This thesis contains details of a study of the synthesis, characterisation, photochemical and photophysical properties of a series of novel free base porphyrins, metalloporphynns and their complexes with metal carbonyl fragments. The systems employed in this study have potential use in energy/electron transfer processes. Chapter 1 contains an introduction to the chemistry of porphyrins, metalloporphynns and their excited states as well as highlighting the mam principles of photochemistry and the bonding in metal carbonyl complexes. In chapter 2 the photochemistry of free base porphyrins and metalloporphynns, when complexed to metal centres, is discussed along with literature relevant to this topic. The photochemistry (both time-resolved and steady state) and photophysics (lifetimes, fluorescence spectra and quantum yield) measurements of mono 4-pyndyl-10,15,20- tnphenyl porphynn (MPyTPP) and its W(CO)s and Cr(CO)s complexes are discussed in chapter 3. In each case the tnplet and singlet excited state photochemistry is found to be located on the porphynn moiety. The presence of the M(CO)s group altered the electronic charactenstics of the complexes when compared to the uncomplexed free base porphynn. Chapter 4 descnbes the photochemistry and photophysics of porphynns when disubstituted with W(CO)s and Cr(CO)s moieties, which were produced from cw-5,10-di-4- pyndyl-15,20-diphenyl porphynn (m-DiPyDiPP). Similarly to the wcwo-complexed analogues the results obtained suggest that the excited state photochemistry was again centred on the porphynn component. Changes observed for the di-complexed porphynns are similar to those of the mowo-complexed porphynns except that the shifts are increased due to the presence of the two metal carbonyl units. The work presented in chapter 5 concerns the metalloporphynns, ZnMPyTPPW(CO)s and ZnMPyTPPCr(CO)5 Complexation of Zn to the centre of a porphynn dramatically alters the electronic properties of the porphynn. The effect of the M(CO)s unit on the zinc porphynn complexes was investigated using photochemical and photophysical techniques. The results are compared to zinc tetraphenyl porphynn (ZnTPP) and ZnMPyTPP because ZnMPyTPP polymenses through co-ordmation of the N atom of the pyndine to the Zn(II) centre. In chapter 6 the vanous charactensation methods and expenmental conditions for the synthesis and analysis of all complexes are descnbed. Complexes and ligands were charactensed by a range of spectroscopic methods such as NMR, IR and UV/Vis.