SELF ASSEMBLY OF SUPRAMOLECULAR PHOTONICS

This part of our research is directed towards the formation of supramolecular photonic devices. The photoactive materials for these devices are self-assembled by: (i) metal ion coordination, (ii)hydrogen-bond molecular recognition, (iii)electrostatic interactions, (iv)a hybrid of the above. The rich photo- and electro- chemistry of porphyrins and phthalocyanins make these chromophores ideal building blocks. This research has several main objectives, including the understanding of the thermodynamics and kinetics of the self-assembly process, formation of light harvesting systems, formation and study of new photonic materials, and new synthetic methods for aldehydes and porphyrins.

The synthesis and characterization of combinatorial libraries of meso--tetraphenylporphyrin (H2TPP) derivatives - core structured libraries- is reported.  The libraries are readily further derivatized to create libraries of amphipathic porphyrins.  These amphipathic porphyrins are then screened for DNA binding, isolated, and examined for their ability to sensitize formation of singlet oxygen and cleave plasmid DNA.  Several novel porphyrins are identified and indicate multifunctional, amphipathic porphyrins bind more strongly than heretofore known homosubstituted porphyrins; thus, may be lead compounds for photodynamic therapeutics.

COMBINATORIAL CHEMISTRY AND MOLECULAR RECOGNITION

MEMBRANE ELECTROSTATICS AND CONDUCTION

We propose limits to the contributions to the total inner membrane potential by lipid head group components and by the orientation of water.  These assessments are based on electrostatic calculations that were an integral part of our explanation of the photogating of ionic currents across the lipid bilayer.  Our purpose is to describe an easy, fast method to calculate and examine the electrostatic consequences of various membrane structures and orientations, not to get embroiled in controversies regarding membrane structure.  We do show how variations in these membrane dimensions and structures affect the dipole potential of the membrane by using a range of values quoted in the literature.   The averages of these ranges are used as the parameters to calculate the total membrane potential.

PORPHYRIN PHOTOPHYSICS

In collaboration with Dewey Holten, Kevin Smith, John Shelnutt, and Jack Fajer we are looking at the complex photodynamics of distorted Nickel porphyrins.

The recent realization that most, if not all, porphyrins found in nature are at least somewhat distorted from the planar geometry we normally think of them.  A consortium of investigators literally from coast to coast have teamed up to investigate the photophyical and chemical consequences of these distortions.  The model that is emerging is that these distortion play a vital role in the pysical properties of the macrocycle such that subtle peterbations in the geometry or the local environment have dramatic consequences on the reactivity of the porphyrin.  This is well illustrated by nickel(II)dodecaphenylporphyrin and by meso-nickel(II)tetra-tert-butylporphyrin.

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