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Heinz Langhals

Publications and source records attributed to Heinz Langhals.

9 recordsLinked to original sources
PubMed2006

Methoxyperylene bisimides and perylene lactame imides: novel, red fluorescent dyes.

The synthesis of methoxyperylene bisimides and perylene lactame imides with aliphatic N-substituents is described. Both classes of dyes exhibit fluorescence in the bathochromic region of visible light so that red light is obtained. The lightfastness of the dyes is very high, thus, there is special interest for diverse applications.

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PubMed2006

Naphthalene amidine imide dyes by transamination of naphthalene bisimides.

Derivatives of naphthalene-1,4,5,8-tetracarboxylic acid with amidine structures have been prepared. The light absorption of the bisimide derivatives in the UV region is shifted to the visible for the amidine imides, which also fluoresce with a large Stokes shift. It has been shown how the bisimide-lactam rearrangement can be extended to amidine structures.

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PubMed2003

The restoration of the largest archaelogical discovery--a chemical problem: conservation of the polychromy of the Chinese terracotta army in Lintong.

The conservation of the polychromy of the terracotta army of the first Chinese emperor Qin Shihuangdi represents a special problem because of the deterioration of the ground layer consisting of organic material. This was triggered due to it having spent more than 2200 years in water-saturated soil. The consolidation of the polychromy was achieved through polymerisation of a specially adapted combination of monomers.

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PubMed2002

Bichromophoric perylene derivatives: energy transfer from non-fluorescent chromophores.

The energy of excitation at non-fluorescent chromophores such as fluorenone and anthraquinone has been trapped by a fast energy transfer to the highly fluorescent perylene bisimides. To this end, anthraquinone, fluorenone and anthracene derivatives have been linked to the perylene bisimides by non-conjugating spacers and fluorescence quantum yield of such assemblies have been determined as a function of the wavelengths of excitation. Energy transfer in such assemblies is strongly influenced by the orientation of the two chromophores. This is of interest for the construction of fluorescence switches.

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PubMed2002

The rapid identification of organic colorants by UV/vis spectroscopy.

A rapid UV/vis spectroscopic method for the identification of organic colorants by the use of Gaussian analysis is presented. Sets of parameters are obtained for the screening with a low number of data. An optical distance using line positions and intensities is defined as a measure for the similarity of UV/vis spectra.

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PubMed2002

DPP dyes as ligands in transition-metal complexes.

The DPP dyes (=diketopyrrolopyrrole) 1 are deprotonated to give the corresponding dianions 2. These are treated with two moles of the transition-metal complexes [L(n)MX]=[(Ph(3)P)(2)MX] (M=Cu, Ag; X=Cl, NO(3)), [(Ph(3)P)AuCl], [(Et(3)P)AuCl], [(tBuNC)AuCl], [(Ph(3)P)(2)PdCl(2)], and [(Ph(3)P)(2)PtCl(2)] to give the novel bismetalated DPP dyes [L(n)MN[C(3)R(1)(O)](2)NML(n)] (4-10). In comparison with the starting materials, these compounds show better solubilities, high fluorescence quantum yields (Phi > or = 80 %), and bathochromic absorptions. The compounds 4 c, 5 a, 6 b, 6 c, 6 e, 7 c, and 8 c were characterized by X-ray crystallography. The copper and silver atoms in 4 c and 5 a are trigonal planar and are surrounded by the P atoms of the phosphane ligands and the N atom of the DPP dianion 2. Both metals are somewhat forced out-of-plane, and the P(2)M plane and the phenyl planes of R1 are twisted by > or = 70 degrees and < or = 25 degrees, respectively, towards the chromophore plane. The gold atoms in 6-8 are linearly coordinated to one N and one P (6 b, c, e, 7 c) or one C atom (8 c), respectively. The gold atoms are only slightly pressed out-of-plane, and the P substituents are staggered so that there is enough space for the planarization of R(1) into the plane of the chromophore. Compound 8 c shows intermolecular d(10)-d(10) interactions between Au(I) centers of different molecules, and these interactions lead to infinite chains of parallel orientated molecules in a gauche conformation of neighbors (torsion angle=150 degrees) in the crystal.

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