3 results for Albrett, Amelia

  • Design of a water soluble amethyrin macrocycle

    Albrett, Amelia; Brothers, Penelope; Aguilar, A; Lee, JT; Sessler, JL (2006-07)

    Conference poster
    The University of Auckland Library

    This JPP issue contains all abstracts accepted for presentation at the Fourth International Conference of Porphyrins and Phthalocyanines (ICPP-4) which was held in Rome, Italy, July 2-7, 2006 and coorganized by Drs Roberto Paolesse and Pietro Tagliatesta from the University of Rome “Tor Vergata”. The printed book of abstracts was given to all ICPP-4 attendees, being a necessary tool to follow the rich scientific program of the meeting, and should also prove useful to those readers of JPP who were not able to attend the biennial scientific meeting of the Society of Porphyrins and Phthalocyanines (SPP).

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  • DFT survey of monoboron and diboron corroles: regio- and stereochemical preferences for a constrained, low-symmetry macrocycle.

    Albrett, Amelia; Conradie, J; Ghosh, A; Brothers, Penelope (2008-09-07)

    Journal article
    The University of Auckland Library

    The structures of a number of mono- and diboron corrole complexes have been optimized using DFT methods in order to establish regio- and stereochemical preferences for bonding of one or two boron atoms to the corrole macrocycle. The formulations of the complexes were suggested either from preliminary experimental results (to be reported elsewhere) or by analogy with related diboron porphyrin compounds. The computational results suggest for the monoboron corroles BF2(H2corrole) and BPhH(H2corrole) that the regioisomer in which the boron is bound to a dipyrromethene site adjacent to the bipyrrole is preferred over the other possible regioisomers in which boron coordinates either in the bipyrrole or in the dipyrromethene site opposite the bipyrrole. In the N-substituted corrole complexes there are only two possiblities and, for each complex, the regioisomer with boron in the dipyrromethene site adjacent to the bipyrrole is lower in energy. For all four monoboron complexes the stereoisomers in which boron and both its substituents are displaced out of the mean N4 plane are more stable than the boron in-plane stereoisomers. These regio- and stereochemical preferences are rationalised by an analysis of the deformations to the corrole macrocycle and the geometry at the boron atoms. The lowest energy structures in all cases correspond to the least strained configurations. In addition, all four complexes show significant BFHN hydrogen bonding and BHHN dihydrogen bonding interactions, which are maximised in the lowest energy configurations for each structure, indicating that these are important additional stabilising interactions. Three different regioisomers, each with cisoid or transoid stereochemistry were optimised for the diboron complex PhBOB(corrole) which contains a bridging BOB group. The dipyrromethene/dipyrromethene isomer is more stable than either of the dipyrromethene/bipyrrole isomers and cisoid stereochemistry is preferred over transoid. This contrasts with porphyrin complexes containing BOB groups for which both stereochemical possibilities are observed, and reflects the contracted size of the corrole macrocycle. Three further diboron corroles were investigated, the diboranyl cation [B2(corrole)]+ and its one- and two-electron reduced derivatives B2(corrole) and [B2(corrole)]−. These calculations were undertaken to determine whether the site of reduction of [B2(corrole)]+ is likely to be the diboron moiety or the macrocycle. The B–B bond lengths do not shorten upon reduction and an analysis of the molecular orbitals of each species indicates that reduction will be most likely to occur at the macrocycle, offering a potential route to an example of the two-electron reduced corrole ligand, an analogue of the 20-electron isophlorin ligand observed in the corresponding reduced porphyrin complex B2(porphine).

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  • Synthesis of boron corrole complexes

    Albrett, Amelia (2009)

    Doctoral thesis
    The University of Auckland Library

    Boron complexes of porphyrin analogues are rare and typically difficult to prepare. The possibility of extending this chemistry further to include corroles was intriguing and provided the main motivation for this work. The coordination chemistry of boron with corroles was explored. The aim was to see whether boron could be coordinated within the corrole N4 core and if so whether novel or similar structural types resulted, relative to the closely related porphyrin system. Boron halides and aryl halides were reacted with free base corroles in the presence of diisopropylethylamine. The methodology employed was similar to that used for boron porphyrin systems. As well as free base corrole, an N-methyl corrole and trilithiated corrole were also used as starting materials. Several boron corrole structural types were obtained. The reaction of free base corrole with boron trifluoroetherate led to the first structurally characterised corrole with boron bound within the N4 core, B2OF2(corrole). From this reagent a mono-boron species, BF2(corrole) was also obtained. With dichlorophenylborane, several boron corrole complexes were prepared including PhB2O(corrole), PhB2(corrole) and B2Ph2H(corrole). The latter species was structurally characterised and the bridging hydride is proposed to form through a reductive coupling process. Use of N-methyl corrole effectively blocked one boron binding site and subsequently mono-boron corroles BF2(N-methyl- corrole), BPh(OH)(N-methyl corrole) and BPhF(N-methyl corrole) were prepared in good yields. The reaction of lithiated corrole and dichloroplenylborane afforded B2Ph2Cl(corrole). Overall, several new boron corrole species were prepared, significantly extending the library of known boron complexes with ligands related to the porphyrin system.

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