Katja Dahms

Trinity College Dublin, Dublin, Leinster, Ireland

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Publications (19)56.88 Total impact

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    ABSTRACT: 5,10-Disubstituted porphyrins are more recent additions to the family of meso-substituted porphyrins. A crystallographic comparison of 5,10-diphenylporphyrin with the regioisomeric 5,15-disubstituted system reveals striking differences in their conformation. In the free base porphyrins the former uses mainly out-of-plane distortion to alleviate steric strain while in-plane core elongation predominates in the latter. In contrast, the structure of the Cu(II) complex is planar and forms strong π-π aggregates with very small lateral shifts. Macroscopically, the packing is similar to that of porphyrin sponges of the 5,10,15,20-tetraphenylporphyrin type.
    Zeitschrift fur Naturforschung B 02/2015; 70(2):119-123. DOI:10.1515/znb-2014-0217 · 0.77 Impact Factor
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    Mathias O Senge, Katja Dahms
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    ABSTRACT: 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 1.910 (2) Å in the two mol-ecules. The mol-ecules form a closely spaced lattice structure in which neighbouring porphyrins are oriented in a nearly perpendicular fashion to each other. The compound was prepared via nucleophilic substitution of (5,15-diiso-butyl-porphyrinato)nickel(II) with n-butyl-lithium.
    Acta Crystallographica Section E Structure Reports Online 07/2014; 70(Pt 7):m251. DOI:10.1107/S1600536814012884 · 0.35 Impact Factor
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    ABSTRACT: Several different methods have been utilized for the effective synthesis of a new class of porphyrins that contains the synthetically intriguing propadienyl (or allenyl) functional group. Of these approaches, successive Horner–Wadsworth–Emmons couplings proved impossible, but Pd-catalyzed cross-coupling reactions enabled quick and easy synthetic access to allenylporphyrins. The conditions for the Suzuki–Miyaura cross-coupling reaction of bromoporphyrins with allenylboronic acid pinacol ester were optimized. This reaction represents the first successful use of this boronic acid in a Suzuki-type coupling. Although this routine was successful for the syntheses of porphyrins that contain aromatic substituents, a more robust method was also developed that involves a Sonogashira coupling of a bromoporphyrin with N,N-diisopropylprop-2-yn-1-amine followed by a Pd-catalyzed rearrangement to give allenylporphyrins in high yields. For both routes, the applicable metalation states of the porphyrin core were investigated with mixed results. The utility of the addition of the allenyl functional group was then probed with both directly linked allenylporphyrins and those containing a phenyl “spacer”.
    European Journal of Organic Chemistry 03/2013; -(8):1566–1579. DOI:10.1002/ejoc.201201535 · 3.15 Impact Factor
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    ABSTRACT: 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. Thus, the intramolecular dipole moment in these tetrapyrroles is positioned along a β-β vector passing through two pyrrole rings. This is opposite to the situation of the frequently used 5,15-A(2)BC porphyrins for which the dipole moment is oriented along a meso-meso axis. We have elaborated syntheses of the 5,10-A(2)B(2) porphyrins by using transition-metal-catalyzed transformations of 5,10-A(2) porphyrins or direct substitutions reactions thereof; this gives the target molecules in 22-77% overall yields. The compounds exhibit interesting structural, spectroscopic, and optical features and can serve as building blocks for new porphyrin arrays and applications.
    Chemistry - A European Journal 11/2011; 17(48):13562-73. DOI:10.1002/chem.201101934 · 5.70 Impact Factor
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    ABSTRACT: 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.
