Amino acid derivatives of perylenediimide and their N-H···O peptide bond dipoles-templated solid state assembly into stacks

A methodology is proposed to provide direct access in good yields to peptide residues-appended perylenediimides PDI-(Cl(4))-[Gly-Ala(OEt)](2), 2a, PDI-(Cl(4))-[Gly-Val(OEt)](2), 2b and PDI-(Cl(4))-[Gly-Gly(OEt)](2), 2c from a generic perylenediimide (PDI) platform symmetrically functionalized with carboxylic acids at the imide sites, PDI-(Cl(4))-[Gly(OH)](2), 1. The latter is obtained in good purity by a non classical two-steps route avoiding the many, notoriously cumbersome successive chromatography steps typical of PDI chemistry, and including a single final purification allowing to crystallize the water soluble pure diacid 1, of great interest in its own right for further developments in a variety of fields. Then, the synthesis, crystallization and analysis of the crystal structures of 2a and 2b reveal a common pattern of self-assembly of the outer peptide residues based on collections of parallel N-H···O peptidic hydrogen bonds running alongside stacks where the constraints imposed upon on the inner PDI skeletons by long range interaction of these parallel electric dipoles reduce the dihedral angles around the bay regions by as much as 11% down to 32°.     

Polymerization of tetrafluoroethylene initiated by fluorinated petroleum coke

The polymerization of tetrafluoroethylene initiated by the inorganic polymer fluorocarbon material CF_0.95 prepared by the high-temperature fluorination of petroleum coke has been studied. The kinetics of the process has been examined, and the dependences of the rate of polymerization and the yield of polymer on monomer pressure and temperature have been considered. The free-radical mechanism of the process is established by ESR. The kinetic features of initiation and polymerization leading to an exponential growth in rate in the initial non-steady-state portion of kinetic curves are discussed.     

Evolution of the roughness of amorphous quartz surfaces and Cr/Sc multilayer structures upon exposure to ion-beam etching

The effect of ion-beam etching on surfaces of Cr/Sc multilayer structures and amorphous quartz roughness is studied. The dependence of roughness on the depth of etching, incidence angle, and ion energy is considered. Optimal parameters of etching which provide minimal evolution of surface roughness are presented.     

Formation of μ(2)-hydroxo-bonded (MgPc)2OH- assemblies and (C60(-))2 dimers in ionic fullerene {(MgPc)2OH-}2·(C60(-))2·(cation+)4 complexes

Ionic complexes containing μ(2)-hydroxo-bonded (MgPc)(2)OH(-) phthalocyanine assemblies and C(60)(-) anions: {(MgPc)(2)OH(-)}(2)·(C(60)(-))(2)·(PMDAE(+))(4)·(C(6)H(5)CN)(4) (1); {(MgPc)(2)OH(-)}(2)·(C(60)(-))(2)·(TMP(+))(4)·(C(6)H(5)CN)(3)·(C(6)H(4)Cl(2))(2.5) (2) (where PMDAE(+) is the cation of N,N,N',N',N'-pentamethyldiaminoethane and TMP(+) is the N,N'N'-trimethylpiperazinium cation) have been obtained as single crystals. The ionic ground state of the complexes is justified by the EPR spectra and the spectra in the IR and NIR ranges. The C(60)˙(-) radical anions are dimerized both in 1 and 2 in the 240-220 K range. Dimerization is accompanied by the reversible transition of the complexes from paramagnetic to diamagnetic state. MgPc forms unusual (MgPc)(2)OH(-) assemblies, in which the hydroxo-anion coordinates to two MgPc molecules by a μ(2)-fashion. The length of the Mg-O bonds is 1.936-1.955(2) ?, the Mg-O-Mg angle is 133.37-135.27(4)° and the displacement of the Mg atoms out of the mean 24-atom phthalocyanine plane is 0.77-0.86 ?. The packing of spherical fullerene and planar phthalocyanine molecules is attained in a crystal by the insertion of fullerenes between phenylene groups of phthalocyanines. It has been shown that metal phthalocyanines in ionic complexes with C(60) form M(II)Pc·(L(-)) assemblies, whereas metalloporphyrins form M(II)porphyrin·(C(+)) assemblies.     

Synthesis and characterisation of selected group 14 derivatives of the 2,5-(CF3)2C6H3 (Ar) ligand

Selected group 14 tetrahalides EX(4) (E = Si, Ge or Sn; X = Cl or Br) have been reacted in various molar ratios with ArLi, where Ar = 2,5-(CF(3))(2)C(6)H(3). The compounds Ar(2)SiCl(2)1, Ar(3)SiF 3, Ar(2)Si(OH)(2)4, Ar(2)GeCl(2)7, Ar(2)Ge(Br)Ge(Br)Ar(2)8, Ar(3)SnCl 10, Ar(4)Sn 11 and Ar(3)SnBr 12 have been isolated, and characterised by single-crystal X-ray diffraction, elemental analysis and (19)F solution-state NMR spectroscopy.     

Using Ion-beam etching to smooth fused silica surfaces

The roughness of fused silica, silicon, and sapphire substrates from different manufacturers is studied. Features of the substrates for imaging optics in the soft X-ray (SXR) and extreme UV (EUV) ranges are discussed. The first results from smoothing quartz substrates by etching with neutralized 50–500-eV argon beams are reported. Surface smoothing has been observed in the spatial-frequency range of 10^-1-10^-2 μm^-1.     

New framework hydrous silicate K3Sc[Si3O9] · H2O related to the high-temperature anhydrous silicate K3Ho[Si3O9] and symmetry analysis of a phase transition with prediction of structures

Crystals of a new framework silicate K₃Sc[Si₃O₉] · H₂O, space group Pm2₁ n (nonstandard setting of space group Pmn2₁ = C _2v ⁷), are obtained under hydrothermal conditions. The structure is determined without preliminary knowledge of the chemical formula. The absolute configuration is determined. The structure is close to that of the high-temperature K₃Ho[Si₃O₉] phase, which was obtained upon the heating of K₃HoSi₃O₈(OH)₂. This structural similarity is due to the specific conditions of synthesis and an analogous formula, where holmium is replaced by scandium. A symmetry analysis shows that the high local symmetry of a block (rod) is responsible for the first-order phase transition of both the order-disorder (OD) and displacement type. The number of structures in which the simplest and high-symmetry layers are multiplied by different symmetry elements are predicted.