The substitution of a pyrrolide ring for one (or more) pyridyl rings within the ubiquitous terpyridine (tpy, A) scaffold results in more open geometries of the pyridine-pyrrolide chelate ligands. DFT calculations (B3LYP-GD3BJ/6-31G**) demonstrate that the more open geometries of the unbound ligands are mismatched with the "pinched in" geometries required to chelate transition metal ions (e.g., Zn). The strain which builds within these ligands (Δ E) as they bind transition metal ions can be related to changes in a single geometric parameter: the separation between the two terminal N atoms (ρ). This relationship applies more generally to other three-ringed tridentate pincer ligands, including those with different donor groups. The approach was applied to homoleptic iron(II) complexes to investigate the contribution of the steric effects operating within the ligands to the different magnetic properties, including spin crossover (SCO) activities, of these systems.

A variety of organic hydride donors (OHDs) have been tested as reagents for the transfer of hydride to iron formato complexes in the activation and reduction of carbon dioxide. Theoretical calculations show that the selection of OHD and solvent is crucial when planning systems involving OHD cooperativity. Strong consideration is given to the likelihood that metal centers may deactivate formate to hydride attack, since, in general, the formate group has more resonance stabilization energy when complexed to a metal center compared to an organoformate or formic acid. It is experimentally demonstrated that 1,2dihydropyridine is not a competent reducing agent for carbon dioxide.

A range of substituted benzhydrols and fluorenols were prepared and subjected to acid catalysed methanolysis. Analysis of the rates of each of these processes showed correlation with Hammett σ(+) parameters as is consistent with the significant build-up of positive charge adjacent to the ring. In combination with the similarity of the electronic susceptibility of the processes, these data suggest that both reactions proceed through a unimolecular rate-determining step. This shows that the effect of fusion of the phenyl systems (and hence potentially introducing an antiaromatic carbocation intermediate) is only to slow the rate of reaction rather than change the mechanism of the process.

A series of ruthenaindene complexes containing electron-donating and -withdrawing groups were synthesized and characterized. The ruthenaindenes were synthesized from ruthenium butenynyl complexes which were formed by the treatment of Me 2 Ru(PMe 3 ) 4 with 1,4-diaryl-1,3-butadiynes in methanol. Electrochemistry of the metal center in ruthenaindenes showed that the complexes with electron-donating groups on the aromatic ring have significantly lower oxidation potentials in comparison to complexes with electron-withdrawing groups. Even though the substitution of the aromatic ring with electrondonating/-withdrawing groups is remote from the metal center, the electronic properties of the substituents are relayed effectively to the metal center, indicating that the metal center in the ruthenaindenes is quite intimately embedded into the organic aromatic framework.