    The Journal of Organic Chemistry 06/2011; 76(12):5143-8. DOI:10.1021/jo200357e · 4.64 Impact Factor
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    ABSTRACT: A series of 3,7-bis(9,9-di-n-hexylfluoren-2-yl)-N-arylphenothiazine-S,S-dioxide trimers and (9,9-di-n-octylfluorene-2,7-diyl-co-N-arylphenothiazine-S,S-dioxide) co-polymers, with varying ratios of phenothiazine-S,S-dioxide units, have been prepared in good yields by palladium-catalyzed cross-coupling reactions. The materials are deep blue emitters and show no solvatochromism or evidence for an intramolecular charge-transfer state. The photoluminescence quantum yields of the trimers are Phi(PL) 15-30% in solution and 14-25% in films. The polymers demonstrated very high values in solution (Phi(PL) 74-84%) and Phi(PL) values in films of 28-47%. The estimated HOMO energy levels are between -5.64 and -5.62 eV for the polymers with 15% incorporation of the phenothiazine-S,S-dioxide units. An analogous N-arylphenothiazine co-polymer shows significantly red shifted absorption and emission. Solution electrochemical data and density functional theory calculations are also presented. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1129-1137, 2011
    Journal of Polymer Science Part A Polymer Chemistry 03/2011; 49(5):1129 - 1137. DOI:10.1002/pola.24527 · 3.54 Impact Factor
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    Mathias O Senge, Katja Dahms
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    ABSTRACT: 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 1.931 (2) Å. In line with the asymmetrical substituent pattern, the degree of distortion is slightly larger at point of attachment of the meth-oxy(phen-yl)methyl residue than at the unsubstituted meso position. The meth-oxy group attached to the chiral C atom is disordered in a 0.534 (4):0.466 (4) ratio.
    Acta Crystallographica Section E Structure Reports Online 02/2011; 67(Pt 2):m265. DOI:10.1107/S1600536811002960 · 0.35 Impact Factor
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    ABSTRACT: Multiporphyrin arrays are a complex class of molecules with numerous potential applications in energy transfer, photomedicine, and light harvesting. We have developed a facile/versatile route to a class of triptycene-linked porphyrin arrays via both Suzuki and Sonogashira cross-coupling methods, which makes use of the rigid three-pronged orientation of triptycene to construct trimeric porphyrin arrays linked either in the meso or β-position with various linker groups. In order to understand the properties of these potential antenna systems and probe their potential applications, the coordination behavior of zinc(II) derivatives with mono- and bidentate N-donor ligands was investigated. Depending on ligand concentration, both one- and two-point binding was observed with a bidentate ligand. Also/in addition, different cavity sizes, obtained by the use of different linker groups, resulted in differences in the binding properties of each trimeric system.
    Tetrahedron 02/2011; 67(6):1126-1134. DOI:10.1016/j.tet.2010.12.025 · 2.82 Impact Factor
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    ABSTRACT: The reaction of diphenyl sulfone with 2,3-dibromophthalazine-1,4-dione in the presence of n-butyllithium gave a spiro-9H-thioxanthene-10,10-dioxide derivative in 45% yield, the structure of which was proved by X-ray crystallography.
    Tetrahedron Letters 12/2010; 51(50). DOI:10.1016/j.tetlet.2010.10.048 · 2.39 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 02/2010; 41(7). DOI:10.1002/chin.201007258
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    ABSTRACT: Palladium-catalysed Suzuki–Miyaura cross-coupling proved to be the simplest and most efficient method for attaching an unsubstituted allene, a novel substituent and potential functional group, to the porphyrin periphery. Comparative studies on various allenyl synthetic pathways show that this method, which makes use of a bromoporphyrin and allenylboronate, affords the corresponding allenylporphyrin in the presence of an appropriate base and THF.
    Tetrahedron Letters 05/2009; 50(21):2566-2569. DOI:10.1016/j.tetlet.2009.03.097 · 2.39 Impact Factor
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    ABSTRACT: Recent developments in the synthesis and transformation of porphyrins and their derivatives are presented. In connection with the Fifth International Conference on Porphyrins and Phthalocyanines (ICPP-5) a survey of current method developments and reactivity studies is made. The review focuses on synthetic advances in porphyrin chemistry. A brief survey of important developments covers selectively the literature from 2004 to late 2007.
    Journal of Porphyrins and Phthalocyanines 10/2008; 12(10):1053–1077. DOI:10.1142/S108842460800042X · 1.36 Impact Factor
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    Katja Dahms, Mathias O. Senge
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    ABSTRACT: The synthesis of novel porphyrin trimers covalently linked by one central, rigid triptycene unit is described. Reaction of 2,6,14-triiodotriptycene, generated in a three-step synthesis from triptycene, with borylated porphyrins under Suzuki cross-coupling conditions afforded porphyrin trimers. In addition, Sonogashira cross-coupling conditions could be successfully applied for the synthesis of trimeric porphyrin arrays as well.
