crystalline hydrates. The decahydrate, [Nd(OH₂)₉]Cl₃·15-crown-5·H₂O, is orthorhombic, P2₁2₁2₁, with (at −150 °C) a = 10.571(4), b = 15.220(7), c = 15.686(7) Å, and D_calc = 1.71 g cm⁻³ for Z = 4. These crystals are stable to the moisture in air. Each Nd is nine-coordinate with tricapped trigonal prismatic geometry. The nine coordinated water molecules are hydrogen bonded to two symmetry related crown ethers, all three chloride ions, and the tenth water molecule. The crown has a total of six hydrogen bonds, four on one side (two to a single oxygen atom) and two on the other. This ether exhibits conformational disorder. The hexahydrate, [NdCl₂(OH₂)₆]Cl·15-crown-5 is deliquescent, dissolving in air and recrystallizing as [NdCl₂(OH₂)₆]Cl. Crystals of this complex are monoclinic, P2₁/n, with (at 20 °C) a = 9.821(3), b = 16.978(9), c = 12.849(8) Å, β = 94.06(5)°, and D_calc = 1.80 g cm⁻³ for Z = 4. The Nd atom exists in a distorted dodecahedral geometry with one chlorine in an A site and one in a B site. The coordinated chlorine atoms accept hydrogen bonds producing polymeric zigzag hydrogen bonded chains along c. The third noncoordinated chloride ion accepts four hydrogen bonds, three from one formula unit and one from a second formula unit related by a unit translation along a. The crown ethers accept five hydrogen bonds, two on one side, and three on the other, thus separating the zigzag chains along b.     

Conformational changes of β2-human glycoprotein I and lipid order in lipid-protein complexes

We studied the conformation of β2-human glycoprotein (β2GPI) in solution and bound to the anionic lipids palmitoyl oleoyl phosphatidylglycerol (POPG), dimiristoyl phosphatidylglycerol (DMPG) and dipalmitoyl phosphatidylglycerol (DPPG) as a function of the temperature. We used the infrared amide I' band to study the protein conformation, and the position of the antisymmetric stretching band of the methylene groups in the lipid hydrocarbon chains to study the lipid order. Lipid-protein complexes were studied in media of low and high ionic strengths. In solution, β2GPI displayed a conformational pre-transition in the range 47-50°C, characterized by a shift in the band of β secondary structure, previous to the main unfolding at 64°C. When the protein was bound to the anionic lipid membranes at 25°C, a similar shift as in the pre-transition in solution was observed, together with an increase in the band corresponding to α-helix secondary structure. Lipid-protein complexes formed large aggregates within the temperature range 10?60°C. At temperatures above the protein unfolding, the complexes were disrupted to yield vesicles with bound protein. This finding indicated that the native fold was required for the formation of the lipid-protein aggregates. Cycles of heating and cooling showed hysteresis in the formation of aggregates.     

f-Element/crown ether complexes. 1. Synthesis and structure of [Y(OH2)8]Cl3·(15-crown-5)

The crystal and molecular structure of [Y(OH₂)₈]Cl₃·(15-crown-5) has been determined by single- crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P2₁/n with Z = 4. Lattice parameters are a = 9.202(2), b = 17.247(3), c = 15.208(3) Å, and β = 92.39(2)°. The structure was solved by Patterson and Fourier techniques and refined by least-squares to a final conventional R value of 0.081. The Y(III) ion is eight coordinate, bonded to the oxygen atoms of the eight water molecules. Three of the water molecules are hydrogen bonded to crown ether molecules. The three chloride ions participate in hydrogen bonds with the remaining five water molecules. The YO(water) distances range from 2.322(6) to 2.432(7) Å and average 2.37(4) Å. The average O(water)···Cl and O(water)···O(crown) hydrogen bonded separations are 3.08(4) and 2.76(7) Å, respectively.     

Synthesis,vibrational and mössbauer spectra studies of complexes of organotin chlorides and 2-pyridinecarboxaldehyde thiosemicarbazone

The complex formation between organotin chlorides and 2-pyridinecarboxaldehyde thiosemicarbazone (PT) has been investigated. In only one case is a substitution reaction observed whereas in all other cases, 1:1 addition complexes are formed. The solid state configurations of the complexes have been studied by ^119mSn Mössbauer and far infrared spectroscopy. The chelating ligand (PT) functions as a bidentate ligand towards diorganotin chlorides giving octahedral coordination geometry around the tin atom.     

