Sonya M. Scott

Synthesis, reactivity and spectroscopy of ferrocene-functionalised porphyrins, with a conjugated connection between the ferrocene and the porphyrin core

Several new ferrocene-functionalised porphyrins and a ruthenocene-functionalised porphyrin have been synthesized and studied using electrochemistry, electronic absorbance and resonance Raman spectroelectrochemical techniques. The porphyrin and ferrocene are observed to have limited effect on each other with the properties of the porphyrin dominating the spectroscopy of these molecules.

Ru(II) and Rh(III) porphyrin complexes of primary phosphine-substituted porphyrins

Primary alkynyl phosphine porphyrins were prepared by AlHCl2 reduction of the corresponding alkynyl phosphonates. Dephosphorylation of the alkyne proved to be a major side reaction. Using LiAlH4 as reducing agent, the alkyne was found to be partially reduced to give the trans-alkenyl phosphine selectively. The primary phosphines coordinate to both ruthenium(II) and rhodium(III) porphyrins and readily form bis-phosphine complexes. The 1H and 31P NMR spectra for the ruthenium complexes show a pattern characteristic of an [AX2]2 spin system with an unusually large 2JPP coupling constant of 620.6 Hz. The IR spectrum of the complex (PAPH2)Ru(CO)(porphyrin) (PAPH2 = phenylacetylenephosphine) indicates weak σ-donor properties of the ligand. In contrast to the corresponding tertiary phosphine complexes, the bis-phosphine complexes with both ruthenium(II) and rhodium(III) porphyrins are more stable than the mono-phosphine complexes, as judged by NMR spectroscopy, and they can also be detected in the gas phase by LDI-TOF MS. In all cases the complexes could not be isolated and they degrade within hours at ambient temperatures when kept in solution. These compounds may therefore not be suitable for the construction of larger multiporphyrin systems, but their accessibility makes it possible to study their coordination behaviour with other transition metals.

Energy transfer and structure determination of porphyrin dimers linked via a phenylenebisvinylene bridge. A time- resolved triplet electron paramagnetic resonance study

The photoexcited triplet state in a series of homo and hetero dimers was examined by time resolved electron paramagnetic resonance (TREPR) spectroscopy. The systems studied here consist of free-base tetraxylylporphyrin (H2TXP) and Zn(II) tetraxylylporphyrin (ZnTXP) and held together covalently by phenylenebisvinylene bridge at different positions. Experiments were carried out on the dimers, dissolved in an isotropic matrix (toluene), and in an anisotropic matrix of a liquid crystal (LC). Analysis of the results demonstrates that the dimers exhibit different geometries, depending on the linkage. Specifically, the triplet line shape analysis indicates that the para-dimers have a planar structure, the meta-dimers reveal the existence of two structural conformers, i.e. planar and slightly bent, while the ortho-dimers are characterized by the strongly bent molecular structure. The dimers exhibit efficient intramolecular singlet energy transfer (EnT) from ZnTXP to H2TXP subunit. On the other hand, EnT in all he...