Synthesis and thermal degradation of some ferrocene-containing polyazines and poly-schiff bases

A series of ferrocene-containing polymeric azines and polymeric Schiff bases have been synthesized by means of acid-catalyzed solution polycondensations. The molecular structures of the polymers synthesized have been determined, and information concerning their thermal behavior has been obtained. Comparative thermal stabilities of the products of polymerization of aliphatic and aromatic diamines with 1,1′-diformylferrocene and 1,1′-diacetylferrocene were investigated by thermogravimetric analysis both in air and in an inert atmosphere. In the inert atmosphere, initial weight loss due to thermal stress did not occur below 300°C in all cases, and in many cases 50–70% residue of polymer sample remained at 700°C. The use of a fluorinated diamine led to the synthesis of a polymer which did not exhibit any significant enhancement of thermal properties. Investigation of the polymer products by direct inlet mass spectroscopy led to the observation that several of the systems contained significant amounts of cyclic dimers, although linear polymers were the major products in most cases. Extraction of the cyclic dimers followed by molecular weight determination by vapor phase osmometry confirmed their molecular structures.     

All-optical sampling with a monolithically integrated Mach-Zehnder interferometer gate

An all-optical sampler consisting of a polarization-independent monolithic Mach-Zehnder interferometer with integrated semiconductor optical amplifiers and a temporal resolution of 1 ps is presented. As an example, a simple 320-Gbit/s pattern has been successfully sampled, demonstrating the functionality of this scheme for high-bit-rate waveform characterizations in light-wave systems.     

Topological phases: An expedition off lattice

Motivated by the goal to give the simplest possible microscopic foundation for a broad class of topological phases, we study quantum mechanical lattice models where the topology of the lattice is one of the dynamical variables. However, a fluctuating geometry can remove the separation between the system size and the range of local interactions, which is important for topological protection and ultimately the stability of a topological phase. In particular, it can open the door to a pathology, which has been studied in the context of quantum gravity and goes by the name of ‘baby universe’, here we discuss three distinct approaches to suppressing these pathological fluctuations. We complement this discussion by applying Cheeger’s theory relating the geometry of manifolds to their vibrational modes to study the spectra of Hamiltonians. In particular, we present a detailed study of the statistical properties of loop gas and string net models on fluctuating lattices, both analytically and numerically.     

Modelling of emission spectra of Pr I by summarizing hyperfine patterns of overlapping spectral lines

We present studies of the the hyperfine (hf) structure of spectral lines of Praseodymium (Pr) by laser spectroscopic investigations as well as by analyzing Fourier Transform (FT) spectra. The experimental part of our work is done with the technique of laser-induced fluorescence (LIF) spectroscopy in a hollow cathode lamp. We present detailed studies of the very small region of 1.5 Å (from 5810.5 Å to 5812.0 Å) in the visible area of the FT spectrum where at least 14 spectral lines are overlapping. In the investigated region we discovered two new even levels and three new odd levels and could classify 11 new spectral lines. The final goal is to model the emission spectrum by a sum of the hf profiles of all spectral lines in a certain region. Application of such modelling may be found in analyzing highly resolved stellar spectra.     

EFFICIENT FORMATION OF A CROSSLINKABLE HMT MONOADDUCT AT THE Kpn I RECOGNITION SITE

Abstract The double-stranded Kpn I linker, CGGTACCG, is readily crosslinked by 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT). Under identical conditions, the corresponding Bam HI linker, CGGATCCG, is resistant to modification. The differential reactivity of HMT towards the two sequences is also observed with SV40 DNA where the Kpn I restriction site is ten-fold more susceptible to HMT modification than the Bam HI site. Selective reaction with the Kpn I site is attributed to preferential intercalation of HMT into the TpA sequence. The availability of crosslinked Kpn I linker has allowed us to characterize the kinetics of photoreversal. Upon irradiation at 254 nm, the diadduct reverses at a faster rate than the monoadduct, leading to an accumulation of the latter. The resultant monoadduct reforms crosslink rapidly upon irradiation at 365 nm. DNA oligomers like the Kpn I linker, which can be modified by the above protocol to contain a crosslinkable HMT monoadduct, could he exploited as photoreactive sequence-specific probes.     

Molecular properties of some new cyclic ethynylsilanes

Summary The question about conjugation between -CC- and -SiMe ₂- groups in [-CC-SiMe ₂-] _n withn=4 and 5 has been investigated by AM 1 calculations which show strong conjugation. In the structure determination (AM 1, X-ray) and in the Raman spectra no significant differences to normal values are observed. The NMR Si-Ccoupling constant and UV spectra are presented.This paper is dedicated to Professor Dr. mult. Victor Gutmann on the occasion of his 70th birthday with warmest personal wishes     

2,2′-Bifurylidene-5,5′-diones,Coumarins, 3a, 7a-dihydro-1H-inden-1-ones,and 5H-furo[3,2-b]pyran-5-ones from propyne and carbon monoxide

The [Co₂ (CO)₈]-catalyzed reaction between propyne and CO in acetone at 110° and 170 bar was re-investigated. There are five major products: (E)-3,4′-dimethyl-2,2′-bifurylidene-5,5′-dione ( 4 ), 3,5,8-trimethylcoumarin ( 8 ), 3a, 7a-dihydro-2,4,7,7a-tetramethyl-1H-inden-1-one ( 9 ), 2,6-dimethyl-5H-furo [3,2, -b]- pyran-5-one ( 11 ), and 2,7-dimethyl-5H-furo 3,2-b-pyran-5-one ( 12 ); of these, only one, 4 . had previously been recognized. In parallel experiments were obtained 2,6-dipentyl-5 H-furo[3,2-b]pyran-5-one ( 13 ), 2,7-dipentyl–5H-furo[3,2-b]pyran-5-one ( 14 ), 3a, 7a-dihydro-2,4,7,7a-tetrapentyl-1H-inden-1-one ( 15 ). And 3a, 7a-dihydro-2,4,6,7a-tetrapentyl-1H-inden-1-one ( 16 ) from hept-1-yne, and two further types of products from two atypical 1-alkynes: 3,6,9-tri(tert-butyl)-1-oxaspiro[4.4]nona-3,6,8-trien-2-one ( 20 ) from (tert-butyl)acetylene and the exo-dimer 21 of 2,5-bis(trimethylsilyl)cyclopenta-2,4-dien-1-one ( 22 ) from (trimethylsilyl)acetylene. Compounds 11,12 , and 20 were identified by X-ray analysis.