Modelling of formation processes of inclusion complexes of coumarin laser dyes and β-cyclodextrin by the MM2 force field method. I. 7-Amino-4-methylcoumarins

In order to improve the generating and photochemical properties of coumarin laser dyes, the following active media were synthesized: inclusion complexes of -cyclodextrin (-CD) and 7-amino-4-methylcoumarins (COU1, COU102, COU120). Complex formation processes were studied, and the structure of the inclusion complexes was estimated using the method of MM2 molecular mechanics. The data obtained suggest the reasons underlying the complex structure effects on their spectral, luminescent and generating characteristics.     

γ-Tubulin complexes in microtubule nucleation and beyond

Tremendous progress has been made in understanding the functions of γ-tubulin and, in particular, its role in microtubule nucleation since the publication of its discovery in 1989. The structure of γ-tubulin has been determined, and the components of γ-tubulin complexes have been identified. Significant progress in understanding the structure of the γ-tubulin ring complex and its components has led to a persuasive model for how these complexes nucleate microtubule assembly. At the same time, data have accumulated that γ-tubulin has important but less well understood functions that are not simply a consequence of its function in microtubule nucleation. These include roles in the regulation of plus-end microtubule dynamics, gene regulation, and mitotic and cell cycle regulation. Finally, evidence is emerging that γ-tubulin mutations or alterations of γ-tubulin expression play an important role in certain types of cancer and in other diseases.     

Synthesis,characterization and antitumour properties of some metal(II) complexes of 2-pyridinecarboxaldehyde 2′-pyridylhydrazone and related compounds

Metal complexes of 2-pyridinecarboxaldehyde 2′-pyridylhydrazone (PCPH) and related compounds with manganese(II), iron(II), cobalt(II), nickel(Il), copper(II), zinc(II) and platinum(II) were synthesized and characterized by magnetic susceptibility measurements down to liquid nitrogen temperature and also by electronic, infrared, electron spin resonance and Mössbauer spectra. All the metal(II) complexes appeared to be monomeric, high-spin, five-coordinate (square-pyramidal) (X = Cl⁻ or OAc⁻), except for Ni(PCPH)Cl₂ which is polymeric, high-spin, six-coordinate. Each ligand behaved as a tridentate NNN donor, via the pyridine nitrogen, azomethine nitrogen, and pyridine or quinoline nitrogen. One of the most active agents of this series, Cu(PCPH)Cl₂, showed antitumour activity against a variety of transplanted tumours, including Sarcoma 180, Ehrlich carcinoma and L1210 leukaemia sensitive to α(N)-heterocyclic carboxaldehyde thiosemicarbazones. This agent caused inhibition of ³H-thymidine and ³H-uridine incorporation into DNA and RNA, respectively, of Sarcoma 180 ascites cells; protein biosynthesis was relatively insensitive to the action of this agent.     

The interaction of D-galactonic acid with CrVI and CrIII. Structure,stability and physical properties of CrIII—aldonate complexes

The redox reaction between D-galactonic acid and potassium chromate yields ((lyxonateH₋₁)(galactonateH₋₁)Cr(OH₂))K·H₂O_n, with both aldonate molecules acting as bidentate ligands with the carboxylate and one alkoxo function as the donor sites. The shift of the CO₂^{poststaggered−} stretching vibration towards lower frequencies upon coordination and the high value of Δv indicate that the carboxylate acts as a monodentate donor site. Magnetic susceptibility data for the compound in the temperature range 3–300 K exhibit a drop in the effective magnetic moment with temperature below 70 K, which is indicative of antiferromagnetic interactions between the Cr^III centres. The molar magnetic susceptibility versus temperature plot could be fitted with the Fisher Hamiltonian for the case of infinite chains, equation-modified for the presence of monomeric species. The EPR and UV-Vis spectroscopic studies reveal that, in solution, the complex retains the distorted octahedral local coordination geometry. The ((lyxonateH₋₁)(galactonateH₋₁)Cr(OH₂))K_n dissociates slowly in aqueous solution but faster at high [H⁺], because of the rapid protonation of the alkoxo bridges linking the monomeric units. The potentiometric evaluation of the closely related binary system Cr^III-d-galactonate shows that the (Cr(galactonateH_−n)₂)^{1 − 2n} complexes are the major species in the 4–12 pH range, when a 1:2 Cr^III:ligand ratio is used. ¹³C NMR reveals that theCO₂^{poststaggered−} group is one of the coordination sites of the ligand.