The Effect of electronic structure on molecular first hyperpolarizabilities of highly conjugated (polypyridyl)metal-(porphinato)zinc(II) chromophores

摘要

Electronic structural modifications of previously reported highly conjugated (polypyridyl)metal-(porphinato)zinc(II) NLO chromophores have been carried out. A primary focus of these modifications probed the role played by the porphyrin macrocycle in effecting large molecular hyperpolarizabilities; specifically, its meso-aryl substituents were replaced with electron withdrawing perfluoroalkyl groups. In doing so, we are effectively lowering HOMO and LUMO of the porphyrin fragment by 0.35eV while retaining the extensive mixing of B, Q, and CT states, and enforcing head-to-tail transition dipole alignment of the component metal-polypyridyl and porphyrin based chromophoric building blocks; this enables supermolecular structures with singly degenerate excited states polarized along the long donor-to-acceptor (D-to-A) charge transfer axis. This work will be placed in the context of ongoing electrooptic experiments and efforts aimed at fabricating new materials from these supermolecular chromophoric species.