    Tetrahedron Letters 09/2008; 49(37):5397-5399. DOI:10.1016/j.tetlet.2008.07.008 · 2.39 Impact Factor
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    ABSTRACT: 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. The calculated energy barriers of the preferred pathways are compared with experimental activation enthalpies determined by variable-temperature (VT) NMR spectroscopy.
    The Journal of Organic Chemistry 04/2008; 73(6):2182-90. DOI:10.1021/jo702443x · 4.64 Impact Factor
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    ABSTRACT: 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. Relatively ruffled porphyrin core conformations were established for the transition states of the dithianyl rotation, resulting in a lower rotational energy barrier for the nickel(II) complex 4 compared to that of the free base systems. The data obtained and the first depiction of a rotational transition state for the rotation of bulky meso-alkyl substituents illustrate the close structural interplay between meso-alkyl substituents and the macrocycle conformation in porphyrins.
    The Journal of Organic Chemistry 09/2007; 72(16):6224-31. DOI:10.1021/jo0708700 · 4.64 Impact Factor
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    ABSTRACT: Formylporphyrins were prepared by using either the 1,3-dithian-2-yl residue as a precursor for the CHO group or by the Vilsmeier reaction. Two synthetic routes for the introduction of the 1,2-dithian-2-yl group were explored. Furthermore, reactions of the 1,3,5-trithian-2-yl group with porphyrins were examined as well as spirobisdithiane derivatives as precursors for the ultimate assembly of porphyrin spirobisdithanyl-linked bioconjugates. The obtained formylporphyrins were reacted with organomagnesium or organophosphorus compounds. A series of hydroxyporphyrins resulting from the Grignard reaction of 5,15-substituted porphyrins were synthesised in high yields. Several porphyrins with unsaturated residues introduced by the Wittig reaction were obtained in moderate yields. The less sterically hindered 5,15-substituted porphyrins show increased reactivity and give higher yields; their reaction products are higher in stability relative to other porphyrin systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
    European Journal of Organic Chemistry 08/2007; 2007(23):3833 - 3848. DOI:10.1002/ejoc.200700380 · 3.15 Impact Factor
  • European Journal of Organic Chemistry 08/2007; 2007(23):3773-3773. DOI:10.1002/ejoc.200790052 · 3.15 Impact Factor
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    Katja Dahms, Mathias O Senge
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    ABSTRACT: Introduction: Porphyrins are a unique class of compounds that are ubiquitous in nature and function in a wide variety of roles ranging from oxygen transport, electron transfer, and oxidation catalysts to photosynthesis. Tetrapyrroles also play a central role in disparate areas such as photodynamic therapy, malaria, porphyrias, and unsolved medical problems such as drug-induced neuropsychiatric disorders. Due to these properties they are some of the most important fine chemicals in industry and are utilised in an ever-expanding array of applications. The Wittig reaction of meso-formylporphyrins offers an alternative approach to Pd-catalysed reactions for the synthesis of olefinic-substituted porphyrins. This type of reaction allows the use of milder reaction conditions, which results in similar products with yields of 61 to 81 %.[3]
    20th International Symposium: Synthesis in Organic Chemistry, University of Cambridge, Cambridge, UK; 07/2007
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    ABSTRACT: 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. 2-Formyl-1,3-dithiane can be used directly in pyrrole condensation reactions to regioselectively yield porphyrins with up to four dithianyl residues. Likewise, 5-dithianyldipyrromethane could be prepared quantitatively as a key building block for various porphyrin condensation reactions yielding the respective free base formylporphyrins after deprotection. Additionally, dithianyllithium can be used as a reagent for the direct aromatic substitution of metallo- and free base porphyrins under nucleophilic conditions.
    Journal of the American Chemical Society 11/2004; 126(42):13634-5. DOI:10.1021/ja045223u · 11.44 Impact Factor