Synthesis of an extended structure porphyrin lanthanide complex for use as a near infra-red imaging agent

This paper reports the synthesis and thennal Bergman cyclization of 2,3,12,13tetraethynyl-5,10,15,20-tetraphenylporphyrin to generate the chromophoric superstructures bis-piceno[20,1,2,3,4,5,10,11,12,13,14,15-fghij]porphyrin and 2,3diethynyl-5,20-diphenyl-piceno[10,11,12,13,14,15-fghij]porphyrin. Problems concerning the cyclization and new routes to our desired compound are discussed within. These chromophores, when paired with a near-IR emitting metal center, have potential as in vivo imaging agents. Introduction In order for a molecule to work as an effective near infra-red imaging agent in vivo, it must absorb light in the red region of the electromagnetic spectrum, and emit light in the near infra-red region. These types of molecules are potentially useful in biological systems because human tissue is largely transparent to both red and near infra-red wavelengths. For an effective imaging agent to be designed, the molecule requires two parts: a chromophore and an emissive band in the desired spectral region with a high quantum yield. If this molecule is to be delivered into a human system, light would be directed through the skin and absorbed by the chromophore. In the system we are designing, this absorbed energy is then passed into the metal center of the molecule. This metal center would then emit light in the near IR region, where it can be detected by an imaging system. To best fulfill this requirement, a member of the lanthanide series will serve as our metal center. Their optical properties, such as line-like emission spectra and long luminescence lifetimes have been studied.[1] These properties make this series of