Publications by authors named "Katja Dahms"

(5-n-Butyl-10,20-diiso-butyl-porphyrin-ato)nickel(II).

Acta Crystallogr Sect E Struct Rep Online

July 2014

The asymmetric unit of the title compound, [Ni(C32H36N4)], contains two independent mol-ecules exhibiting an overall ruffled conformation of the porphyrin macrocycle and differing mainly in the positions of the methyl groups. The average Ni-N bond lengths are 1.912 (2) and 1.

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Current applications in porphyrin chemistry require the use of unsymmetrically substituted porphyrins. Many current industrial interests in optics and biomedicine require systems with either push-pull (electron-donating and -withdrawing groups) or amphiphilic systems (hydrophobic and hydrophilic groups). In this context we present the class of 5,10-A(2)B(2)-type porphyrins for which two different substituents are positioned in diagonally opposite meso positions.

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New functionalized phenylpyridine ligands and their derived heteroleptic cyclometalated Ir(III) complexes have been synthesized. The complexes possess a combination of important properties: (i) blue emission, (ii) good photoluminescence quantum yields, and (iii) good solubility in organic solvents, making them very attractive as phosphorescent dopant emitters for solution-processable light-emitting devices.

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The title compound, [Ni(C(40)H(28)N(4)O)], was obtained from a Grignard reaction of the respective formyl-porphyrin to yield {5-[hy-droxy(phen-yl)meth-yl]-10,20-diphenyl-porphyrinato}nickel(II), followed by crystallization from methyl-ene chloride/methanol. The mol-ecule exhibits a ruffled macrocycle with an average deviation of the 24 macrocycle atoms from their least-squares plane (Δ24) of 0.26 Å and an average Ni-N bond length of 1.

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In order to investigate the mechanism of the NH-tautomerism in porphyrins, three meso-dithianyl-substituted porphyrins of different substitution pattern were studied theoretically. The corresponding trans-, cis- and saddle-point geometries were optimized with DFT methods, and the macrocyclic conformations obtained were analyzed using normal-structure-decomposition (NSD) analysis. Special attention was given to the influence of the participating out-of-plane and in-plane conformations on the NH-tautomerism, and the interplay of substituents, core conformations and energies of the transition-state structures was critically evaluated.

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An investigation of the conformational landscape of 1,3-dithian-2-yl bearing porphyrins and the rotational behavior of the dithianyl substituents in meso position was carried out by variable-temperature (VT) NMR spectroscopy. Additionally, theoretical results for alternative conformations and energy barriers were obtained by molecular modeling. The study revealed different NH trans tautomers with regard to the orientation of the dithianyl ligands for the free base porphyrins 1-3.

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Vilsmeier formylation is one of the most widely used substitution reactions for the functionalization of porphyrins. However, its utility is limited by the electrophilic/acidic reaction conditions, deactivation of the aromatic system and regiochemical problems, the requirement for metal complexes and necessity for subsequent demetalation under harsh conditions, and low functional group tolerance. To overcome these limitations, the dithianyl group has been utilized as a latent formyl synthon in porphyrin chemistry.

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